Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Tubes and Hybrids => Topic started by: Bajaguy on July 30, 2013, 05:27:05 PM

Title: Another cool but dangerous antique
Post by: Bajaguy on July 30, 2013, 05:27:05 PM
Last night I went to a local swap meet and poked around for a couple of hours. I ran across a guy that had a couple of old guitars on his table, and after talking to him for a bit was given this old tube amp. Yea, it's one of the old line voltage man killers everyone talks about (series chained heaters, hot chassis, no transformers of any kind, etc.). I tried looking it up and found no reference to it at all on the web. It's in poor shape, more than likely not worth anything, and free (still my favorite part of any amp project :tu:)

 The two drivers are 50EH5 and for some reason somebody stuck an EL84 in where the preamp goes.... The good thing is all of the tubes tested good :dbtu:

 I'm still trying to decide what I want to do with it, mabey a hybrid with a couple of 12ax7's and a nice 15 to 20 watts of chipamp goodness......

 Just thought you'd enjoy the pictures!

(http://i210.photobucket.com/albums/bb79/TheJester357/2013-07-23_07-21-22_976_zpsbd6de162.jpg) (http://s210.photobucket.com/user/TheJester357/media/2013-07-23_07-21-22_976_zpsbd6de162.jpg.html)

(http://i210.photobucket.com/albums/bb79/TheJester357/2013-07-23_07-20-27_39_zps9fae98c4.jpg) (http://s210.photobucket.com/user/TheJester357/media/2013-07-23_07-20-27_39_zps9fae98c4.jpg.html)

(http://i210.photobucket.com/albums/bb79/TheJester357/2013-07-23_07-22-10_505_zps0229ac3d.jpg) (http://s210.photobucket.com/user/TheJester357/media/2013-07-23_07-22-10_505_zps0229ac3d.jpg.html)

(http://i210.photobucket.com/albums/bb79/TheJester357/2013-07-23_07-23-02_635_zps1dc6b7d1.jpg) (http://s210.photobucket.com/user/TheJester357/media/2013-07-23_07-23-02_635_zps1dc6b7d1.jpg.html)

(http://i210.photobucket.com/albums/bb79/TheJester357/2013-07-23_07-23-36_133_zpsf8d8f3a1.jpg) (http://s210.photobucket.com/user/TheJester357/media/2013-07-23_07-23-36_133_zpsf8d8f3a1.jpg.html)

 Baja
Title: Re: Another cool but dangerous antique
Post by: QReuCk on July 31, 2013, 08:53:23 AM
Found this on the interweb:
http://www.guitar-museum.com/guitar-39483-VINTAGE-TEISCO-AUDITION-GUITAR-AMP-BATTERY-OPERATED (http://www.guitar-museum.com/guitar-39483-VINTAGE-TEISCO-AUDITION-GUITAR-AMP-BATTERY-OPERATED)

Looks like Audition is/was a local brand of Teisco. Maybe a good start for your searches.
Title: Re: Another cool but dangerous antique
Post by: Roly on July 31, 2013, 07:45:05 PM
Free is my favorite price - I do most of my "shopping" down at the local tip.

You have nowhere to go but up, any and everything you do to this will be pure profit.  Shop around and see if you can find a suitable isolation tranny to fit.

Somebody has obviously already spent some time re-capping this one, but they were starting at the wrong end - the front panel should be marked "Off, On/Incinerate".   :trouble

I'm a bit dubious about that speaker, but we'll see how it goes after you render it harmless.

I dunno, maybe it's because I've spent my whole life dealing with 240/415 volt mains, but these live chassis jobbies give me the leaping willies.   :duh

Well spotted @QReuCk, but I wonder if he meant two sixty volt batteries.  ;)
Title: Re: Another cool but dangerous antique
Post by: Bajaguy on August 01, 2013, 12:43:07 PM

Somebody has obviously already spent some time re-capping this one, but they were starting at the wrong end - the front panel should be marked "Off, On/Incinerate".   :trouble

 No kidding there! I've been looking through a couple of old schematics on some of the tube radio sites trying to get a few ideas on which direction to go. There's some really good single end schematics for the 50EH5's, but I've been looking around for a push pull for them and nobody seems to have anything close.

 Maybe it's destined for a TDA2003 with a good preamp. Ya think anyone would look inside to see if it is still a tube amp :duh

 Baja
Title: Re: Another cool but dangerous antique
Post by: J M Fahey on August 01, 2013, 08:58:40 PM
Short ago I read a post by a guy who stuffed a Crate Powerblock (literally the size and weight of a brick) inside the carcass of an *old* (think a Silvertone from the 50's or similar) worn cabinet and fitted a generic 12" Eminence made "pull" .
Everybody and his brother later congratulated him om his killer vintage tone. :lmao:
Title: Re: Another cool but dangerous antique
Post by: Roly on August 02, 2013, 11:38:21 AM
First you render it safe with an isolation tranny,   :trouble
then you get it working properly as a single-ended,
then you take Berlin ... (maybe)

Once made safe, see how it goes as a S.E.er and you might be satisfied with the tone and power.

