Difference between revisions of "BIO-RAD 3000Xi"

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[[File:BIO-RAD 3000Xi Overview Photo.jpg|thumb|300x300px|BIO-RAD 3000Xi Powered on]]
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[[File:BIO-RAD 3000Xi Overview Photo.jpg|thumb|300x300px|BIO-RAD 3000Xi Powered on|alt=]]<br />
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From the [[:File:BIO-RAD 3000Xi Instruction Manual.pdf|user manual]]:<blockquote>Bio-Rad's computer controlled Model 3000xi Power Supply is the most powerful electrophoresis power supply avail­able. It produces constant voltage to 3,000 volts, constant current to 300 mA, and constant power to 400 watts. This fully switching, microprocessor cootrolled unit may be used with any electrophoresis instrument. The high outputs make the Model 3000xi Power Supply ideal for electrofocusing, DNA sequencing, and isotachophoresis. The supply is useful as a general purpose instrument, and is recommended for SDS-PAGE electrophoresis, two-dimensional electrophoresis, native gel electrophoresis, electrophoretic blotting, and DNA/RNA separations. <br> <br>
+
{| class="wikitable" style="left; margin-left:1em; width:22em; font-size:90%;"
 +
! colspan="2" style="text-align:center; background:#eee; font-size:115%;" |Bio-Rad 3000Xi
 +
|-
 +
! colspan="2" style="text-align:center; font-style:italic;" |Computer-Controlled Electrophoresis Power Supply
 +
|-
 +
!Manufacturer
 +
|Bio-Rad Laboratories
 +
|-
 +
!Model
 +
|3000Xi
 +
|-
 +
!Era
 +
|Late 1980s – 1990s
 +
|-
 +
!Output
 +
|25–3000 V DC, 0–300 mA, 0–400 W
 +
|-
 +
!Control
 +
|Microprocessor, fully programmable
 +
|}
  
−
The Model 3000xi Power Supply is a fully programmable and computerized instrument that incorporates several unique features. The supply offers four operating modes: standard, time, volt-hour, and step. The operator has a choice of running electrophoresis manually, for a set period of time, or for a set number of volt-hours. These parameters can be com­bined using the step mode. While operating in any one of the four modes, the user simply enters the desired power condi­tions and begins the run. The operational parameters are displayed on the LCD. Output voltage, current, and power are displayed on the LED display.</blockquote><br />
+
The '''Bio-Rad 3000Xi''' is a microprocessor-controlled high-voltage power supply intended for laboratory electrophoresis — SDS-PAGE, 2-D electrophoresis, native gel, electrophoretic blotting, isoelectric focusing, DNA/RNA separations, and isotachophoresis. It produces a regulated DC output up to '''3,000 V''', '''300 mA''', and '''400 W''', with constant-voltage, constant-current, and constant-power operating modes. Date codes on the silicon place this generation of the design at '''1987–1988'''.
 +
 
 +
This article documents an ongoing teardown / reverse-engineering effort. Each internal sub-assembly has its own section below.
 +
----
 +
 
 +
==Description from [[:File:BIO-RAD 3000Xi Instruction Manual.pdf|User Manual]]==
 +
Bio-Rad's computer controlled Model 3000xi Power Supply is the most powerful electrophoresis power supply avail­able. It produces constant voltage to 3,000 volts, constant current to 300 mA, and constant power to 400 watts. This fully switching, microprocessor cootrolled unit may be used with any electrophoresis instrument. The high outputs make the Model 3000xi Power Supply ideal for electrofocusing, DNA sequencing, and isotachophoresis. The supply is useful as a general purpose instrument, and is recommended for SDS-PAGE electrophoresis, two-dimensional electrophoresis, native gel electrophoresis, electrophoretic blotting, and DNA/RNA separations. <br> <br>
 +
 
 +
The Model 3000xi Power Supply is a fully programmable and computerized instrument that incorporates several unique features. The supply offers four operating modes: standard, time, volt-hour, and step. The operator has a choice of running electrophoresis manually, for a set period of time, or for a set number of volt-hours. These parameters can be com­bined using the step mode. While operating in any one of the four modes, the user simply enters the desired power condi­tions and begins the run. The operational parameters are displayed on the LCD. Output voltage, current, and power are displayed on the LED display.
 +
----
 +
==System Architecture==
 +
 
 +
The instrument is built as a modular stack of plug-in PCBs interconnected by ribbon cables and discrete wiring harnesses. The boards observed so far are silkscreened with '''OEM No.''' part numbers (Bio-Rad's internal designators):
 +
 
 +
{| class="wikitable"
 +
!Module!!Function (inferred)!!Status
 +
|-
 +
|[[#OEM No. 125B|OEM No. 125B]]||''TBD''||Not yet documented
 +
|-
 +
|[[#OEM No. 126C|OEM No. 126C]]||''TBD''||Not yet documented
 +
|-
 +
|[[#OEM No. 127A — HV Controller Board|OEM No. 127A]]||HV controller / regulator / telemetry||'''Documented''' below
 +
|-
 +
|[[#OEM No. 128B|OEM No. 128B]]||''TBD''||Not yet documented
 +
|-
 +
|[[#OEM No. 130C|OEM No. 130C]]||''TBD''||Not yet documented
 +
|-
 +
|[[#OEM No. 131A|OEM No. 131A]]||''TBD''||Not yet documented
 +
|-
 +
|[[#Auxiliary Power Supply Module|Aux PSU module]]||Switch-mode housekeeping supply||Not yet documented
 +
|-
 +
|[[#Mains Transformer|Mains transformer]]||Multi-secondary line transformer||Partially documented
 +
|-
 +
|[[#High Voltage Generation Module|HV generation module]]||Multi-PCB HV switcher and multiplier stack||Not yet documented
 +
|}
 +
 
