Hiwatt Gurus: Help your friend Bob!

[daveC55]

I do not have a solution for you...
I had a similar problem on my first homebrew.
Same resistor would let go.
In your picture, the green resistor next to the two diodes on the single turret strip (power supply end).
Turned out to be a bad batch of resistors. (I've not ordered again from that supplier)
An 'old' resistor from the junk drawer held up after several 'new' ones cooked.
A switch to a different brand (Xicon) and problem solved...
Mine had new caps, and everything else.
My opinion... for what that is worth... is probably an electrolytic power supply cap is letting go.
Here is the logic, enough current draw on start up to stress that resistor, caused by a bad cap trying to build up.
I do not know if 'reforming' the caps would help, it might make it better temporarily.
If the amp went unused for a while, then was under immediate heavy use (really loud settings) it might be too much too quick.
If it worked fine under lower loads, but won't take abuse... I'd lean in that direction.
I am sure, other, more knowledgeable people, would have better ideas...

[mhuss]

It looks like the cap cans (and their attendant resistors) were replaced. I second what Dave suggested, if the tubes are good it almost has to be a bad cap, unless there's a stray bit of solder somewhere, and I don't see anything suspicious in the pictures.

--mark

[Hiwatt Bob]

thanks guys--

so the guy at Savage said that it looked like whoever replaced the caps replaced that resistor with a 3W and that they replaced it with a 5W (which also blew). this time they again replaced it with a 5W and it's been running fine all week. they were going to hold onto it for another week to see if they can replicate the problem (get it to fry again)--if it does they'll try a 10W, if not, i'll probably have to chalk it up as a fluke. i asked about the electrolytics--they said that they looked fine and that all the wiring appeared correct/properly done/etc.

[menace2u]

to see if they can replicate the problem (get it to fry again)--if it does they'll try a 10W

Unless the original schematic called for a 10 watt I would put my foot down with those guys. If not you are going to find out the REAL problem in a way you might not be happy with. There is something wrong here and you have folks much smarter than me stumped- but losing an original Partridge transformer or some other major component while hunting a ghost would be a terrible shame.

JMHO

m2u

[mhuss]

I agree with menace -- putting a bigger and bigger resistor in there is like repeatedly putting a larger value fuse in every time it blows, until something much more valuable burns up. Who is this guy at Savage and what is he thinking??

--mark

[Hiwatt Bob]

well they kept it for about a week and a half now and it performed fine for them. i picked it up today and it fires up, sounds great. so we'll see how it goes.

i asked him again what they'd do if it blew again, this time he didn't mention the 10 watt resistor (so maybe i misunderstood what he was saying before)--he just said that they'd have to get more in depth which would probably involve more costly stuff, which they want to avoid if nothing is really showing itself to be the cause. he said the trannies and electrolytics (and everything else for that matter) is performing the way it should be reading wise.

i guess we'll just have to see.