The 20 minute Jubilee *updated*

[Spyderg0d]

*UPDATE* Hi all,
I ended up taking the amp to a local music shop. They sent it to their repair guy. Repair guy said I need 4 new power tubes. End charge was $250. I got the amp back and it was exactly the same as when it went in. I called a friend, got a couple used but good preamp tubes. When I popped one in the 3rd preamp tube spot the amp was back to glory. $36 tube. Safe to say I'll never be going back to that shop for anything besides buying brand new stuff.


*original thread*


Recently, after starting to regularly turn up the amp past 6, and about 20-30 minutes of playing the amp, it loses a tad of volume, gain and most bass. And oddly after I turned the standby switch on then the amp off, the amp still made sound while the power and volume slowly faded.

I am sending it back to marshall, as it's less than a yr old and under warranty for sure.

But if I can get out of the few month long wait of having marshall deal with it, by one of you gents knowing whatsup with it, I would be happier than a pig in...
....... a blanket.
Thanks.

 

[Tatzmann]

First problem, is a problem.

2nd one (amplifies after shutting off) is normal behavior of many valveamps.

To 1. Simple first. Do you use the efx loop or never touch it?

 

[Jethro Rocker]

Could also try power tubes.

 

[maico996]

If it only happens when you're cranking it up past 6 and playing for a while, that might indicate something in the power section is failing? Maybe heat related?

 

[Spyderg0d]

First problem, is a problem.

2nd one (amplifies after shutting off) is normal behavior of many valveamps.

To 1. Simple first. Do you use the efx loop or never touch it?

That was my first "test". I unplugged the entire effects loop. I also went directly corded from guitar to the amp. Made no difference. Even after turning the amp back on, same loss of bass and gain. On both 50watt and 100watt settings.

 

[Spyderg0d]

If it only happens when you're cranking it up past 6 and playing for a while, that might indicate something in the power section is failing? Maybe heat related?

It was wierd when it happened. Exactly as if it had "lost" power or a portion of the amp just stopped working. All the mids and highs are there, but bass left the building for the most part.

 

[Spyderg0d]

I'm reading that bad power tubea can cause loss of bass.
So.. I might as well figure how to test them. If I find any bad ones, looks like a tryout of kt88 is in order. Maybe of different preamp tubes as well. If I can find any reading material on it.

 

[maico996]

Have you checked the bias?

 

[Spyderg0d]

Have you checked the bias?

Don't know how. But I have a feeling ill be learning it all very shortly. Took it in to a shop first thing this morning.

 

[Kuga]

I suspect from some bad tin solder.

 

[Spyderg0d]

Well. I'm not a complete newb to electronics. I can do pin outs rather well and precise on modern vehicles, so I (hopefully) should be able discern BS from something that makes sense.