 +
----
 +
 
 +
==High-Level Block Diagram==
 +
 
 +
<pre>
 +
                ┌─────────────────────────────────────┐
 +
                │  Front-Panel Microprocessor (μC)    │
 +
                │  (LCD, keypad, programming logic)  │
 +
                └────────────────┬────────────────────┘
 +
                                  │ ribbon (J-16)
 +
                                  ▼
 +
  ┌─────────────────────────────────────────────────────────┐
 +
  │  OEM No. 127A — HV Controller Board                    │
 +
  │  ┌────────────┐  ┌────────────┐  ┌─────────────────┐  │
 +
  │  │ Opto-iso.  │─▶|  TC4584    │─▶│ AD7543 12-bit  │  │
 +
  │  │ rcv (TLP)  │  │  Schmitt  │  │ serial-in DAC  │  │
 +
  │  └────────────┘  └────────────┘  └────────┬────────┘  │
 +
  │                                          ▼            │
 +
  │                                ┌────────────────────┐  │
 +
  │                                │ IR3M02 PWM ctrl ×2 │───┼──▶ J-14 (drive)
 +
  │                                │ (V loop / I loop)  │  │
 +
  │                                └─────────┬──────────┘  │
 +
  │                                          ▲              │
 +
  │  ┌────────────┐  ┌────────────┐  ┌───────┴────────┐    │
 +
  │  │ Opto-iso.  │◀─│ AD654 V/F  │◀─│ LF353 / LM358  │◀────┼── HV feedback
 +
  │  │ tx  (TLP)  │  │ converter  │  │ signal cond.  │    │  (J-13/J-14)
 +
  │  └────────────┘  └────────────┘  └────────────────┘    │
 +
  │                                                        │
 +
  │  Protection: LM358 comp. → TC4013 latch → IR3M02 SD ◀───┼── J-15
 +
  └─────────────────────────────────────────────────────────┘
 +
                                  │
 +
                                  ▼
 +
              HV generation module (resonant switching → step-up
 +
              transformer → rectifier/multiplier → output jacks)
 +
</pre>
 +
 
 +
----
 +
 
 +
==OEM No. 127A — HV Controller Board==
 +
 
 +
This is the analog/digital control board that bridges the front-panel microprocessor and the high-voltage power module. It accepts a digital setpoint from the μC, generates two PWM drive signals to control the HV switcher, and reports back the actual HV and HC values via a frequency-isolated telemetry path. It also handles fault detection and shutdown latching.
 +
 
 +
===Connector Map===
 +
 
 +
{| class="wikitable"
 +
!Connector!!Direction!!Function
 +
|-
 +
|'''J-12'''||In||Three transformer secondaries plus a ground-tie wire — feeds the on-board rectifiers and ±15 V / +12 V / +5 V regulators (see [[#J-12 Power-Input Topology|J-12 Power-Input Topology]] below)
 +
|-
 +
|'''J-13'''||In/Out||HV module interface (signal/feedback, near IR3M02 #1)
 +
|-
 +
|'''J-14'''||In||Feedback from HV module output stage
 +
|-
 +
|'''J-15'''||In/Out||Protection circuit (short / overcurrent / arc detection)
 +
|-
 +
|'''J-16'''||In/Out||Ribbon to embedded controller — serial DAC code in, telemetry and status out via optocouplers
 +
|}
 +
 
 +
===J-12 Power-Input Topology===
 +
 
 +
J-12 carries three transformer secondary windings plus a single ground-tie wire. The transformer itself has no center tap or earthed reference — the system ground is '''established on the board''' by bonding the negative DC output of one rectifier to the positive DC output of another, using the lone green wire. This stacks two of the rectified supplies end-to-end to produce the bipolar ±V<sub>unreg</sub> rails feeding the ±15 V analog regulators, while the third (blue) winding feeds an independent positive rail for the digital regulators.
 +
 
 +
====Stacked Topology====
 +
 
 +
<pre>
 +
        +Vunreg  ──▶  μA 78M15  ──▶  +15 V analog
 +
            ▲
 +
  ┌────────┴────────┐
 +
  │ Yellow pair    │ ← secondary winding #1
 +
  │ → bridge rect.  │
 +
  └────────┬────────┘
 +
            │ "−" output of yellow rectifier
 +
            ●━━━━━━━━━━━●  ◀── GREEN wire (system ground, 0 V)
 +
            │ "+" output of red rectifier
 +
  ┌────────┴────────┐
 +
  │ Red pair        │ ← secondary winding #2
 +
  │ → bridge rect.  │
 +
  └────────┬────────┘
 +
            ▼
 +
        −Vunreg  ──▶  μA79M15A ──▶  −15 V analog
 +
 
 +
 
 +
  ┌─────────────────┐
 +
  │ Blue pair      │ ← secondary winding #3 (independent)
 +
  │ → bridge rect.  │
 +
  └────────┬────────┘
 +
            ▼
 +
        +Vunreg(logic) ──┬──▶ LM340T-12 ──▶ +12 V
 +
                        └──▶ μA 78M05  ──▶  +5 V digital
 +
</pre>
 +
 
 +
====Wire Color Map====
 +
 
 +
{| class="wikitable"
 +
!Wire!!Conductors!!Function!!Feeds
 +
|-
 +
|'''Yellow'''||pair||Secondary winding #1, feeds bridge rectifier whose "+" output becomes +V<sub>unreg</sub>||+15 V regulator (REG2)
 +
|-
 +
|'''Red'''||pair||Secondary winding #2, feeds bridge rectifier whose "−" output becomes −V<sub>unreg</sub>||−15 V regulator (REG1)
 +
|-
 +
|'''Green'''||single||Ground bond — ties "−" of the yellow rectifier to "+" of the red rectifier, establishing the 0 V system reference||Analog ground for the entire board
 +
|-
 +
|'''Blue'''||pair||Secondary winding #3 (independent), feeds bridge rectifier for the positive logic rail||+12 V (REG3) and +5 V (REG4) regulators
 +
|}
 +
 
 +
====Notes on the Topology====
 +
 
 +
*The transformer has '''three independent floating secondaries''' — no center tap is brought out. The bipolar ±15 V rail pair is synthesized on the board by stacking two single-ended supplies via the green ground-tie wire.
 +
*The green wire is a '''current-carrying ground return''', not just a reference. The imbalance current between the +15 V and −15 V loads flows through it back to the rectifier diodes, so it should be a reasonable gauge and routed for low loop inductance. Lifting it during service work will collapse the entire analog ground reference of the board.
 +
*Because the "+" pin of the red bridge rectifier is bonded to ground, the red supply's '''negative''' DC output is the rail that goes down to the −15 V regulator. This is normal for a stacked topology but can be confusing if you expect the rectifier "+" pin to be the rail output.
 +
*Keeping the digital +5 V / +12 V supply on its own winding (blue) isolates digital switching noise from the ±15 V analog rails, which carry the precision references for the AD7543 DAC and the AD654 V/F converters.
 +
 
