Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dpm309 on November 29, 2016, 10:52:48 am
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Have a Hotrod Deluxe III Custom and the clean channel is hardly working. With the volume up to 10, you get a very weak signal. The drive channel works just fine. Have not been able to locate the schematic for the HRD III but from what I have read online, there were only a few changes from the original schematic which I have. I have not pulled the chassis yet but was wondering if anyone has experienced this with the HRD. Am wondering if it could it be in the switching circuit?
Thanks,
Dan
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Does the drive sound like it did before or a bit weaker too? It may just be the first preamp tube. If it's a lot like my Blues Deluxe (I believe they're pretty similar with minor tweaks to improve drive etc), then the switch just routes the signal through the drive triode after the first one, so if it 'fixes' it, and the tone is identical pre 'problems' it's more likely just a tube or something related to that section of the circuit. If not, then it may be something about the switching not fully actuating well in the 'clean' mode, yes... not sure if thats a 'thing' as I'd think the relay just 'works' or it 'doesn't' not some weird middle ground.
~Phil
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No, the drive channel sounds just like it should. These amps are known for their channel switching problems but this amp is not experiencing the usual problems such as sudden switching back and forth, stuck on one channel etc. It seems like the clean channel signal is not getting to the power section. I will poke around a bit to see if I can determine where I am losing the clean channel signal.
Thanks
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"poke around"
Yes, literally. Use a chopstick. In my amp the channel switch lost its solder connection to the board. Remember in these amps, every solder connection is a cold joint which can fail anytime.
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Thanks, Zapp. I already built the Hoffman listening amplifier and was getting ready to go through the circuit. Before I started, I started poking around the board with a chopstick and tapped on the channel switching relays a few times. Tried the amp one more time and the clean channel came alive. Don't think it was a cold joint as I have been running this for awhile and have not been able to recreate the original problem, even with tapping on the relays. I must have somehow "unstuck" the relays. Anyway, all is well and this has got to be one of the easiest repairs I have made.