Fender Hotrod Deluxe relay chatter...

[nevetslab]

Glad you confirmed the +/- 16V supplies were stable during the relay chatter. I just repaired a HR Deluxe 112 where U3 had failed (TP34 readings confirmed that), and after replacing that part, I suddenly found 42VDC instead of 16V at one of the TP34 conditions. The 16V Zener was now sitting with one end no longer in the solder pad, and both ends were oxidized form long-term heating. Part was still good, cleaned up fine. Resoldered it, back in, repaired solder fractures on teh 5W resistor associated with it, and replaced the other IC's that got subjected to that high voltage, just to be on the safe side.

Waiting to hear the outcome on this one.

[Danglin' Fury]

Yeah all my zeners and 4448 diodes are intact... I changed C46 and C47 yesterday to no avail.... I bought a BA 4560 yesterday so im gonna install that and see how it goes.... And even though the +/- 16 volts are stable, Im gonna replace those resistors with 10 watt parts... Maybe they will get at least a little less hot.... There is brown under them on the board... You can tell they got plenty hot....They havent pulled any traces yet but maybe the 10 watters will help that some....

[Danglin' Fury]

How old is this amp? There was an early problem with some of these amps where the relays would float. There was a TSB about it, change a resistor in the feedback loop of the drive opamp (I think).

I'm not in the shop until Saturday, but when I am I'll look up the models and dates involved. Unless you solve the problem before I can look it up and post it here.

This! I will have to search this topic....Thank you sir!

[tubeswell]

When you're done fixing the relay, be sure to shift* the 5W cement resistors further off the board, and replace the IC filter caps with better ones

*i.e. put in new ones that are mounted further off from the board

[Danglin' Fury]

I actually bought 10 watt resistors... And I did mount them off the board... Well I finally got this dude repaired....Fighting mysrlf all the way... so I replaced Q4 today... that made the amp get stuck in the drive channel... Racked my brain as to what it could be... Then I changed R78 and R79 to 470 ohm 10 watt resistors...still stuck....Then I looked at Q4... NPN dummy! I put a PNP there by mistake so I switched it to an NPN... still stuck... Apparently the trace on the +16 volt line was just barely not touching the pad after I replaced them.... so.... finally.... After all of that, Im thinking the trace on thre +/- 16 volt supply was very brittle and intermittent on and off caused the original problem.... Q4, Q3, and U3 being bad is what caused my grief... The brittle traces probably caused it all... I remedied that... lol! Thanks again everybody! This forum is the best!