Hi all,
It seems the control board is defective, as it is not switching the compressor correctly. All other functions appear to be working normally.
I am looking for a replacement board, as well as wiring diagrams if available.
For troubleshooting, I connected the compressor directly to power and it runs properly, which suggests the compressor itself is OK and the fault is likely on the board or in the control circuit.
Any help would be appreciated.
Hi there thank you for your reply I also think that it can be fixed because usually it can be some relay on the board but I don't know how to identify it.
I'm mainly work on Leica cryostat . In similar situation usually the SSR is failing..
It will be great if you can help me with this.
Thank you!
The SSR is in the upper left section of the board (viewed from the back). IIRC there are two SSRs there, so you'd have to trace the connections (if it isn't obvious which one has failed).
Note: it may have burned up some traces on the board, if the compressor was hard-starting. It should be repairable, if there isn't too much damage (or if it is just the SSR that has failed open).
Edit: you'll want to monitor it carefully, to be sure that it isn't hard-starting. If it is, you may need to replace the starting components or the compressor, or you'll have another board failure soon.
this is the board , the compressor connector is marked with orange circle. can you please mark the SSR?
Thank you!
here is a link to the board photo:
https://drive.google.com/file/d/1Ldhma4t0OXZIkuvADy32GTf8oQUDlg2x/view?usp=drive_link
I have had to replace these before. In my case it was obvious though as a faulty compressor left them charred.
https://www.pasteboard.co/zHMTSGzcr3rk.png
Honestly, the most common issue is the start cap relay. This is directly connected to the 3 pins on the compressor. I would recommend getting a supco 3 'n 1 Start relay as a replacement first as they are a lot cheaper than the board and more common than the board itself. When ive had issues with the compressor and the board it usually has other issues on top of it and the most common issues ive had have been the compressor not shutting off, so I would try a 3 'n 1 first directly on the compressor and wired into the units power (very easy to do) and see if it starts, then i would look at troubleshooting the board if that doesnt work.
If the compressor won't shut off by the time it gets to, say, 2C below the set temp, it almost certainly is a shorted SSR.
As for starting issues, other than a failed SSR, I've had better luck replacing the start cap and the OEM-specified start relay (current relay, or whatever) on the side of the compressor, than I have had with the SUPCO hard starts (although that might work as a troubleshooting method).
Peter N:
Sorry, I didn't see your last posts. I hope you have repaired it by now. I don't currently have my technical information with me, but I seem to recall that there are two SSRs in the upper left. One is to turn on/off the compressor, and the other is probably for a solenoid. Maybe there's another one. Since you've found the connector from the compressor, just Ohm it to find the SSR for the compressor. The SSR and/or PCB traces might show damage from overheating.
And if you repair the board (i.e. replace the SSR and/or repair traces), you should at least also replace the starting components on the compressor (cap and start relay), because it was probably hard starting or short cycling. It might be time to replace the compressor, or find what was causing it to hard start.
Personally, I think that a larger, higher current SSR should have been installed on the chassis, so that it only used the SSR on the board to switch the bigger, more robust SSR. That way a failure would only require replacing a $100 part, instead of a $5k board.
Hi Ross,
Thank you for your input. I totally agree regarding the idea of adding an external SSR.
In this case, I preferred not to take any chances with the original board, since all the other board functions are still working properly. The external controller I installed now manages the compressor independently and isolates the compressor load from the original board.
For now, the unit is working well, and the customer is happy with the solution — so I’m happy as well.
I also agree with your point about checking the compressor starting components and the possible cause of the original failure. That is something I’ll keep in mind if the unit shows any further issues.
