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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 />
{{Infobox
| title = Bio-Rad 3000Xi
| subtitle = 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.
----
== 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-tap line transformer || Not yet 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. │─▶│ Logic + │─▶│ AD7541 12-bit │ │
│ │ rcv (TLP) │ │ shift reg │ │ multiplying 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 || Multi-tap transformer secondaries → on-board rectifier/regulator section
|-
| '''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 — DAC code in, telemetry out via optocouplers
|}
=== 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 AD7541JN''' || "AD7541JN" || 18-DIP || CMOS 12-bit monolithic '''multiplying DAC''', R-2R ladder. Receives the digital setpoint from the μC and converts it to an analog reference into the IR3M02 control loop. 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/media/en/technical-documentation/data-sheets/ad7541a.pdf AD7541A PDF (current)] · [https://www.alldatasheet.com/datasheet-pdf/pdf/66279/INTERSIL/AD7541.html Intersil AD7541 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 || [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. Used together with TC4011/TC4025 to implement serial-to-parallel conversion for the AD7541 inputs ''and'' as a fault-latch for the protection circuit. || [https://toshiba.semicon-storage.com/info/TC4013BF_datasheet_en.pdf Toshiba PDF]
|-
| '''TC4025BP''' || "TOSHIBA 8844HB TC4025BP JAPAN" || 14-DIP || Triple 3-input NOR gate || [https://toshiba.semicon-storage.com/info/TC4025BF_datasheet_en.pdf Toshiba PDF]
|-
| '''TC4584BP''' || "TOSHIBA 8848H TC4584BP JAPAN" || 14-DIP || Hex Schmitt-trigger inverter — cleans up the slow edges from the optocoupler outputs before they enter the synchronous logic. || [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 serial DAC-load (data + clock + strobe), reset / enable, plus the two AD654 frequency-out telemetry channels. || [https://uk.farnell.com/toshiba/tlp621-4-gb/optocoupler-quad-5kv-transtr-o/dp/1225839 Farnell page]
|-
| '''TLP621''' (×1) || "T7K P621" || 4-DIP || Single-channel version. Probably an additional status / interlock line. || [https://toshiba.semicon-storage.com/us/semiconductor/product/isolators-solid-state-relays.html Toshiba family]
|}
==== 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)]
|}
{{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 ===
{| 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 '''AD7541 12-bit DAC''' confirms this is a fully digital setpoint architecture, not a potentiometer-driven supply. The controller writes a 12-bit code; the AD7541 produces a precise reference that the IR3M02 servo loops track. 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 two TLP621-4 quads only provide 8 isolated channels and the AD7541 has 12 parallel data inputs, the data must be '''shifted in serially''' on the board. The TC4013 / TC4011 / TC4025 cluster between the optocouplers and the DAC is doing exactly that — serial-to-parallel conversion plus a strobe latch.
# 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.
# The '''TC4013 dual flip-flop''' likely also serves as the fault-latch: a comparator output from J-15 (short / overcurrent) sets a latch that pulls the IR3M02 shutdown pin until the μC issues a reset.
# '''TC4584 Schmitt''' at the digital input is correct practice for cleaning up the output side of the optocoupler before any synchronous logic.
=== 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)
* Map the colored wires at J-12 to the transformer secondary windings
* 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 8 optocoupler channels at J-16 and assign each a function (DATA / CLK / LATCH / RESET / V-FREQ / I-FREQ / +2 spare)
----
== 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. Provides the bulk DC rails fed into J-12 of the OEM No. 127A controller board.''
== Mains Transformer ==
''Multi-tap line-frequency transformer visible at the top-left of the chassis. Secondaries route to the rectifier and on-board regulators of the OEM No. 127A board. Voltage taps and current ratings TBD.''
== 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.''
[[Category:Reverse Engineering]]
[[Category:Bio-Rad]]
[[Category:Power Supplies]]
[[Category:Laboratory Equipment]]
[[Category:High Voltage]]