Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: spunko on July 28, 2024, 05:38:26 pm

Title: Fender HRD III - No Reverb but Tank and RCA cables are OK.
Post by: spunko on July 28, 2024, 05:38:26 pm: Hello friends.
I got this amp cheap w/o speaker, and with all the common problems, bad IC caps, bad traces, bad solder joints, and no reverb. All is good and working now except for the reverb, first time with this problem.
Tested the tank with my multimeter and both ends read ok, I have another tank to compare and test. Also both RCA cables test OK for continuity.

If I hit the tank with my hand it sounds, if I touch with my finger the tip of the RCA cable (wht - from reverb to amp) it HUMs, so I guess U2 (4560) is ok.
I don't have a scope, but I have a home made signal tracer and there is no signal present on the tip of the RCA that goes into the tank imput (red - from amp to reverb). No signal on pin 1 U2A (TP20), no signal on TP19, nor TP13.
Where should I start tracing the signal? Could U2 (4560) be bad?
This one is new for me :help:

Thak you very much!
Title: Re: Fender HRD III - No Reverb but Tank and RCA cables are OK.
Post by: AlNewman on July 28, 2024, 05:53:55 pm: Does it work with the footswitch plugged in?
Title: Re: Fender HRD III - No Reverb but Tank and RCA cables are OK.
Post by: Latole on July 29, 2024, 03:11:55 am: If voltages are good on U2, yes, it could be bad.
And if printed circuit ( or connector ?) are good.

To my use a scope will be more reliable to see
Title: Re: Fender HRD III - No Reverb but Tank and RCA cables are OK.
Post by: spunko on July 30, 2024, 09:56:45 am: Yay! It is fixed. U2 (4560) was the problem.
Thanks for the help! :icon_biggrin:
Title: Re: Fender HRD III - No Reverb but Tank and RCA cables are OK.
Post by: Latole on July 30, 2024, 10:56:40 am: Quote from: spunko on July 30, 2024, 09:56:45 am
Yay! It is fixed. U2 (4560) was the problem.
Thanks for the help! :icon_biggrin:

Congrat, you are a good tech !