 +
===Active Components===
 +
 
 +
====Switching-Regulator Controllers====
 +
 
 +
{| class="wikitable"
 +
!Part Number!!Marking!!Package!!Function!!Datasheet
 +
|-
 +
|'''Sharp IR3M02''' (×2)||"SHARP IR3M02 78XD / 78SD"||16-DIP||PWM switching-regulator control IC; upgraded IR9494 with under-voltage lockout. The two devices most likely implement the '''constant-voltage loop''' and '''constant-current loop''' independently — the active loop dominates per Bio-Rad's CV / CC / CP mode behavior.||[https://www.alldatasheet.com/datasheet-pdf/pdf/42889/SHARP/IR3M02.html PDF] · [https://www.datasheetcatalog.com/datasheets_pdf/I/R/3/M/IR3M02.shtml datasheetcatalog]
 +
|}
 +
 
 +
====Digital-to-Analog Converter====
 +
 
 +
{| class="wikitable"
 +
!Part Number!!Marking!!Package!!Function!!Datasheet
 +
|-
 +
|'''Analog Devices AD7543JN'''||"AD7543JN"||16-DIP||CMOS 12-bit '''serial-input''' monolithic multiplying DAC, R-2R ladder. Has an internal 12-bit serial-in parallel-out shift register (Register A) plus a separate 12-bit DAC input register (Register B), so the chip accepts serial setpoint data directly from the μC — no external shift register required. The two-register architecture lets the μC clock in a new code while the DAC continues to hold the previous value, then transfer it cleanly with a LOAD pulse. Asynchronous CLEAR input zeroes Register B for safe initialization. With 12-bit resolution this gives '''~0.7 V resolution at 3000 V full-scale''' — consistent with Bio-Rad's published 1 V step granularity. The "multiplying" feature is convenient because V<sub>REF</sub> can be scaled by an external precision reference for absolute-voltage trim.||[https://www.analog.com/en/products/ad7543.html AD7543 product page] · [https://wiki.recessim.com/w/images/f/fc/AD7543.PDF PDF]
 +
|}
 +
 
 +
====CMOS Logic (Toshiba 4000-series)====
 +
 
 +
{| class="wikitable"
 +
!Part Number!!Marking!!Package!!Function!!Datasheet
 +
|-
 +
|'''TC4011BP'''||"TOSHIBA 8838B TC4011BP JAPAN"||14-DIP||Quad 2-input NAND gate. Likely used to combine fault / interlock / reset signals into the IR3M02 shutdown line and possibly to gate the AD7543 control inputs.||[https://toshiba.semicon-storage.com/eu/semiconductor/product/general-purpose-logic-ics/detail.TC4011BP.html Toshiba page] · [https://www.alldatasheet.com/datasheet-pdf/pdf/31627/TOSHIBA/TC4011BP.html PDF]
 +
|-
 +
|'''TC4013BP'''||"TOSHIBA 8836HB TC4013BP JAPAN"||14-DIP||Dual D-type flip-flop with set/reset. Strong candidate for the '''fault latch''' — set by a comparator output from J-15 (short / overcurrent / arc), output ties into the IR3M02 shutdown pin and stays latched until the μC issues an explicit reset. The second flip-flop may serve as a sync stage or as a divide-by-2 in an AD654 gate-timing chain.||[https://toshiba.semicon-storage.com/info/TC4013BF_datasheet_en.pdf Toshiba PDF]
 +
|-
 +
|'''TC4025BP'''||"TOSHIBA 8844HB TC4025BP JAPAN"||14-DIP||Triple 3-input NOR gate. Typical use in this kind of design: combining multiple shutdown sources (over-current, over-voltage, interlock-open, μC-stop) into a single active-high enable signal.||[https://toshiba.semicon-storage.com/info/TC4025BF_datasheet_en.pdf Toshiba PDF]
 +
|-
 +
|'''TC4584BP'''||"TOSHIBA 8848H TC4584BP JAPAN"||14-DIP||Hex Schmitt-trigger inverter. '''Confirmed''' to sit in the signal path between the input optocoupler bank and the AD7543, cleaning up the slow optocoupler-output edges and inverting them before they reach the DAC's clocked inputs (SRI / STB / LD / CLR), which require sharp transitions. With 6 cells available and 4 used for the DAC interface, up to 2 cells remain — likely used either for additional input cleanup (master enable, fault input from J-15) or configured as an RC oscillator providing a local time-base for AD654 gate timing.||[https://www.datasheetcatalog.com/datasheets_pdf/T/C/4/5/TC4584BP.shtml PDF]
 +
|}
 +
 
 +
====Operational Amplifiers (National Semiconductor)====
 +
 
 +
{| class="wikitable"
 +
!Part Number!!Marking!!Package!!Function!!Datasheet
 +
|-
 +
|'''LF353N''' (multiple)||"LF ⊗ 353N M8818"||8-DIP||Dual JFET-input op-amp, low input bias, used where high Z input is needed (V/F front-end, integrator stages, HV-divider buffer).||[https://www.ti.com/lit/ds/symlink/lf353.pdf TI PDF]
 +
|-
 +
|'''LM358N''' ''(probable)'' (multiple)||"LM ⊗ … M8836"||8-DIP||General-purpose dual op-amp, used as comparator / signal-conditioning. Suffix not fully readable in photos.||[https://www.ti.com/lit/ds/symlink/lm358.pdf TI PDF]
 +
|}
 +
 
 +
====Voltage-to-Frequency Converter (Analog Devices)====
 +
 
 +
{| class="wikitable"
 +
!Part Number!!Marking!!Package!!Function!!Datasheet
 +
|-
 +
|'''AD654JN''' (×2)||"AD654JN M8824A"||8-DIP||Low-cost monolithic V/F converter, 0–500 kHz, ±0.03 % linearity. One channel measures '''HV''' (output voltage), the other measures '''HC''' (output current) — both reported back to the μC as a frequency through the optocoupler isolation barrier. Frequency-domain telemetry sidesteps optocoupler CTR drift.||[https://www.analog.com/media/en/technical-documentation/data-sheets/AD654.pdf AD PDF] · [https://www.analog.com/en/products/ad654.html AD page]
 +
|}
 +
 
