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Technics SA600 Relay not engaging.

V

ViciousVinyl

New Member
Hi,

I’ve got a Technics SA-600 that I’m completely stumped on. I used it throughout my college dorm room days and it worked fine but the relay took a long time to engage, usually a minute or so. When I moved out of residence I gave it to my friend and he used it for years but said that it took a long time to warm up, one time I was hanging out with him and it took just under an hour to finally click. I took it back from when the relay no longer engaged and it has sat at my bench since.

I have replaced the capacitors around the relay circuit, I have tested the relay out of circuit and it works fine, I checked the output transistors and none are open or shorted, and I was able successfully bias both channels but nothing has helped. I checked for voltage at the speaker contacts of the relay and get around 10 to 12 mv or so on both channels but I’m not sure if that would cause this.

Any ideas?
 
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I'm just thinking out loud...

Maybe using some CRC electronic cleaner or deoxit on the inside of that relay could help.
I just wonder if that relay has needed some sort of lubrication?

I'm probably way off base though.

I have two sa 600 and then sa-800
 
I have wondered about the voltage supply to that relay myself.
Mine only take about 5 seconds in order to click on.
And I dread the day that it starts taking longer like yours...
Hopefully never.
There are some very good knowledgeable technicians here that will have better answers within a day or two you should know exactly what to do
 
The protection circuit is powered from a -32VDC Zenered supply. Make sure you have -32VDC on the anode of D903. The time delay for the relay is by R904, R905, R914, C903, Q904 and Q905. Check the voltage on the collector of Q904, should be -.8VDC, and check the base of Q905, should be -.75VDC.

Craig
 
Another quick check before the relay energizes are the outputs of the amplifiers, check for DCV on the fuses, F5 and F6.
 
ViciousVinyl said:
speaker contacts of the relay and get around 10 to 12 mv or so on both channels but I’m not sure if that would cause this.
Click to expand...
No issue there.. actually very good.
Have you given the relay a light tap? if it kicks in and holds it's not getting enough to excite it.
You have couple low V rated caps there 6v &16v? I'd replace might as well replace that 33v rated to. ^^as said check the zener diodes.
sm pdf pg. 15 location F-13 shows the circuit. easy to refer to basic voltages.. little luck and have that pup up and running. (however it is 40 yrs old.)
https://www.hifiengine.com/manual_library/technics/sa-600.shtml
 
Binkman said:
No issue there.. actually very good.
Have you given the relay a light tap? if it kicks in and holds it's not getting enough to excite it.
You have couple low V rated caps there 6v &16v? I'd replace might as well replace that 33v rated to. ^^as said check the zener diodes.
sm pdf pg. 15 location F-13 shows the circuit. easy to refer to basic voltages.. little luck and have that pup up and running. (however it is 40 yrs old.)
https://www.hifiengine.com/manual_library/technics/sa-600.shtml
Click to expand...

I have already replaced the capacitors in the relay circuit, even the non-polar one, but no dice. I’ll check the diodes and the voltages at the transistors this weekend.

It’s 40 years old but it’s been a decent sounding amp for me up to this point. Once I get this receiver working it will be going to another friend of mine that is trying to build a record listening setup.
 
llwhtt said:
The protection circuit is powered from a -32VDC Zenered supply. Make sure you have -32VDC on the anode of D903. The time delay for the relay is by R904, R905, R914, C903, Q904 and Q905. Check the voltage on the collector of Q904, should be -.8VDC, and check the base of Q905, should be -.75VDC.

Craig
Click to expand...

While I was testing I remembered I’m missing D902 which I must have removed during my initial troubleshoot years ago and I have no idea where I put it or what to replace it with considering the service manual only has a panasonic part number SVDMZ424B. My best guess would be a 24v zener diode. It probably affects these readings.

I measured the anode of D903 and it is -33v DC

Here is what I found for the transistors:

Q901
E 0v
B 0v
C -27v

Q902
E 0v
B 0v
C -27v

Q903
E 0v
B 0v
C -27v

Q904
E -26v
B -27v
C -33v

Q905
E -27v
B -26.5v
C -53v
 
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