Forgot to mention that diode check is a resistance reading with the power OFF.

 

Forgot to mention that diode check is a resistance reading with the power OFF.

Going red lead on cathode black lead on anode reading is 2.6M ohm and reversing leads gives 0.75K ohm for D501 and for D503 gives me 25M ohm and 4M ohm

 

Sounds like D503 is open.
One more check, there should be +12 dc volts on the cathode of D503.

 

Cathode of D503 is giving me 0.97V ac on cathode and 1.5dc on anode it seems

 

I would replace D503 at this point.
Normally for diode checks one lead of the diode should be lifted from the circuit board when testing.

 

I would replace D503 at this point.

Okay, thank you for the help. Will try source a replacement

 

Your welcome.
A 1N4002 or 1N4007 diode should work.
Going OFF LINE now

 

Is the amp board removed from chassis ?

 

Show a picture of your amp. How it is now when you are taking measurements

 

Okay so Q501 has: B: -0.69 C: -1.5 E: -0.69
And Q502 has B: -1.5 C: -6.67 E: -6.67
Or perhaps positive numbers, unsure on meter leads way-aroundness when testing to chassis / GND

When you have time could you recheck those voltages on Q501-502 please. Make sure the negative lead of the meter is grounded.
Also DC voltage readings on capacitors C502 and 504.

 

Hey folks I saw some other threads here about this amp and similar issues and I'm at the end of what I can understand by myself.

I have an SU-V3 with the speaker relay not closing off after power on, however when I manually close the contacts I get good sound on the speakers.

I've been playing around and found the following:
The relay seems to be receiving 40vdc,
And
When I investigate SVITA7317p, I get strange readings that don't match any scenario in the service manual:
1: -0.8v
2: 0v
3: 0v
4: 0v
5: +0.8v
6: -40v
7: 0v
8: -40v
9 -3v
The -40vdc readings seem out of place

I also noted when I accidently bridge legs 4 and 5 on the SVITA7317P, the relay closes, so it doesn't seem like a faulty relay
Any help would be appreciated

Where the service manual you talk about?

 

Here is the Technics SU-V3 service manual.

 

Show a picture of your amp. How it is now when you are taking measurements

Acessesing the board like so, it has an access panel I removed

When you have time could you recheck those voltages on Q501-502 please. Make sure the negative lead of the meter is grounded.
Also DC voltage readings on capacitors C502 and 504.

Will check these after work, thanks

 

check

Acessesing the board like so, it has an access panel I removed
Will check these after work, thanks

Sounds good.

 

check

Sounds good.

Capacitors: C504 has 198mV. C502 has -18mV. This is with amp off, and with amp on:
504 has 1.5v
And 502 has: 0.7v AC. Unable to get DC reading

Q501:
B : 1.5v
E : 1.5v
C : 0.68v

And Q502:
B : 0.68v
E : 0.7v
C: 1.5v

This is all I have time for tonight, but I will be around tomorrow. Thanks again for the help

 

I would replace D503 at this point.
Normally for diode checks one lead of the diode should be lifted from the circuit board when testing.

Will give this a go today

 

Update: with a lot of guidance from sghioto, we found D501 to be shorted. After replacing both D501 and D503, the relay clicks on after 5 seconds as it should
Much thanks team, very happy to have this amp working

 

For the record this is the part of the schematic where the problem was.
D501 was loading down the 9Vac junction of R507 and R506 to appx 0.9Vac.
This also drop the normal 12 vdc at the cathode of D503 to 1.5 vdc

 

Nice Job.