Fisher TX-1000

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CJ

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transistor technology ala 1967,

Stereo Master Control Amplifier

never had the lid off,  50 years old, works like a charm,
 

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all 4 transistors are good ,

hfe @450 ma about 50 to 54,

crankin some Dave's Picks Grateful Dead San Berdoo 1978 Franklin's Tower, the bass is wonderful,

 

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slight bubble on an output cap but we let it slide for collector value,

first time i have seen Eromet caps used in a US chassis, (W Germany)

cool heat sinks on the drivers,


 

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service manual>

http://www.fisherconsoles.com/non%20console%20manuals/fisher%20tx1000%20beg%2010001.pdf

power amp only shows large voltage swing on one of the E-B junctions of the output transistors, probably due to the nature of the circuit? i hope,



 

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CJ said:
service manual>

http://www.fisherconsoles.com/non%20console%20manuals/fisher%20tx1000%20beg%2010001.pdf

power amp only shows large voltage swing on one of the E-B junctions of the output transistors, probably due to the nature of the circuit? i hope,
Quasi-complementary where they trick  one  NPN to act like a PNP power device with a pnp driver. Generally they must over-compensate those to deal with the extra lag (delay) from the added inversion.

Except for the poor power device technology du jour that is a roughly modern design. I've seen some early solid state amps that looked like a tube design but with transistors dropped in place of the tubes. 

JR
 
> surprised to see a current feedback in a design of that time.....

Fisher was doing Variable Damping in the early 1950s. This is the same thing.

And yes, the bass can be wonderful, for some speakers, for some tracks.
 
You are provoking  a white smoke by using uninsulated test clips at speakers terminals.
 

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good eye!  too lazy to screw down wire leads,

and we pull amp chassis' without taking out the tubes first which is another bad habit,

it is cap output so no danger unless signal is cookin,
 

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