 +
====Optocouplers (Toshiba)====
 +
 
 +
{| class="wikitable"
 +
!Part Number!!Marking!!Package!!Function!!Datasheet
 +
|-
 +
|'''TLP621-4''' (×2)||"T8K TLP621-4 GB"||16-DIP||Quad transistor-output optocoupler, 5 kVrms isolation, CTR 100–600 %. Together they provide 8 isolated digital channels — sufficient for the AD7543's serial interface (SRI data, STB clock, LD load, CLR clear), master enable, fault status, plus the two AD654 frequency-out telemetry channels.||[[:File:TLP621 datasheet.pdf|Datasheet]]
 +
|-
 +
|'''TLP621''' (×1)||"T7K P621"||4-DIP||Single-channel version. Probably an additional status / interlock line, or a high-priority signal kept on its own isolation domain.||[[:File:TLP621 datasheet.pdf|Datasheet]]
 +
|}
 +
 
 +
====Linear Voltage Regulators (Confirmed from photos)====
 +
 
 +
{| class="wikitable"
 +
!Position!!Part Number!!Marking!!Output!!Datasheet
 +
|-
 +
|'''REG1'''||Fairchild '''μA79M15A''' (Korea)||"μA79M15A UC871x KOREA"||'''−15 V''' analog rail||[https://www.ti.com/lit/ds/symlink/lm7900.pdf 79xx PDF (TI)]
 +
|-
 +
|'''REG2'''||Fairchild '''μA 78M15''' (Korea)||"μA 78M15 UC8704 KOREA"||'''+15 V''' analog rail||[https://www.ti.com/lit/ds/symlink/lm340.pdf 78xx PDF (TI)]
 +
|-
 +
|'''REG3''' ''(or REG4)''||National '''LM340T-12'''||"EM340T12 7812 P+" 8730||'''+12 V''' rail||[https://www.ti.com/lit/ds/symlink/lm340.pdf LM340 PDF (TI)]
 +
|-
 +
|'''REG4''' ''(or REG3)''||Fairchild '''μA 78M05''' (Korea)||"μA 78M05 UC8731 KOREA"||'''+5 V''' digital rail||[https://www.ti.com/lit/ds/symlink/lm340.pdf 78M PDF (TI)]
 +
|}
 +
 
 +
<div style="border-left:4px solid #f0ad4e; background:#fcf8e3; padding:0.5em 1em; margin:1em 0;">
 +
'''Note:''' REG3 vs REG4 silkscreen position needs confirmation against the TO-220 part numbers — only the REG1/REG2 silkscreen was clearly visible in image 3.
 +
</div>
 +
 
 +
===Passive Components===
 +
 
 +
{| class="wikitable"
 +
!Type!!Description
 +
|-
 +
|'''Trim pots''' (VR1–VR6)||Blue 25-turn cermet, Bourns 3296-style. Marking "78205" / "5028L" on the side is the manufacturer's part/style code, '''not''' the resistance. The resistance code is on the top face under the screw. Used for setting V/F scale & offset (per AD654 channel) and HV setpoint trims. [https://www.bourns.com/docs/Product-Datasheets/3296.pdf Bourns 3296 datasheet]
 +
|-
 +
|'''Large blue radial electrolytics'''||"CEW M97 / M404 85 °C" — Japanese-made (Nichicon or similar), main reservoir & rail filtering after the bridge rectifier.
 +
|-
 +
|'''Rubycon "25v 100μF"'''||Visible near REG3/REG4 — local rail decoupling.
 +
|-
 +
|'''Smaller blue electrolytics'''||Bypass and decoupling on each rail and around the IR3M02s.
 +
|-
 +
|'''Brown axial film cap''' (left edge)||Metalized polypropylene; safety / snubber.
 +
|-
 +
|'''Green disc ceramics'''||High-voltage Y-rated ceramic discs.
 +
|-
 +
|'''Two small bare-copper toroids''' (bottom)||Output filter inductors.
 +
|-
 +
|'''Large copper-wound toroid''' (top right)||Common-mode line-input choke.
 +
|}
 +
 
 +
===Reverse-Engineering Notes===
 +
 
 +
#'''Two IR3M02 controllers''' fit Bio-Rad's published behavior of independent constant-voltage and constant-current regulation with automatic crossover. Whichever loop demands the lower duty cycle wins, which is the textbook way to implement CV/CC/CP modes. The pairing of trim pots VR1+VR2 / VR3+VR4 next to the two AD654s is consistent with calibrating two independent feedback channels (one for V, one for I).
 +
#The '''AD7543 12-bit serial-input DAC''' confirms this is a fully digital setpoint architecture, not a potentiometer-driven supply. The controller clocks a 12-bit code into the DAC's internal Register A through one optocoupler channel (SRI) timed by another (STB), then issues a LOAD pulse on a third channel to transfer the new code to the DAC output (Register B). With 4096 codes across 3000 V full-scale, that's ~0.73 V LSB — Bio-Rad spec'd 1 V steps, which matches.
 +
#Because the AD7543 has its own internal serial-in shift register, the '''TC4013 / TC4011 / TC4025 logic cluster is not performing serial-to-parallel conversion for the DAC'''. Instead, that logic most likely handles: (a) fault-latching (TC4013 D-flip-flop set by a comparator output from J-15, output ties into the IR3M02 shutdown pin until the μC issues a reset), (b) generating local timing or gate windows for the AD654 measurement cycle, and/or (c) combining manual-reset, interlock, and over-temperature signals into the master enable line.
 +
#The '''AD654 + TLP621-4 telemetry path''' is the classical isolated-precision-measurement trick. Two channels — one for HV, one for HC — give the μC the data it needs to display "actual" values and run constant-power calculations. Frequency-domain transmission across the optocoupler sidesteps CTR drift and aging.
 +
#'''TC4584 Schmitt is confirmed in the optocoupler-to-DAC path.''' Each of the four AD7543 control signals (SRI, STB, LD, CLR) passes through one Schmitt-inverter cell after the optocoupler before reaching the DAC. Note that the TC4584 cells are '''inverting''' — the logic polarity at the DAC pin is opposite the polarity at the optocoupler output, which matters when probing. Combined with the optocoupler's own inversion (the output transistor pulls low when the LED is on), the net polarity from μC to DAC is non-inverting.
 +
#The '''J-12 power-input topology''' (three independent floating secondaries with on-board ground synthesis via the green ground-tie wire) means the entire OEM 127A board is referenced to ''its own'' analog ground, not chassis. Anything probing this board during operation must reference scope grounds to that node, not to chassis or earth, to avoid blowing up secondary windings or injecting ground loops.
 +
 
