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Valve amp just stopped working. Bit odd. Any ideas?

ATOMIC SUPLEX

ATOMIC SUPLEX

Member Since: 1985 Post Count: 3
My valve head has been working perfectly with no issues at all. (Orange Dark Terror)
Usually if some valves are on the way out issues begin to show before they blow.

Yesterday I was happily playing my guitar, no problems. Turned it all off as usual, no bangs or pops.
I turned it on today and . . . . nothing.
Power light comes on and I can hear the normal power hum, valves appear to light up.
I switch it from stand by and nothing. Total silence.

Power fuse seems ok (which makes sense as the power light comes on), and the internal fuse inside looks ok (I think).
The two valves at the back that I can see look in incredibly good nick.

IMG_20230715_134250.jpg

Any ideas? I'm not rolling in money so I'd rather not experiment with buying a full set of replacement valves/tubes (£150) or taking it to an amp man (goodness knows how much or even where I could take it)
 
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I guess so. Carl once told me he used to fix amps for vox or jimi hendrix or something. . . I just remember years ago asking if they could service an 80s marshal and they said no. . . and couldn't recommend anyone,
 
So even though the main fuse looked good, I tested it with a multimeter this morning and its blown. Just need to know why. It was a very gentle blow. I cant see the normal fuse damage, just the usual blob is missing.
 
Absolutely.
But I have heard valves going before and it is usually kind of obvious . . in fact I never had one blow or blow a fuse, They have just gone shite and began to endanger the amp (but sound waaaaay shit / weird before that).

I am wondering if I should cross my fingers and how it was a power surge. (I have researched the fuse and it's the fuse to protect the amp from a surge).
 
Oh hold on, the manual says that the fuse that has blown blows in the event of an output valve shorting.
What is an output valve and how does it short? What is shorting?
 
I'll swear that I remember being told that if you take the back off a tv (when that was a thing) and see one of the valves isn't lit then that valve has gone. I checked one reference though and said not to do that because it's dangerous and not all valves are lit brightly anyway.
 
ATOMIC SUPLEX said:
Oh hold on, the manual says that the fuse that has blown blows in the event of an output valve shorting.
What is an output valve and how does it short? What is shorting?
Click to expand...
Output valve will be the one connected to the output transformer to drive the speaker.

A short circuit could be due to a wire coming loose and connecting to ground or a capacitor could have broken down causing a short.
 
two sheds said:
I'll swear that I remember being told that if you take the back off a tv (when that was a thing) and see one of the valves isn't lit then that valve has gone. I checked one reference though and said not to do that because it's dangerous and not all valves are lit brightly anyway.
Click to expand...
It's usually the heater that goes in valves and best to check in dim lighting.
 
As I also recall from my time following tv repairmen around 50 years ago :) , vibration could mean the valves come unseated. The solution again as I recall was (a) disconnect the set from the mains (b) wait for some time for capacitors and things to discharge and (c) push each of the valves down and wiggle them a tad to reseat them.
 
xenon said:
Obligatory careful now All I know is don’t touch anything you shouldn’t in a valve amp. High current capacitors.
Click to expand...
I only read on line last night that they can still retain a charge that can kill you after they are disconnected and powered down.
I have had the bottom off and been poking around on the boards after only unplugging and flicking the on off switch a couple of times.
 
ATOMIC SUPLEX said:
My valve head has been working perfectly with no issues at all. (Orange Dark Terror)
Usually if some valves are on the way out issues begin to show before they blow.

Yesterday I was happily playing my guitar, no problems. Turned it all off as usual, no bangs or pops.
I turned it on today and . . . . nothing.
Power light comes on and I can hear the normal power hum, valves appear to light up.
I switch it from stand by and nothing. Total silence.

Power fuse seems ok (which makes sense as the power light comes on), and the internal fuse inside looks ok (I think).
The two valves at the back that I can see look in incredibly good nick.

View attachment 383363

Any ideas? I'm not rolling in money so I'd rather not experiment with buying a full set of replacement valves/tubes (£150) or taking it to an amp man (goodness knows how much or even where I could take it)
Click to expand...
A couple of years ago my Fender Blues Junior died in the middle of a rehearsal - electronics seemed OK but no speaker output. Took it to a great repair guy (he services Bill Nelson’s gear) and it was a resoldering job as the old stuff had cracked with age and use. Cost me about £100 to get right but it’s been fine ever since. ETA - Valves were fine.
 
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