Relay not switching on in Marantz SR 8010 DC - voltage problem.

[Dawid Ratal]

Hello,

I have a problem with the relay. I replaced the power amplifiers and the famous STK3082 with the old NTC1339 (correct replacement). Well, I don't know if the diagram accurately reflects the receiver I have. I use the SR 8000 DC service manual. But I noticed that the voltage on the relay coil is 14.5V. The voltage that enters the board for the relay is 30V. According to the diagram, the emitter voltage of Q711 should be 1V, I have 14.5. Voltage on Q710 - base: 14V, collector: 14.7V emitter: 14.7V. I replaced the transistors with 2SC1400 (Q710) with KSC1845. I don't know if there is any logic in this receiver. Does the diagram differ from SR8010? I don't know where to look for the cause. The relay is TYPE MU2U 24VDC

Marantz SR 8010 DC - I use this service manual.

Relay board.




Power Supply Board. The voltage on pin J814 is the voltage to the relay.



diagram

Where would you look for the cause? I would be grateful for your help.

Best!
David

 

[Steven Tate]

Sorry, I'm really not familiar with these later models. But in general, if a relay is not closing, the first thing to do is be sure you don't have an amp putting out high DC. You normally measure that at the speaker terminals, but if the relay has not closed, you can't measure it there. So you have to find the input points at the relay where the outputs of the amps enter the relay,, and measure DC there. If it is a direct coupled amp design you should have less than 50 mV at those points - hopefully less than 10 mV. If the relay is not closing, the protect circuit may be working, and preventing the relay closure due to high DC from an amp. If that is the case, you have to track down what is wrong with the amp putting out the high DC.

 

[LBPete]

I no experience with this model but @Steven Tate's advice is correct. The relay's purpose is to protect the speakers from being exposed to excessive DC voltage. Looking at the schematic for the P700 board you will see two coils L701 and L702. Each of these coils have a resistor in parallel, R705 and R706. Measure the DC voltage at each of these pairs and chassis ground. The voltage should be very low. If it's over roughly 200mV, you have an amp problem.

If you have not already done so, build a Dim Bulb Tester and power the receiver through it while you are testing.

- Pete

 

[Dawid Ratal]

Hello, I wanted to thank you very much for your support and knowledge. What you wrote is clear to me and of course I checked it at the very beginning. Today, however, I managed to find the cause. It turned out to be a micro crack on the final power board of the transistors. One of the paths reduced the voltage from 30V to 14.5V. A simple thing and so many problems. The Marantz is now adjusted and playing.

Thank you again for your tips.
Best!
David