Damn it - Black Pearl Issues!! Can anyone help?

[Dave_Mc]

Cheers Dave, between us we've had some right dramas with these!!

yep definitely

[DrumAl]

Sorry for the delay in posting my update, I've not really played it so had no experiences to really report!

I put the new rectifier in and it seemed to sort the problem. I played at home at all volumes with no bother.

However I took it to rehearsal tonight and played for 2 hours with no bother, then lost volume for about 2 mins again before it came back again for another hour. Any ideas on what to try now anyone?

Any chance it could be power valves or the phase inverter? I never changed them once the rectifier switch worked out.

Cheers guys!

[ICBM]

If you changed the rectifier and the problem went away, and then eventually came back again, and you touched nothing else, it sounds like it could be a fault with the rectifier socket - either a poorly-tensioned contact or a bad solder joint on it. Changing the rectifier might have disturbed it enough to 'fix' it for a while.

[Dave_Mc]

can't really add anything, just posted to commiserate. that sucks

[DrumAl]

Cheers guys,

Thanks for the commiserations and advice!!

I take it that to re-tension the socket ICBM, I just get a suitable implement and try and bend the contacts to make them tighter?

I'm going to try all the other valves when I get chance over the festive period and see if I can find a problem at all. The worse thing I suppose with this is that it's intermittent so finding fault may be hard.

Cheers,

Al

[DrumAl]

Hi all, thought I'd place an update to say how things are going!

Today I got brave with the screwdriver and removed the chassis from the combo, I had a good look around and couldn't see any arcing or burn marks anywhere inside. Next I tightened every god damn screw and bolt I could lay tools on to check and make sure nothing was vibrating, and to be fair only a couple seemed overly loose.

Next I removed all the valves one by one and noticed that 3 of the 4 EL84's seemed to rattle excessively, so I switched all 4 for a matched quad of EH ones. Also the PI rattled like mad (Ruby 12AX7A, longer plate) so I swapped that too for another JJ 12AX7 (shorter plate) I had. V1 seems a bit rattly too, but I've left that for now to test it out. Turned it on and played for a while at various volumes and all seems well at the minute (guitar straight in, no fx) so I shall keep going and see if the problem re-occurs.

Another thing I thought I'd mention too is that the amp was QC'ed in June 2006 so it had been stored for a good 6 years prior to me buying it. Could some of the issues be due to the amp settling in after so long untouched?

ICBM - Do you think the above mentioned rattling valves could have been causing the issues? Or would a valve just fail and not fault intermittently? (Someone did reply to say it was unlikely to be an actual valve as it was a recurring problem).

Thanks!

Al

P.s. Forgot to say, once I installed the El84's and turned on I noticed a very small blue glow around the tips of the mica spacers, I've heard that its not a good sign a blue glow (the ones I took out didn't have it anyway) should I be wary? Thanks

[Dave_Mc]

^ thanks for the update. good to hear the valves might solve the problem.

i thought blue glow on valves (assuming that's what you mean) was ok, but don't quote me on that and wait to see what ICBM or some of the other amp guys say.

where did it say it was QCed in 2006, out of interest? i didn't notice anything like that on mine (but i didn't remove the chassis on mine).

[ICBM]

A faulty phase inverter could definitely have been the cause, yes. If one side was intermittently not working that would also reduce volume and probably cause increased hum. As before, it could be a socket contact problem as well, so I would test the valve you took out in another position.

Blue glow is normal in power valves, and is almost always a sign of a valve working properly. "Blue glow is a bad sign" is one of the biggest myths about valves there is, I have no idea how it came about.

[DrumAl]

^ thanks for the update. good to hear the valves might solve the problem.

i thought blue glow on valves (assuming that's what you mean) was ok, but don't quote me on that and wait to see what ICBM or some of the other amp guys say.

where did it say it was QCed in 2006, out of interest? i didn't notice anything like that on mine (but i didn't remove the chassis on mine).

Cheers Dave and ICBM,

The QC date was inside the chassis Dave, I was impressed with the quality in there too. The PCB is very thick and all the solder joints looked shiny and well finished (what I could see anyway!).

The internet is as much a source of misinformation as it is information!! I did a quick search prior to asking on here and it was 60/40 that the EL84s were bad! Hence I thought I'd ask someone who knows what they're talking about :-)

Cheers Guys

[ICBM]

The internet is as much a source of misinformation as it is information!! I did a quick search prior to asking on here and it was 60/40 that the EL84s were bad!

Because of the blue glow? Unbelievable .

It really saddens me how many good valves must have been needlessly throw away over the years because of this nonsense - particularly as some of the valves that glow most blue are those ultra-high-quality US 6L6GCs from the 1970s and early 80s, especially the Sylvanias. Years ago I tested a large number of old ones, and it was noticeable that the ones that performed best had the strongest blue glow.

Almost all power valves also show a small amount of blue glow inside the plates too, this is a useful indication that the valve and the HT circuit that supplies it is working when you're troubleshooting an amp.

It's purple or pink glow that's a definite bad sign - that's caused by gas discharge in the valve and sign that it's got minutes to live at most, but you'll probably know about it before you actually see the glow, unless you happen to be looking in the back of the amp at the time.