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