Yamaha CR-240 problems

[wd409]

Ok, before yesterday, the last time I plugged this thing in was a year or more ago. it had alot of hiss in the pots and what not so i set aside, not having time to fool with it.

so yesterday, I picked up the radioshack version of de-oxit and hit each pot with 2 shots each and turned the knobs 30-40 times per.

I then let it sit for 3 hours just to be sure that stuff had dried, and powered it up.

well, it powers up. but no sound. I had observed that the magnetic relay switch wasnt triggering, so this morning I took the plastic cover off of the relay and manually triggered, and got sound on the left channel of my headphones.
(I think I need to hit the headphone jack with de-oxit also, thats probably why the right channel had no sound)


so, popped the bottom cover off to look for broken solder connections and saw none.

any idea's on why the relay isnt triggering on its own? it doesnt move on any speaker selection setting.

note: I havnt tested with my meter yet to see if power is getting to the relay, but there is no apparent damage to the relay so for the time being im assuming that it is not.

the upside to all of this, is while i was manually holding the switch down, there was no static at all

 

[dspear99ca]

I'm sure you have the best of intentions, but I cringe when I read posts like yours about people holding safety devices closed... you are BEGGING to cause more damage or hurt yourself. The relay is there for a reason, and there are far better ways to determine the cause than forcing it closed... if you value your headphones or speakers, that is.

If the relay isn't closing, there are several possible causes:

1. The protection circuit is working properly and there is a DC voltage riding on your output. To test for this set your multimeter for DC volts and check the pins where the signal goes IN to the relay. If there's DC voltage greater than, let's say 100mV, you've got a problem that's not related to the relay. Track down the source of the DC voltage, fix it, then proceed.

2. The protection circuit is not working properly due to a failed / failing relay. Check for proper voltage at the relay coil. If you have proper voltage but the relay isn't closing, replace the relay.

3. The protection circuit is not working properly due to a failed / failing transistor which powers the relay coil. Test as in #2. If you DO NOT have proper voltage, check input voltage to the drive transistor(s) which provide power to the relay coil. If you've got proper supply voltage, pull and test the transistor(s). If it's bad, replace it. If the transistor tests OK, check other components proximate to it in circuit.

4. The protection circuit is not working properly due to a power supply issue. Test as in #3 above. If you do NOT have proper supply voltage to the relay coil activation transistor(s), work backwards and find out where you're losing your power.

My last bit of advice is that 3 hours is NOT enough time for all the liquid to dry up. It's a confined space with zero air flow. I wait overnight. Hell, the thing's been storage for a year, one more day isn't going to kill you.

 

[merrylander]

It is quite possible that the protection circuit is doing its job and the power amp pack for the right channel is toast. Pin 7 of the pack is the output and as dspear99 has noted anything higher than about 100mV is bad news.

 

[wd409]

You listed some very helpful advice here, and I take no offense to any of it.

I did however use crap headphones tho, I have several pair of junky ones that do my initial testing to receivers just incase something I didnt think/know to check goes south in a hurry.

also, I guess I didnt consider that something may have failed on its own, I was pretty sure I did something wrong with the de-oxit stuff and that maybe the speaker selector was just gummed up. (it was my first time, and waiting over night before testing future stuff is definately noted)

anyway, I just got home from my thrift circuit a little while ago and am too tired to work on this thing today, but ill get out the meter and go to work on it in the morning and report back with findings.


on a side note, I got some great finds today

on another note: ill never force a relay again.