Electronics > Repair

Keithley 2306 Dual PSU / Battery simulator repair

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SparkyBruce:
Hello, I have just started a repair of a Keithley 2306 dual PSU/ battery simulator. I have not been able to find any schematics for the unit , but the service manual does have a BOM list and component location drawing.

The initial state was the unit would display Initialising on the screen after about five seconds but not anything else.

So far I have found that the rear fan has died and that the message display is coming from the micro on the front panel itself. The main micro on the lower digital PCB is running code from the Flash ROM (32PLCC) and I can see accesses to the main RAM , but nothing to either of the two I2C serial flash config chips.

There is no communications to the front panel board (looks like a two wire serial link), and only the main supplies (12V and 5V rails) are up.

If I remove the main Flash chip then the micro appears to just cycle through the address lines so it does look like it is running some code, just not talking to the front panel. I guess the code must be failing to configure something and it is just sat there in a tight loop waiting.

The dual PSU channels look like they use a front end 12V to +25V boost converter (isolated) per channel , then they do post regulation on the outputs of these on the analogue PCB.

I have not been able to find any pictures of the inside of the unit (2302/2303/2304/2306 or 2308) on the web so I will take some pictures and post them over the next couple of days.

There do appear to be a number of these units on the market at the moment due to the shutting down of a number of mobile phone development centres.

If any body has any suggestions as to my next step then please let me know.

Thanks

Bruce

KJDS:
I've fixed two of those just by unplugging and plugging back together everything I could so unplug, though I assume that was the first thing you tried.

SparkyBruce:
Hello,

Yes it has been to bits a few times mostly to clean out all the dust.

I was hoping that it monitored the fan for rotation , but that doesn't seam to be the case. I will check the thermistors tomorrow to see if any of them are tripping , but I would expect them to be flagged on the screen rather than a no-boot.

It could even be a failed flash upgrade , so I will try a new chip with the latest firmware that I have been able to download off the Keithley support site. It is still a shame that the schematics aren't available.

Thanks

Bruce

picburner:
Hi,
 
this was the same fault of my 2306.
In my case the culprit was K6T4008 (U124) memory.
The instrument, at power on, performs a hardware self test.
If it finds something wrong it lock without giving any error message.
As you've already noticed "Initialized" is produced by the display circuit only.
The fault may be RAM, ROM (checksum error), or TMS9914.
If there is no complete activity on the address/data bus XTAL or CPU.
You can find the update firmware on Keithley forum.

Good luck
Giampiero

SparkyBruce:
Thanks,

I have checked that initially the main micro reads from the Flash , and briefly does some SRAM accesses , then it looks to be reading from flash then accessing something else (not the SRAM or the GPIB chip from looking at the chip selects).

From a quick look at the actual chip selects for the micro I couldn't see any of them toggling so I need to check that I have the correct version of the datasheet.

So I will need to buzz out which chip selects go to which devices. I guess they have some simple byte wide I/O ports to control the rest of the system.

Thanks

Bruce

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