.50 Caliber+ Combo help!

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ant_riv

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Hello and thanks for checking out my thread!

I had great fortune when Kekam35 solved my DC-3 problem and I'm hoping someone (kekam35 are you there?) can help with this problem.

I plugged in my .50 Caliber+ combo and after about 15 minutes, the signal fades (loses volume) and then comes back up to normal volume. It continues to cycle like this. The signal hasn't dropped to zero, but it does drop to about 5-10% of whatever volume I am set at.

I am hoping this is just a tube that needs to be replaced.

Thanks for any advice you can pass along!
 
It sounds like power tubes starting to go.
I would get a replacement set right away.
I would also replace the Phase Inverter tube (V5) at the same time.

If this doesn't do the trick, it could be any number of things. Might have to take it to a tech.
Also, if this doesn't work, keep the old power tubes as spares. If the volume issue goes away with the new tubes, do not keep the old ones!

The easy things to try would be:
Re-tension and clean the tube sockets - Should most likely do this when you replace the tubes.
There should be numerous threads here about how to do this. If you can't find any, give me a call and I'll walk you through it.
Replace the power & PI tubes.

The not so easy things would be......
Old power supply filter caps
Leaky LDR's
Bad solder connection
Bad Output Volume pot

Hope this helps,
Andy
 
Thank you for the info Andy! I appreciate you taking the time to post.

I have a spare 12ax7 for the PI but I don't think I have a pair of 6L6GCs.

Should I wait to replace the PI until I can also replace the power tubes?
 
It shouldn't hurt to try a new PI.
You could try the spare tube in V2 & V3, one at a time.

I forgot that the Loop is series in your amp.
You could also try a short instrument or patch cable from the Send to the Return jack.
 
Well, I have a separate question, but it might be an easier one.

Would it be possible the problem was in the power tube sockets?

Before I plugged the amp in today, I wiggled the power tubes to make sure they were in tight. There was a very little amount of play.

I then figured I would plug the amp in and let it warm up to make sure once I started replacing things I could recognize the difference. The amp sat for about 10 minutes before I started playing through it. I have been playing off and on for 2+ hours now and it hasn't done it since.

Make sense?

I really do appreciate the advice I am getting! Thank you!
 
Re-tension and clean the tube sockets - Should most likely do this when you replace the tubes.

Yep! That is a huge problem with older amps that is super easy to fix.
Here's how to fix it: http://www.fenderforum.com/forum.html?db=&topic_number=571400
 
Thanks Andy!

You called it correctly and because of your recommendations I was able to solve the problem!

I really appreciate your advice! Thank you!

I hope you and your family have a great thanksgiving.

:D
 
Not sure if you're still following this post but if the problem recurs clean the effects send and return jacks with some contact cleaner. I spoke with a guy at mesa about this problem and he immediately identified it and was correct.
 
Thanks for the reply asmela!

I haven't used the amp in a while, but if it happens again, I'll certainly keep that in mind to try.

I have a Crate V3112 that sometimes needs the Send/Return jacks cleaned in this way. I was told there is a contact that, if not used, slightly corrodes causing a disconnect in the circuit. I expect this is the same issue.
 

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