Crate BV-60H Arcing Sound

[The Dude]

Crate Blue Voodoo on the bench. Customer says, "Makes a ticking sound".

He's right. It does. The problem is that in two days running on the burn in bench, I've only heard the sound maybe 10 times. Very intermittent. As near as I can tell, it seems to be coming from the PT area, but again, it happens only every couple hours and it "ticks" one time. So, you don't have much time to find the source. Just wondering if anyone else has encountered this or something like it. I'm about 70% sold on the PT arcing, but that's an expensive "guess".

Edit: I should say that I've already subbed/swapped tubes and rebiased. Everything seems normal there.

[TomCarlos]

And if you were to put any other amp on the bend for a day and let it run all day, would you get 5 ticks? Just wondering if the tick is coming from the house power source feeding through the amp? Just curious...

[The Dude]

Never heard anything like it before in the shop and I often burn in amps for several days to make sure I have intermittents sorted. That coupled with the fact that the owner of the amp described the problem, eliminates anything in my shop as the problem, IMO.

A little more on the problem. The sound is similar to the sound I hear when I bang on the PT with a small screwdriver (I've chopsticked all over this thing and can't create the symptom myself). It's "mechanical" sounding and as near as I can tell, the audio is not affected, though I could be wrong about that.

Edit: That is a valid thought/idea though, Tom. I appreciate any ideas put forth!

[TomCarlos]

Ahhh... gotcha. If you replicate what the customer hears, then it is in the amp. I missed that. Sorry.

A totally different amp but one that had sporadic "ticking" - it was an Ampeg bass head, solid state. I took my time and touched up questionable looking solder joints. Somehow, that solved the problem. I know, it's a crap shoot but an hour of soldering sure beat days of scratching my head.

Good luck !

[The Dude]

Maybe some luck? I turned off the lights for a bit and saw a small arc in the filament fuse. On close inspection of the fuse, there is a hairline fracture in the middle of the fuse. How it worked at all is a mystery to me, but the amp ran for days with this fuse! I'm going to have to run the thing for a while to make sure this is the cause of the problem and not a symptom of the problem, but it needs replacing anyway, regardless. Might be hard to tell from a picture, but here it is.

[TomCarlos]

Excellent detective work. So we now have one more item too add to our checklist for debugging - "turn off the lights and look for suspicious arching or electrical flashes" !!!

[J M Fahey]

Oh, that's a given for "spark" sounding problems, for obvious reasons.

I also turn lights off and look at speakers from the back (pull them out if closed cabinet) to catch frayed tinsel wires, blue spark show anybody?
Then on turning lights on again discoloured copper is visible around the sparking area, although not obvious if you are not expecting it.

[The Dude]

Well, I guess not so lucky. Was running it today and still random clicks. Now I'm wondering if it is the PT arcing and that's what damaged the filament fuse? This thing is a PITA!

[Enzo]

PT or OT for that matter.

I use the dark method looking for arc sparks all the time.

Damaged the fuse? Not likely. Correlation is not causality, after all this is also a leap year, we can't blame it on that either. Fuses are not vacuum filled, you had a cracked fuse, and that is a mechanical issue. I suspect it is not related to your main issue. I could be wrong.

See if you can eliminate anything. Disconnect the existing OT, and use clip wires to connect some other OT in its place. It really doesn't matter impedance or anything, all we want to know is if it is the cause of the clicks. Hook it up and let it run.

I forget, did we determine the click is in the preamp too? You could remove the OT altogether, or just disconnect its lead to the B+, then monitor what comes out the preamp or FX send. Is the click on that? Have we tried leaving it running with a shorting plug in the FX return or power amp jack? Sorry if we covered this earlier, I am a little foggier than usual today. A preamp click could be the preamp itself or power supply, but it would eliminate the power amp at least.

I know a guy who invented his own storage scope. He hooked his scope to something, expecting a transient, and left it running. he aimed his camcorder at the scope and left that running. If he heard the glitch, he could rewind the video and see what appeared on the scope.

[The Dude]

Just an FYI to close the thread. I did determine with relative certainty that it was the PT arcing. The customer refused the estimate, so we will never know for sure. The amp was a GC repair sold used from their website. The transformer cost was more than they had in the amp.