blues deluxe is dying!

[silentvelcro]

my blues deluxe just started to die on me the past couple days. it works fine for about a minute after i turn it on and then it just starts cutting out at random times. it sounds fine, and then just goes silent for a second or two, then works again, then silent.... i've noticed that the 'drive' channel light also lights up when it cuts out, if that means anything.... but it's not actually switching to the drive channel (just the light). I'M FREAKING OUT RIGHT NOW PLEASE HELP!!!!!!! Ive also noticed that if i leave the amp on for ~10 minutes until the tubes are super hot, the problem seems to go away for the most part... but this makes it extremely difficult to just pick up the guitar and play whenever. I'm pretty sure this isn't a tube problem either, as i've tried 3 sets and none have done any good.

ps its a 93 blues deluxe reissue (usa made)

-thanks

[Gunny]

are you familiar with the 2 resistors in the low voltage power supply section that get so hot they unsolder themselves, somewhat? This can cause intermittent channel switching. If they are the problem you can replace them and keep a space between the replacements and the board.

[52 Bill]

Welcome to the both of you.

Gunny is right, as there are a lot of problems with the low voltage supplies in these amps.

If you remove the back panel from the amp you will find the two large white block resistors located at the lower center of the pc board. See if either of them is loose from the board. Carefully turn on the amp and see if proding or pushing on these resistors will cause the amp to go into fault mode. Use a wooden stick or some other insulated tool to do this.

If moving either resistor causes the problem to show up, then the resistor has unsoldered itself, and will need to be resoldered.

Let us know what you find out.

[silentvelcro]

THANK YOU,
this is exactly the problem
a simple tap with a ballpoint pen on these two block resistors causes the problem to show up

ps. GOD BLESS YOU TWO

i have been loosing sleep over this!

pps. how difficult is it to re-solder this part myself? i assume i'd have to take out the whole board solder from behind? i haven't had to solder much in my life :|

[Gunny]

It may be best to let a pro do the job. My recollection (I've done about 4 of these, but it's been a while) is that the resistors have epoxy or some kind of silicon goop holding them on the board. It takes skill to unsolder these without damaging the board and yes, that means removing the entire board and removing all the potentiometer fasteners etc. The shortcut would be to reflow the solder joints, but you'll always wonder when the heat (from the resistors) will cause the fault to return. I replace them with new resistors and leave a gap between the resistor and board.

[silentvelcro]

ok, good to know. and thanks again, you guys have been a great help.

[Alex R]

Using high-melting-point solder (like the lead-free stuff) on joints that suffer from heat works for me, no comebacks yet.

Myself I feel resistors like those famous two are a bit heavy to be mounted off the board without some support, I'd expect the wires to break, what with all the heat in amps and them being moved around a lot, but this is not a fully scientific observation! I've seen some little ceramic standoff things in amps but never from a supplier, wonder if they are available...

[R.G.]

If you simply must leave resistors in there instead of converting to three terminal regulators,
(a) use higher-watt rating resistors
or
(b) make the existing resistor higher-wattage by clamping aluminum fins to them to more efficiently carry heat away.