50's Magnavox tube stereo...

[Tonegeek]

I acquired a vintage tube component stereo today (tuner/preamp and separate power amp). It appears to be a Magnavox from the '50s. I made a crude antenna, fired it up and the thing actually works. The power amp has 4 Sylvania 6v6gta black plate tubes, 2 CBS 5y3wgta black plate rectifiers and 1 GE 12ax7 grey plate in the PI. The PT is a Stancor and the OT has Magnavox inked on it but no metal stamping that I can see.

I would like to find out more about the 5y3wgta tubes. Should I hack this up for guitar use or keep it as is since it works? It is not pretty as you can see. There is no cabinetry or faceplate for that matter. I think I see another guitar amp in my future.

[passfan]

Could be worth up to a buck/50 on ebay. Would probably need another preamp tube to get any gain out of a guitar amp. Cool find if it was free as these thing sell like hotcakes.

[Structo]

Around 1970 my friends older brother had a Magnavox console.
It was like a piece of furniture, real nice looking.

Not sure but I seem to remember it having 15" speakers, but more likely 12" and tweeter of some sort.

The first time I heard The Doors was on that console.

Eventually we figured out how to hook up a guitar to it and could jam along with the records.

You might check eBay and see if there is a demand for that amp.

I hate to see amps chopped up but I've done it myself.

[Phil_S]

I have a minor addiction to trolling eBait for things like this. If it actually works, as you determined it did, and sells with tubes, I'd expect it to fetch something north of $100 -- maybe $150 or more on a good day -- and the buyer pays shipping. Shipping will be high because there are two units.

I don't think there is anything holy about units like this. IMHO, they are made to be raided or converted to guitar amps, or possibly reworked or restored for hi-fi stereo use. Consider for just a moment, the conservative eBait value of useful components if you strip it:
4 6V6 tubes, 2 5Y3, one 12AX7 @ $5ea = $35
1 big Stancor PT $30
2 decent OT's $50
Other assorted junque $10
Not sure what is good on the second chassis, tuner, but let's say $25 for everything because it works.
Estimated salvage value $150 give or take a few dollars.

The iron is more than likely good for guitar amps. Tubes, too. If you tried to purchase new equivalent PT and OT, just how much would you pay? I'm going to guess $150 or more for a pair of run of the mill Hammond PT and OT (not that there is anything wrong with Hammond). Then, you still need everything else!

If it were mine, I'd do the conversion right inside that chassis. You are good for a 2x 6V6 amp. Remove the other OT and save it for another project or sell it on eBait. For $100, possibly half that, you can make an amp that would cost you $400 from a scratch kit. You just have to be flexible with layout, which won't be too difficult in that particular chassis. It's a large chassis and making it into a 2x 6V6, you'll end up with plenty of real estate inside. You can have fun making it PTP or you can plant a board in there. Depending on the PT and OT, you might be good for 2x 6L6, too.

[passfan]

That's actually a mono amp Phil with one ot and a choke under the hood.

[Phil_S]

That's actually a mono amp Phil with one ot and a choke under the hood.

Wow! I took the OP at his word, by the title of the thread. That's actually good news. It means you can build it 4x 6v6 or 2x 6L6 with the same iron.

I'd move the choke outside, drill the front for pots/jacks, and put a board between the pots and the power tubes. I think I'd opt for 2x 6L6 and use two of the octal sockets for 6SL7's.

Decent looking generic boards for reasonable prices:
http://www.ebay.com/itm/1-Fiberglass-Tu ... 3cb29d7899
http://www.ebay.com/itm/1-Fiberglass-Tu ... 3a6099bf43
Dirt cheap:
http://www.ebay.com/itm/Terminal-Board- ... 3caf1b89e0
http://www.ebay.com/itm/Terminal-Board- ... 3caf1b8358
My personal favorite, extra dirt cheap, very versatile, Steve at Apex Jr sells them, too:
http://www.ebay.com/itm/2PC-Tag-Board-f ... 3a5e4d2cbf
If you don't want to buy from China:
http://www.ebay.com/itm/LONG-Yellow-Tur ... 5647521b23
Angela seems to be having very good deals on some today:
http://www.ebay.com/sch/angelainstrumen ... m270.l1313

When I get a piece like this, I wait until it inspires me and then I try to build what will fit with it. I like this particular one. It has great potential.

[xtian]

Wow! Thanks a lot, Phil.

[Phil_S]

In case you can't tell, this is the sort of project that really gets me going. Anyone [1] can build any amp in a blank undrilled chassis. This type of stuff is much more fun and is a great mental exercise because it's not cookie cutter simple. I can't wait to see what the OP will do with it!

[1] OK, not anyone, but probably anyone here!

[rdjones]

Magnavox was mostly known for their console HiFis and stereos, which is probably why these are 'bare'.
Fairly common to find these, and especially the later AstroSonic solidstate consoles.
They do seem to sell well on eBay, there're guys out there mounting the chassis' to wood bases for the current fad of tube hifi stuff.

... 2 CBS 5y3wgta black plate rectifiers ... I would like to find out more about the 5y3wgta tubes...

