Yamaha CR-2020 Faulty, No sound, SB Mods.

asmd

Active Member
Yamaha CR-2020 Faulty, No sound, SB Mods

My Yamaha CR-2020 receiver gave up the ghost recently. No sound and the FM tuning meter swung left to about the 50% mark. From the threads here and Merrylanders help, its apparently caused by by the parts that are covered by the service bulletin mods and repairing that should rectify the problem.

Well, ive got my fingers crossed and have ordered the parts including a Weller WLC 100 Soldering Iron to get the job done. I plan to document my adventure (or misadventure) as i have no experience in these things but am willing to learn and documenting it will help me ask for help for troubleshooting as well as help the next fella who needs to go through this. :)


These are the parts ive ordered from digikey:

1) Vishay/Dale RES 33 OHM 5% 3.25W SILICONE WW - http://search.digikey.com/scripts/Dk...54667205842508
2) Vishay/Dale RES 22 OHM 5% 3.25W SILICONE WW - http://search.digikey.com/scripts/Dk...54667205842508
3) STMicroelectronics TIP41C - http://search.digikey.com/scripts/Dk...54667205842508

for the problem that as of right now looks like this.

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I would certainly appreciate any and all suggestions.
I think im pretty much armed with all the info i need to get it done.
If theres anything else (apart from change out the lights, which i plan to do), do chime in.

regards,
asmd.
 

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ok....

pulled her apart this morning.
have removed the board with the transistors and have unsoldered/removed the 2 sd234 transistors.
finally had my first look at the HUGE caps under the board.. and frankly they scare the bejezus out of me.
was advised to swap out the two 50v 1000uf caps on either side of them...

now heres the question.. i have no interest in shocking myself and caps as i understand it store energy. ive had old camera flash caps go Bzzztt and its not friendly... and these things are gimormous!!!!

err... question is... how does one discharge the caps?? do i even need to discharge them..? are they safe to handle.. and if anything else, how do i handle them.. safely that is without running the risk of stopping my heart.

all work stops for now until somebody gets back to me on this.

all replies and help is very much appreciated.
 
Im happy to report that after several hours of work and a cap discharge question, shes up and singing like a bird thanks to the information and help ive received here on AK.

I am very grateful for the help and wish to thatnk you all for your help. Special thanks goes to Merrylander who provided heaps of help specific to the receiver i have.

Will post pics and walkthrough shortly.
 
Walkthrough.

This is the area that concerns the service mods.
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To get to the boards to perform the SB mods, I first removed the two screws and pulled the board back removing it from the 6 pin connector that connects it to the capacitor board.

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Remove the two blue wires on the left and lift the board up and to the right. Be careful of the orange capacitor in the image below. I had trouble getting it to clear it and there was some wiggling involved. I tried to remove as few wires as possible.

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In the image above the board had blackened due to heat where the SD234 transistors are. Fortunately, the traces were still good.
 

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Remove the SD234 transistors.

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View from the top after removal of the transistors.

Note in the above image, loosen (thanks for the tip Merrylander) the two screws holding down the bracket that fastens the two large capacitors. Dont remove the screws, loosen them and slide the bracket back and remove it. Remove the one black and two red wires from the top left of the capacitor board.

Theres a bracket that holds the capacitor board down. loosen the two screws on either side and slide the bracket down. Be careful to watch the clearance of the right large capacitor as if not lifted up slightly, it will snag below preventing the capacitor board from sliding down so it can be released from the bracket mounting and lifted up and out as in the image below.

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Image from above of the components that need replacing.
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After removing the components that need replacing and cleaning the board, noticed the trace had lifted and was damaged by the heat.
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Populate the board with the replacement components. I also as per Merrylanders advice, replaced the two smaller capacitors on the board.

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With no idea on how to repair a trace, i bridged broken trace using the leg of the resistor.

EDIT:
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Ooops, forget this important bit. Merrylander mentioned to check the solder joints on the 6 pin connector, and sure enough, they were cracked!! Note in the image above, the circular ring on the solder joint, wiggling the connector makes it more obvious, 4 of the 6 joints were cracked! I refreshed the joints with new solder.

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After pic with all the components in. Note: Service Bulletin says to mount the 33ohm resistor 1/4 inch above the board, i made the mistake of mounting both the 33ohm and 22ohm resistors that way. The 22ohm resistors have to be mounted flush to the board. If its mounted higher, the boards dont seat properly when attaching the 6 connector pin. (found that out the hard way)

Once all the components are replaced, reverse the procedure to replace the boards.

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Image of the jumper wire as per the service bulletin.

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Image of all the components i replaced.

