Sansui AU719 protection relay repair....please help!

[mcgreg66]

R17 is 811Ohm
But C16 is 415 dropping under 400

You think TR10 is ok?

 

[mcgreg66]

Goes down to 380uF

 

[petehall347]

try a new cap

 

[mcgreg66]

Hey Pete,
Installed a new C16 470uf cap.....(from local store / just right within tolerance 415uf)
Tried to set DC and Bias
Right channel DC semms to be more stable but still incredibly hard to adjust and then jumping over 40mV
Still no bias !
Relay starts clicking after powered on for 5-10min but doesn’t stay engaged.

Thanks
Gregor

 

[petehall347]

the trimmer may need replacing for a new one

 

[mcgreg66]

I just wanted to say....
.....maybe the trim pot is bad.
I gave a little tunerspray ......and there is correct bias.
DC still hard to adjust and fluctuating, but only a few mV and nearly within spec.
But relay only clicking.......

 

[petehall347]

get tr603 voltages .protect circuit .

 

[mcgreg66]

TR603
E 0v
C 38,8v
B 0,47-0,6v

 

[petehall347]

so the base is shifting around ?
suggest changing c603 .
but before that lets see all pin voltages of protect circuit first to see if something amiss there .
tr603 cant be ruled out yet .
i seem to remember c601 causing this problem a long time back .

 

[mcgreg66]

Yes Base TR603 is shifting around 0,47-0,6v

Pin voltages F-3101
01 -80-+80mv
02 -80-+80mv
03 -80-+80mv
04 -80-+80mv
06 -90-+90mv
07 -90-+90mv
08 -90-+90mv
09 +55,5v
10 +56v
11 -55,5v
12 -56v
13 0
14 0
15 +32,5v
16 0
17 -32,5v
18 +42-44,5v
19 0
21 +3-7mv
22 -12mv
23 0
24 0
25 14-28v
26 14-28v
27 0
28 0

 

[mcgreg66]

I ordered a few KSA945C and will change TR601 and 603

 

[mcgreg66]

Hi Pete,
Still need you advice!
I changed TR601 + TR603 and c603
......but still protection mode.

 

[petehall347]

tr603 base ?
tr602 collector
are those steady voltages now ?

 

[mcgreg66]

TR603
E 0
C 32,5-38v
B 560-600mV

TR602
E 0
C 6,5v
B jumping -20-120mV

But even again no bias at right channel!
I’ll wait for the trim pots and change them first!
If the channels are not stable it makes no sense to work on the protector! Right?!

 

[petehall347]

try lifting one end of d606 and see what happens .. just want to rule something out . also check all soldered joints .
there is a chance of zd601 being bad .

 

[mcgreg66]

Lifted anode of d606 and powered on ..... still protection!

 

[petehall347]

am thinking change the other capacitors and then see

 

[Hyperion]

This

18 +42-44,5v

Should be 1.6V

And this

25 14-28v
26 14-28v

Should be ~3.7V

Should be investigated I think.

 

[mcgreg66]

I’m expecting a mouser order with all electrolytic caps and known citical parts within the next days.
For example the big 470uf on PSU/protector board look bad become of infamous Sansui glue.
Maybe they are leaking !

Hi John,
Yes that’s way too much.....
25 + 26 going to led 01
18 to head amp
What do you suggest to do?

 

[Hyperion]

What do you suggest to do?

Check the readings.