NAD: Ampeg V-4. O - M - G !!!!!

StuartV · #1 01-30-2012, 10:59 PM

Okay, I love my SVT 2 Pro. Seriously. And I miss it. I moved from FL to CA 6 months ago and my SVT had to stay in storage for now. I've been living with only my Promethean 1x10 combo. Last weekend, I scored an unbelievable deal on an Ampeg V-4 on eBay and it arrived today.

It is in ridiculously good shape! I knew from the auction pics that it was in good shape on the outside, but I couldn't really tell about the inside and I really had no idea what kind of tubes were in it or anything like that. As it turns out, it's a little dusty inside the cab. And it seems like the Reverb doesn't work. But, I think the tubes are all original! And it seems to work just fine. All the knobs and switches do just what they're supposed to (except the Reverb), with just a very small amount of crackling on a couple of them.

And THE SOUND!!! I love my SVT 2 Pro. And maybe this is just new love versus old hat that I haven't seen in 6 months, but, THIS IS WHAT A BASS SHOULD SOUND LIKE!!

The first thing I plugged in was my '66 P with TI flats. Boom!! The sound I've been waiting for since I first picked up a bass.

I know the rules, so without further blathering...

StuartV · #2 01-30-2012, 11:00 PM

And now a couple of questions:

The 3rd power tube from the left seems shorter than the other 3. I.e. it doesn't hang down as far. Any idea what's going on there?

StuartV · #3 01-30-2012, 11:02 PM

And next, I was going to take the back panel off to get a better look at the tubes. But, I have never sen a fastener like these before. Can anybody tell me what they are? I don't think I have the right tool to undo them.

StuartV · #4 01-30-2012, 11:03 PM

ps. The transformer on the left, that looks orange, isn't really. It's just the lighting and the glow from the power tubes making it look like that.

Spaldo · #5 01-30-2012, 11:04 PM

I feel all warm just looking at this....

JimmyM · #6 01-30-2012, 11:08 PM

Hot! That's a beauty head. Used to have one just like it.

No idea why the one tube hangs down lower. If it works, I wouldn't sweat it.

Those are called clutch head screws, and you can get a clutch head screwdriver for it. I got one at the local hardware store...it's got a square tip on the end.

StuartV · #7 01-30-2012, 11:12 PM

Thanks, Jimmy. I'm pretty sure I have some square tip screwdrivers. But, the holes don't look square and I wasn't sure if they're more hourglass shaped on purpose, or they've just been, uhhh, massaged...

StuartV · #8 01-30-2012, 11:15 PM

Another question: The Reverb doesn't seem to work. I tried it with the Reverb Lock on the back in both the In and Out positions.

I "unlocked" the Reverb (i.e. moved the Lock so it sticks out) while the amp was on. Would that matter?

If the Reverb is working, I should be able to hear it clearly, right, even playing a bass through it? It's not something that would only affect guitar frequencies, is it?

StuartV · #9 01-30-2012, 11:16 PM

3 of the power tubes, I can't really see any writing on them, with the back panel on. But, one of them I can see that it says 7027A on it. That's what makes me think all the tubes are original. Or at least, darn near old enough to be original.

StuartV · #10 01-30-2012, 11:38 PM

I took the back panel off to look at the tubes. The 3rd one (from the left) appears to be a different kind of tube than the rest. The 2 on the left have writing I can see that says U.S.A. 7027A. I can't see any writing on the 3rd tube, though. The 4th tube looks like the first 2, but I can't read any writing on it, either.

The 7027A tubes each have 1 loop-looking thing sticking down at the bottom. Tube 3 has 2 of those things sticking down.

Anybody know what Tube 3 is? I'm guessing the other 3 are possibly original and Tube 3 is a replacement of a different type that was put in somewhere along the way?

