Keithley 2601 SMU internal hardware photos

Keithley Series 2600 System SourceMeter instruments are often the workhorses used by electronic component and electronic devices manufacturers as a scalable, high throughput, highly cost-effective solution for precision DC, pulse, and low frequency AC source-measure testing.

Building on the tightly integrated source-measure technology originally developed for Keithley’s popular Series 2400 SourceMeter line, Series 2600 instruments provide from two to four times the test speed of competitive solutions in I-V functional test applications. Models in 2600 series also have much better developed infrastructure and power envelopes for most of typical tasks for SMU.

Now that there are few of these in repair queue it’s nice to take some high-resolution photographs as reference. Let’s start with the heart of the instrument – analog output board:

SMU module with terminal block output, one channel

Eight layer PCB is revision E. Main controller realized in Xilinx Spartan XC2S200 FPGA running off 48 MHz XO Y1. EEPROM nearby with 24LC64 label store calibration data for the module perhaps?. Interfacing to earth-referenced logic done via six optocouplers near connectors J1012. J1011 looks like JTAG interface port for me :)

SMU programming done with a help of two Linear Technologies LTC1650CS (U43 and U50) DAC which are low-glitch 16-bit voltage chips. VR3 in thru-hole package is a main reference zener for discrete integrating ADC + DAC solution on this module. This is good enough to meet the specifications of Keithley 260X SMU and saves money as well instead of go-to LM399 we often see in the higher end measurement equipment. Board is filled with ADG509, DG408, DG444 switches and LM339 to control them. There are some factory-looking reworks near the output terminal block connectors. Electromechanical TQ2SS-L-5V relays are used to switch output on/off and implement four-wire sense switching.

Bottom side is quite busy with passive components in 1206 size such as resistors and capacitors.

Fully featured dual-channel Keithley Model 2602 incorporate two of these output modules, with independent control and interfaces, while “half”-output single channel 2601 uses only one module.
Power transistors in TO-246 packages (IRF910 and IRFP9210) were already removed for repairs.

Main output shunt is Vishay Precision Group VCS301T with nominal resistance 0.1 Ω. These non-inductive foil shunts are rated for 3 W of power dissipation in free air and have maximum TCR about ± 3 µΩ/Ω.

PCB layout analysis with see-thru layering.

Sadly board is too large to fit completely into the imaging box to make one nice uniform span pano.

Author: Ilya Tsemenko
Created: Jan. 17, 2025, 3:19 a.m.
Modified: Jan. 22, 2025, 5:14 a.m.

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