In addition to the service bulletin repair parts as listed in the first post, i also replaced the two 1000mfd/50 capacitors with 63v/1000mfd capacitors per merrylanders advice and two 1000pf/100v ceramic capacitors behind the SD234 transistors.
 

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Shes been running for about 5 hours straight now and me with a grin on my face.

The T1P41C transistors seems to run hot. Theres still that hot spot over the vents.
Is this normal?
Seems like its cooler than before but still hot though.

I hope the pics ive posted helps some else. At least as a visual cue of what to expect.

regards,
asmd.
 
Great job! Heat from the vents is most likely from the power output transistors and is quite normal.
 
These do run hot.
The heat from above the power supply PCB is normal and explains the toasty areas you can see around the transistors. Some have added additional heat sinks to the 2 PS transistors but you must be very careful that they don't touch any other components (or each other) lest the smoke get out.
It would be a wise idea to position the CR-2020 with nothing on top of it to facilitate proper cooling.
These are beauties; enjoy the music.
JimB
 
Great work! BTW the 'toasted' area around the two transistors is mostly old glue that I usually scrape off and then clean out the small holes with a #63 drill. If you get bigger heat sinks the best practice is to use either mica insulators and silicone grease or just use silicone insulators, then there is no worry about them touching.

The reason that I change those two caps is if I get a 2020 or 1020 showing the missing 25 volt clue is that I have never heard the unit. Since the 25 volt supplies also power the tone board and phono amp you will get a terrible hum if they are bad. It is such a PITA to get in there I hate to do it twice, so swap them out just in case.
 
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My 2020 needs that..........You make it sound and look so easy, I want to jump in and do it; It can save some serious Euros......I have no soldering experience and my 2020 is sitting here for almost a year now.

Great job you have done! Thank you for sharing your experience...
 
@ GLobalWarming - your welcome. its the least i could do to return the favor to the community. i just wanted to consolidate the experience of the forum members here into one thread with pictures detailing the service bulletin mods.

I cleaned and used the original heatsinks after burring off the crud around the bottom of it using a dremel. The only thermal transfer compound i had on hand was some Arctic Cooling MX3 thermal paste from my recent pc build. Pictured below.

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Added a step to the walkthrough. (that i forgot)

the solder joints of the 6 pin connector were cracked. if it werent for Merrylanders guidance, i never would have noticed it. its really fine and more obvious when you wiggle the connector. Added picture to the walkthrough.
 
The new capacitors dont quite look as well made as the originals. (?)

I havent stacked anything on the CR-2020. All the vents are exposed, and i'll continue to use a small cooling fan (9cm pc case fan) running off the switched AC output to cool that area. wish i didnt have to, it takes away from the beautiful look, but it kinda gives some peace of mind. :)

While my soldering work isnt the prettiest, im glad ive got her up and runniing again. i do hope ive done the old girl justice to run for another 30 years. :)

i was just he guy who held the tool. it was you chaps who guided me. :)

regards,
asmd.
 
My CR-2020 is in a case with glass doors and a closed back. Now I did put a 4x4 12 volt fan on the back panel with a foam filter. It is driven by a 12 volt wall wart plugged into the switched outlet of the 2020. Been like that for the last 7 or 8 years, no problems.
 
I just fixed the same amp with the same troubles last week !
The TIP transistors are definitely not originals, make sure that if you put the correct ones back, nothing has been changed around them.
The 2SD234 must be replaced by 2SD525 as per Yamaha mod. The fuse resistors should also be replaced by fixed ones with higher power rate (I think 3.25W was what Yamaha recommended unless its 0.75W, I couldn't determine what the rating meant, as it was written as 3 with 1/4 smaller upright the 3).
Lots of capacitors were replaced in my amp before I serviced it but the big ones were left, most probably because they're fine.
 
Timely post as my Yamaha CR-2020 just croaked the same awful death. I've ordered the service manual and some new LED's and am in a holding pattern for now.
 
I just fixed the same amp with the same troubles last week !
The TIP transistors are definitely not originals, make sure that if you put the correct ones back, nothing has been changed around them.
The 2SD234 must be replaced by 2SD525 as per Yamaha mod. The fuse resistors should also be replaced by fixed ones with higher power rate (I think 3.25W was what Yamaha recommended unless its 0.75W, I couldn't determine what the rating meant, as it was written as 3 with 1/4 smaller upright the 3).
Lots of capacitors were replaced in my amp before I serviced it but the big ones were left, most probably because they're fine.

hi, i was made to understand the t1p41c were suitable replacements.
any problem in the long run to use them?



regards,
asmd.
 
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It'll be sitting up on an audio rack.
post repair and sitting pretty.
the jerry rigged fan will be replaced with something more comely soon enough.

the new and the old. :)

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