CJ

Fisher TX-1000
« on: March 06, 2019, 06:38:50 PM »
transistor technology ala 1967,

Stereo Master Control Amplifier

never had the lid off,  50 years old, works like a charm,
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html


CJ

Re: Fisher TX-1000
« Reply #1 on: March 06, 2019, 06:41:11 PM »
has the PEC tone chips,  PC508 in this case,
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Fisher TX-1000
« Reply #2 on: March 06, 2019, 06:42:33 PM »
plenty of I/O available,
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Fisher TX-1000
« Reply #3 on: March 06, 2019, 06:47:23 PM »
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,

If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Fisher TX-1000
« Reply #4 on: March 06, 2019, 07:02:51 PM »
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,


If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Fisher TX-1000
« Reply #5 on: March 06, 2019, 07:04:58 PM »
sprayed out the switches, pwr sw still works,

If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Fisher TX-1000
« Reply #6 on: March 06, 2019, 07:09:00 PM »
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,



If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

JohnRoberts

Re: Fisher TX-1000
« Reply #7 on: March 06, 2019, 10:28:32 PM »
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
John Roberts
http://circularscience.com
Tune it, or don't play it...

analogguru

Re: Fisher TX-1000
« Reply #8 on: March 07, 2019, 06:44:00 PM »
I am surprised to see a current feedback in a design of that time.....

...... the bass is wonderful,.....
Hmmm.... even with only a 1200µF output coupling capacitor ?
« Last Edit: March 07, 2019, 06:51:04 PM by analogguru »

CJ

Re: Fisher TX-1000
« Reply #9 on: March 07, 2019, 07:27:24 PM »
not that loud but dip and rich,  probably just Phil Lesh,

caps measure out at about 1600uf, doing a reform to get leakage down,
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html


PRR

Re: Fisher TX-1000
« Reply #10 on: March 07, 2019, 08:58:54 PM »
> 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.

moamps

Re: Fisher TX-1000
« Reply #11 on: March 08, 2019, 04:20:40 AM »
You are provoking  a white smoke by using uninsulated test clips at speakers terminals.

CJ

Re: Fisher TX-1000
« Reply #12 on: March 08, 2019, 03:32:03 PM »
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,
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html


 

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