Yamaha CR 840 Protection mode

bmc1987

Active Member
Hey guys, I was replacing bulbs in my cr 840 and the wires for the tuner indicator light touched... sparked, blew the fuse (2A 250V). I replaced the fuse and the light. Now all the lights work-it LOOKS great, however, the relay wont click :confused: I checked the other fuses and they're fine. Just got the schematics now to determine the problem...
 
Yes, it was fully operational. It just needed the indicator bulb to be 100%. So much for that...
 
have you figured out how to use the test points on it?

I doubt you blew the drivers by changing a bulb, but who knows. Lots of 840 threads in this section - I'll try and link a few for you later.
 
Check the power supply dc voltages at the power supply output posts against the voltages listed on the schematic to narrow down the problem.
 
have you figured out how to use the test points on it?

I doubt you blew the drivers by changing a bulb, but who knows. Lots of 840 threads in this section - I'll try and link a few for you later.

I haven't been able to determine much. The only schematics I can find is an owners manual. It shows a block diagram and a schematic diagram.
 
Ive been looking at some other cr 840 threads and measured the pre and power drivers. My Pre's are 701: 13. -3.0 14. 3.5 and 702 13. 3.5, 14. 2.8
Power's are Pin 3 Front: -0.4 Rear: 0 and Pin 8 Front: -0.3, Rear: 0.1
I was referencing this post http://www.audiokarma.org/forums/showthread.php?t=101956 and another and the power driver numbers were the most different. Checked transistor 805 had 27, 29, 27 voltages, transistor 801 was 47, 62 and 46. Checked the 9 pin cluster for orange wire 26.9,white was -46.6 and red was 46.7. Diode with green band next to 3 jumpers was 1.8@200OHMs. Orange wire to blue was 46.8, Blue to yellow was 23.7 and yellow to orange was 70.4. this was the other post http://www.audiokarma.org/forums/showthread.php?t=426547
Lots of info out there, just not sure what to do with it...
 
And on the foil side of the board, the relay has dark discolouration on its connection points with a dark mark in the foil aswell.
 
Try measuring DC offset at the relay to see what you have. Or scope the output at the relay.... Amp side of relay..... These are touchy amps 7 & the modules are problems... I have one on the bench that refuses to work. I pull it out every few weeks and try more tricks, but no luck yet... I don't think the modules on Ebay are any good...Real PIA
 
Hey guys, I was replacing bulbs in my cr 840 and the wires for the tuner indicator light touched... sparked, blew the fuse (2A 250V). I replaced the fuse and the light. Now all the lights work-it LOOKS great, however, the relay wont click :confused: I checked the other fuses and they're fine. Just got the schematics now to determine the problem...

I'm currently having this exact same problem. i, too, was replacing bulbs and had a brain fart by keeping it plugged in. now, i have no clue what to do.. replace the relay? i dunno..
 
It is very unlikely that the relay is the problem.

Have you checked fuses? Does the lighting work at this point?

chazix
 
I'm sorry for taking so long to reply, I've recently become an uncle, and have had to step up responsibilities on the job front so i haven't been online for a while.
anyway, I'm at the same point i was before. and to answer your question, no. no lights. it powers on, but no relay click and no sound output. i don't really know where to go from here..
thank you for your time and your help is very much appreciated :)
scott
 
Congrats on uncle-hood!

So, what signs of life DOES the Yamaha have? Is the red power LED coming on?

chazix
 
Maybe a "cut to the chase" is more appropriate for a busy guy: The only quick fix that I think anyone here would be able to guess at is a blown fuse. There are two on the amplifier circuit board, which seem like the most probably suspects.

(There is another fuse that I think is off on a small circuit board by itself, but that's the one that's on the primary side of the power transformer. If that one was blown, there would be no signs of life at all.)

Please unplug the receiver before trying to check or replace fuses.

There is a rather large space of other possibilities for where the problem could lie. It's not infinity, but you can see it from there. (Hey, I think I might have just coined a bon mot - if you borrow it, attirbute it to chazix, y'hear?) Anyway, if it's NOT just a blown fuse, it's going to need some real diagnosis - probably starting with a check of power supply and power amp voltages. If that's not practical, it might be time to take the receiver to a repair shop.

Cheers,

chazix
 
As long as I'm goofing off from the day job, and running off at the mouth:

Like others who have gone looking for a freely available CR-840 schematic, all I've found is a not-so-hot owner's manual scan. However, for problems with the power supply, power amplifier, and illumination circuitry, I notice that the CR-640 schematic is very similar, certainly close enough to serve as a guide. And the CR-640 service manual is available with good scans on hifiengine.com and probably other places. (There is a CR-640 schematic scan in the AK database, too, but I haven't checked out that one.)
 
Hey guys! I know it's been a while since the last post but I am having similar issues from a unit I picked up at Goodwill last night. I took it home, plugged it in and everything seemed to be working as expected, except that the sound was super scratchy and unbalanced. I figured that the pots were very dirty so I sprayed Deoxit where I could to clean it up and after about an hour of drying I turned it on and the relay switch did not click. I did have a faint sound (headphones) of static but the radio wasn't turning on nor any of the inputs. After a while it just sounds completely dead, no noise, nothing. I did what I could be removing the plastic cover of the relay switch and cleaning it via Deoxit, but still nothing.

Now it just turns on and there is no sound at all. What could be the issue?
 
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