Hello everyone,
I have recently bought a Sinclair DM235 Multimeter for very little Money.
It seems to be a pretty rare multimeter since not much info is available.
Sadly it has two Problems:
1.The case was completely destroyed in shipping.
2.The Display shows negative overload no matter what setting is selected, or what is connected.
I was able to track down the service manual:
http://dasarodesigns.com/~medasaro/DM235_SM.pdfI have already checked the PSU voltages and they seem to be fine.
No traces look corroded or otherwise damaged.
In Fault Finding, step 4 the Service Manual says: "Check TR9 and associated circuitry"
I have replaced TR9 with a BC547 and nothing changed, but I still don't get what associated circuitry means.
The Service Manual also advises to connect 1V to the Input and check if pin3 on IC4 reads 0.8V but in my case, it reads close to -0.9V
I have also checked R25 and R21 and they are fully in spec.
I will now try to purchase a new CA3130E to replace IC4.
But in the meanwhile is there anything else I can try, anything I'm missing?
Thanks for the help!