 +
===Items Still to Confirm===
 +
 
 +
*Resolve whether the +12 V regulator sits at REG3 or REG4 (silkscreen vs. position)
 +
*Confirm "LM ⊗ M8836" parts are '''LM358N''' (vs LM833 etc.) under magnifier
 +
*Verify all "M8818 LF" parts are '''LF353N''' (suffix not visible in all shots)
 +
*Identify what J-13 carries (likely shares the HV-module signal bus with J-14)
 +
*Probe the AD654 output frequencies at full-scale HV and full-scale HC to determine the monitoring scale factors
 +
*Identify the two TO-220 transistors visible near the heatsinks at top-left of the board (driver pre-stage between IR3M02s and the HV switching FETs?)
 +
*Trace the 9 optocoupler channels at J-16 (8 across the two TLP621-4 quads plus the 1 in the TLP621 single) and assign each a function. Expected set: AD7543 SRI / STB / LD / CLR (4), master ENABLE (1), FAULT status out (1), HV frequency out (1), HC frequency out (1), plus 1 reserved/interlock.
 +
*Determine what role the TC4013 / TC4011 / TC4025 logic plays now that the DAC handles its own serial-to-parallel conversion (fault latch and/or AD654 gate-timing oscillator are the leading hypotheses).
 +
 
 +
----
 +
 
 +
==OEM No. 125B==
 +
 
 +
''Module not yet examined. Photos and reverse-engineering pending.''
 +
 
 +
==OEM No. 126C==
 +
 
 +
''Module not yet examined. Photos and reverse-engineering pending.''
 +
 
 +
==OEM No. 128B==
 +
 
 +
''Module not yet examined. Photos and reverse-engineering pending.''
 +
 
 +
==OEM No. 130C==
 +
 
 +
''Module not yet examined. Photos and reverse-engineering pending.''
 +
 
 +
==OEM No. 131A==
 +
 
 +
''Module not yet examined. Photos and reverse-engineering pending.''
 +
 
 +
==Auxiliary Power Supply Module==
 +
 
 +
''Switch-mode housekeeping supply visible at the right side of the chassis. Not yet examined in detail.''
 +
 
 +
==Mains Transformer==
 +
 
 +
Multi-secondary line-frequency transformer visible at the top-left of the chassis. Has at least three independent floating secondary windings brought out to the OEM No. 127A controller board via J-12:
 +
 
 +
*'''Yellow pair''' — secondary winding #1, feeds the +15 V analog rail
 +
*'''Red pair''' — secondary winding #2, feeds the −15 V analog rail
 +
*'''Blue pair''' — secondary winding #3, feeds the +12 V and +5 V digital rails
 +
 
 +
A single '''green wire''' also exits the harness at J-12 to bond the rectifier outputs into a stacked bipolar topology (see [[#J-12 Power-Input Topology|J-12 Power-Input Topology]]).
 +
 
 +
Voltage taps and current ratings TBD. Additional secondaries (if any) feeding the [[#High Voltage Generation Module|HV generation module]] are routed separately and have not yet been documented.
 +
 
 +
==High Voltage Generation Module==
 +
 
 +
''Multi-PCB high-voltage assembly. Comprises the HV switching power stage, step-up transformer, and a Cockcroft–Walton or similar diode/capacitor multiplier producing the 0–3000 V output. Driven by J-14 from the OEM No. 127A controller; returns voltage and current sense signals via J-13 (and possibly J-14).''
 +
 
 +
----
 +
 
 +
==References==
 +
 
 +
*Bio-Rad 3000Xi product information — historical Bio-Rad documentation (now superseded by the [https://www.bio-rad.com/en-us/product/powerpac-hv-high-voltage-power-supply?ID=b64403c7-43a2-4085-aba0-ce78c2b6f330 PowerPac HV] family).
 +
*[https://www.spectralabsci.com/equipment/biorad-3000xi-computer-controlled-electrophoresis-power-supply/ Spectralab Scientific — 3000Xi listing]
 +
*[https://www.artisantg.com/Scientific/77033-3/Bio-Rad-3000xi-Computer-Controlled-Electrophoresis-Power-Supply Artisan Technology Group — 3000Xi page]
 +
 
 +
----
 +
 
 +
''This article documents an ongoing teardown. Identifications are best-effort from photographs of date-coded components (1987–1988). Please verify physically before relying on any information here for repair or redesign.''

Latest revision as of 21:45, 10 May 2026

BIO-RAD 3000Xi Powered on


Bio-Rad 3000Xi
Computer-Controlled Electrophoresis Power Supply
Manufacturer Bio-Rad Laboratories
Model 3000Xi
Era Late 1980s – 1990s
Output 25–3000 V DC, 0–300 mA, 0–400 W
Control Microprocessor, fully programmable

The Bio-Rad 3000Xi is a microprocessor-controlled high-voltage power supply intended for laboratory electrophoresis — SDS-PAGE, 2-D electrophoresis, native gel, electrophoretic blotting, isoelectric focusing, DNA/RNA separations, and isotachophoresis. It produces a regulated DC output up to 3,000 V, 300 mA, and 400 W, with constant-voltage, constant-current, and constant-power operating modes. Date codes on the silicon place this generation of the design at 1987–1988.

This article documents an ongoing teardown / reverse-engineering effort. Each internal sub-assembly has its own section below.

Description from User Manual

Bio-Rad's computer controlled Model 3000xi Power Supply is the most powerful electrophoresis power supply avail­able. It produces constant voltage to 3,000 volts, constant current to 300 mA, and constant power to 400 watts. This fully switching, microprocessor cootrolled unit may be used with any electrophoresis instrument. The high outputs make the Model 3000xi Power Supply ideal for electrofocusing, DNA sequencing, and isotachophoresis. The supply is useful as a general purpose instrument, and is recommended for SDS-PAGE electrophoresis, two-dimensional electrophoresis, native gel electrophoresis, electrophoretic blotting, and DNA/RNA separations.

