HELP my ampeg!!!!

[Orgazmo]

i was pretty much GIVEN a 1969 ampeg v-22 2x12 combo amp. same as a V-4 head.

great looking amp on the outside and no visual signs of mods other than a pair of carvin vintage speakers.

so, i get it home, check to make sure the tubes [all 400 of them] are all in their sockets, plug it in, hit the switch and a HUGE, LOUD LOW END HMMMMMMMMMMMM comes blasting out!! tubes are not lit when this happens and it appears no power is getting to them.

i know there could be a zillion reasons for something like this and i am no tech.

any suggestions where to start? i will be taking it in unless its something relatively easy enough for me to do.

i have been playing for almost 40 years and FULLY realize the dangers of these big 'ol glass monsters and will not attempt anything i havnt done before. i have some electronics experiance, no degree, but a gigging, [poor] musician with all the practical knowledge it entails like tube changing, caps and resisitors. light stuff.

but it appears NO power is getting to the tubes when this huge low hum comes out INSTANTLY when the switch is engaged.

[Jazz P Bass]

A problem such as this cannot be identified by symptoms alone.
As you have noticed, there are a boat load of tubes in there.
And capacitors, and resistors, and diodes........
My guess is you will find an overrated fuse in the fuse holder.
(The original having blown)
Take it to a qualified tech.

[Enzo]

Pull all the power tubes from their sockets, and fire up the amp without them. Does it still hum? If it does, there will not be good news.

Now look at each of the power tubes - is the peg in the middle of the base broken off of any of them? WHich means one or more of them could have been in their sockets facing the wrong way.

[Orgazmo]

ok. i just did that.

checked the fuse [13 amp instead of the 6 amp thats required]. it wasnt blown. then i pulled all the power tubes and plugged it in. hit the switch and there was a real quick hum but imediately went off. i waited about 4 seconds and no huge hum.

i shut it off, waited about 15 seconds and turned it back on and NO hum. i waited another 5-6 seconds and no hum.

whats next enzo?

[Enzo]

Check that fuse again. A loud hum that quit sure sounds like it was screwed up and blew the new fuse. The fact you found a fuse twice the size it should be is a bad sign.

First, go look up "light bulb limiter" and build one and use it.

If the power tubes are out there should be nothing to make sound out the speaker. If you got a loud hum, it starts to sound like your output transformer primary has a short to frame or maybe you will luck out and have an arcing power tube socket.

[g1]

Those have an internal "safety" fuse inside. It blows if someone puts to large of a fuse in the regular fuse holder and the amp has a problem.
Don't run it anymore until you find out why the fuse is blowing. And, NEVER run an amp with a fuse that is too large. Turning it on again with the 13amp fuse (where there should have been a 6Amp) may have just caused more damage. More damage costs more money to repair.

[Orgazmo]

how does this limiter help me?

its an easy build, but, what do i do with it?

how do i hook it up to my amp?

[The Dude]

A common problem with the Ampegs of this vintage is the flyback diodes shorting. I've seen some of the V-4's that have these and some that don't. An easy thing to check. That would certainly make it blow fuses!

Edit: Just re-read the thread. Realized you stated that the amp doesn't hum and holds the fuse without the tubes installed. Not likely the flyback diodes. Apologies for not reading thoroughly.

[Enzo]

At least some of those bulb limiter articles should describe its use.

If you just slap a new fuse into an amp that is blowing them, it puts a lot of stress on the amp and its parts. By using the bulb, if the amp would have blown a fuse, now instead it makes the bulb come on bright. This substantially reduces the current that can run through the amp, and thus any such stress. Plus if nothing else, it saves you a BUNCH of fuses.

[Orgazmo]

i am not a tech enzo, just a lifetime guitar whore!!

that explained things and i get the concept. i appreciate your advice and time.

but, thats why you make the BIG bux!!!

down to home depot for parts....................

[Orgazmo]

THE DUDE:

a shout out to you also. GREAT info!!

its nice to actually hear from folks who are knowlegable who actually reply with info instead of "go search the billion of pages of archives, you'll find it"...... .

fly back diodes huh? as i said, i am not a tech. that is a new thing to me. i know what diodes are and what they do, but what exactly do "fly back" diodes do in the amp?

[The Dude]

Actually, if that was directed at Enzo, he's VERY knowledgeable and he's helped thousands of people with their problems for FREE. He hands out free advice on this and many other forums and it's always both good and helpful. There are not many who would spend so much of their time helping other people with little or no benefit to themselves.

That said, as I stated in my last post in the EDIT, if your amp holds the fuse with the tubes removed, the flyback diodes are NOT the problem. If that is indeed the case, my first step would be to test all of the tubes. If you don't own a tube tester, you can do it by substitution, or maybe find a local shop that will test them for you. You could also put them back into the amp one at a time and see which one blows the fuse.

[Orgazmo]

THE DUDE:

ENZO got his props. and then i gave yours.

i see you around the board dishing out info to the clueless and desperate [like me] and i doubt your getting paid.

as i said, its refreshing to get actual answers instead of a go fetch reply. and i am one that usually tries to check archives, but, with boards that have been around a while and have hundreds upon hundreds of members, its like trying to read WAR AND PEACE!! and some of the things you find are close, but not exactly what you need.

it's THEN that i seek out the masters and their infinite wisdom.

thanks again fellas!!!

[The Dude]

It's all good. I often seek advice from this forum. That is my "payment". I figure I can return the favor whenever possible. I try to contribute as much as I take away. Again, I would start with assessing the tubes. If that does not solve your problem, repost and possibly we can help you figure out the problem.

[g1]

I'm fairly sure the internal back-up fuse is blown. You said it quit humming after 4 seconds, that's probably when the back-up fuse blew. It is inside the chassis in series with the main fuse. I think right now you will find there is no power light, and none of the preamp tubes heaters are lighting up with the power switch turned to "on" position.