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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
Hi all.
Turned on my previously working Gould OS1100A 'scope (old clunker but did work fine) and was greeted with a flickering trace. Adjusted a few things then... nothing :( GRRR
Any ideas? thinking maybe G1 or something similar failed..
Registered Member #2123
Joined: Sat May 16 2009, 03:10AM
Location: Bend, Oregon
Posts: 312
Do you have ~-1KV to -2KV on the CRT cathode? I'm assuming the anode is at ground. Also check the first grid, (the blanking grid), if it is ~7 volts more negative than the cathode, that may kill the beam also.
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
The easy solution the is to just go around with a can of cold (or a can of spray air turned upside down to give liquid) and start freezing components. I suspect is a capacitor that has dried out and become leaky.
Registered Member #1334
Joined: Tue Feb 19 2008, 04:37PM
Location: Nr. London, UK
Posts: 615
Conundrum wrote ... Turned on my previously working Gould OS1100A 'scope (old clunker but did work fine) and was greeted with a flickering trace. Adjusted a few things then... nothing :( GRRR
Does sound like a problem with the HVPSU, probably, as has been mentioned, a dried out electrolytic. I've recently fixed a Tek 7000-series scope with this problem and a Tek 2430A with the same problem but in the LVPSU side.
In your case, the presence of the trace initially means that I'd start on the HT side...
Statement of the bleedin' obvious: Be ever so careful...
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
My job is repairing industrial electronics, since we give a 1 year warranty on our work we ALWAYS replace ALL small electrolytics as a matter of procedure. (yes they can be that unreliable, especially the small smd electrolytics). This will usually fix about half of all faulty equipment ! The majority of other faults are man-made e.g. over-volting inputs. With crt-based equipment I'd guess three quarters of the faults are cured by a cap change, so definitely I recommend that you replace ALL the electrolytic capacitors. The sooner you do it the better as the leakage from electrolytics corrodes pcb tracks, often leading to more serious faults.
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
hmm. turned on today and it worked fine.
Its been pretty damp recently so that could be something to do with it.
FWIW I had it looked at about two years ago and the techie (qualified TV/video repairman) said he'd changed a few caps and resoldered everything in sight.
if it plays up again i'll change the caps, thanks for the advice. -A
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OS1100A flickering trace then N/G any ideas?
