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Sound Technology 1000A Stereo Generator problems

P

Pete KE9OA

Jan 1, 1970
0
Hi,

Has anybody ever run into a problem with this unit, whereby the 19kHz pilot
level is intermittent? It doesn't seem to be a thermal problem, and I have
cleaned the switches and controls. I don't know if the phase adjustment pot
on the main board might have a problem.
Looking at the 19kHz signal on an oscilloscope appears to show a steady
state signal level; however, the modulation meter on the RF generator itself
shows an erratic level, suggesting later stages in the signal chain.
Can anybody help?

Pete Gianakopoulos
 
M

mark

Jan 1, 1970
0
Pete said:
Hi,

Has anybody ever run into a problem with this unit, whereby the 19kHz pilot
level is intermittent? It doesn't seem to be a thermal problem, and I have
cleaned the switches and controls. I don't know if the phase adjustment pot
on the main board might have a problem.
Looking at the 19kHz signal on an oscilloscope appears to show a steady
state signal level; however, the modulation meter on the RF generator itself
shows an erratic level, suggesting later stages in the signal chain.
Can anybody help?

Pete Gianakopoulos
If your interested In the 19khz signal and it looks ok at the output
of the generator if thats what your saying then wouldn't you check the
modulation producing circuits or the meter chkt itself.
 
T

TimPerry

Jan 1, 1970
0
Pete said:
Hi,

Has anybody ever run into a problem with this unit, whereby the 19kHz
pilot level is intermittent? It doesn't seem to be a thermal problem,
and I have cleaned the switches and controls. I don't know if the
phase adjustment pot on the main board might have a problem.
Looking at the 19kHz signal on an oscilloscope appears to show a
steady state signal level; however, the modulation meter on the RF
generator itself shows an erratic level, suggesting later stages in
the signal chain.
Can anybody help?

Pete Gianakopoulos

it might be time to replace some caps and do the maintenance that is usually
needed on old test equipment. check solder joints, broken wires, etc.

look at the left minus right signal at the output with the 'scope. use a low
audio frequency like about 100 Hz.
if it looks like a string of beads (double sine wave) you are in pretty good
shape.
expand the 'scope to view the crossover point closely, the waveform should
be symmetrical.

if you are referring to a jitter that occurs when audio such as music is fed
to left and right it could very well be a normal situation. the demodulated
FM pilot usually shows some jumping around even on the some of the finest
broadcast generators that are made.
 
P

Pete KE9OA

Jan 1, 1970
0
Hi Tim,

Thanks for the insight. The erratic indication on the meter shows up with
the 19kHz only; this is with no other audio input, including the internal
oscillator.

Pete
 
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