Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dude on February 15, 2022, 10:35:10 am
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And back to where it cam from...! This V-4 was my daughter's boyfriends, he got it as a basket case. After five years they broke it off and I never finished refurbishing the amp, gave it back to the old boyfriend, unfinished. Well, she met another guy who's friend got the amp from my daughter's old boyfriend, he had it for five years still unfinished but he 6550's I bought for it were not with the Ampeg. ($100's worth of tubes). So the old friend of a friend gave me the the head, free, said "it's all yours if you want it". Of, course I said yeah, when I got the head I never thought about it being the head I once started to fix, like ten years ago till I opened it and notes were inside (my hand writing) explaining what I did so far. Wow, this is the Amgep V-4 I started years ago. Crazy world.
Anyway, is this 100 watt beast of any value now-a-days..? I remember I replaced all the filters, several R's in power supply, bias supply, and more. At the time this Head had no PT, no power tubes, we got a new PT for $300 from an Fliptop Ampeg site, I used single electrolytes in series where needed for the filters, all of them and several other fixes. The PC board is built like a rock with good looking traces.
Should I sell it as a basket case, part it out, put it back to original specs with 6550's. Looking for suggestions on what you guys might do with it..?
The original schematic is glued to the plate inside, it's very legible. If I attempt to finish this V-4, I'd most likely need some help here as the schematic looks a little over my head, the only thing that's kind of stopping me is the price of (4) 6550's or the original 7027's. This beast must weight over 50 pounds, probably 60..., a monster. Where do I start?
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Nice amp ! I would start giving it a nice cleaning on everything, outside and inside, that would be a good start!
Also share the schematic and some really nice high resolution pics from all the guts!
Go on the most intuitive things to check first, that is probably a logical path!
put it back to original specs
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At Mac's Radio Service Shop the FIRST thing is Barney takes the set in the back room, sprays the chassis with carbon-tet under a fume-hood, a mini-vac to suck out the case, before Mac will even look at the problem.
I just found out that auto detailers have a clay, now a silicone gel, you press on dirty details and lifts the dirt out of cracks and stitches.
https://www.amazon.com/Cleaning-Detailing-Cleaner-Interior-Keyboard/dp/B08921F1XR
https://www.amazon.com/Keyboard-Universal-Keyboards-Calculators-ColorCoral/dp/B07GW9TJ3G
I don't think you will get rich fixing and flipping this beast. IMHO these things were TOO DARN LOUD!! And heavy, specially in VT-40 form (four Tens). But they were a milepost on the way from a couple 6V6 to today's 800W class D toys, a Real Amplifier, a barn burner (too loud for the garage). Somebody "should" buy it and keep it limber for the next generation.
Yes, Barney started working for Mac in 1947, and seems to have disappeared by 1960, perhaps due to all the carbon-tet fumes.
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> Also share the schematic
There were at least three variant designs (early had rear controls, late had front knobs, and later ones had the odd triple-triode) and four versions of each (VT-4, VT-40, VT-22, etc: head, speakers, 2 power bottles or 4). Ampeg has the general plan for the 1971 VT-40. All the '71s use this plan. The late 1960 amps were more conservative (had separate screen supply).
https://ampeg.com/support/files/Schematics/V%20Series/VT-40/VT-40%20Schematics.pdf
Oh wait--- that plan lacks "Distortion" (a nasty buzztone). I guess Dude wants the mid-1970s plan.
Try https://www.ampegv4.com/schematics.php
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I just found out that auto detailers have a clay, now a silicone gel, you press on dirty details and lifts the dirt out of cracks and stitches.
https://www.amazon.com/Cleaning-Detailing-Cleaner-Interior-Keyboard/dp/B08921F1XR
https://www.amazon.com/Keyboard-Universal-Keyboards-Calculators-ColorCoral/dp/B07GW9TJ3G
if you're meaning for cleanup, i have found just about nothing works better than the tire shine foam from walmart. put on old tee shirt (to wick away the grime) over a cinderella-style scrub brush and once the foam subsides go to town scrubbing that tolex. extra dirty might require another go around but it ends up looking like brandy new tolex
i've also been known to take an old toothbrush and some chrome polish to clean up a chassis. best done while sitting in front of the boob tube as it's tedious
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Schematic V-4 Ampeg head
Most likely will not spend the capital to fix this amp as it’s an outdated beast.
Fixed, probably worth $500/600 at most, maybe more to a deaf guy, ha. The PT and OT might bring a couple hundred of not more, PT is brand new, cost $300 from Fliptop. Knobs and switches are hard to find for the collector. Plus the filters l put in are worth $50, their new. I’ll probably part it out on eBay as it’s way to loud and outdated.