Ampeg V4 Distorting/Quiet

[NTEK]

hi all, i have a 60's ampeg V4 that has been recently recapped and retubed. A couple days ago i plugged into it and it had very little volume level (i could turn up to almost 10 with little volume increase) and it was distorting at all levels. I usually use the top speaker output on the back of the head. When i switched to the other speaker jack, the problem seems to have gone away. I'm thinking it may be the output transformer; the amp had been left on about an hour or so without a speaker load attached. any ideas?

[R ski]

If the speakers jacks are parallel, then the jack is dirty, if the output has a separate tap wire, coming from the output tranny, then the continuity should be compared with the resistance readings, they would appear as almost as a short

[Don Moose]

Most likely a loose or dirty jack - especially if the amp relies on that mechanical ground rather than a wire to the jack's ground terminal.

Next most likely is a loose or broken wire to the jack.

The OT (and the rest of the amp) is most likely OK if the symptoms have disappeared.

(Never heard of an OT with separate windings for different speaker jacks)

Hope this helps!

[NTEK]

okay so it looks like its one of the output jacks. one of them (for lack of a proper term) has a sort of switch that opens when the speaker cable is plugged into it. i noticed that if i plug into it with any speaker cable or adapter then the other jack works fine. not sure if this is how its supposed to operate or not.
Now i'm back to the previous problem i was having with the amp which is a fluctuation of tone... It will drop to a really deep low then back to the original tone or higher. Could a worn pot cause this? There is also a loud pop when i switch from standby to on.

[52 Bill]

Many tube amps including your V4 have a shorting switch on the main speaker jack, that shorts the output in case you forget to plug in a speaker cabinet. This protects the output section from damage, as tube amps don't like running without a speaker load. Some are marked "MAIN" or "INTERNAL", and some even say "USE THIS JACK FIRST". This is normal and you should that jack for your speaker hook up.

As for your tone drop out, it could be any number of things. Dirty pots, switches and tube sockets are the first things I would check. The front panel rocker switches on these amps are often a source of the type of problem you describe.

[Tom Phillips]

Also check the integrity of the impedance select switch and the switch on the power amp in jack.
There are lots of things that can cause the symptoms your amp has.

Seems to me that lots of people lately jump to the conclusion that it's the most expensive part in the amp (The output transformer).
Kind of like waking up with a headache and assuming that you must have brain cancer.

Regards,
Tom

[sam the wizer]

Output transformer

I have a '74 V4-B that is experiencing a similar problem. I've checked all the jacks, replaced the tubes (needed it anyway) and have pretty conclusively determined that it is the transformer. I had suspected as much anyway as I had let someone I thought was trustworthy borrow it shortly before the problems had started and found out later he had mistakenly plugged speaker 1 into speaker 2 (I cringed at the thought). When mine was in the process of going out, it would crackle after having operated correctly for a period of time varying between minutes and hours, and then the volume output would become almost inaudibly quiet and distorted. This can be caused by a variety of things, as others have mentioned, so you should systematically check for loose solders, poorly seated tubes, re-bias or even replace tubes before replacing the transformer, however don't completely discount this possibility, as you do have an older amp, and these things do happen, especially if the amp has been operated with an improper load (speaker) or without a load.