NexGen: Lab:B&K Precision 3010 Function Generator - Repair

13 Apr 2020

THEN

NOW

Black (Hot) and White (Neutral) ended up switched so 110 VAC ended up on my ground-plane! Push on connectors are a must!
I replaced the bridge with 4 100vdc 5 amp monsters. It took quite a bit of heat to solder the big leads so I sub in an IR bridge 12DB6A
I have a lot of harmonics to fix.
The function generator parts still work. that is to say triangle, sine and square wave are ok just with harmonics. Most likely killed some caps!

PROBLEM	DEAD DIODES
FIXED	NEW BIG DIODES

Top Comments

skan743 over 3 years ago in reply to phoenixcomm

Today I was observing test point 11 again and I obtained a different result than yesterday, during today's tests up to test point 8 the results coincide with the graphs provided by the schematic, from IC7 everything is a disaster, all The pots around it are damaged, although that does not explain the problem of the --14.XX VDC on the output. Tomorrow I will test that stage from the amplitude pot without any AC or DC signal at the base of Q9, I have simulated it and it should have the same DC voltages at each point that the schematic diagram specifies if I adjust the DC offset pot at 0vdc

Pd: the simulator is Proteus and thanks for the comment and the help.
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phoenixcomm over 3 years ago in reply to skan743

skan743 I am looking at my schematic I wonder what you see at the top the amplitude pot? I feeds the base of Q9. its collector (11) feeds the base of Q11 which drives the output pairs Q12 & Q13.
BTW it is a pain to work on out of the case.
~~Cris
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skan743 over 3 years ago

Currently he tried to repair the same generator for my studies, I have replaced capacitors and potentiometers in bad condition and at the moment I have managed to obtain all types of signals, however I have not been able to see them in the 600ohm output. Until Q9 everything works great (test point 11), however at the 600ohm output there is only a static -14.XX VDC and no AC signals.
The TTL output works great.

Any idea what might be failing?

As for the harmonics I recommend checking the symmetry in test point 1 ^^
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kk99 over 4 years ago

Nice, quick repair
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phoenixcomm over 4 years ago in reply to cstanton

cstanton when I put it back together by putting 115 on White and Neutral on black! ie I shot myself in the foot! and the "harmonics" looks like an ungrounded scope probe!
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