Interesting SVT comparison

[johnallg]

Elys - probably more like 2N3055's or 2N3772's in that one!

[kojakcurtis]

Actually, I prefer JJ Tesla 7027A's in my V4-B. I didn't care much for the Svetlana 6550's.

[elysrand]

Neither do I! When I (curmudgeonly)grew up, in the very early 60s and late 50s, we were building Conelrad bomb shelters in our backyards because of the Soviets of that era.

For my original pair of SVT 1969 blue-lines, I have three cases of original RCA 6146B tubes, with the plate cap plugins on top of each tube, bought new in 1970, that I am using out of. Lord help me when these run out.

For my 14 various V4-B heads, from 1970 to 1972, I am using out of five cases of (144 each case) original new RCA 6550 that I bought in 1971 (for maybe 85 cents each in wholesale quantity then). None of these heads came with 7027A in them, so I don't use 7027A in them yet.

Some day, these tubes will be gone, but until then my white and red boxes, and some black and grey boxes, all made 100% new in America will keep the Original Ampeg Sound alive. (insert flag-waving animated GIF here). With regular bias adjustments , I may never need to start using Soviet tubez

[kojakcurtis]

I thought the V4-B's came with 7027A's stock. Mines a '74 and it says 7027A on the back of the chassis where each of the 4 power tubes are.

[elysrand]

By then they were using 7027A and not 6550 any longer. Your 74 was made long after the original plant in Linden NJ was shut down, and new owners Magnavox consolidated its hold on manufacturing and moved them to a wholly different plant, with different engineers and new designs. They were, if I recall correctly, using the 7027A pin-compatible successor to the 6550 by then. But not when mine were made, though.

[rictified]

I believe you but have never seen a V4-B with 6550's except for modified heads for when 7027A's were scarce a while back. I had an old one at one time, don't remember if it was a Linden NJ head but think it was and it had 7027A's from the factory. A 7027A is basically a heavy duty 6L6. I bought an SVT in Lima Peru where I lived for a while which had had 6L6's put in it with no modifications, that amazed me as the plate voltage is about 150 V too high for them in an SVT. They didn't run hot either, also the bias was all the way on on one side and all the way off on the other. They were old GE's from Fender amps which has made me eternally love NOS GE tubes, of course I changed them and put in 6550's along with almost totally rebuilding the output circuit. One reason they didn't run away was that it was wired for 240 and the voltage in Lima is 220 and the all the voltages in the amp were a little low. I had to rewire it for 120 when I brought it back (on a plane believe it or not)
Incidently I use 6146A's for my old Heathkit DX-100 100 watt ham transmitter

[rictified]

I believe you Elys but have never seen a V4-B with 6550's except for modified heads when 7027A's were scarce a while back. I had an old one at one time, don't remember if it was a Linden NJ head but think it was and it had 7027A's from the factory. A 7027A is basically a heavy duty 6L6. I bought an SVT in Lima Peru where I lived for a while which had had 6L6's running in it with no modifications, that amazed me as the plate voltage is about 150 V too high for them in an SVT. They didn't run hot either. They were old GE's from Fender amps which has made me eternally love NOS GE tubes, of course I changed them and put in 6550's along with almost totally rebuilding the output circuit.
Incidently I use 6146A's for my old Heathkit DX-100 100 watt ham transmitter

[charlyg]

I'm a ham myself, and I have been chuckling at the mention of familiar power tubes! I've built a few Heathkits in my day, well the test equipment anyways. We did build a HW-100. I'm pretty sure that was the model. we used it as a mobile. Interesting side story. I am from SDak, and my Dad and I would hop into the car in the evenings, drive to a county where no hams lived, and check into the County Hunters Net. Boy were we popular! We would manage to get to 4 or 5 counties before heading home. We would take turns logging, and of course, you had to do the QSL thing for proof.

There were also Knight kits, and I think Lafayette made a few.

[elysrand]

Still have an original built-it-myself Benton Harbor Lunchbox too, 2m version. No one in our area was doing much 6m, or I might have built one of those too. Allied (in Chicago?) made 80-10 kits then too.

Tough to find A-batteries these days... B-batteries too!

[elysrand]

You guys would love this, BTW!! When I was a kid, I would drool over the Collins catalog, but never could afford any gear

Last month, an ad appeared in the local paper for a lady selling all the "dusty old ham junk" that her deceased husband had. Got it all,the whole shack, for $1000, included a complete set of S-line - with the 2kW Rockcrusher. All original tubes and spares included, a wealth of other rigs, parts, and three boxes of tubes Some Eimacs with spare chimneys too. Had to leave the tower though... TA-33 in bad shape and Rohn 40 base set in concrete.

(uhh, just realized how far off-topic I have wandered - sorry!)

[elysrand]

Bob, you are certainly right about regular production. Part of the reason for the V4 design I am sure was to be able to use a more economical 35 watt (plate dissipation rating) RCA tube design in place of a costlier GE 42 watt tube design. I do know that all 14 of these heads were built for a touring company, for lighter handling weight than the SVT. They were part of a larger order of who knows how many heads bought en masse from Ampeg. I bought them six months after they were delivered, and got to pick out the ones I wanted. I found ten that had apparently never been used, and picked out the best four of the rest. They must have had 50 to 100 of them in that warehouse, I don't know. It took a whole afternoon of lifting and sorting to see them all. My buddy who worked with me at the studio, and who had turned me on to the purchase opportunity, told me the guy who ran the company found that they preferred a newer solid-state amp that came along less than a year after ordering all these heads from Ampeg, and never roaded the remaining ten heads. That is why they looked so perfectly new. I had a tech tell me, after I bought them and was having them checked out, that "they had been souped up to nearly 150 watts, and had different transformer part numbers from Ampeg". I never thought about it since, but I am reading through the dusty old manila folder right now for the first time in thirty years that has in it the original bill of sale and service history, and all my service records since. It is almost certain that these are not bone-stock 1969-1970 heads, but almost equally without question these came from Ampeg like this. Four of them are pretty ragged out, having been contract-toured for six months, but the other ten today are still flawlessly new in appearance, perfect tolex and chrome corner surfaces, no rust on the transformer plate lamination surfaces, chassis plating un-dulled, etc. No apparent mods visible in the soldering and wire dress from underneath.

What a mystery, because all the outside history I find on the V4 series says that production units for the life of the unit were the later RCA 7027A. All my boxes of original spares for these heads are GE tube boxes, and all say 6550A.

[soundmasterg]

Elys, thats a cool find that you got on those Ampegs! I hope they've been in periodic use over the years so the electrolytics haven't dried up?

My grandpa was a ham operator also, and when he died last year I inherited a lot of his tubes and hi-fi things. Tubes were mostly new and used American 6146B's, 7591A's, and Telefunken preamp tubes. The ham stuff they were going to sell but as far as I know they haven't yet. I know another lady who wants to sell her late husband's ham gear too. Lots of Collins and Hallecrafters and other things like that. I'll probably help her put it on ebay one of these years.....