Ampeg cracks me up

[Randall]

I got a 70's Ampeg V3 in for restoration. Hasn't been switched on in 30 years. It had a frayed suspicious looking cord with a beat up 1/4" enclosed plug hanging out of the speaker hole. I clipped it and set to work on the amp.

Today, the final thing to do before testing was replace the speaker jack, or so I thought. Turns out, the schematic inside the amp shows the 4 pin XLR arrangement Ampeg sometimes used for speaker connections, like on the B-15's. But this one does not have that. The hole labeled speaker was placed too close to one of the output tube sockets, so that if a 1/4" jack is installed, the plug actually comes in contact with two of the socket pins!

It would appear Ampeg instead installed a pigtail with an enclosed 1/4" female jack instead, leaving it dangling from the back of the chassis. No evidence that this was done later, since the hole is painted on the inside edge, and factory labeled "Speaker" just above it. Now on the other hand the ext. speaker jack is the original 1/4" jack as one would expect.

So, what's up with that? Did Ampeg goof on this and improvise a solution so as not to waste any chassises? (or whatever the plural of chassis is)

[g1]

Could it not have been an XLR connector hanging from that cable? The schematic does not specify chassis mount and only shows 2 wires connected to the XLR.
I believe the cable would have been long enough to go to the cab.
http://www.tremolo.pl/Firmowe/AMPEG/V3.GIF

[Leo_Gnardo]

It would appear Ampeg instead installed a pigtail with an enclosed 1/4" female jack instead, leaving it dangling from the back of the chassis. No evidence that this was done later, since the hole is painted on the inside edge, and factory labeled "Speaker" just above it. Now on the other hand the ext. speaker jack is the original 1/4" jack as one would expect.

So, what's up with that? Did Ampeg goof on this and improvise a solution so as not to waste any chassises? (or whatever the plural of chassis is)

60's Ampegs, maybe into early 70's, had this "flying lead" as the main speaker connector. Earliest ones used a 4-pin XLR/Cannon (mic) connector. 2 of the prongs carried speaker signal, the other 2 operated as a "fool proof" method for muting the amp when the connector wasn't plugged into one of their cabs with the mating 4-pin. Many techs bypassed this interlock feature and removed the cable, replacing it with a quarter inch jack. Others just stuck a phone plug on the end of the cable. That way you could use any speaker cab, not just the Ampeg cabs equipped with 4-pin jacks. FWIW my test cab for the last 25 years is a V4 4x12, and it has one of those 4-pins on the back. Next to it, someone drilled a hole and mounted a quarter inch jack.

You can be sure Ampeg made full use of whatever chassis they had in stock. And the plural of chassis is . . . chassis.

Randall, any chance of a photo of this V3? I've run across V2, V4, V9 but never a V3. Must be a rare beast.

[Randall]

Aha! A hanging XLR did not occur to me, but I bet that's what it was at one point. That's the good news. The bad news is I just discovered one side of the OT is open. I'm feeling a little remiss that I didn't check that before I put all the other work into it. My bad. I'm pretty sure the guy will still want it done, it was his first real amp and he is sentimental about it.

I'll get some shots of it up asap, I have a new camera arriving any day now. I had never seen one before this either.

[Leo_Gnardo]

The bad news is I just discovered one side of the OT is open. I'm feeling a little remiss that I didn't check that before I put all the other work into it.

Oh I've done that, more than once. Now OT continuity is one of the first things I do when checking out an amp.

For one fellow with a busted B-25, I put in a generic Magic Parts Bassman OT. Now he has a choice of output impedances. No complaint about tone nor reliablilty. He had been running his Cerwin Vega 4 ohm cab off a 16 ohm OT. No wonder it fried.

[Randall]

Randall, any chance of a photo of this V3? I've run across V2, V4, V9 but never a V3. Must be a rare beast.

Here you go Leo!

[Leo_Gnardo]

Here you go Leo!

Thanks for the photos Randall. Well that one has "the wide open spaces" inside don't it.

Looks like that generic Bassman/SuperRev transformer would fit it just fine.

[drewl]

Yeah, I've seen those heads and I had an Ampeg tall 4x12 cab that used the four pin connector.
The guy I bought it from made an adapter to 1/4" and I used that cab with my 50w plexi.

[g1]

Nice pics!
This series of amps is what I like to point out to people who complain about printed circuit boards in tube amps. Great example of the right way to do it. Power tubes and jacks are chassis mounted, all boards have access plates so board removal is not required when replacing components. I believe RG took this idea even further with his workhorse amps with access plates for pot replacement?
The rubber mounts for the V series Ampeg's meant the solder held up much better than modern equivalents. 40 year old examples like this one have often seen less resoldering of preamp sockets than a 15 yr. old HR or blues type Fender amp.
I'll take a well thought out pc board amp like this over any PTP any time (tired eyes & shaky hands are not PTP friendly ).

[drewl]

Hmmm.....i see alot of bad PC board connections on old Ampegs.

[g1]

Hmmm.....i see alot of bad PC board connections on old Ampegs.

Agreed, I see them too, but I think the shock mount chassis reduces the problem immensely. The ones I do have to resolder, it's not like they've had to have it done many times over in their 40yr old life. I meant they are much less susceptible to the problem than modern stuff, not that they are immune to the issue.

[drewl]

I'll give you that, but the shock mount chassis is a pain in the ass to deal with and you can easily pinch your fingers on those floating side pieces if not careful.
I find it easiest to stand the amp on its side, power trans down and slide the chassis out.
Then you have to be careful setting into an amp cradle to work on as the floppy sides sure as hell can't support the amp.

[Randall]

Interesting to note that the board has the provision to mount the big tube sockets on it. Notice the three circular solder pad arrays.

[Enzo]

That is left over from the B-25 the board was originally used in. They used the same B25 preamp and left the rest of the board empty, and built a power amp in the chassis.

[g1]

I'll give you that, but the shock mount chassis is a pain in the ass to deal with and you can easily pinch your fingers on those floating side pieces if not careful.
I find it easiest to stand the amp on its side, power trans down and slide the chassis out.
Then you have to be careful setting into an amp cradle to work on as the floppy sides sure as hell can't support the amp.

I do the same as you, stand on it's side and slide it out. But I put a spacer in between the transformer and the side plate, so once it is out of the cab, it remains standing on it's side. Then I do as much work as I can with it on it's side.
If I have to lay it down, I put blocks under the transformers to raise it above the level of the side plates.
The real problem is the sheer weight. No matter the design, it would still be a pain to deal with .