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

 

Measured from ground it should read .7 volt on the base and close to zero on the collector of Q706 when the relay is activated.
Does the LED blink for several seconds when first powered ON?

 

Im unable to find Q706 anywhere on the schematics... Am I missing something?
I will check about the LED when I get home, I do know the "class a" sign lights up

Measured from ground it should read .7 volt on the base and close to zero on the collector of Q706 when the relay is activated.
Does the LED blink for several seconds when first powered ON?
[/QUOT

 

Im unable to find Q706 anywhere on the schematics... Am I missing something?
I will check about the LED when I get home, I do know the "class a" sign lights up

My bad, was looking at the wrong model amp.
I have the correct one now, will get back soon.

 

To start, connect the negative lead of your meter to pin3,4 or pin7 which should be ground on the SVITA7317 chip.
With the amp OFF place the other lead on pin8.
Turn on the amp, the voltage should rise to appx 1.3 volts in 5 seconds and activate the relay.
See what happens.

 

If you have the schematics of the amp, measure the DC voltage at the amplifier output, not at the speakers.
If the DC voltage exceeds a given threshold, the relay will not be activated. This is a safety feature to prevent blowing your speakers.

 

If you have the schematics of the amp, measure the DC voltage at the amplifier output, not at the speakers.
If the DC voltage exceeds a given threshold, the relay will not be activated. This is a safety feature to prevent blowing your speakers.

Would this mean measuring at the speaker terminals (without speakers attached)?
I have the schematics but am still learning to interpret
I forgot to mention, and I'm unsure if it's important but when I manually close the relay with amp on and speakers connected I get good sound coming through

 

Would this mean measuring at the speaker terminals (without speakers attached)?
I have the schematics but am still learning to interpret
I forgot to mention, and I'm unsure if it's important but when I manually close the relay with amp on and speakers connected I get good sound coming through

No. The purpose of the relay is to connect to the loudspeaker only if it is safe to do so.
You don't need to disconnect the speakers but it would not hurt for you to disconnect them.

You need to take the voltage measurements inside the amplifier at test points TP1 and TP2 as shown for the LEFT channel.
You need to do the same at the RIGHT channel at TP3 and TP4 (all voltages with respect to ground or chassis).

You can get the same information by measuring the voltage on the legs of R349 and R350. Any side of the resistor will do.

 

I will have a look at your data on the SVITA7317P MUTING/RELAY DRIVE later today or tomorrow.

 

I forgot to mention, and I'm unsure if it's important but when I manually close the relay with amp on and speakers connected I get good sound coming through

Have you had a chance to measure the voltages on the chip as I suggested?
It's important to take these readings to start eliminating what's working.

 

To start, connect the negative lead of your meter to pin3,4 or pin7 of the SVITA7317 chip.
With the amp OFF place the other lead on pin8.
Turn on the amp, the voltage should rise to appx 1.3 volts in 5 seconds and activate the relay.
See what happens.

Just tried this, I'm getting 42.7mv DC between pin 3 and 8, both immediately and after 5 seconds. My original measurement on pin 8 of 40v may have been a misreading of the meter by me

No. The purpose of the relay is to connect to the loudspeaker only if it is safe to do so.
You don't need to disconnect the speakers but it would not hurt for you to disconnect them.

You need to take the voltage measurements inside the amplifier at test points TP1 and TP2 as shown for the LEFT channel.
You need to do the same at the RIGHT channel at TP3 and TP4 (all voltages with respect to ground or chassis).

You can get the same information by measuring the voltage on the legs of R349 and R350. Any side of the resistor will do.


View attachment 335743

View attachment 335744

Thank you, I appear to have no, or very little (reading around 1.2mV) on these resistors. (R349 and R350)

 

Just tried this, I'm getting 42.7mv DC between pin 3 and 8, both immediately and after 5 seconds. My original measurement on pin 8 of 40v may have been a misreading of the meter by me




Thank you, I appear to have no, or very little (reading around 1.2mV) on these resistors. (R349 and R350)

I suspect that capacitor C503 on pin 8 is defective/shorted.

EDIT: correct capacitor is C503.

 

By the way, what is your GND reference. Chassis or some where else.

 

I suspect that capacitor C508 on pin 8 is defective.

Would that be C503?
I'm getting a reading of the correctish capacitance of 3.7, it's voltage is reading -42mv

 

By the way, what is your GND reference. Chassis or some where else.

Hey, I've seen you in a few threads about similar issues, amps
Chassis for GND

Would that be C503?
I'm getting a reading of the correctish capacitance of 3.7, it's voltage is reading -42mv

Let me try that again, I had misread your post
Edit: understood, thanks

 

Correct C503 on pin8
What voltage do you read from pin3 to pin9?

 

What voltage to you read from pin3 to pin9?

Seeing -3.13v between pin3 and pin9

 

That should be + 3.13 volts. Are you sure you don't have the meter leads reversed?

 

Over 40m

That should be + 3.13 volts. Are you sure you don't have the meter leads reversed?

Ahh yes I did. 3.1v when leads the other way around. Not something I had thought of, I'm used to taking very rough measurements for my job and just ignoring the - or + on the meter

 

OK. NOW WITH THE AMP OFF read the resistance from pin3 to pin8 please.