I've had this 3240PE integrated on my bench for a while now.
The symptom is that it has high offset on the right channel. 36 volts. Wow.
Checking the rails, the high voltage rails appear to be correct - + 76V and -76V
The positive low voltage rail is screwy - at +60V. The negative voltage rail is correct at -43 V.
Thinking that it could be a leaky component from the high voltage side, I disconnected PTC1 and PTC2, which disconnects the +/- 76 V rails.
But the difference in the low voltage rails persists.
Now, the offset is way lower in the right channel at +6V but it also appears in the left channel with the high voltage rails disconnected.
Any ideas from the experts?
Schematic for reference:
The symptom is that it has high offset on the right channel. 36 volts. Wow.
Checking the rails, the high voltage rails appear to be correct - + 76V and -76V
The positive low voltage rail is screwy - at +60V. The negative voltage rail is correct at -43 V.
Thinking that it could be a leaky component from the high voltage side, I disconnected PTC1 and PTC2, which disconnects the +/- 76 V rails.
But the difference in the low voltage rails persists.
Now, the offset is way lower in the right channel at +6V but it also appears in the left channel with the high voltage rails disconnected.
Any ideas from the experts?
Schematic for reference:
So update...
Found two of the four rail diodes bad. D421 and D422.
They are obsolete BY500-100 rectifier types.
Measure about 0.5 V drop. Rated at 5 amp, 100V.
I the nearest looking thing I have on hand are some BYC8 (8 amp 600V) fast rectifier diodes.
Otherwise maybe STTH5L06 (5 amp 600V) rectifiers?
Can you think of any particular reason why they wouldn't work (other than the form factor of the BYC8's T0220 case)?
Found two of the four rail diodes bad. D421 and D422.
They are obsolete BY500-100 rectifier types.
Measure about 0.5 V drop. Rated at 5 amp, 100V.
I the nearest looking thing I have on hand are some BYC8 (8 amp 600V) fast rectifier diodes.
Otherwise maybe STTH5L06 (5 amp 600V) rectifiers?
Can you think of any particular reason why they wouldn't work (other than the form factor of the BYC8's T0220 case)?
blimey ive worked on loads of these and never had those go before, thats one of the later model schemes as well
the diodes are available from digikey
been overdriven, these can if they are pushed for long periods
the diodes are available from digikey
been overdriven, these can if they are pushed for long periods