Hello!
I have been working a bit more on the oscilloscope, based on your comments
and my very own ;-) ideas. Well, almost everybody agreed about a power
supply capacitor trouble causing the trace distortion. But I have measured
the AC component of the regulated voltages and all are very low... So I
have done some checkings, as looking at the CALIBRATOR output on another
oscilloscope and it is fine, without any distortion. I have also looked at
the SAWTOOTH A and +GATE A outputs and both signals are fine. But looking
at the VERT SIG OUT I got some ripple. What is supposed to be at that output?
On another hand, I have checked the 1A1 plug-in CH1 SIGNAL OUT and there I
get also a distorted signal, similar to what I get in the 545B but without
the 'trace back' (it has just some bumps on it). If I put the CHANNEL 1 in
GND mode I get also distortion, as shown in the picture at my WEB page
(center line should be an straight line, as it is GND)
The picture is overexposed in some parts. In fact, trace is fine and focus,
astigmatism, brightness and other controls work just fine. The bright spots
are really 'trace backs' (I mean the trace goes to the left and a bit up
for a while and then goes back to the right)
So I am not so confident about the power supply. I need to check more
things about that.
Somebody commented about the power supply temporized startup. It is clear
that there is a vacuum relay(?) which in turn activates a large multi-pole
relay. My unit took about 30 seconds from cold to activate that relay and
then measured power supply voltages are right. But, lately, it took close
to a minute. And, one time, it has not started at all. I have left it get
cold and then have retried. It has started but after a while I found some
burnt smell. After a fast power off, I have started to look for the burnt
part. And, to my surprise, it seems to be the power switch!. It smells to
burnt bakelite... Is this a common fault?. Could the switch be repaired?.
Anyway, I prefer a damaged switch than any other part, as it would indicate
a major trouble.
So, summing up, I have found that the scope takes some times too much time
to start up. Could you comment about the usual starting up sequence?. I
have also found that the neon bulbs in the circuit have a curious startup:
first, all of them light. Then they start to put off gradually (not all
same time). And then, when the power relay clicks, some of them light
again. Is this usual?. Did they mean anything about the health of the
scope?. Missing the schematics is really a bad thing :-( (I got some
e-mailed scans but the low voltage power supply part is unreadable; I would
appreciate a better scan)
Please, any hint about where to look for the source of the trace
distortion, apart of the electrolytics, would be welcomed. Also, if there
is any way to check the scope (at least part of it) WITHOUT the 1A1 plugin,
I would love to hear about that, as I have no other plug-in and I think
perhaps the plugin is faulty. What should be shown on the scope without the
plug-in?
Thanks for your help!
JOSE
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73 EB5AGV / EC5AAU - JOSE V. GAVILA
La Canyada - Valencia (SPAIN)
EB5AGV Vintage Radio Site:
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