View Full Version : Yamaha CR-600 problem / in protection


4seatPilot
02-08-2012, 12:12 PM
Again I couldn't decide which forum to put this in, here or the Yamaha forum - but I think more traffic through here, and perhaps the experience will be educational for non-yamaha owners too.

I had been PM'ing with the very helpful ML, but the problem seems to have gotten a little more complex so I feel bad for monopolizing his time. He said moving to a thread would be fine with him.

First the catch-up, here's what where we've been with this CR-600. Italics are my text, regular is ML's reply.

I have a CR-600 that was running great, at my parents house. They left it turned on when they went to church Sunday AM, when they returned it was not working. The Power LED and the illumination lamps still work, but the FM & Stereo lights were out, tuning meters don't move at all, and no relay click.

If the relay does not operate it indicates either DC voltage on the output or possibly a transistor failure in the protection relay circuit. Measuring for DC voltage at the speaker terminals will not work because the relay cuts them out. You will need to measure ahead of the relay at the choke (that is the vertical round red thing with a white plastic core. Look at the schematic, there will be a 2 watt resistor of about 4.7 ohms across the choke coil, measure there and the chassis. Also look underneath to see if any of the four fuses are blown.

Ok... managed to get my leads on those two resistors... green ones, positioned just underneath the chokes. (one on each side of the relay) I Got aprx .01V DC between the resistor leads and chassis. I measured on both sides of the resistor as I couldn't figure out which side I was supposed to measure - got same value on both sides. After a few min all the values dropped to about .008v.

OK so that leaves the protection circuit as the likely culprit since that is not enough DC to cause the relay to not operate.

There is a violet wire at the bottom of the amplifier boad that should have +12 volts on it, oh yes the ground is supplied to the amplifier board over a black wire so you can take out the two big screws and tilt it up, just put something non-metallic under it so you don't short out anything. I had asked if I could lift the whole main amp board and heatsink out for testing... and yes, you can

Indeed - measured violet to chassis, no volts. So... find out where the 12 v is supposed to come from I guess.... and why it's not.

It comes from the power board and to get at it undo the yellow wire at the tuning cap and the red and green ones at the plug on the rear panel.

Now take out the red headed screws on the sides and maybe there are some on top, can't remember. The whole front panel should now tip forward so you can see the power board. Note the white fusitors, they have a nasty habit of going open or changing values. BTW the power amp adjustments are the same for the CR-600 as the CR-800. If the fusistors are open replace them with 1/4 watt resistors except the big one that should be 1/2 watt.

Sure enough – one of the fusistors was open.

http://audiokarma.org/forums/picture.php?albumid=2059&pictureid=13622

close-up of the main power board, near the top middle... upper fusistor tested open - no conduction. Problem found? :)

4seatPilot
02-08-2012, 12:19 PM
So I got a 220 ohm 1/2 watt resistor, checked it with a meter (read 217 ohms, so pretty close), put it in, re-assembled the boards and powered on to check the idle & midpoint voltages again. No relay click still... and then before I could get the voltages checked a capacitor blew up on the main amp board. :dammit:Just before the explosion, I did manage to measure 13V DC at that violet wire where before there was 0 volts, so I guess that was progress...

So - my question now is, did the original fusistor go because of a bad capacitor? Or is there a different problem - and because I just put in a straight resistor that the problem just manifested at the next weakest link - the capacitor?

I was contemplating a re-cap of the power and main amp boards anyway, I guess that's a must now. I just wonder if there is something else I should be checking so that I don't just blow up another set of capacitors. I did go over both boards visually very closely, found no shorts, cut traces or bad solder joints - to my (somewhat inexperienced) eye, everything looks good.

It was the capacitor on the bottom of the board that went... the matching one on the right side was swollen when I took it off the board too - but not sure if it was like that before the resistor replacement or if the explosion of one and imminent explosion of the other one only happened after the resistor.

http://audiokarma.org/forums/picture.php?albumid=2059&pictureid=13663

(above) lower cap in the picture is the one that blew...

(below) here is the main amp board:
http://audiokarma.org/forums/picture.php?albumid=2059&pictureid=13662


So... anything I should check before just changing the caps? Am i on the right track? Just put the new capacitors in and go for it?? Perhaps firing it up with the new caps on a dim bulb first would be wise...

