1940's RCA amp, tech advice

[will33]

I bought this today for $150.

RCA MODEL MI-1222 15 watt amp (circa 40s)

It powers up and plays, scratchy pots, etc. I can give it a good cleaning, etc. I'm not a real tech but I do have some common sense. Have a 1kiloohm and 10 kiloohm resistor rigs for draining caps if need be. I don't have a variac but could borrow one although this thing was used somewhat regularly in a studio and was powered up on saturday so we're not dealing with totally dry caps, etc.

The guy printed out some datasheets for it with schematic and parts list. It has rca Raytheon tubes in it and is inscribed on the back "new tubes 11/30/46.

It's riding around in the car with me at work today, can't do anything with it until tonight. If someone wants to grab the pics from that ad and put them here, that's cool. I'll also be using this thread to drag myself out of the 80's and get you guys some before/after, gutshots, etc. posted here.

[Horny Toad]

[gerryjazzman]

Here's the rider manual for that amp.

http://www.theused.com/manuals/rca/rca_mi-12202_a_b.pdf

[BurningSkies]

I love the description saying it was good for rooms of up to 2000 people. Talk about tube watts.

That's a neat little unit, and has cool vintage styling. I'd be thinking about rejuvenating it and maybe re-doing the externals...chrome out that cover and it would be pretty flashy.

[T. Alan Smith]

That's rad as hell!

[Marial]

Very cool. My oldest brother picked up a 1940s Gibson guitar amp that he calls The Tombstone since that's exactly what it looks like. Those old amps have all kinds of mojo.

[will33]

Thanks you guys for grabbing the pics and datasheet. I'll get more up to speed on this as we go.

@BS. The thing looks like a piece of military equip. now. I'd like to keep stuff as original as possible but you never know. I do have a 1949 National lap steel this may be sort of a "period correct" amp for. It has "mic" and "phono" plugins with a switch that says "music" and "speech".

Freq. response in the datasheet is listed as +/- 2db, 50-7000 cycles. Good for instrument amp.

I can get more pics, details later.

[will33]

There are screw terminals on the back for 4, 8, 15 and 250 ohm speakers. I guess if you strung enough speakers together in series, you could use the 250 ohm tap and rock a 2000 seat arena.

[BurningSkies]

I say you shine that little guy up and use it with one of the new fearLESS cabs when they come out! Or the pair of them...and you'd have a killer mini-rig!

[will33]

Some pics.

Snapbucket :: 40's rca picture by will335 - Photobucket

[will33]

I think that link works. Can get this pic things sorted from a real computer later. If you can see it, it's dusty in there. Got some hodgepodge of old tubes. The 2 on the front right are 6l6's but one's a Sylvania and the other an rca and they certainly look different although both say 6l6. The big one in back is a Raytheon and the front 2 are old GE's.

Can get a better look at this stuff when I clean it up later.

[BurningSkies]

In one of those posts it looks oddly similar to a silverface Fender...

I still say you clean it up and give it the treatment!

[dhsierra1]

hang onto those old tubes if they're still functional. What are your plans for this amp? 15 watts would make for a very nice small club guitar amp.

[Steve]

Just out of curiosity, is there any evidence of makers name or initials on that thing?

There's a pretty good chance my grandfather might have made it.

He was an electronics and sound engineer for RCA all through the 40's.

[will33]

Originally Posted by Steve

Just out of curiosity, is there any evidence of makers name or initials on that thing?

There's a pretty good chance my grandfather might have made it.

He was an electronics and sound engineer for RCA all through the 40's.

RCA "Radio Corporation of America", Camden, N.J., made in usa

MI-12222 with the letter "Y" stamped after the model #

Serial # 7513

Several patent #'s

Handwritten upsidedown on the tag "new tubes 11-20-46" or 11-30-46, hard to tell.

Can get more detail later, we're still riding around at work.


@dhsierra1-- yeah, little guitar/lapsteel amp. Probably do a little sealed 2x8 or 2x10 bass cab for it too. I think it's made for playing records and or voice anouncements, has a phono and mic input with separate volumes for each. May have to do a little modding or stick a pre in front of it or something for instrument input, don't know yet.

I grabbed it on somewhat of a whim, I like old equip. like this. The guy I got it from used it in his studio to play digitally recorded guitar tracks through and record them back through a mic'ed speaker, like re-amping.

[dhsierra1]

if it takes phono and mic, even those old crystal elements from the 40s I'd imagine you wouldn't need an instrument preamp based on the schematic. I'm no expert by any means, though. OTOH, a nice little tube pre in front of the amp would open up more tonal possibilities.

BTW, you're going to do a 3 conductor grounded power cable conversion w/a fuse on this thing, right?

Congrats on a great find and bringing it back to a useful life Keep us posted on how it sounds etc.

[will33]

Ya, still has a brown 2 prong brown lampcord on it with a white end that just kinda pulls apart. I don't know if that's original but it's at least old and needs to be changed.

[will33]

Some gutshots if they work.

Well, nevermind, it keeps giving me errors. If this link works, they're there.

Snapbucket :: 40's amp picture by will335 - Photobucket

Some work was done at some point. There are a few newer looking caps and many that look like they survived the war.

Also stamped on the bottom cover is "Wired Music, 501 Stewart Bldg., Houston, Texas". and several stamps reading 68F5, 6SF5, 6Nsomething, some are wore off. Have to track that place down, maybe they did some work on it in the past. Also the power cord is twisted onto the power wires on the inside with some loose black tape around it...nice Perhaps that explains the mismatched power tubes, someone just stuck stuff in there and rigged it up to play.

Anyway, that's about all I can tell at the moment, have to spend some "no distractions, careful time" with this thing later.

[dhsierra1]

was this amp operational at all when you bought it or was it collecting dust?

[will33]

Originally Posted by dhsierra1

was this amp operational at all when you bought it or was it collecting dust?

Was powered up Saturday. Pots are all scratchy but if you find a spot inbetween the scratches, it works.....don't know for how long. Use to see somewhat regular use in a "studio", whatever that means. Tubes all light up and it does make sound.