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New guy vs CR-840

Kirk V9 said:
I’m surprised how cheap those components are.

Is that where you normally order your parts from?
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If you're in Canada, I find Digikey faster then Mouser..... Same cost for shipping ($8.00) but I typically get my package in a day or 2 max. Mouser is always around 5-7 days. Essentially same stocks n prices...
 
TR801 802 and 803 all had continuity between Collector and Emitter in CCT.

All three were tested getting 0VDC on each of the five tests (out of the cct board).

804 and 805 showed open between C and E. with no further tests done on those.
 
There going to charge you for shipping each order. Get all that you think you may need in one order.
 
avionic said:
Yours is fancier than mine..:thumbsup:
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Fancier than my DBT too. It is just an old lamp with a spliced cord.

The Fuxtor said:
If you're in Canada, I find Digikey faster then Mouser..... Same cost for shipping ($8.00) but I typically get my package in a day or 2 max. Mouser is always around 5-7 days. Essentially same stocks n prices...
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In Ottawa, they are about the same. Both usually get here the next day, mouser is a bit more likely than digikey to take an extra day but never more than that.
Mouser is a bit cheaper, and a bit different stock sometimes.
Digikey is cheaper for small orders since shipping is less.
 
I placed an order for all the capacitors and the one transistor (TR803) that Avionic recommended starting with.

I also ordered a cool little testing rig off amazon. The Kumon Mega 328 component tester. It wasn't very expensive and is super easy to operate. Just plug the component in that you want to test and hit the button. The tester automatically identifies the component you are testing and spits out the values that it is reading.

I did some manual testing with two transistors from the 840 and I deduced that one was good and one was faulty. The good transistor identified on the Kumon as a PNP and gave some numerical values, the suspected bad transistor (TR803) was identified as a resistor and not a transistor (different from the serviceable one) so I guess this is how it will identify.
 

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Kirk V9 said:
I placed an order for all the capacitors and the one transistor (TR803) that Avionic recommended starting with.

I also ordered a cool little testing rig off amazon. The Kumon Mega 328 component tester. It wasn't very expensive and is super easy to operate. Just plug the component in that you want to test and hit the button. The tester automatically identifies the component you are testing and spits out the values that it is reading.

I did some manual testing with two transistors from the 840 and I deduced that one was good and one was faulty. The good transistor identified on the Kumon as a PNP and gave some numerical values, the suspected bad transistor (TR803) was identified as a resistor and not a transistor (different from the serviceable one) so I guess this is how it will identify.
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Handy little tools , I especially like being able to identify transistor pinouts . Very good! Just watch out when testing bigger caps, they will fry the poor little guy! Ask me how I know....
 
The Fuxtor said:
Handy little tools , I especially like being able to identify transistor pinouts . Very good! Just watch out when testing bigger caps, they will fry the poor little guy! Ask me how I know....
Click to expand...

Hey how do you know that the bigger caps will fry the poor little guy?

How big are we talking before a meltdown happens?
 
Kirk V9 said:
Just joined up a few days ago and I have a project that I want to try to get going. From my previous career in the AF I have some electronics training that was quite a while ago but is slowly coming back to me.

Last week I picked up a rough CR-840 off of the local classifieds. It’s not pretty but it gives me something to work on. The unit is complete although a little dirty, it definitely been sitting for quite a while unused most likely because it doesn’t work.

I’ve downloaded some really bad copies of the owners manual, parts list and service manual online.

When I got it home I plugged it in to see what there was to see or not see. After cleaning the power switch so that would work properly I pressed it and the red power light comes on. It starts dim and gradually gets to its maximum brightness, on shutdown it is the opposite. Starts bright and slowly dims.

The speaker relay does not click or activate, non of the display lights come on, and there is no movement in the signal or tuning meters.

All the fuses have been checked and are serviceable.

There is definitely minor bulging on some of the electrolytic caps.

I have tested the power supply voltages and got the following readings:

Blue & Yellow - 27.5 VAC
Blue & Orange - 51.7 VAC
Yellow & Orange - 79.9 VAC

From another thread I read that TR801 regulates the 41 V, this is the one with the square tube heatsink near the big caps. TR805 (same type of transistor near the 9 pins) regulates a 26V B supply to the tuner board. If either of those transistors are toast the protection circuit will not work.

TR801: -4.5 VDC
69.6 VDC
0.1 VDC

TR805: 36.4 VDC
36.4 VDC
35.9 VDC

Also from another thread The three wires going to the tuner board should be; white = neg 41V, red = pos 41V, and orange = pos 26V. If all three voltages are correct then the transistors are OK.

My readings at these points:
White: - 46.5 VDC
Red: - 4.5 VDC
Orange: + 35.7 VDC

So after saying all of this I am not certain but it seems to me (and my limited knowledge) that the voltages at TR801 and 805 are incorrect.

So my questions are for anyone who can help:

1. Do you see any problems with my testing so far?
2. What would be my next step?
3. Where can I get some decent schematics, block diagram and service manual (paper or PDF) that will allow me to zoom in and read the small print?

Thank you

Kirk
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As mentioned, the CR-x40 models have integrated modules (Yamaha custom STK) and the modules are like hen's teeth to find. Here is a thread that is very long, but has a wealth of information related to diagnosing and repairing this series of receivers. Plus a work in progress of building replacements. It will be well worth your time to read through it. https://audiokarma.org/forums/index.php?threads/ongoing-saga-of-the-yamaha-cr-n40s.145244/
 
Skywatcher said:
As mentioned, the CR-x40 models have integrated modules (Yamaha custom STK) and the modules are like hen's teeth to find. Here is a thread that is very long, but has a wealth of information related to diagnosing and repairing this series of receivers. Plus a work in progress of building replacements. It will be well worth your time to read through it. https://audiokarma.org/forums/index.php?threads/ongoing-saga-of-the-yamaha-cr-n40s.145244/
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Fantastic! Thank you.
 
Skywatcher said:
At AK, we aim to please. :D And get back to enjoying the music :music: as soon as possible. :beerchug:
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Oh I can't go without my music. I have 4 receivers. My CR-1000 is being restored by Racoon, I am running a CR-620 right now, I have a Nikko on the shelf that is serviceable and the 840 that I am working on. I got the 840 to get back into the electronics and if it turns into a paperweight because I have messed it up no great loss. I should have researched more about the internals of the 840 and the rarity of the ICs in the pre driver and power circuits. Live and learn. Hopefully the faulty transistor I found will solve the problem.
 
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