Looking for suggestions... :yes:

ryuuoh
02-08-2012, 06:55 PM
Yes, use a dim bulb tester after you replace the parts. I'd order all the caps for that board.
Good luck!

petehall347
02-08-2012, 07:12 PM
resistor did its job , replace the caps all should be fine ..

4seatPilot
02-08-2012, 07:27 PM
Yes, use a dim bulb tester after you replace the parts. I'd order all the caps for that board.
Good luck!

that's what I was planning... some caps are different colours, are they different types? I'm just going to try and get matches - not going to venture on any "upgrade" adventures just yet, unless someone has sure-thing suggestions. Planning on doing the power board as well... they're both pretty easy to work on.

And roger on the dim-bulb... hopefully it'll catch a problem before a cap blows up again if there is another problem...

ryuuoh
02-08-2012, 08:37 PM
Different color could be a bi-polar, or a specialized cap like low leakage.

4seatPilot
02-18-2012, 07:34 AM
Just getting to ordering these caps - on the power board, there are 3 16V, 47uf capacitors. They are all nippon chemi-con. One is pale green, the other two are black - that is pretty much all I can identify. There is also a small black nippon chemi-con 6.3v 100uf, and a 50v 1uf. The rest of the capacitors (other than discs) are all Nichicon.

Picture is attached, they are the ones surrounding the relay.

As far as I can tell, the two black 16v 47uf caps are in the signal path - or at least there is one per channel, and the other 3 seem to be for the protection circuit. From the schematic, the green one is not labeled (so "electrolytic"), the others are labeled BP (BiPolar). I thought all the can capacitors on the board were Bi-Polar?

Can someone just confirm for me that the nichicon KZ or FG will work fine here? Or are some of these specialized cap as ryuuoh indicated? The best I could determine was that they used these instead of nichicon because they were cheaper - and perhaps not in critical audio locations.

:dunno:I'm just struggling with where I need to have regard for low leakage, or low esr, or low/higher ripple currents. :dunno:

sorry for the rambling...

4seatPilot
02-18-2012, 07:54 AM
While I'm at it...
are these ok to replace the big 4700uf 50V?
They're a bit smaller physically, but higher value (6800, 63v)

http://ca.mouser.com/ProductDetail/Nichicon/UFW1J682MRD/?qs=kArNe9LFxXliyMzWVyxaUg%3d%3d

Ken Boyd
02-18-2012, 01:51 PM
I just recently repaired a Yamaha M70 amp with the help of Avionics in the Yamaha thread, he said do not put that amp on a dim bulb tester because of the type of power supply. I don't know that much about your amp but you might want to check if this amp is ok to put on a dim bulb tester.

4seatPilot
02-18-2012, 09:12 PM
I will check into that for sure... I'm couple dozen solder connections away from that, so I will have time to investigate.
Still need to select those last few electrolytics first.
I'm thinking that Yamaha didn't use nichicon in those 5 locations just as a cost savings... I've been unable to determine any special properties of them like low leakage etc, so I'll probably just use an economical option of identical values.

Any other capacitor wisdom before I order?

Nice that they are cheap parts... I can pick two options and order both if i'm not sure, and it only adds a couple dollars to the whole project.

*****EDIT - SEE NEXT POST - THEY'RE BI-POLAR, (as suggested above)******

4seatPilot
02-19-2012, 09:18 PM
Just getting to ordering these caps - on the power board, there are 3 16V, 47uf capacitors. They are all nippon chemi-con. One is pale green, the other two are black - that is pretty much all I can identify. There is also a small black nippon chemi-con 6.3v 100uf, and a 50v 1uf. The rest of the capacitors (other than discs) are all Nichicon.

As far as I can tell, the two black 16v 47uf caps are in the signal path - or at least there is one per channel, and the other 3 seem to be for the protection circuit. From the schematic, the green one is not labeled (so "electrolytic"), the others are labeled BP (BiPolar). I thought all the can capacitors on the board were Bi-Polar?

Can someone just confirm for me that the nichicon KZ or FG will work fine here? Or are some of these specialized cap as ryuuoh indicated? The best I could determine was that they used these instead of nichicon because they were cheaper - and perhaps not in critical audio locations.

:dunno:I'm just struggling with where I need to have regard for low leakage, or low esr, or low/higher ripple currents. :dunno:

sorry for the rambling...

