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Old Tube Amplifier, Origin unknown.

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elektroda.net NewsGroups Forum Index - Electronics Others - Old Tube Amplifier, Origin unknown.

Robbie Hatley
Guest

Wed Oct 12, 2016 6:23 am   



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):

http://tinyurl.com/hexs4za

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


--
Cheers,
Robbie Hatley
Midway City, CA, USA
lonewolf [at] well [dot] com
http://www.well.com/user/lonewolf/
https://www.facebook.com/robbie.hatley

Reinhard Zwirner
Guest

Wed Oct 12, 2016 11:43 pm   



Robbie Hatley schrieb:
Quote:

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):

http://tinyurl.com/hexs4za

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


Sorry, but obviously only Facebook members can see your photos.

Regards

Reinhard

guijarrosoy
Guest

Thu Oct 13, 2016 9:28 am   



El martes, 11 de octubre de 2016, 21:23:23 (UTC-3), Robbie Hatley escribió:
Quote:
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):

http://tinyurl.com/hexs4za

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


--
Cheers,
Robbie Hatley
Midway City, CA, USA
lonewolf [at] well [dot] com
http://www.well.com/user/lonewolf/
https://www.facebook.com/robbie.hatley


Hi. The booklet shown there https://www.facebook.com/photo.php?fbid=10207186437121226&set=a.10207179647791497.1073741865.1291915359&type=3&theater
....is a "Sams Photofact", the schematic and some service hints should be there.

As an experienced tech let me share my impressions:

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

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, connect 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 Mike, these are hard to see.

A modern dynamic microphone should have high impedance and level (10,000 ohms 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 should be around 10 watts. Quality of sound should be well above a common solid state
amplifier (provided all components are in working condition)...

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

guijarrosoy
Guest

Thu Oct 13, 2016 9:47 am   



El martes, 11 de octubre de 2016, 21:23:23 (UTC-3), Robbie Hatley escribió:
Quote:
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):

http://tinyurl.com/hexs4za

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


--
Cheers,
Robbie Hatley
Midway City, CA, USA
lonewolf [at] well [dot] com
http://www.well.com/user/lonewolf/
https://www.facebook.com/robbie.hatley


Let me correct myself, most capacitors look modern in the picture. The exception 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 disconnect it from the circuit and install modern axial capacitors... Hope that helps... best regards...

elektroda.net NewsGroups Forum Index - Electronics Others - Old Tube Amplifier, Origin unknown.

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