Fender Hot Rod Deluxe

[bsco]

Happy New Year to everybody......haven't been on this forum for awhile.....illness and other things always seem to get in the way of normal living...anyway I just wanted to post this in case it can help somebody out. A friend on mine dropped off a HRD and it is pretty old and in need of a major cleanup and repair. When powered up it made a very nasty crackling and sizzling sound with some hum....all controls turned down and no input...A good inspection showed that some of the tube sockets had no solder on the pins and some had very little.(this was repaired some time before).. The 470 ohm/5W resistors had scorched the board. Tubes were very old. and the amp overall very dirty.I decided to approach this a different way.....instead of just jumping in I stood back and thought for a bit...and I took account of everything that I could see that needed attention....I resoldered all the pins on all tube sockets....I tried the amp again...same thing...but not as bad...So I popped out the main board, replaced the plate load resistors(they were never replaced before and the amp is very old)... and also the 470's as well....and I raised these up off the board surface. Also had to remove the two didoes there as well and clean the leads so fresh solder would stick to them...Repaired the traces and pads that had lifted from the heat generated by the resistors and cleaned up the entire area...Soldered all the connections to all the jacks and tried it again noticed another improvement but still not good. Removed the 3 12AX7's and tried it again. I still had some noise. So the problem now appeared to be in the amp section and not the pre-amp....I sprayed some cleaner into the power amp in jack and tried it again....it improved drastily...but not completely.....sprayed it again and it improved again. Decided to replace the darn thing and noise disappeared...installed the old tubes and it sounded bad...installed new ones and it sounded great...so, I had a bunch of problems here that I had to tackle one by one and then re-check. I did learn one very valuable lesson by doing this.... this could have been a case where the only problem could have been a faulty power amp in jack...in this particular case however it was not and the visual inspection confirmed that......but rest assured from now on this is going to be the first component I will check in an amplifier that has one.....and I strongly suggest that anybody who repairs amps for fellow friends and musicians and the unit is equipped with a power amp in jack and you are having a noise issue, check this first.....not saying that this is the only problem you might have but you never know......a final note.....I am going to make up a sort of flow chart for myself for different problems so that I will have a systematic approach and hopefully, this will speed up the diagnostic and repair process and improve my troubleshooting ability........

[52 Bill]

Very nice lesson here, thank you for posting it and the others.

There's one more jack on these amps that needs to be checked whenever they come in, and that is the extension speaker jack. There is a switch on the jack that selects the output impedance tap and when it becomes oxidized it will cut off the entire signal to the main speaker jack. I have yet to have one go completely open, but most of them are bad enough to cause signal breaks when touched.

[bsco]

Thanks for the reply...and yes..you are so right about that jack..I had forgot to mention it but I had to clean that one up as well....it however did not cause any trouble but i cleaned it anyway....Thanks for the reminder....

[g1]

At the top of the maintenance page is a sticky post, "the dreaded switching jack problem".
It has more info about various types of places they are used and the problems they can cause.
They are a very common cause of all kinds of issues.

[bsco]

Thanks g-gone....I saw it there..I will check that out for sure....I see you like Lemmy as well....

[pdf64]

For a formalised diagnostic, see Tube Amplifier Debugging Page
Pete

[bsco]

Ok Thanks for that info....I will check that out...
Bernie
Just fired up the amp...sounds nice and clean...no noise and static...has great tone....extremely loud for it's size.....the owner will be very happy......

[bsco]

Checked that out Pete and there is a ton of info there....Thanks for that...

[bsco]

pdf64.....checked out your video...Sounds good...I have a Les Paul as well....1974...Tobacco Sunburst...wouldn't part with it for the world... play it through a 1976 Marshall 50 watter with 4X12 cabinet..Cabinet was made in mid sixties...blow the head right off you..