BIO-RAD 3000Xi

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-tap line transformer	Not yet 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.  │─▶│ 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)

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	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

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 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_REF can be scaled by an external precision reference for absolute-voltage trim.	AD7541A PDF (current) · Intersil AD7541 PDF

CMOS Logic (Toshiba 4000-series)

Part Number	Marking	Package	Function	Datasheet
TC4011BP	"TOSHIBA 8838B TC4011BP JAPAN"	14-DIP	Quad 2-input NAND gate	Toshiba page · 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.	Toshiba PDF
TC4025BP	"TOSHIBA 8844HB TC4025BP JAPAN"	14-DIP	Triple 3-input NOR gate	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.	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 serial DAC-load (data + clock + strobe), reset / enable, plus the two AD654 frequency-out telemetry channels.	Farnell page
TLP621 (×1)	"T7K P621"	4-DIP	Single-channel version. Probably an additional status / interlock line.	Toshiba family

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

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.