The Model 3000xi Power Supply is a fully programmable and computerized instrument that incorporates several unique features. The supply offers four operating modes: standard, time, volt-hour, and step. The operator has a choice of running electrophoresis manually, for a set period of time, or for a set number of volt-hours. These parameters can be com­bined using the step mode. While operating in any one of the four modes, the user simply enters the desired power condi­tions and begins the run. The operational parameters are displayed on the LCD. Output voltage, current, and power are displayed on the LED display.

System Architecture

The instrument is built as a modular stack of plug-in PCBs interconnected by ribbon cables and discrete wiring harnesses. The boards observed so far are silkscreened with OEM No. part numbers (Bio-Rad's internal designators):

Module Function (inferred) Status
OEM No. 125B TBD Not yet documented
OEM No. 126C TBD Not yet documented
OEM No. 127A HV controller / regulator / telemetry Documented below
OEM No. 128B TBD Not yet documented
OEM No. 130C TBD Not yet documented
OEM No. 131A TBD Not yet documented
Aux PSU module Switch-mode housekeeping supply Not yet documented
Mains transformer Multi-secondary line transformer Partially documented
HV generation module Multi-PCB HV switcher and multiplier stack Not yet documented

High-Level Block Diagram

                 ┌─────────────────────────────────────┐
                 │  Front-Panel Microprocessor (μC)    │
                 │  (LCD, keypad, programming logic)   │
                 └────────────────┬────────────────────┘
                                  │ ribbon (J-16)
                                  ▼
   ┌─────────────────────────────────────────────────────────┐
   │  OEM No. 127A — HV Controller Board                     │
   │  ┌────────────┐   ┌────────────┐  ┌─────────────────┐   │
   │  │ Opto-iso.  │─▶|  TC4584    │─▶│ AD7543 12-bit   │   │
   │  │ rcv (TLP)  │   │  Schmitt   │  │ serial-in DAC   │   │
   │  └────────────┘   └────────────┘  └────────┬────────┘   │
   │                                           ▼             │
   │                                ┌────────────────────┐   │
   │                                │ IR3M02 PWM ctrl ×2 │───┼──▶ J-14 (drive)
   │                                │ (V loop / I loop)  │   │
   │                                └─────────┬──────────┘   │
   │                                          ▲              │
   │  ┌────────────┐  ┌────────────┐  ┌───────┴────────┐     │
   │  │ Opto-iso.  │◀─│ AD654 V/F  │◀─│ LF353 / LM358  │◀────┼── HV feedback
   │  │ tx  (TLP)  │  │ converter  │  │ signal cond.   │     │   (J-13/J-14)
   │  └────────────┘  └────────────┘  └────────────────┘     │
   │                                                         │
   │  Protection: LM358 comp. → TC4013 latch → IR3M02 SD ◀───┼── J-15
   └─────────────────────────────────────────────────────────┘
                                  │
                                  ▼
              HV generation module (resonant switching → step-up
              transformer → rectifier/multiplier → output jacks)

OEM No. 127A — HV Controller Board

This is the analog/digital control board that bridges the front-panel microprocessor and the high-voltage power module. It accepts a digital setpoint from the μC, generates two PWM drive signals to control the HV switcher, and reports back the actual HV and HC values via a frequency-isolated telemetry path. It also handles fault detection and shutdown latching.

Connector Map

Connector Direction Function
J-12 In Three transformer secondaries plus a ground-tie wire — feeds the on-board rectifiers and ±15 V / +12 V / +5 V regulators (see J-12 Power-Input Topology below)
J-13 In/Out HV module interface (signal/feedback, near IR3M02 #1)
J-14 In Feedback from HV module output stage
J-15 In/Out Protection circuit (short / overcurrent / arc detection)
J-16 In/Out Ribbon to embedded controller — serial DAC code in, telemetry and status out via optocouplers

J-12 Power-Input Topology

J-12 carries three transformer secondary windings plus a single ground-tie wire. The transformer itself has no center tap or earthed reference — the system ground is established on the board by bonding the negative DC output of one rectifier to the positive DC output of another, using the lone green wire. This stacks two of the rectified supplies end-to-end to produce the bipolar ±Vunreg rails feeding the ±15 V analog regulators, while the third (blue) winding feeds an independent positive rail for the digital regulators.

Stacked Topology

        +Vunreg  ──▶  μA 78M15  ──▶  +15 V analog
            ▲
   ┌────────┴────────┐
   │ Yellow pair     │ ← secondary winding #1
   │ → bridge rect.  │
   └────────┬────────┘
            │ "−" output of yellow rectifier
            ●━━━━━━━━━━━●  ◀── GREEN wire (system ground, 0 V)
            │ "+" output of red rectifier
   ┌────────┴────────┐
   │ Red pair        │ ← secondary winding #2
   │ → bridge rect.  │
   └────────┬────────┘
            ▼
        −Vunreg  ──▶  μA79M15A ──▶  −15 V analog


   ┌─────────────────┐
   │ Blue pair       │ ← secondary winding #3 (independent)
   │ → bridge rect.  │
   └────────┬────────┘
            ▼
        +Vunreg(logic) ──┬──▶ LM340T-12 ──▶ +12 V
                         └──▶ μA 78M05  ──▶  +5 V digital

Wire Color Map

Wire Conductors Function Feeds
Yellow pair Secondary winding #1, feeds bridge rectifier whose "+" output becomes +Vunreg +15 V regulator (REG2)
Red pair Secondary winding #2, feeds bridge rectifier whose "−" output becomes −Vunreg −15 V regulator (REG1)
Green single Ground bond — ties "−" of the yellow rectifier to "+" of the red rectifier, establishing the 0 V system reference Analog ground for the entire board
Blue pair Secondary winding #3 (independent), feeds bridge rectifier for the positive logic rail +12 V (REG3) and +5 V (REG4) regulators

Notes on the Topology

  • The transformer has three independent floating secondaries — no center tap is brought out. The bipolar ±15 V rail pair is synthesized on the board by stacking two single-ended supplies via the green ground-tie wire.
  • The green wire is a current-carrying ground return, not just a reference. The imbalance current between the +15 V and −15 V loads flows through it back to the rectifier diodes, so it should be a reasonable gauge and routed for low loop inductance. Lifting it during service work will collapse the entire analog ground reference of the board.
  • Because the "+" pin of the red bridge rectifier is bonded to ground, the red supply's negative DC output is the rail that goes down to the −15 V regulator. This is normal for a stacked topology but can be confusing if you expect the rectifier "+" pin to be the rail output.
  • Keeping the digital +5 V / +12 V supply on its own winding (blue) isolates digital switching noise from the ±15 V analog rails, which carry the precision references for the AD7543 DAC and the AD654 V/F converters.