:withstpd:answered my own question... from the schematic, they're BP - bi-polar. Which is different from most of the other capacitors that do have a +ve and -ve orientation. :bash: Duh. So I've double checked the rest to make sure I got the right ones for each spot. Hopefully get this order put in this week.

avionic
02-20-2012, 03:04 AM
I just recently repaired a Yamaha M70 amp with the help of Avionics in the Yamaha thread, he said do not put that amp on a dim bulb tester because of the type of power supply. I don't know that much about your amp but you might want to check if this amp is ok to put on a dim bulb tester.

Dim bulb is fine with this unit.These are the yamaha X-power supply models.
A-760,A-760 II,A-960,A-960 II,A-1060,B-6,M-50,M-70,R-1000 & R-2000.

4seatPilot
02-20-2012, 08:55 AM
thanks avionic... good info to file away.

4seatPilot
05-05-2012, 08:37 PM
So... recall from the start of the thread, my conversation with merrylander - we traced the problem to an open fusistor on the power board that had failed open.

Then I blew up a capacitor, and a couple fuses. So I finally got the replacement capacitors and re-capped the entire main amp board. This time though, I hooked it up through a dim-bulb tester with a 25watt bulb... :thmbsp: it stayed dim! But no relay, still in protection. Hmm.

Got out the meter again, tested voltage at TP 7 & 3, and it was about 26v. This is supposed to read at or near zero, higher apparently indicates a problem with the outputs.

So - pull the board off the heatsink, and check the outputs. 2 were kaput. Probably fried at the same time the capacitor blew up... Lucky me, I had ordered extra outputs for a CR 820, and they were also the recommended sub for this unit, so put them in. Off to the races, right? :scratch2:

Turned on the bulb tester again... :eek: Bright bulb!! Turned off. No fireworks, so the bulb saved the receiver...

Anyway - :headscrat now I'm confused. A short somewhere? Obviously... but where. I used a meter to check every solder joint before proceeding... looked again, all checked out ok - no crossed solder, conduction where it should be and none where it shouldn't be.

So I looked up the board diagram in the service manual, to see the output transistor orientation as to which were supposed to go where - even though I had taken a picture to remind myself. Confession time - apparently I had mis-oriented them for my "reference" picture, and I had the NPNs where the PNPs were supposed to go and vise-versa. :screwy: Oops. :bash: Double oops actually - fried two outputs with that screw-up. Thank goodness I used the dim bulb when the replacements were in.

Once again, replaced the outputs... the right way around, with the NPN above the PNP like the service manual says they should be... fresh heatsink grease and mica (again)... flip the switch on my dim-bulb (the tester, not the one in my head), and it stayed dim! :D Wait, wait... CLICK! :huge: And bulb stayed dim! :huge:

I hooked up my bench speakers, and voila! :music:

And even though I might have gone a little over-board with the emoticons on this post... I think one of these are in order now: :banana:

4seatPilot
05-05-2012, 08:52 PM
Here's the TO-3 output transistor details:

The originals were 2SD371 NPN and 2SB531 PNP.

I had MJ15015 NPN and MJ15016 PNP from mouser - which also work for CR 820 (and others too probably)

I have the service manual from the CR 800 downloaded, which used different TO-3 parts, so I had to look at the diagram - which showed TR717 and TR718 positioned above TR719 and TR 720, which are near the bottom of the sheet - near where all the little wires are attached.

Looking at the schematic, it indicated that 717 and 718 were SC793 parts, 719 and 720 were SA663 transistors. So I looked up data-sheets for those and found that the 793 are NPN type, and the 663 are PNP parts. So - with that I could determine that the NPN outputs were supposed to be positioned above the PNP.

When I saw that I had the 15015 NPN parts at the bottom of the sheet... I knew I had found the problem. :thmbsp:

Now all I have to do is re-cap the power board, replace a few more fusistors on it as well... adjust the voltages & idle currents, and enjoy! :music:

***4 month edit... still singing beautifully, the CR-600 is my daily-driver in the living room. It's run a pair of Koss CM1030s, Mirage SM1s and currently Realistic Optimus T300. Ive now picked up another non-working one to bring back from the dead! If anyone wants a list of capacitors that I used, PM me... I have a mouser project I can send you.