And the rest of the innards:

lowend1 · #11 01-30-2012, 11:42 PM

Some 7027As are different sizes, depending on the brand. RCA / Sylvania are taller than GE, which are sized more like a 6L6.
Clutch head screws are supposed to look like that.
If the reverb lock is in the out position, the reverb should work. If you turn the knob up and still get nothing, it's time to check the reverb driver tube, tank connections or something in the guts. The tank could also be bad.
Top Notch amp, BTW - I have one each V4, V4B, SVT - all early 70s

JimmyM · #12 01-30-2012, 11:45 PM

Quote:

Originally Posted by StuartV

Thanks, Jimmy. I'm pretty sure I have some square tip screwdrivers. But, the holes don't look square and I wasn't sure if they're more hourglass shaped on purpose, or they've just been, uhhh, massaged...

Well I use the square head screwdriver on mine without problems, but Fliptops.net does sell an actual clutch head screwdriver, though I'd bet you could find it for less.

StuartV · #13 01-30-2012, 11:47 PM

Thanks, lowend1.

I'm going to take it to my local tech as soon as he can get me in, to get it checked out. I'd like the Reverb to work, just 'cause, even though I don't foresee using it.

If he can't get me in soon and my curiosity gets the best of me, is there any trick to removing and reinstalling the power tubes? Do they just pull straight out and push straight back in? Anything special I have to do before pulling them besides just make sure the amp is unplugged? I'm definitely curious now about the Mystery Tube.

StuartV · #14 01-30-2012, 11:48 PM

Quote:

Originally Posted by JimmyM

Well I use the square head screwdriver on mine without problems, but Fliptops.net does sell an actual clutch head screwdriver, though I'd bet you could find it for less.

Thanks, again, Jimmy. I used a square tip and it worked fine. The screws were just snugged down, but not tight, so they came out easily.

lowend1 · #15 01-30-2012, 11:50 PM

Quote:

Originally Posted by StuartV

ps. The transformer on the left, that looks orange, isn't really. It's just the lighting and the glow from the power tubes making it look like that.

Actually, I think the tranny has a copper strap around the laminations. That's probably what the orangey color is.

VanillaThundah · #16 01-30-2012, 11:56 PM

Sweet amp! Congrats on that score

StuartV · #17 01-31-2012, 12:02 AM

Quote:

Originally Posted by lowend1

Actually, I think the tranny has a copper strap around the laminations. That's probably what the orangey color is.

Yep. It definitely looks like copper in there.

StuartV · #18 01-31-2012, 12:03 AM

Quote:

Originally Posted by VanillaThundah

Sweet amp! Congrats on that score

Thanks!

lowend1 · #19 01-31-2012, 12:20 AM

Quote:

Originally Posted by StuartV

If he can't get me in soon and my curiosity gets the best of me, is there any trick to removing and reinstalling the power tubes? Do they just pull straight out and push straight back in? Anything special I have to do before pulling them besides just make sure the amp is unplugged? I'm definitely curious now about the Mystery Tube.

First you'll have to push the metal "bear trap" retainers down (up?) for them to release their grip on the tube. While doing so, GENTLY rock the tube in a circular motion while pulling it out. The operative word here is gently, as you don't want to break the center guide pin or knock the tube against the head casing. The center guide pin is indexed with a bump in one spot that fits a corresponding slot in the tube socket. Aw hell, if it sounds good, leave it alone till you see you tech with it. Why tempt fate?
The mystery tube may be a different variety of 7027. I don't think it's a GE because it has dual getters at the top of the bulb. I'm pretty sure the GE has the getter on the side. I've seen dual top getter RCAs, but your others only have a single getter. FYI, the 7027A is a special tube, but the "special" parts of it aren't used by the V4. In most cases you can sub a high-quality 6L6 without any issues.

nashvillebill · #20 01-31-2012, 07:58 AM

That 3rd tube is a replacement, it is very obviously a different construction than the others. You can get a new matched quad of Sovtek or JJ 7027's now so it's not necessary to pay big bucks for old NOS tubes.

The reverb may not be working for several reasons, have a tech check it out.

This amp looks to have the original capacitors in it. A recap job is a priority, those caps are approaching 40 years old, and failing caps can cause all sorts of major problems (like taking out your brand new power tubes...)