Kepco BOP36-5M is a bipolar power amp. - overload alarm below nominal voltage

[golashki]

Kepco BOP36-5M is a bipolar power amplifier with a voltage range of approx. +/-36V and +/-5A. It can be powered from the internal reference voltage, which enables operation as a four-quadrant DC power supply or working as an external signal amplifier. Very solidly built and interesting device.

My item has some problems with controlling the full 36V voltage (+36V/-36V). The overload alarm is triggered at approximately 18 volts. I measured the power transistors and they are all OK. The control boards also look OK (capacitor ESR, transistor, diodes, etc.). However, something is not as it should be. Without a schematic and instructions, I am unable to find the problem.

This is an older model, probably one of the first amplifiers of this type produced by Kepco. Only service manuals of later models are available on the Internet, those with both voltage and current control. I really searched all the links from eevblog (by the way, collecting over a dozen service manuals for other KEPCO power supply models).

I know that I can buy a print version on eBay, but the cost of shipping to Europe exceeds the cost of the service manual ...

Does anyone on the forum have an electronic version of the service manual exactly for this model: Kepco BOP36-5M? Or at least for models: 36-1.5M, 72-1.5M, 72-5M?

[precaud]

I found the main problem with that whole Kepco series to be interconnection issues. Everything, including the output devices, is on plug-in connectors, whose fingers look robust but contact deteriorates with time. A thorough cleaning of all of them is pretty much required to have any confidence.

[alm]

Have you tried emailing Kepco? In 2016 I sent them an email (hq@) for a BOP 100W unit with voltage and current control, and a nice employee promptly responded with a PDF manual with full schematics. The manuals were available on their website, but without schematics. The one they emailed included schematics.

[Scrapcollector]

Does anyone have a transistor comparison / replacement recommendation or just some basic data for these old devices? 119-0113 or the 0119-0128 in a 72-5m.
Are these general purpose low gain 100...150W transistors or darlingtons?
I mailed the company but no success so far.