Mitsubishi receiver relay slow to turn on

[Montycat]

I was testing a Mitsubishi DA-R11 receiver today and at first it didn't seem to work.However after a few minutes of prodding and contact cleaning it would turn on. The relay was just taking a long time to trip.

I turned it on and off a number of times and would sometimes trip in a few seconds, but often take quite a few more. Once on it would stay on and everything seems to work pretty well with no obvious issues other than that.

Would this be caused by old capacitors being slow to charge or something? The relay is in the power supply area (with 2 10,000uf caps in it) of course and adjacent to and IC marked "protector" in the schematic.

http://www.hifiengine.com/manual_library/mitsubishi/da-r11.shtml

 

[GUNN]

I was testing a Mitsubishi DA-R11 receiver today and at first it didn't seem to work.However after a few minutes of prodding and contact cleaning it would turn on. The relay was just taking a long time to trip.

I turned it on and off a number of times and would sometimes trip in a few seconds, but often take quite a few more. Once on it would stay on and everything seems to work pretty well with no obvious issues other than that.

Would this be caused by old capacitors being slow to charge or something? The relay is in the power supply area (with 2 10,000uf caps in it) of course and adjacent to and IC marked "protector" in the schematic.

http://www.hifiengine.com/manual_library/mitsubishi/da-r11.shtml

Does sound like those two caps and if not the capacitors around ic701.

 

[JURB]

Highly highly highly suspect R706. Also a possibility of leakage in C706.

Those high value resistors go open, most likely because of their construction. They also increase in value. They also do it intermittently.

Then C706 could be intermittently leaky, which could cause the same thing. They're only running 5.4 volts on a 16 volt unit which would make one think that leakage or shorts would not be a problem but that is not true. Look at all the 6.3 volt jobs that went leaky when there was only like a volt max across them. It just happens to certain types of caps.

 

[Montycat]

Highly highly highly suspect R706. Also a possibility of leakage in C706.

Those high value resistors go open, most likely because of their construction. They also increase in value. They also do it intermittently.

Then C706 could be intermittently leaky, which could cause the same thing. They're only running 5.4 volts on a 16 volt unit which would make one think that leakage or shorts would not be a problem but that is not true. Look at all the 6.3 volt jobs that went leaky when there was only like a volt max across them. It just happens to certain types of caps.

I'll replace those and see how it goes before doing the main PS caps. Thanks!

 

[JURB]

You could just measure the voltage at C706 and if it is not getting up, disconnect it. That will make the relay fire up immediately on turnon if R706 is good. Alternately, you could throw a 270K across R706 to see if it is open. But if C706 is just slightly leaky you get a wrong indication.