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Sony TC-580 help

With r727 unsoldered at one end and power on I got "0" with switch open and 22vdc with it closed at the violet wire.
The voltage on both ends of the lifted r727 was just a few mv.
the resistance across r737 was OL.
James
 
Now, can you check the voltage at where the violet wire goes into the ESP board (where you lifted the lead of R727 with the switch unpressed and pressed?
*** Also, measure the voltage at the circuit trace right where you unsoldered the lead to R727.
 
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That's good. So why is it that when you have R727 installed you measure 0v at the same place.
  • R727 should isolate it from the 0v on the base of Q706
  • R727 has the correct resistance and is not open or shorted
Turn off power and solder R727 back in place. Turn power back on, then measure the voltage where the violet wire attaches to the ESP board.
Also, measure the voltage from black lead on ground to each side of R727.
 
Yes.
So, you measured 0v on both sides of R727... that means that no current is flowing through the resistor. Current flowing through a resistor + resistance value = voltage drop.
Do you have some jumper wires available?

Just to check... you are pressing/unpressing the play reverse button (<), S616 while checking these voltages, correct?
*** And the brown wire on the Play Rev switch stays at 22v whether the switch is open or closed... correct?

Do you have a capacitor solder to the back side of your board like this (pink circle)?
Can you try to unsolder one wire of the cap (arrow) (make note where it was soldered) then measure the voltage on at the violet wire again with < button unpressed/pressed?

Screenshot 2025-08-19 142855.png
 
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I was not pressing the reverse play button while making the measurements.
With it pressed I have 22 vdc at the violent wire on the ESP board and .6 vfc on the other side of r727.
For some reason the reels are no
 
Sorry, I accidently sent this incomplete.
If I release the play button after pressing it I get no voltage on the ESP board on either side of the resistor.
 
Tennangler said:
black probe on chassis ground.
violet wire in reverse, a few mv, basically 0
press forward play. violet wire is no change. the R2R does not come out of reverse play.
blue wire in reverse. 0vdc
blue wire holding forward play down 22vdc
Click to expand...
Wait a second. Here is what you previously said in post #58.
Violet wire was basically 0v whether pressed or not. Now it sounds like when you press the rev button you get 22v on the violet wire?
 
Sorry this is taking so long. What would take minutes on the bench takes hours going back and forth. Keep up the good work.
 
dankik,
Yes, it is 22vdc if I press the reverse play and continue to hold it down. If I release the button it is playing in reverse and the voltage goes to zero. Sorry for the confusion. Thanks for hanging in there with me.
James
 
I disconnected the forward/reverse solenoid reasoning it could not go in reverse. when I turned it on the forward light stayed on and the solenoid did not move. However it it still played in reverse when I pushed the forward play button.
The ff also went to fast reverse.
Is this a clue what may be making it reverse?
Thanks
James
 
rojoknox said:
Greetings from RojoLand!

You're probably looking at something on the ESP control board. The AUTO REV switch (actually two switches) should be throughly cleaned as well.

This is a fairly complex deck, and I would not be trying to make it into a forward-play-only rig unless you are a glutton for punishment. Consider, too, that certain parts have long been unobtainium except for scrounging from donor decks. For example, my TC-730 had a broken slide switch (there are four of them in this deck), and it took YEARS for me to finally find a donor board. The switch went NLA from Sony back in the early 1980s.

Take care,
—
J. E. Knox "The Victor Freak"
Click to expand...
I got the last 3 slide switches from Sony in 1981 for the TC-780. That ESP control board is where I'd begin troubleshooting. The unit I was servicing had 3 defective switches. This is a complex deck to repair. They took 4 months to get. A bear of a deck to repair, very complex machine.
 
It's been a week since I looked at this, so we need check a few things. The voltages going to the collector of Q711, Q710, Q709 (0v) are OK for fwd.
Were those previously measured in play, or stop? If that was in play, then somewhere it is not getting the 24v for reverse on R737.
  1. Measure the ECB voltages for Q707, when play is momentarily pressed and when you hold it down
  2. Measure the ECB voltages for Q711, same conditions as above
  3. Measure the ECB voltages for Q713, same conditions as above
Screenshot 2025-08-25 182408.png
 
dankik,
all measurements are in reverse play

q709. collector 280mv pressed or held
q710. 0. 0
q711. 0. 0

q707. e 0, c. 0, b. .6v
q711. e. 0, c. 0, b. .6v
q713. e. 0, c. 0, b. .7v
same readings in pressed or held
 
Still not conclusive. How about taking the ECB voltages of a couple of more transistors?
Q705, Q706, Q707, Q708

Screenshot 2025-08-27 075710.png
 
dankik
all measured in reverse play in e,c b order

q705. 0. 225mv. 0. pressed
0. 225mv. 0. held

q706. 0. 0. .5v. pressed
0. 0. .5v. held

q707. 0. 0. .6v. pressed
0. 0. .6v. held

q708. 0. 0. 0. pressed
0. 0. .6v. held

James
 
Odd voltages... they seem to show that you are in reverse play (except Q707(B) which is in fwd mode. Can you measure the voltages on both sides of these resistors (with black lead on chassis ground)?
R718, R723, R725
 
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