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

[mcgreg66]

Hi members,
After infected by the Sansui virus I came across a AU719 in good cosmetic condition but won`t come out of protection........
I checked a lot of things and took measurements but need some help of the professionals to interpretate and how to go on......
- when powering on protection led keeps flashing
- tried to set DC offset - left channel ok! (Incredibly sensitive to adjust!)
- right channel jumping DC; sometimes staying around 0mV then jumping over 40mV
- when trying to adjust DC relay starts trying to engage on and on but doesn`t stay

Checked voltages from the schematic
- PSU alright; all voltages little under schematic but i think ok! Probably different model series!
- drivers; both channels get 55v over pin 10 fine!

BUT now it starts
RIGHT CHANNEL / LEFT CHANNEL
TR16 - jumping 0-0,4v should be -0,55v. / Stable -0,57v!
TR15 - 0,9v falling to 0 going up to 0,9v aso. / Stable 0,63v!
TR14 - 0,03-0,05v should be 1,15v. / Stable 1,17v
R38 - 0- - 30mV should be 1,15v. / Stable 1,22v
So far I went....

The Protector comes after the drivers......
So I have for example 43-47v on pin 18 and 37-44v on the relay coil.
For sure it stays in protection!

Any suggestions!

Many Thanks

Gregor

 

[mcgreg66]

Maybe better to move this to Exclusively Sansui

 

[petehall347]

all pin voltages for power supply . protect circuit and main amp circuit should make it easier . . all in nice lists .

 

[mcgreg66]

Hey Pete,
Thanks for replying!
Here is what we need......

PSU
Pin01 41V
Pin02 40V
Pin03 41V
Pin04 40V
Pin15 32V
Pin16 0
Pin17 -32V
Pin27 -18-18mV
Pin28 -18-18mV

PROTECTOR
Pin09 55V
Pin10 56V
Pin11 -55V
Pin12 -56V
Pin13 0
Pin14 0
Pin18 42-46V
Pin19 0
Pin21 0,02V
Pin22 -0,07V
Pin23 0 but when the relay tries to engage 20V
Pin24 0 “ “ “ 56V

.............DRIVER LEFT / RIGHT
Pin01 0/0
Pin02 0/0
Pin03 0/0
Pin04 56,2/56,5V
Pin05 0,63/-0,08V !!!
Pin06 0,03/-0,06V !!!
Pin07 0,01/-0,06V !!!
Pin08 -0,575/-0,08V!!!
Pin09 -56,2/-56,2V
Pin10 56,2/56,2V
Pin11 0/0
Pin12 -56,3/-56,7
Pin13 20/56V !!!
Pin14 0,2/0,2V

Left and right board have different numeration for Pin14 and 11 but they connect the same !

 

[petehall347]

its looking to me like you need to be changing the fuse resistors on the driver boards .

 

[petehall347]

but then there is this
protect
Pin21 0,02V
Pin22 -0,07V

driver
Pin13 20/56V

maybe errors with your reading ?

 

[petehall347]

right channel has lost base voltages at outputs . pins 5 and 8 should be around +- 600mv
have you been twiddling the bias pots ? vr02

 

[mcgreg66]

Yes it’s mV on Pin13 driver boards
These have direct connection!!!
Pin21 19mV connected to Pin13 17mV left channel
Pin22 -71mV connected to Pin13 60mV right channel

Bias current left channel 23mV
....................right channel no bias/not possible to adjust!!!

I noticed after powered on for a while the relay is ticking like clock and I see it move little but only on left side for left channel....!!!

 

[mcgreg66]

I had a look for fuse resistors.....and there should none in AU719

 

[petehall347]

best sort the right channel first .
check
r36
r42
both 33 ohms

 

[mcgreg66]

R42 33,3ohm
R36 34 ohm

 

[petehall347]

base voltages
tr13
tr14
see if they adjust with vr02

 

[mcgreg66]

TR13 -0,48v
TR14 -0,55v
No adjustment possible with VR02

Left channel is
TR13 1,8v
TR14 -1,8v

Thanks a lot that you go with me......

 

[petehall347]

all voltages BCE
tr10
tr11
tr12

 

[mcgreg66]

Ok....

TR10 B-0,57v C-0,48v E-0,55v
TR11 B 53v C2,5v E53,8v
TR12 B -53,7 C-1,6v E-54v

 

[petehall347]

r29 120 ohms .
but tr10 base also bad .
so first check voltages each side of r36

mmmm .this is odd . tr11 voltages are throwing me off now .

 

[petehall347]

am thinking you got tr10 and tr11 mixed up .

 

[mcgreg66]

Ok I’ll check TR10 and 11 again

R36 is 55v before and after
R29 is 120 Ohm

 

[mcgreg66]

TR10B 53v C2,5v E53,8v
TR11B-0,57v C-0,48v E-0,55v
TR12 B -53,7 C-1,6v E-54v

You’re right I mixed it up
That’s how it is right

 

[petehall347]

r31 56 ohms
check that first