Spuriosity
New Member
I recently managed to acquire a broken BWD 820 CRO for $20 and was planning on fixing it. According to the person I bought it from, it was working fine until the fuse blew in it - now, the fuse blows whenever you replace it and try to turn it back on. Does anyone with experience repairing CROs know a) what the cause of this could be?
UPDATE:
Replacing the quick-blow fuse with a slow-blow type fixed the initial issue. Luckily, there are more issues to deal with!
Once the scope cathode had been allowed to warm up for a while (~30 seconds), with an audible 50Hz hum (presumably from the transformer), I could see a single trace present on the screen. However, it looked very unusual - rather than a thin, green line, faint spots of green were visible. Trying to adjust the position of the trace has no measurable effect. The only controls that I could successfully manipulate were focus and intensity.
Worrying that leaving the system energised could cause further damage, I unplugged the unit at the wall.
Schematic and service guide:
https://www.eserviceinfo.com/downloadsm/67446/BWD_820.html
(I've worked with high voltage before by the way, but this is my first time repairing a CRO)
UPDATE:
Replacing the quick-blow fuse with a slow-blow type fixed the initial issue. Luckily, there are more issues to deal with!
Once the scope cathode had been allowed to warm up for a while (~30 seconds), with an audible 50Hz hum (presumably from the transformer), I could see a single trace present on the screen. However, it looked very unusual - rather than a thin, green line, faint spots of green were visible. Trying to adjust the position of the trace has no measurable effect. The only controls that I could successfully manipulate were focus and intensity.
Worrying that leaving the system energised could cause further damage, I unplugged the unit at the wall.
Schematic and service guide:
https://www.eserviceinfo.com/downloadsm/67446/BWD_820.html
(I've worked with high voltage before by the way, but this is my first time repairing a CRO)
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