The 5Y3WGTA is electrically the same as other 5Y3s.
It's just undergone the additional level of screening of JAN "war" tubes.
You might think the W tubes would be out of place, but I've seen quite a bit of JAN tubes in '50s consumer gear.

reddog

[Phil_S]

Yeah, they will go for a good price. I'm not quite sure why. Someone has let the secret out? Here's one with two SE EL84, 12 bids, already over $100:
http://www.ebay.com/itm/Vintage-Magnavo ... 2c644ba88f and this isn't anywhere near as nice a piece as the one we're discussing here, except it's stereo.
Here's the same model with a silly wood base like RD mentions, 5 bids, $108. http://www.ebay.com/itm/MAGNAVOX-SE-6BQ ... 19cf407bff
Yet another double SE EL84 unit, tricked out a bit, up to $237 http://www.ebay.com/itm/MAGNAVOX-STEREO ... 231ba8f34d
Maybe I'm wrong about eBait value on the OP's piece...maybe north of $200 or more. People are nuts for this stuff.

[Cliff Schecht]

Phil I agree the prices seem too high, especially on that last one, but it looks REALLY cool. It's really clean and has that tiny chassis. I'd love to get my hands on it for $20 .

[rdjones]

If you're gonna do the "naked chassis" on a wood base thing you need to start with something in real nice shape, or spend a lot of time and effort fixing it up.
Not the kind of thing I normally like to get into.

On a badly rusted Sunn chassis I rebuilt I did a quick touchup job.
I thought it was a bit cheesy but the result was a massive improvement over what I started with.

How much time do you want to spend, wire brushing, acid dipping endbells, masking, and spraying ?
A little bit of effort goes a long way but it's also easy to get sucked into a lot of work.

rd

[Tonegeek]

Oops, I did say "stereo", but it is a hefty mono unit.

I ran it to my 2x12 cab today and it gets pretty loud. I really like the bass response on tube amps. To me, that is where you really get the warmth that you don't get from modern stuff. I don't know what I will do with it just yet. I am tempted to try a point to point thing, keeping all 4 6V6 outputs and maybe adding a VVR. The OT has 2 output taps and had some kind of feedback coming off of both of them. I tried Nostalgia Air for a schematic but they don't have one for this model. I just need to determine what impedances are available on the OT. I measured 5.5 ohms on each 12" speaker so I am thinking in total the amp was driving a 4 ohm load off of the one output. I cleaned up the tubes on the power amp and shock tested them for shorts. They seem good as new. I measured 325V on the plates and 328V on the screens (both the screens and plates come off the same supply node). If I decided to gut this thing, before I do I am going to run a send from one of my other amps into it and see what it sounds like. The output tube bias is weird on this thing. It has all the cathodes connect together by 350 ohm resistors with only the last one in the chain going to ground. There are no bypass caps either. No wonder this thing still works, it was barely idling.

The chassis is labelled "AMP 132 A" if anyone happens to have a schematic.

Thanks for the ideas and links.

[Phil_S]

Phil I agree the prices seem too high, especially on that last one, but it looks REALLY cool. It's really clean and has that tiny chassis. I'd love to get my hands on it for $20 .

I've got an informal limit. Generally around $25 without tubes and $50 with tubes. If I really want it, I might go a bit higher. Those amounts include shipping. You have to be very patient to get them at that price. I bid on stuff almost every week. I probably find/win a couple of them every year.

One time, I got a buggered Sears chassis that had two good old stock USA 6L6GC (Sylvania?), a nice PT, and a Stancor A-3801 !!! IIRC, around $40 for that one. I could see the A-3801 in the picture, but there was no mention of it. You have to look for badly captioned, badly written auctions. The prices for those little SE stereo Maggies is silly.

I just "won" an OT from a Bogen Challenger CHB20A that was running the pentode side of a pair of ECL86, with outputs for 4-8-16 ohms and 25V. Just under $16. It will make a nice guitar amp. I'm thinking maybe a something class A running a pair of Ruskie 6L6 wannabe 6P3C's I've got. Should be around 20W and perfect for it. I'll have to wait for the OT to see what it's actual turns ratio is. I'm guessing it has a 9K or 10K primary. But I diverge.

Sorry. I seem to have hijacked this thread. Didn't mean to. I just have real enthusiasm for recycling used gear.

[Tonegeek]

If you're gonna do the "naked chassis" on a wood base thing you need to start with something in real nice shape, or spend a lot of time and effort fixing it up.
Not the kind of thing I normally like to get into.

On a badly rusted Sunn chassis I rebuilt I did a quick touchup job.
I thought it was a bit cheesy but the result was a massive improvement over what I started with.

How much time do you want to spend, wire brushing, acid dipping endbells, masking, and spraying ?
A little bit of effort goes a long way but it's also easy to get sucked into a lot of work.

rd

I do like my work to look good, especially If lots of money and effort goes into it. This thing is rough, lots of corrosion on the chassis. It would take a good bit of work to really make it look sharp. Wish I had a sand blaster...

I like amps to also be practical, portable and protected, so the naked chassis thing is out. I would not mind a metal cage though as long as I can put a handle on it. Might be up for a combo as I need another speaker cab anyway to run FX. If I was really motivated I might try a combo with the power amp in the bottom and the preamp in the top like the Smith combos.