3801 Jackpot!

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MCK
Posts: 618
Joined: Mon Apr 27, 2009 4:49 am

3801 Jackpot!

Post by MCK »

Received a 3801 homebrew amp I bought off ebay. First class packaging & seller. Most recommended!

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... =all&tid=0

Now here's the interesting part. I bought this amp for the 3801 OT and it is indeed great shape. Long uncut leads and all. In addition to this the amp comes with a Stancor PC8412 PT. 400 0 400 V and 5 V + 6.3V. Any idea which wreck this can be used in?

Secondly, all tubes that the amp came with are NOS and are working well. The mica 6L6s alone seem to be covering most of my purchase cost! Not gloating here but I'm quite happy.

Some other interesting tubes in there as well. Especially the RCA6J7 with the top connecting ground. The tube complement is as follows : 6J7, 6SK7, 6SL7, 2x6L6, 5V4. Oh did I mention lots of mallry & sprague goodness in there? All in the picasaweb below.

http://picasaweb.google.com/email.kerem ... directlink

Quite a strange chassis & layout. Reminds me some PA amps I've seen out there. Does it look like anything you've seen before? My plans are to dismantle and reuse the PT / OT and also anything else that is in good shape. The tubes will definitely find good homes in my other amps. Not sure what to do with these preamp tubes yet.

Any ideas? Thanks in advance!
Cliff Schecht
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Re: 3801 Jackpot!

Post by Cliff Schecht »

Others may be able to weight more on the PT but I think the 400VCT output is a bit high for any of the Trainwreck designs. You could always add a power resistor to drop the voltage down but this is wasteful for what is probably a great PT.

I would be weary about a lot of those caps in the amp though. I believe those caps are paper in oil caps which can eventually dry out and can't take nearly as much voltage. They eventually will fail and leave you with either an open circuit (safe) or a short circuit (dangerous!). I have quite a few NOS paper in oil caps of various vintage but I'm always hesitant to use them because even if they look new, they may not be up to handling a constant 400+ Volts.
Cliff Schecht - Circuit P.I.
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Phil_S
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Location: Baltimore, MD

Re: 3801 Jackpot!

Post by Phil_S »

It happens. I recently bought an old Sears organ(?) chassis that someone had bolted an A-3801 to. I came with good 6L6's, a good PT and other stuff. It wasn't usable as it was and I made something else with it. I think I paid $38 shipped. I thought I was dreaming.

No, I didn't build a TW. Probably should have, tho'.
MCK
Posts: 618
Joined: Mon Apr 27, 2009 4:49 am

Re: 3801 Jackpot!

Post by MCK »

Thanks for the comments. $38 for a PT & OT + tubes sound like a sweet deal. Yes I should not rely on the paper/oil stuff. They sure look pretty though!
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Noel Grassy
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Location: Vacuum Tube Valley-Cali

Re: 3801 Jackpot!

Post by Noel Grassy »

On US made caps, you can tell the paper in oil ones by the little "pour spout" shaped lead immediately exiting the cap on one end.
AFAIK those don't dry up or turn $hitty. It's the electrolytics with the paper tube that spins freely around the metal container which tend to bubble on the (+) end before bursting outright.

On the Sprague cap it kinda looks like a funnel nearly twice the size of the lead that exits it. The picture makes it look like a blob of solder but I have some unopened packages of these "bees" and
the one end looks like a little funnel or pour spout. These go off their stated value [usually increasing] but they don't fail or explode spitting heinous venom over everything like a 'lytic cap.

BTW, great little score nonetheless!

Noel Grassy.
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