Active Components

Switching-Regulator Controllers

Part Number Marking Package Function Datasheet
Sharp IR3M02 (×2) "SHARP IR3M02 78XD / 78SD" 16-DIP PWM switching-regulator control IC; upgraded IR9494 with under-voltage lockout. The two devices most likely implement the constant-voltage loop and constant-current loop independently — the active loop dominates per Bio-Rad's CV / CC / CP mode behavior. PDF · datasheetcatalog

Digital-to-Analog Converter

Part Number Marking Package Function Datasheet
Analog Devices AD7543JN "AD7543JN" 16-DIP CMOS 12-bit serial-input monolithic multiplying DAC, R-2R ladder. Has an internal 12-bit serial-in parallel-out shift register (Register A) plus a separate 12-bit DAC input register (Register B), so the chip accepts serial setpoint data directly from the μC — no external shift register required. The two-register architecture lets the μC clock in a new code while the DAC continues to hold the previous value, then transfer it cleanly with a LOAD pulse. Asynchronous CLEAR input zeroes Register B for safe initialization. With 12-bit resolution this gives ~0.7 V resolution at 3000 V full-scale — consistent with Bio-Rad's published 1 V step granularity. The "multiplying" feature is convenient because VREF can be scaled by an external precision reference for absolute-voltage trim. AD7543 product page · PDF

CMOS Logic (Toshiba 4000-series)

Part Number Marking Package Function Datasheet
TC4011BP "TOSHIBA 8838B TC4011BP JAPAN" 14-DIP Quad 2-input NAND gate. Likely used to combine fault / interlock / reset signals into the IR3M02 shutdown line and possibly to gate the AD7543 control inputs. Toshiba page · PDF
TC4013BP "TOSHIBA 8836HB TC4013BP JAPAN" 14-DIP Dual D-type flip-flop with set/reset. Strong candidate for the fault latch — set by a comparator output from J-15 (short / overcurrent / arc), output ties into the IR3M02 shutdown pin and stays latched until the μC issues an explicit reset. The second flip-flop may serve as a sync stage or as a divide-by-2 in an AD654 gate-timing chain. Toshiba PDF
TC4025BP "TOSHIBA 8844HB TC4025BP JAPAN" 14-DIP Triple 3-input NOR gate. Typical use in this kind of design: combining multiple shutdown sources (over-current, over-voltage, interlock-open, μC-stop) into a single active-high enable signal. Toshiba PDF
TC4584BP "TOSHIBA 8848H TC4584BP JAPAN" 14-DIP Hex Schmitt-trigger inverter. Confirmed to sit in the signal path between the input optocoupler bank and the AD7543, cleaning up the slow optocoupler-output edges and inverting them before they reach the DAC's clocked inputs (SRI / STB / LD / CLR), which require sharp transitions. With 6 cells available and 4 used for the DAC interface, up to 2 cells remain — likely used either for additional input cleanup (master enable, fault input from J-15) or configured as an RC oscillator providing a local time-base for AD654 gate timing. PDF

Operational Amplifiers (National Semiconductor)

Part Number Marking Package Function Datasheet
LF353N (multiple) "LF ⊗ 353N M8818" 8-DIP Dual JFET-input op-amp, low input bias, used where high Z input is needed (V/F front-end, integrator stages, HV-divider buffer). TI PDF
LM358N (probable) (multiple) "LM ⊗ … M8836" 8-DIP General-purpose dual op-amp, used as comparator / signal-conditioning. Suffix not fully readable in photos. TI PDF

Voltage-to-Frequency Converter (Analog Devices)

Part Number Marking Package Function Datasheet
AD654JN (×2) "AD654JN M8824A" 8-DIP Low-cost monolithic V/F converter, 0–500 kHz, ±0.03 % linearity. One channel measures HV (output voltage), the other measures HC (output current) — both reported back to the μC as a frequency through the optocoupler isolation barrier. Frequency-domain telemetry sidesteps optocoupler CTR drift. AD PDF · AD page

Optocouplers (Toshiba)

Part Number Marking Package Function Datasheet
TLP621-4 (×2) "T8K TLP621-4 GB" 16-DIP Quad transistor-output optocoupler, 5 kVrms isolation, CTR 100–600 %. Together they provide 8 isolated digital channels — sufficient for the AD7543's serial interface (SRI data, STB clock, LD load, CLR clear), master enable, fault status, plus the two AD654 frequency-out telemetry channels. Datasheet
TLP621 (×1) "T7K P621" 4-DIP Single-channel version. Probably an additional status / interlock line, or a high-priority signal kept on its own isolation domain. Datasheet

Linear Voltage Regulators (Confirmed from photos)

Position Part Number Marking Output Datasheet
REG1 Fairchild μA79M15A (Korea) "μA79M15A UC871x KOREA" −15 V analog rail 79xx PDF (TI)
REG2 Fairchild μA 78M15 (Korea) "μA 78M15 UC8704 KOREA" +15 V analog rail 78xx PDF (TI)
REG3 (or REG4) National LM340T-12 "EM340T12 7812 P+" 8730 +12 V rail LM340 PDF (TI)
REG4 (or REG3) Fairchild μA 78M05 (Korea) "μA 78M05 UC8731 KOREA" +5 V digital rail 78M PDF (TI)

Note: REG3 vs REG4 silkscreen position needs confirmation against the TO-220 part numbers — only the REG1/REG2 silkscreen was clearly visible in image 3.

