Author Topic: Jalopy Amps. (Read 12172 times)

DummyLoad · « **on:** August 28, 2009, 10:01:22 pm »

well, so as not to butcher slucky's rock-ola thread, i started a new one. hope the mods keep it here so it doesn't get buried in the amp building forum.

please, only post stuff you'd like to butcher, or see butchered. not something you're building, have questions about building, repair, or design.

DummyLoad · « **Reply #1 on:** August 28, 2009, 10:06:51 pm »

i'll start...

this one looks interesting...

7C5 - 6J7ish (citation needed)
7F7 - 6SL7
6L6 - yada, yada, yada...

should make a nice little screamer. that's one nasty shade of green though. i'd paint it ferrari red or ford grabber blue.

RicharD · « **Reply #2 on:** August 28, 2009, 11:26:18 pm »

Here's one I'ma gonna butcher.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=290342264973&ssPageName=STRK:MEWAX:IT

DummyLoad · « **Reply #3 on:** August 29, 2009, 12:02:24 am »

bloodthirsty sparky! :icon_pirat:

DummyLoad · « **Reply #4 on:** August 29, 2009, 12:27:21 am »

she may very well be the bench queen, but still bury my dykes in her

nastyoldtech · « **Reply #5 on:** August 29, 2009, 01:23:02 am »

Blood spatter everywhere with this one...

Next I use this (me having a bad hair day)

sluckey · « **Reply #6 on:** August 30, 2009, 07:45:54 am »

Well, my thread has already come to a fork in the road, so here's my old jalopy, a 1954 Rock-Ola jukebox amp. This project is completed, I think? Page 4 of this pdf shows the conversion schematic.

DummyLoad · « **Reply #7 on:** August 30, 2009, 11:04:13 am »

nice touch w/ the 5R4... def. has the frankenstein motif working now just to get some coke bottle 6L6s for it...

i see you called it rocky... rockey frankenfurter perhaps?

again, nice work on the re-wire... :glasses9:

jhadhar65 · « **Reply #8 on:** August 30, 2009, 02:11:53 pm »

Yeah, really nice.

What have you got going with the pot and 2nd filter? I couldn't figure out what "1540 with center tap" meant, either.

Weber was working on a field coil if you're interested, but that might take a while now.

So do you still think it might need 6SL7's?

You should start your own thread, by the way!

sluckey · « **Reply #9 on:** August 30, 2009, 03:24:15 pm »

Quote

What have you got going with the pot and 2nd filter? I couldn't figure out what "1540 with center tap" meant, either.

It's not a pot. It's a 1540Ω power resistor with a fixed tap. Think of two 770Ω resistors connected in series. That's an original part. I decided to keep it. Here's a closer view.

jhadhar65 · « **Reply #10 on:** August 30, 2009, 05:08:32 pm »

Oh, yeah... I saw that in another pic. I've got one like that in a radio I'm working on. I should have remembered and recognized it on the schematic.

DummyLoad · « **Reply #11 on:** August 30, 2009, 07:29:57 pm »

and now, for the door-stop de jour!! click me!

tubesornothing · « **Reply #12 on:** August 30, 2009, 08:02:57 pm »

I lovethat panel lighting! too cool.

jhadhar65 · « **Reply #13 on:** August 30, 2009, 08:46:25 pm »

I dig that, too. It looks like something you'd see on a table or counter somewhere in a Dick Tracy movie. I'd like to have a house totally decked out in retro 30's/40's stuff. I know that item is younger than that, but it fits with my definition of ultra-cool.

nastyoldtech · « **Reply #14 on:** August 31, 2009, 12:39:50 pm »

When I was a kid I used to find stuff like that all the time out on the curb in peoples garbage. I drove my mother nuts bringing all that crap home. I destroyed a small pile of that stuff trying to figure out what went where. It's a wonder I was not electrocuted to death. That and not being blown up making homemade fireworks, or shot in the eye from BB gun block wars...

I guess someone upstairs was looking out for me?

DummyLoad · « **Reply #15 on:** September 03, 2009, 10:06:03 am »

slurp, smack... drool...

DummyLoad · « **Reply #16 on:** September 04, 2009, 11:09:58 am »

oh, hell yes!

too bad the chrome bands are missing...

DummyLoad · « **Reply #17 on:** September 04, 2009, 11:16:27 am »

i think i'll bid on this one...

RicharD · « **Reply #18 on:** September 04, 2009, 08:53:53 pm »

The Stromberg Carlson arrived. It has a schematic.
http://www.sotxampco.com/Schematics/AU-57.pdf
Looks like the only existing Tom Foolery is the replacement of 1 volume pot and the mic jacks were changed to 1/4". Interesting rectifiers.

The little RCA amp came in and it appears to be completely unmolested ..... yet.

I'm gonna reverse engineer it tonight.

Geezer · « **Reply #19 on:** September 04, 2009, 09:48:45 pm »

Here's a few that I've done..........

Bogen K10 flipped to a Matchless Spitfire>>>

Bell Sound "Pacemaker" flipped to a 5C3/5D3 hybrid type>>>

PRR · « **Reply #20 on:** September 05, 2009, 12:34:13 am »

> Interesting rectifiers.

5U4 is worked direct to a cap, peak-catcher, 1.414.

6X4 feeds a choke, averaging filter, 0.9 times AC rms.

If we assume perfect rectifiers and 400V on 6L6G plates, the AC is 280V rms, and the 6X4 will make about 250V.

Note that 6L6G is rated 360V plate and 270V screen. We is supposed to run G2 well below plate voltage (until 5881 came along). Shave a few numbers here and there, it's right about right.

It is of course a 25 Watt amp. But not run quite like 6L6G 25W AB1 condition. Rk is wrong. It may be a 10KCT OT.

Somebody got real nuts about preamp 1.

DummyLoad · « **Reply #21 on:** September 05, 2009, 06:54:26 am »

It is of course a 25 Watt amp. But not run quite like 6L6G 25W AB1 condition. Rk is wrong. It may be a 10KCT OT.

brimar 6l6g data sheets show conditions as the per the schematic - so do RCA 6l6gb data sheets.

Rl shown is 9k instead of typical 6k-6k6 Rl seen w/ 6l6.

perhaps AU-57 was designed with 6l6gb in mind but brimar showed 6l6g could be used instead?

no disrespect, but i think we're getting off track with this thread though... getting too technical. i hope buttery starts a thread in the building forum.

DummyLoad · « **Reply #22 on:** September 05, 2009, 07:07:57 am »

geezer, you chopped up that k10 pretty good...

i just made changes as per PRR's recommendations and added tone stack & bastardized NFB . thought it sounded pretty good as mostly was.

very nice work.

your possesion of that amp brings up a question, do you still have the original OT? if yes, wanna sell it?

DummyLoad · « **Reply #23 on:** September 06, 2009, 01:58:31 pm »

chop! chop!

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Author Topic: Jalopy Amps. (Read 12172 times)