If not, plan AB1...   8)
Title: Re: Another cool but dangerous antique
Post by: Bajaguy on August 02, 2013, 03:33:13 PM
Yea, it seems kind of a shame not to at least fire it back up and put those 50EH5's to work before I do something different. I pulled a couple of single ended schematics from various spots on the web, so I'll find a PT that will work and see if I can make something happen.

 Baja
Title: Re: Another cool but dangerous antique
Post by: Jack1962 on August 12, 2013, 07:01:57 AM
I am unable to view the pictures you posted , which Teisco Audition is this , several where made?
Title: Re: Another cool but dangerous antique
Post by: JHow on August 12, 2013, 04:02:57 PM
What are the tubes on this? I heard you say 50EH5, some kind of preamp (not EL 84), but what about rectifier?  Solid state? 35Z4?
Title: Re: Another cool but dangerous antique
Post by: Roly on August 13, 2013, 10:18:11 AM
Appears to use three 7-pin valves and a single silicon diode for the HT rectifier.

Typical application;
(http://diyaudioprojects.com/Tubes/50EH5/50EH5-Single-Ended-Tube-Amplifier-Schematic.png)
Title: Re: Another cool but dangerous antique
Post by: Bajaguy on August 16, 2013, 10:35:46 AM
I haven't been able to find any information on this amplifier anywhere. Looking through the web has been a bust, and even my local tube guru was stumped with this one. I'd be happy to take some more gut shots if anyone would like to see anything else, just let me know.

 Baja
Title: Re: Another cool but dangerous antique
Post by: JHow on August 17, 2013, 02:02:21 PM
I think this one you will have to make your own schematic.  It is only three tubes, however.  I have seen magnavox record players that had 12ax7 and 50eh5 and AC power, but I think those were stereo.  It does look you have dual volume control in there, but it is hard for me to get the whole circuit looking at fuzzy pictures.
Title: Re: Another cool but dangerous antique
Post by: Bajaguy on August 19, 2013, 05:48:55 PM
Yea, that's the problem with cell pictures, it's just not a camera. I'll try to take some better pictures of the setup it currently has and add a few values here and there.

 Baja
Title: Re: Another cool but dangerous antique
Post by: Bajaguy on April 22, 2014, 07:06:13 PM
I got some time to play with this last weekend, and did some sketching on the schematic. AFter doing some research on the web, I have a couple of questions before I procede to dump some time and money into this. It seems that the 50EH5 is not a great little tube, and most of what I found while poking around was suggestions to replace it with something bigger and revamp the amp rather than buying an isolation transformer and keeping it in fairly stock trim. There was alot of people that complained about these amps being horrible hum monsters, and after seeing what I've got in the guts of this little guy I can see what they are talking about. Lead dress is horrible at best, and the fact that it was half wave rectified makes me wonder if it's even worth bothering with.

 I know there's a bunch of guys on here that know tubes and have probably played with these enough to offer a solid opinion on this, so I'd really love some feedback on this before I procede any further.

 Thanks ahead,

 Baja
Title: Re: Another cool but dangerous antique
Post by: Roly on April 23, 2014, 11:15:22 AM
It came for free and owes you nothing.

Me?  Well it's a case and chassis, and it's no secret I think it was a horror the day it escaped from the factory, so I'd strip it and build a proper amp on it, one with a power tranny.  You could do worse than a "Lamington (http://www.ozvalveamps.org/ava100/ava101lamington.htm)".
Title: Re: Another cool but dangerous antique
Post by: Bajaguy on April 23, 2014, 04:51:49 PM
That's a hell of a cool link! I'm thinking that could fit the bill nicely for this amp.....


 Thanks Roly!

 Baja
Title: Re: Another cool but dangerous antique
Post by: smackoj on April 28, 2014, 10:17:04 PM
I second the scrap and build a better outhouse suggestion. Those amps don't seem to make good tone for guitar so I think other ideas would be time better spent. Just one man's opinion mind you.

 :loco
Title: Re: Another cool but dangerous antique
Post by: Roly on April 29, 2014, 11:21:04 AM
It was a crock the day some accountant "designed" it, and the only way from here is up.  Jack up the doorhandles and put a new car in between.

The case seems okay, but a total internal transplant into a nice little 15W boo-teek amp with efficient 12-inch speaker would transform it into something worth owning and taking to a gig.

The only place for a restoration to original is safely in a locked glass case.

The "Lamington" isn't so much a design as a state of mind.  What have you got/can get, how much imagination can you bring to scrounging the hardware?

The original, and a couple of variants;
(http://www.ozvalveamps.org/ava100/ava101lamington/ava100-1top256x192x8.jpg)

(http://www.ozvalveamps.org/ava100/ava100harp/harp-amp-chassis-back-cmhp.jpg)

(http://www.ozvalveamps.org/ava100/ava104ac30/ava104ac30_0461-eb-.jpg)

http://www.ozvalveamps.org/ava100/ava100project.htm (http://www.ozvalveamps.org/ava100/ava100project.htm)