Passive Components

Type Description
Trim pots (VR1–VR6) Blue 25-turn cermet, Bourns 3296-style. Marking "78205" / "5028L" on the side is the manufacturer's part/style code, not the resistance. The resistance code is on the top face under the screw. Used for setting V/F scale & offset (per AD654 channel) and HV setpoint trims. Bourns 3296 datasheet
Large blue radial electrolytics "CEW M97 / M404 85 °C" — Japanese-made (Nichicon or similar), main reservoir & rail filtering after the bridge rectifier.
Rubycon "25v 100μF" Visible near REG3/REG4 — local rail decoupling.
Smaller blue electrolytics Bypass and decoupling on each rail and around the IR3M02s.
Brown axial film cap (left edge) Metalized polypropylene; safety / snubber.
Green disc ceramics High-voltage Y-rated ceramic discs.
Two small bare-copper toroids (bottom) Output filter inductors.
Large copper-wound toroid (top right) Common-mode line-input choke.

Reverse-Engineering Notes

  1. Two IR3M02 controllers fit Bio-Rad's published behavior of independent constant-voltage and constant-current regulation with automatic crossover. Whichever loop demands the lower duty cycle wins, which is the textbook way to implement CV/CC/CP modes. The pairing of trim pots VR1+VR2 / VR3+VR4 next to the two AD654s is consistent with calibrating two independent feedback channels (one for V, one for I).
  2. The AD7543 12-bit serial-input DAC confirms this is a fully digital setpoint architecture, not a potentiometer-driven supply. The controller clocks a 12-bit code into the DAC's internal Register A through one optocoupler channel (SRI) timed by another (STB), then issues a LOAD pulse on a third channel to transfer the new code to the DAC output (Register B). With 4096 codes across 3000 V full-scale, that's ~0.73 V LSB — Bio-Rad spec'd 1 V steps, which matches.
  3. Because the AD7543 has its own internal serial-in shift register, the TC4013 / TC4011 / TC4025 logic cluster is not performing serial-to-parallel conversion for the DAC. Instead, that logic most likely handles: (a) fault-latching (TC4013 D-flip-flop set by a comparator output from J-15, output ties into the IR3M02 shutdown pin until the μC issues a reset), (b) generating local timing or gate windows for the AD654 measurement cycle, and/or (c) combining manual-reset, interlock, and over-temperature signals into the master enable line.
  4. The AD654 + TLP621-4 telemetry path is the classical isolated-precision-measurement trick. Two channels — one for HV, one for HC — give the μC the data it needs to display "actual" values and run constant-power calculations. Frequency-domain transmission across the optocoupler sidesteps CTR drift and aging.
  5. TC4584 Schmitt is confirmed in the optocoupler-to-DAC path. Each of the four AD7543 control signals (SRI, STB, LD, CLR) passes through one Schmitt-inverter cell after the optocoupler before reaching the DAC. Note that the TC4584 cells are inverting — the logic polarity at the DAC pin is opposite the polarity at the optocoupler output, which matters when probing. Combined with the optocoupler's own inversion (the output transistor pulls low when the LED is on), the net polarity from μC to DAC is non-inverting.
  6. The J-12 power-input topology (three independent floating secondaries with on-board ground synthesis via the green ground-tie wire) means the entire OEM 127A board is referenced to its own analog ground, not chassis. Anything probing this board during operation must reference scope grounds to that node, not to chassis or earth, to avoid blowing up secondary windings or injecting ground loops.

Items Still to Confirm

  • Resolve whether the +12 V regulator sits at REG3 or REG4 (silkscreen vs. position)
  • Confirm "LM ⊗ M8836" parts are LM358N (vs LM833 etc.) under magnifier
  • Verify all "M8818 LF" parts are LF353N (suffix not visible in all shots)
  • Identify what J-13 carries (likely shares the HV-module signal bus with J-14)
  • Probe the AD654 output frequencies at full-scale HV and full-scale HC to determine the monitoring scale factors
  • Identify the two TO-220 transistors visible near the heatsinks at top-left of the board (driver pre-stage between IR3M02s and the HV switching FETs?)
  • Trace the 9 optocoupler channels at J-16 (8 across the two TLP621-4 quads plus the 1 in the TLP621 single) and assign each a function. Expected set: AD7543 SRI / STB / LD / CLR (4), master ENABLE (1), FAULT status out (1), HV frequency out (1), HC frequency out (1), plus 1 reserved/interlock.
  • Determine what role the TC4013 / TC4011 / TC4025 logic plays now that the DAC handles its own serial-to-parallel conversion (fault latch and/or AD654 gate-timing oscillator are the leading hypotheses).

OEM No. 125B

Module not yet examined. Photos and reverse-engineering pending.

OEM No. 126C

Module not yet examined. Photos and reverse-engineering pending.

OEM No. 128B

Module not yet examined. Photos and reverse-engineering pending.

OEM No. 130C

Module not yet examined. Photos and reverse-engineering pending.

OEM No. 131A

Module not yet examined. Photos and reverse-engineering pending.

Auxiliary Power Supply Module

Switch-mode housekeeping supply visible at the right side of the chassis. Not yet examined in detail.

Mains Transformer

Multi-secondary line-frequency transformer visible at the top-left of the chassis. Has at least three independent floating secondary windings brought out to the OEM No. 127A controller board via J-12:

  • Yellow pair — secondary winding #1, feeds the +15 V analog rail
  • Red pair — secondary winding #2, feeds the −15 V analog rail
  • Blue pair — secondary winding #3, feeds the +12 V and +5 V digital rails

A single green wire also exits the harness at J-12 to bond the rectifier outputs into a stacked bipolar topology (see J-12 Power-Input Topology).

Voltage taps and current ratings TBD. Additional secondaries (if any) feeding the HV generation module are routed separately and have not yet been documented.

High Voltage Generation Module

Multi-PCB high-voltage assembly. Comprises the HV switching power stage, step-up transformer, and a Cockcroft–Walton or similar diode/capacitor multiplier producing the 0–3000 V output. Driven by J-14 from the OEM No. 127A controller; returns voltage and current sense signals via J-13 (and possibly J-14).

References

This article documents an ongoing teardown. Identifications are best-effort from photographs of date-coded components (1987–1988). Please verify physically before relying on any information here for repair or redesign.

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