Kepco BOP 100-2M Repair - Page 1
Forum section: electronics / repair

author: wriely
author_rank: Contributor
timestamp: January 14, 2025, 05:21:26 pm
content: I acquired a Kepco BOP 100-2M which I'm trying to figure out what to do with. I've been unable to find a service manual for this model and Kepco wants $200 for the service manual which is very customer unfriendly. A bit of digging online has turned up a service manual for the BOP 50-2M which is helpful, but still leaves me in the dark about a couple of things.The instrument itself came missing several parts and with an internal wiring harness cut.The missing parts are all of the 8-pin ICs on the control board (10 in total), two large filter capacitors for the positive and negative voltage rails, and the associated mounting hardware. Above where the filter capacitors should be mounted, I have three sets of wires which must correspond to the positive and negative power supply rails and the ground. It is fairly obvious how these need to be wired, although the lack of two sets of ground wires suggests to me that there may have been some sort of metal strap connecting the common side of both capacitors together and to the ground terminal. What is less obvious is the red/yellow wire in the harness above the capacitors which appears to have been cut. I traced it to the output terminal on the front and the back of the unit. I'm not sure why it's there and I suppose it could be a leftover from the factory assembly although that would seem rather sloppy.The control board for the BOP 50-2M appears very similar to my control board, but not identical. There are some additional ICs on the 50-2M board that are not present on mine. However, the missing ICs on my board do have parts designators which are identical to those on the 50-2M board so I think it's likely they the same parts. A quick check on the power supply pins on the empty sockets confirms that VCC and VEE matches the parts called for on the BOP 50-2M schematic.I removed the power board and removed all of the TO-3 transistors on it so that I could test them. All of the junction voltages are good, so I'm going to assume that the transistors are at least not blown. I tested the driver board transistors in circuit and they all test good, too. I removed several of the ICs on the control board (+5V logic and +/-15V OpAmps) and they all test good. The windings on the main transformer all appear to be intact. I can't find any reason why the instrument cannot be restored to working order so I'm going to order replacement parts for it.I'm not very mechanically inclined and without the original mounts for the capacitors, I'm not really sure how to secure them. I suppose I will use a glue gun to glue them down although I'm not sure how well that will hold capacitors which are 2 inches in diameter and 3+ inches long. If that doesn't work out, maybe I can do something with automotive hose clamps.If anyone owns one of these units and would be willing to send me a picture of the filter capacitor assembly including the wiring harness that runs above it I would greatly appreciate it. It would also be nice to see what the original mounting brackets look like -- maybe there is a 3D printing option I can explore? Also, if anyone has the BOP 100-2M service manual or knows where I can find it, that would be very helpful, too. I do have the "BOP Series" full manual, but while it does contain some service information in it, it does not have complete schematics for any of the individual instruments it covers.Walt

author: jwet
author_rank: Frequent Contributor
timestamp: January 15, 2025, 03:15:45 pm
content: I've repaired a lot of these. They were low volume instruments and Kepco didn't have great configuration control. They made changes along the way. In order to nail down "exactly" what you want, you'd have to get down to board and assembly serial numbers- maybe why Kepco is not so helpful. You can get about 90% of the way there and then have to do some deduction. Even the manuals, you'll find cover a wide range of external assemblies and have tables for variants. They all have a bulk supply that gives DC plus some headroom, a controller board with a bunch of op-amps and then an output/fan assembly that varies with volts and current. The most common failures are output transistors and final out drive transistors. You might have to test at higher voltage and higher currents, the problems are often secondary breakdown or punch through type failures. Using a diode test on a DMM won't tell you everything. Make a bench jig, bolt them to a heat sink and run them as followers, etc. The other failures might be caps though these things generally used military type caps and are much more reliable than generic stuff. Check fuses, there are more than a few and some are just board mounted- you'll have to find them. Low value resistors can also fail usually as a cascade failure of an output.Almost all the op-amps, you'll find will be TL074 type with an occasional OP-07 thrown in for precision.Getting schematics and service manuals- I tried to send you a manual in the chat but couldn't attach anything large. Send me a PM where I can send you a 5-8 Meg PDF- these are scans and quality is just ok. There are some good third party service manual houses that make nice scans and sell them reasonably- support these guys- its a tough business. The very best is Artek (artekmanuals.com). They custom scan stuff at high resolution and sell at good prices. Its run by the widow of the guy that ran it for years- excellent.I have one parts unit around. Its a plus or minus 100v, +-1 amp unit. Its in a very dark spot in my storage off site. If you have no other luck, I will dig it out but its a major PIA and I want to make sure you're serious. You can estimate the size of the caps and see what you can find surplus. My filter won't be the same if the V and I are different.These supplies are great to have around a well equipped lab. They are often used in ATE systems where you need some grunt. You run a standard instrument into them and let them do the hard work. I've used them over the years for automotive and military transient testing- the special instruments for load dump, etc (ISO7637) are really expensive and specialized. I would get the waveform and approximate the test before going to a certified lab to a get real data. The operational part makes them very flexible though unless you need some bandwidth and analog input, a modern HP-IB supply works well.Good Luck. Have fun. Be careful servicing these things- there are high voltages and caps with lots of energy in them.