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Thrift store tube amp. Now what ?

jera

jera

Active Member
OK today I was at my local thrift shop and I got this amp/speaker set up. The amp says sears and roebuck (silvertone on all the tubes? ). It has (4)6bq5 tubes (2) 7025 and (1) 5u4gb tube also three speakers.
I haven't plugged it in yet, or tested the tubes.
My question is what in the world can I do with this thing ? Does anyone know about this amp . year ,wpc etc.. and are they worth fixing? Any help would be great. Also if any one knows about the speakers that would be great to thanks .
 

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If nothing else, restore it and use it as a stand alone amp. Looks like a stereo set up, although it may have a common woofer set up. I would look for a model number and post it as well....BTW, don't plug it in until you do a bunch of reading on this forum. Start with the stickies.....
 
jera said:
OK today I was at my local thrift shop and I got this amp/speaker set up. The amp says sears and roebuck (silvertone on all the tubes? ). It has (4)6bq5 tubes (2) 7025 and (1) 5u4gb tube also three speakers.
I haven't plugged it in yet, or tested the tubes.
My question is what in the world can I do with this thing ? Does anyone know about this amp . year ,wpc etc.. and are they worth fixing? Any help would be great. Also if any one knows about the speakers that would be great to thanks .
Click to expand...

Looks like a reasonable little stereo push-pull amplifier. I am sure others will chime in here, but basically, once you know the chassis model, you should be able to get some schematics for this amp.

From there, you'd want to figure out what has to happen to get an audio signal in (possibly through that proprietary 'preamp' input you show), and how to control power on/off (same issue).

Then you'd want to consider a recap of the metal multi-stage can capacitors (although opinions vary on whether or not that is truly needed in every case).

You'd want to try to bring the system online with the use of a variac.

Finally, if there are no other issues, enjoy.

The tubes can be tested, but chances are reasonably high that they're fine so long as they are intact. Yes, tubes go bad, and even just wear out, but not as commonly as people think.

It all starts with getting the schematic and access to a variac, IMHO.
 
It does seem to be laid out as a stereo amp, but only one set of speakers in the cab and a single external speaker tap.

So, ????
 
The Sams Photofact folder is dated 1960 - I'll put it in the queue to scan. The power transformer appears to have a 1959 date code - which agrees. The 528 prefix is Warwick - a contract manufacturer who mainly manufactured for Sears. Should be about 15 WPC. Output transformer look as large as the Magnavox ones, should have decent bass response. Numbers from the speakers may ID them.

You'll probably nee to jumper two pins on the preamp connector to power it on - which should wait until you have checked or replaced the coupling caps.
 
Earlier than mine and otherwise different, mine used the silicon diode doubler supply and differently proportioned OPTs. Dunno if yours also is a cathodyne "concertina" driver like mine or the paraphase used by Magnavox and others.
http://www.audiokarma.org/forums/showthread.php?t=308827
attachment.php
 
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Looks nice. Isn't there a schematic and other information on the paper in the floor of the console where the speakers are still mounted? Four 6bq5s and two opts is surely stereo. Were the speakers connected when you got it?
 
We don't see the back side of the amplifier which probably has the speaker (or single speaker) connections.

The amp and possible tuner/preamp may have been in the single speaker cabinet and the external speaker connection may be for the other channel single speaker cabinet which he doesn't have or it wasn't there at the thrift store.

It is a stereo amplifier!
 
Should be able to make a stereo amp out of it, but it does only have one speaker output in pic. Maybe another on side?

Anyway don't run a tube amp without a load (speakers or a 16 ohm 25W resistors) or you risk the transformers.

The PS caps (can cap and some under the chassis) can take out the PS Trans. if bad or when they suddenly do. Old caps are the risk. The coupling caps can take out mainly the Output Transformers , but also tubes. They can even kill a PS Trans.

Anyway cheap to recap and those small tubes sound great, are in production, and cheap to buy.
 
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C'mon people! It is a stereo amp! whether you can see the connections or not. Two output transformers, 4 output tubes in push/pull duh!

These old tube amps will not fry the output transformers without a speaker load . . . . I have yet to see one in 40 years that got damaged without speakers.
 
Following this thread, this amplifier reminds me of the Magnavox AMP175 and AMP185 that has the left channel external speaker screw terminals.

This is a stereo amplifier, no questions!
 
And if you look also look closely, the yellow & black wires go into the chassis which would externally connect to back connections. If those were the plate connections, you would see 3 wires, two plate connections and a B+ (red) wire.
 
Wow, thanks for all the info. I have quickly figured two things out . Number 1 I'm in way over my head . number 2 I have a lot to learn . I did test the tubes and they are all fine. I have notplugged it in as I lack the proper equipment . I will be looking for someone locally you may be able to test it .
 
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