Products > Test Equipment
Keithley 2306 Dual Battery Simulator Repair (maybe)
Kean:
On the SRAM pins 16 and 32 are GND and Vcc and my unit reads 4.95V. There is a capacitor C186 across the SRAM supply rails near pin 32.
The SRAM is not battery backed in the K2306 - no battery I can see and no voltage to the SRAM when powered off, so no need to copy any data.
The R1LP0408C SRAM needs 5V +/-10% so 2.5V is bad. If you really have 2.5V then I suspect that may not be caused by a RAM chip fault if you measure 5V elsewhere.
There are a couple of different voltages in the digital section, and a bunch more isolated supplies in the analog area. I will make notes of some measurements for you to compare.
Kean:
OK there are three isolated supply sections on the K2306 main PCB.
I've listed them below along with measurements from my K2306 with the top PCB removed (so no load on analog supplies).
Digital supply "D" (test points near fan) - referenced to GNDD
TP105 Vin = +11.97V
TP106 GNDD
TP109 +6.5VD = +6.47V
TP110 +5VD = +4.96V (this connects to the SRAM Vdd pin 32)
Also there is a second 5V regulator in the digital section at U132 with pin 1 = +6.42V (from +6.5VD via filter) and pin 3 = +4.96V. Not sure what this supplies.
Analog supply "A" - referenced to GNDA
TP100 +5VA = +4.96V
TP101 +15VA = +14.87V
TP102 GNDA
TP103 -15VA = -15.01V
TP104 -5VA = -9.50V
TP111 +25VA = +37.18V
Analog supply "B" - referenced to GNDB
TP200 +5VB = +4.97V
TP201 +15VB = +14.96V
TP202 GNDB
TP203 -15VB = -15.08V
TP204 -5VB = -9.52V
TP112 +25VB = +37.42V
* I was wrong about needing to enable channels to read all measurements - you just need to use the correct GND pin as they are isolated supplies.
Kean:
Before putting my K2306 back together, I took a little look around the main CPU (MC68331)
U129 and U133 are 24LC16B I2C EEPROMs which probably store the calibration data - much better than battery backed SRAM, but not infallible. When I got my unit the calibration was messed up, but that could have been someone playing around before me rather than any kind of failure.
U132 might be a separate 5V regulator for the remote display connector so if it is shorted it doesn't take out the main 5V rail. Or it could be a clean supply for the nearby analog components: 2 x LM393, MAX391, AD706. I don't know what they are used for.
There are 2 x ADM232 which will be for the remote display comms, a ULN2003 for the relay outputs, and some opto-isolators for comms to each of the isolated analog channels on the top PCB.
ottobad:
Hello,
I have the :
TP105 Vin = +11.8V
TP106 GNDD
TP109 +6.5VD = +6.47V
TP110 +5VD = +5V
On U132 in 6.4V out 5VDC but on SRAM pin 16-32 IS still 2.5VDC...Is ok If I take out the memory and mesure again if 5 Vdc is present on pin16-32...maybe is a faulty memory?
On this...I have 0 insted of value you put
Analog supply "A" - referenced to GNDA
TP100 +5VA = +0V
TP101 +15VA = +0V
TP102 GNDA
TP103 -15VA = -0V
TP104 -5VA = -0V
TP111 +25VA = +0V
Analog supply "B" - referenced to GNDB
TP200 +5VB = +0V
TP201 +15VB = +0V
TP202 GNDB
TP203 -15VB = -0V
TP204 -5VB = -0V
TP112 +25VB = +0V
Thank you
Kean:
--- Quote from: ottobad on July 18, 2023, 07:48:40 am ---On U132 in 6.4V out 5VDC but on SRAM pin 16-32 IS still 2.5VDC...Is ok If I take out the memory and mesure again if 5 Vdc is present on pin16-32...maybe is a faulty memory?
--- End quote ---
As you measured 5V OK at TP110, then I suggest measuring the supply pins of a few other components in the digital section other than the SRAM.
Did you try measuring across capacitor C186? Other points to try measure would be between GNDD and VCC on the various 74-series logic ICs, or ther I2C EEPROMs U129, U133.
You could also measure the resistance between the supply pins on various ICs in the digital section and pin 32 of the SRAM (with the power off of course) to see if there is some broken connection.
I don't believe there is a service manual or schematic available. One user here (picburner) created a partial schematic of the digital to analog opto-isolation section at https://www.eevblog.com/forum/repair/keithley-2306-dual-psu-battery-simulator-repair/msg632229/#msg632229 and three people in that thread fixed (or partly fixed) their unit by replacing the SRAM IC.
--- Quote from: ottobad on July 18, 2023, 07:48:40 am ---On this...I have 0 insted of value you put
--- End quote ---
Just to make sure... when you measure these analog section supplies... you do have your DMM black probe on GNDA or GNDB and not GNDD?
I will open mine up again and see if I can identify any other suggestions.
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