Old Tube Amplifier, Origin unknown.

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My friend Mike Rivers recently acquired over Ebay an old monaural
audio amplifier using vacuum tubes. But the person selling it
did not know it's origin or have any information on it.

It looks like this (set of 8 photos):


Query: Does anyone here recognize this amp, or have any idea
how to obtain info (such as schematics) on it?

Robbie Hatley
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Re: Old Tube Amplifier, Origin unknown.
Robbie Hatley schrieb:
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Sorry, but obviously only Facebook members can see your photos.



Re: Old Tube Amplifier, Origin unknown.
El martes, 11 de octubre de 2016, 21:23:23 (UTC-3), Robbie Hatley  escribi

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Hi. The booklet shown there https://www.facebook.com/photo.php?fbid10%207
...is a "Sams Photofact", the schematic and some service hints should be th

As an experienced tech let me share my impressions:

This amplifier had good maintenance. APPARENTLY Capacitors (look like orang
e drop style) are not modern, same as small electrolytic capacitors in the  

Technicians attempting to repair this should be aware of dangerous high d.c
. voltages inside the equipment.

Is your friend a technician? Has he tried to power up the equipment, connec
t speakers and an audio source to see what happens?  

Pass him the following info:

Use the XTAL PU input.

Place the slide switch in PU, not mike.

Unless you have a MAGNETIC TYPE pickup turntable you should not use the mag
 input. BTW this is monoaural one channel only not stereo.

The MIC input should be high impedance intended for an old style Crystal Mi
ke, these are hard to see.

A modern dynamic microphone should have high impedance and level (10,000 oh
ms or more) to work properly here. Unbalanced connection. Electret battery  
powered microphones should work as well.

To me it looks like a push-pull amplifier. Output tubes are 6V6.Output shou
ld be around 10 watts. Quality of sound should be well above a common solid
amplifier (provided all components are in working condition)...

Do not attempt to replace the rectifier(5y3) with solid state. DC voltage w
ill be much more higher, may result in electrolytic capacitors exploding or
 leaking, and decreased tube life or faliure.

Re: Old Tube Amplifier, Origin unknown.
El martes, 11 de octubre de 2016, 21:23:23 (UTC-3), Robbie Hatley  escribi

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Let me correct myself, most capacitors look modern in the picture. The exce
ption would be the high voltage aluminium capacitor that filters the B+, it
 looks like original, then it should be replaced. No need to remove, just d
isconnect it from the circuit and install modern axial capacitors... Hope t
hat helps... best regards...

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