What have I bought? (unknown tube amp)

[DWBH]

So, I saw an ad online about a amp "similar to old tweeds". 2x10" combo, 5 preamp tubes, 1 rectifier, 2 power tubes. For 100€ I said what the heck, and brought it home with me.

It came with:
Philips Miniwatt 12at7
Haltron EF86
Haltron EF86
JJ EC883
JJ EC883

Sovtek 6550WE
Made in Russia (can't identify the brand) 6550C

Mullard GZ34

Speakers are Peerless, models P100FM and D100W (both 8ohm).

There's a cable soldered directly to the board, that in my mind *should* connect to a footswitch of sorts - tremolo (two of the controls don't respond).
4 input jacks.
Seems like two channels, each with Volume and Tone controls.

The cabinet itself does have a homemade feel to it, but the amp's chassis doesn't. It's finished in some kind of green/blue hammerite paint.

Here are some pics:
https://dl.dropboxusercontent.com/u/154 ... 47%201.jpg
https://dl.dropboxusercontent.com/u/154 ... 17%201.jpg
https://dl.dropboxusercontent.com/u/154 ... 25%201.jpg
https://dl.dropboxusercontent.com/u/154 ... 48%201.jpg
https://dl.dropboxusercontent.com/u/154 ... 41%201.jpg

It does work. Second channel has low output and lots of hiss, but channel one gets loud (not crazy loud though) when maxed. It stays mostly clean.

What I do not know is whether the installed tubes are the correct ones, or if someone just shoved them in there, provided they fit the sockets.

It's european for sure. American (old) amps are very rare around these parts.
Construction wise it kinda reminds me of Vox's amps.

Does any one recognize any of this? What old tube amp manufacturers should I be investigating?

[Structo]

It's european for sure. American (old) amps are very rare around these parts.
Construction wise it kinda reminds me of Vox's amps.

Where are you located?

Looks Soviet to me but it could be of another origin, early to late 50's.

[DWBH]

Portugal

[Structo]

obrigado

[jazbo8]

Portugal

Not bad for 100 quids, where did you see the ad if I may ask?

[DWBH]

Olx.pt

Anyone here know any german tube amp forum?
It's probably european, has "Made in Germany" in many of the components. So maybe it's German, right?

And also, I see 7 wires coming from the OT's secondary. Does this make any sense?

[Kagliostro]

The OT looks like a Geloso Output Transformer

[img:529:356]http://www.qsl.net/i0jx/215.jpg[/img]

Usually those Geloso OT has a lot of output impedances

http://el34world.com/Forum/index.php?ac ... tach=21922

http://el34world.com/Forum/index.php?ac ... tach=21924

K

[LeeMo]

I can't help with the pedigree on this one. However , I would love to have some of those knobs and numeric rings. I also dig the "Whoville Twist" on the cap (I guess that's what it is).
I did notice a cap that had "Dublier" on it. French?

LeeMo

[Cliff Schecht]

I can't help with the pedigree on this one. However , I would love to have some of those knobs and numeric rings. I also dig the "Whoville Twist" on the cap (I guess that's what it is).
I did notice a cap that had "Dublier" on it. French?

LeeMo

Cornell Dublier is an american cap manufacturer and would certainly be a period correct part in an amp like this. The Pinex caps I have not seen before or don't recognize them if I do, but they look similar to Fender's brown turds which IMO are not bad caps (also made by Cornell Dublier, coincidentally).

The parts in there date you to the early 50's (just a guess without seeing date codes) but the maker and/or country of manufacture is probably indeterminable. Sort of looks like a kit build to me, the power transformer cutout fits the PT perfectly but the solder joints on there aren't so great. But then the solder joints to the sockets and terminal strips look very old and untouched. Maybe the PT/OT was retrofitted later. Not sure on this one right off the bat. Do the date codes on everything line up decently well?

As far as which tubes go where, a bit of time with the socket pinouts and pen/paper can usually tell you if you're working with the right tube. The fact that it makes sound is a good thing, meaning you probably already have the right tubes in there. I'm betting your weak channel is a bad resistor, cap or a poor tube socket connection.

I'm betting a good few of those really old carbon comps are way out of spec. Easy to check and change out. The caps are a little tricker to check without pulling them out of the circuit but a lot of times they can be tested easily in-circu with little to no modification. I'd change all of the can caps over to regular axial-lead capacitors and simply clip the can caps out of the circuit, that way you still get the cool look they add but you have fresh e-caps which eliminates a big variable in your troubleshooting.

[eniam rognab]

i just want the power transformer, now THAT is sexy and cool, super jealous up here hahaha

[jazbo8]

I believe the amp is from Germany circa 50's, a very unique amp! If I was to restore one - I woud get rid of the JJ ECC833s, and replace them with vintage ECC83s, ditto for the output tubes with EL156s? Don't think they use 6550 in Germany back then... Have fun with this great find.

Here are some tibits on the "dogbone" resistors used through out the amplifier, bold letters are my doing...

The dogbone resitors were already obsolete by 1939, but that didn't stop some manufacturers (Zenith and GE, to name a couple) from using up old stock. They even occasionally turn up in 1946 radios, as companies scrambled to crank them out.

There evidently was a resistor shortage in the early 1950s, and some companies used up old stock or turned to foreign suppliers. I can remember seeing German resistors in some 1951-52 Delco car radios, and dogbone resistors in a couple of TV sets from the same era.

_________________
Tim KA3JRT

from Antique Radio Forum

[Cliff Schecht]

That power transformer really reminds me of stuff one sees in AM radios from the late 40's. Ditto for the output transformer. With the 315-0-315 secondary voltages and relative size of the PT, I'm guessing these transformers at one time powered a beautiful pair of Telefunken EL84's (if it was made in Germany, I'm inclined to agree because of the caps in there). Looks like it was hacked on at one point albeit lightly to convert it into a guitar amp (maybe it came out of a Hammond type deal?).

I'm not a fan of dogbone resistors in the power supply chain, they typically fail literally by cracking after enough years of heating/cooling cycles. Ceramic resistors even nowadays do this if not properly rated and given enough airflow, but I still never like to rely on old dogbone resistors for things like the dropping string or cathode resistor for the power tubes.

[jazbo8]

I'm guessing these transformers at one time powered a beautiful pair of Telefunken EL84's (if it was made in Germany, I'm inclined to agree because of the caps in there).

Don't think it had EL84s, since the 6550s use octal sockets... My eariler suggestion of EL156s aren't right either, since they require special socketes. May be just plain old EL34s? We need a German guitar amp/tube history buff to help us decipher this thing!

[DWBH]

Just a newbish question, which resistors are those 'dogbone'?
Those big, plastic ones? (black and green?)

[jazbo8]

Just a newbish question, which resistors are those 'dogbone'?
Those big, plastic ones? (black and green?)

All the red ones, they have ceramic bodies. The green and black ones are as well, just higher power ratings.