Blown valve / burned board. Fender HR Deville 212.

Steenamaroo

Steenamaroo

...
Hi all,
I've been landed with a Hotrod Deville 212 for repair.

It was stored for a few years and powered up yesterday by the owner.
It played well for about 10 minutes and was (foolishly) left on and unattended for a further ten.
On return there was smoke seeping out of the back.

Anyway, one of the power valves is well and truly blown and the PCB surrounding the valve is pretty well charred.
R59, R60 and R65 and the obscured diode don't seem to be damaged - Just marked.
I'm cleaning it up now for a better look but I wanted to ask, is the blown valve likely to be a symptom or the cause?

I'm not valve-experienced at all, although I'm well aware of safety procedures!

A picture says more than words. :)
SAM_2573.JPG
Any and all thoughts are appreciated.

My thoughts, purely on first visual inspection, are that the valve blew and there was a massive current draw through the main burned out resistor? Most of the black is surface marks but under the resistor it's char.
Is this plausible?
It might also be worth noting that the main charred resistor was no properly soldered in. Both ends are crimped/bent on the other side of the board, but not soldered. I can wiggle it quite freely, but I don't know how free it was before hand.

The plan is replace the tube (pair??), replace the charred resistor, and test/bypass damaged traces.
Seem reasonable?
 
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You guys bollixed it all up, didn't you. :D

Not sure if the tube blew the resistor or the resistor blew the tube......wait, that didn't sound right....but you know what I mean.

Yeah, you got nothing to lose....replace both, and then see if it works.

I fried some resistors once on an amp by playing it dimed non-stop for like 20 minutes with endless power chords...:p...I replaced them, and all was well.
 
miroslav said:
You guys bollixed it all up, didn't you. :D

Not sure if the tube blew the resistor or the resistor blew the tube......wait, that didn't sound right....but you know what I mean.

Yeah, you got nothing to lose....replace both, and then see if it works.

I fried some resistors once on an amp by playing it dimed non-stop for like 20 minutes with endless power chords...:p...I replaced them, and all was well.
Click to expand...

Haha. I take no credit. I'm just the guy who gets landed with this stuff. :p

After some cleaning I can say that the burned resistor is R62. Screen grid resistor.
Sure enough, pins 4+5 are open through to pin 8 on the smoked tube, so that short will have taken the resistor out.

Thanks for the reply Miroslav. :)

Do you know, is there any kind of set up required here or can I just pop in like-for-like parts and cross my fingers?
 
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That should be a stright replacement for the resistor and tube(s)...then rebias the power tubes.

This might be of help to you:

 
Thanks man. I won't.
Since the traces and solder points for that resistor are damaged, it's going to have to go on the exposed back of the board at the next point in the chain.
Theoretically I won't even have to remove the tube board.
 
I've received some further advice.
I just want to make it clear that I will be attempting to repair this but will not be returning it to the owner in 'working condition' while the board is damaged like that, especially since the owner wants it repaired for sale! :eek:
I'm going to try to source a replacement board or consider the possibility of buying this amp myself, if I get it working.

I'll post more pics as the repair progresses.


The attached pic shows
  • where the resistor used to be (between red circles),
  • where I intend to relocate it (between yellow circles)
  • and the three damaged traces (in white circle)

Screen Shot 2014-10-02 at 11.23.44.JPG


Bit of fun for you.
The previous 'tech' had fitted a 5a fuse instead of the rated 1.6. He even included a spare 5a. How nice.
They had also disconnected mains earth at the socket and removed the securing screw completely.
I fear this plot may thicken.
 
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jonny deep said:
you mean the connection that earths the whole amp, including the ground rail of the pcb, and the guitar?!
Click to expand...

Yes, the earth connection in the 3 prong mains UK wall plug.

The man tested the amp, left it on and went to make tea, then returned to find the amp smoking.
Surely he would have been seriously injured had he kept playing until the short occurred?
 
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Steenamaroo said:
Yes, the earth connection in the 3 prong mains UK wall plug.

The man tested the amp, left it on and went to make tea, then returned to find the amp smoking.
Surely he would have been seriously injured had he kept playing until the short occurred?
Click to expand...

It's certainly a possibility - if he was the shortest route to ground. Lucky escape there.
 
Steenamaroo said:
The previous 'tech' had fitted a 5a fuse instead of the rated 1.6. He even included a spare 5a. How nice.
They had also disconnected mains earth at the socket and removed the securing screw completely.
I fear this plot may thicken.
Click to expand...



Yeah, you're right..."tech"...... :laughings:

A new board would be great, it would be as-new then....but f that's a PITA you probably won't have a l ot of trouble jumping the bad traces and installing the resistor in the new spot.

Heck, you can always try that first, and if it gets messy and hard to jump all the traces....then go for the new board.
Does Fender sell parts of that nature to anyone, or do they only provide them to their certified repair centers...?
 
miroslav said:
Yeah, you're right..."tech"...... :laughings:

A new board would be great, it would be as-new then....but f that's a PITA you probably won't have a l ot of trouble jumping the bad traces and installing the resistor in the new spot.

Heck, you can always try that first, and if it gets messy and hard to jump all the traces....then go for the new board.
Does Fender sell parts of that nature to anyone, or do they only provide them to their certified repair centers...?
Click to expand...

Yeah, true that.
I'm going with what you suggest. Try it out the cheap fix first to see if it works out then take it from there.
If the guy's happy to do a cheap sell to me for keeping then that'll save some unnecessary hassle.
If he wants to keep it or sell it on I'll remove the fuses, declare it unsafe, and quote him for output board replacement if possible.

I've no idea about parts. ECC kindly put me in touch with a chap who may be able to answer that question.
The lack of online references makes me think it's certified centres only.
 
I don't know if it applies here Steeno but I recently read a thread saying make sure you get rid of any charred stuff too, because it's a good semi conductor.......
Hope it helps
 
Thanks for that, Rich.
I've totally torn out the damaged traces to prevent any possibility of them shorting, but I'll cut out the char for safety too. :)

Cheers.
 
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Steenmaroo and I have been having "chats" behind the scenes about this matter but I would like to put things straight regarding people's likely accountability with respect to repairs?

In this case it might be possible to cut out the burnt part of the board, clean it up and make it all work fine again. It is also likely that the amplifier would be at least as safe as it was before the burnup.

However, there is always the possibility that the amp could fail again, in a different way and cause a fire. Upon examination the old repair (lashup!) would be seen and the last repairer sought out and prosecuted. It would not matter in law even if you had not profited from the work!

The only safe and acceptable way to repair such damage is a replacement PCB from Fender (or an approved agent if such exists) and even after such action the amp should be PAT tested and a certificate provided (keep a copy!).

Note please that this homily is for general information. It is NOT any criticism of Mr S who has behaved completely properly and responsibly about the whole matter.

Dave.
 
For anyone following this I'm sticking with the safety advice but I just wanted to update and say that the amp is 100% working now.

The speculation was correct, but a preamp valve was also blown. No big deal.
The reverb was also dead but that turned out to be broken solder joints in the pan itself.

There was a little bit of intermittent rustling and fissling once I got it going which turned out to be a weak solder joint on one of the preamp valve sockets. A quick re-solder and that got sorted.

Long story short, she's running perfectly now. :)

Thanks all.
 
The end result is basically this picture but with the burned areas completely cut out. (Got one of those yellow markers wrong in the pic.)

Since it was so brittle I just poked my way through with a blunt tool and then filed out the sides until I got to clean PCB.
The three damaged traces were also completely lifted to avoid any possibility of shorting.

View attachment 89657
 
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