Yamaha CR-620, slight click on turn on

punkzter

Brad
I've read mostly posts about units that pop when turned off. My unit has a click, heard through he speakers, that happens when the relay clicks.

It's not terribly loud, but the receiver is a gift, and I want to make sure it's working correctly before giving it away.

The previous owner did replace the lights with leds. I'm assuming that he did everything correctly there, as they seem to work. Would it be worth removing the leds and replacing them with bulbs from dwojo?

I've already cleaned the volume, balance, and tone control knobs. I adjusted the idling current per the instructions in the service manual.

Thanks!
 
Do you have a DVM? With the speakers disconnected, measure the output (DC) when you turn it on. It might have some offset. Probably nothing to be concerned about, but it would be interesting to know the number. I can compare it with mine. The LEDs shouldn't be an issue and I'd leave them alone.
 
Okay. I'll do that tonight. Thanks!

Out of curiosity, what is a "bad" number?
 
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Don't know exactly but I'd guess an offset of 50-100 mV could result in a slight click. I don't think that unit has an offset adjustment, only bias.
 
Okay. The Left channel jumps to between 50 and 80 mV when the relay clicks. The right is around 30mV.

Both channels quickly drop to 16 mV (right) and 12 mV (left) after a few minutes.
 
Some of these CR-xxx and x models will "pop/click" at power off if the incandescent lamps are burnt out (open). So the LED conversion might be your culprit.
 
I had read that. The click I'm hearing only occurs when it turns on. From what I can tell, and I can double check, the leds work.

If I go the route of ordering replacements, I probably need to do it ASAP, since this has to be done by Christmas. I just wanted to get some insight before I go making changes that could potentially make a problem worse. (I just never know when you open something up).
 
FWIW, I just turned mine on in a very quiet room, with the volume all the way down. All my dial and meter lights are burned out (too lazy to fix 'em). No perceptible click at all, other than the noise of the relay itself. Offset is about zero on one channel and less than 2 mV on the other, with speakers connected. Now, I don't know if yours has an issue or not. A very slight click is probably nothing to worry about. Getting LEDs to shine right on that model is a bit of a pain, so I'd be hesitant to undo the job. Mine did have a couple noisy small signal transistors, so if you hear any irregular staticy hiss, it probably could use some attention. Mine was also a bit unpleasant on FM, but after alignment it's the sweetest receiver a person could ask for.
 
Okay. The Left channel jumps to between 50 and 80 mV when the relay clicks. The right is around 30mV.

Both channels quickly drop to 16 mV (right) and 12 mV (left) after a few minutes.

How much of a delay between pressing the power switch and the protect relay click ?
 
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It's about 2 seconds.

I did decide to go ahead and order the replacement bulbs. If nothing else, I wanted to use them as a learning experience.
 
Two possibilities, maybe more. Replacement of the differential pair in the amplifiers front end of the noisy channel. TR 701 and 703 or TR702 and 704*. With a closely matched (Hfe) pair of 2SA872's , I believe.512-KSA992FBU's from Mouser. Might take 20 or more to find a pair.The higher and closer they are, the better.

http://www.mouser.com/ProductDetail...fvC%2bRqNykF8u%2brmiyNQ3/hY0T80qijeRftj489w==
Could be noisy relay contacts or speaker select switch contacts.
 
I don't have a tool to measure Hfe. I've been looking at the MK-168, as a way to test transistors. Do you have any experience with that unit? I can order it, but I doubt it will arrive in time. The other option would be the Peak DCA55 tester. It's twice as expensive, so it would need to be worth it. The other plus of the MK-168 is it's ability to test low value caps.

What would happen if I install replacements that are not closely matched.

The new bulbs are ordered and will arrive mid next week (Hopefully).

If I end up not getting this issue resolved by Christmas, and just instruct my brother to switch off all speakers before turning on, what risks do I run? I'm just worried that I won't be able to resolve this in time.
 
2 seconds is a short time ..is that normal on these units ?

I have a couple 620's here. Neither are functional at this time. I guess one could Replace the e-caps in the protect circuit. The delay is determined by a RC (resistance/capacitance)time constant. If and electrolytic is dried up it could have changed the delay timing.
 
The delay isn't long- I measured mine with a stopwatch at 2.1 seconds. Random transistor or other part replacement isn't a good troubleshooting method. The issue is probably something very minor and if you change out a lot of parts to find it, there's no telling what the resulting performance will be. I would probably look at C705 and C706, because if they're leaky and not blocking DC, the offset will be high. That would account for the drop in offset for a while after turn-on, and the risk with changing a couple caps is minimal. The receiver also has a known issue with Q671 and Q672 getting noisy and weird, though I don't know if that would cause the click problem. Though it could be the diff pair, I'd do caps first.
 
Okay, thanks for all of the suggestions. I do know how to check a transistor with my dmm, so I can do that before replacing anything. And I have an ESR meter, so I'll be able to check the caps.

I looked over the schematic, and couldn't find Q671 and 672, what are those parts?

Thanks everyone, I really appreciate your help and insight on this.
 
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A quick update. I opened up the case to look at the bulbs, and discovered that the previous owner hadn't done the led conversion. But, one of the bulbs wasn't working. So, the bulb replacement will go on as planned.

I measured, in circuit, C705 and C706 using my Peak ESR meter. One measured 153.2 and .53 and the other was 209 and .44

Both of the ESR measurements are fine, though the cap value of 153 is further off of the original value of 220 uF.

I know that was in circuit, so it may be worth pulling them out to test. If it still measures 153, is that worth replacing? If so, what is a good cap to use?
 
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