CR-2020 Service Bulletin Guidance

Hi Fi Fan

Active Member
Hi everyone, new member here.

I just purchased a working CR-2020. I opened it up yesterday to clean pots, etc. and check to see if the Service Bulletins have been performed. I have modest to average electronic repair skills.

The power switch was shorted, I rebuilt it and added the jumper as advised in the SB. Works great now.

I inspected the electrolytic cap board to see if that SB work has been done. There is some scorching on the board so part locations are difficult to read. There are a few components raised up off the board and the soldering for these parts appears non-factory. Can anyone tell from the attached photos whether the subject SB components have already been replaced?

http://audiokarma.org/forums/index.php?media/img_1787.15983/
http://audiokarma.org/forums/index.php?media/img_1790.15984/

The 2 transistors on the power supply board referenced in the SB appear to me to be original based on the part number. I touched up the solder points and am wondering if these transistors should to be replaced as a matter of course or can I just add larger heat sinks? A quick check online suggested that these parts may have been obsoleted.

http://audiokarma.org/forums/index.php?media/img_1796.15985/

Thanks is advance.
 
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Welcome to AK... Does not look like SB's have been complied with. The resistors in question look OEM to me.
 
Service bulletins are to replace 2 each 22 Ω/3.25 watt and 2 each 33Ω/3.25 watt. As well as rewire the convience AC plug. And replace the power supply pass transistors. I've done all three mods many many times.

Those two were not part of the service bulletin.

And personally I would not have used 5 watt resistors for the service bulletin. There is very limited space where the 22Ω & 33Ω ( service bulletin) reside and the 22 Ω's are suppose to be fusible as well.
http://sportsbil.com/yamaha/cr-2020-servbull1.pdf
http://sportsbil.com/yamaha/cr-2020-servbull2.pdf
http://sportsbil.com/yamaha/cr-2020-servbull3.pdf

 
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Yamaha did at one point get a bad batch of 2SD234 transistors that reacted with the silicon compound used with heatsinks, there is a service bulletin covering this. The also found that in the CR-2020 the 2SD234 was not quite up to the task of being 25 volt regulators and a service bulletin recommended replacing them with 2SD525. These are no longer available so either use a TIP41C or 2SD613. On my own CR-2020 I also replaced the heatsinks on the two with a finned one I found at Radio Shack, just remember to use the mica insulator because there are DC voltages on the metal plate of these transistors.
 
Thanks a lot for the help everyone, I appreciate it!!!

Do any of the capacitors need to be discharged before doing the SBs?

Thank you!
 
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"These are no longer available so either use a TIP41C or 2SD613."

Awesome, is either TIP41C or 2SD613 preferred?

Thank you.
 
"These are no longer available so either use a TIP41C or 2SD613."

Awesome, is either TIP41C or 2SD613 preferred?

Thank you.
Which ever is easiest to obtain. . The 2SD613 is probably obsolete as well.
 
For your absorption regarding the SB resistors :
http://audiokarma.org/forums/index....-41vdc-on-outputs.787761/page-3#post-10992603

KSD526 (available with most suppliers) is a decent sub for TR712/715
Having adequate cooling for these trannies is typical service topic #2 for this unit.
Some inspiration here:
http://audiokarma.org/forums/index....toration-guidance.798122/page-6#post-11128538

Those purple sleeve capacitor(s) should really be replaced; they age very badly, and cause all kind of issues such as a non-engaging relay.
Talking about it, the relay would be typically replaced (by Omron MY2-DC12) as well when your donw there.
 
For your absorption regarding the SB resistors :
http://audiokarma.org/forums/index....-41vdc-on-outputs.787761/page-3#post-10992603

KSD526 (available with most suppliers) is a decent sub for TR712/715
Having adequate cooling for these trannies is typical service topic #2 for this unit.
Some inspiration here:
http://audiokarma.org/forums/index....toration-guidance.798122/page-6#post-11128538

Those purple sleeve capacitor(s) should really be replaced; they age very badly, and cause all kind of issues such as a non-engaging relay.
Talking about it, the relay would be typically replaced (by Omron MY2-DC12) as well when your donw there.

Thanks I will check those links out, appreciate the help!
 
What really really really surprises me is that your unit is seemingly originally missing fusible resistor FR803 !
That is where that black wire jumper is on your board.

IMG_1796mku.jpg

I think 'originally' as your PCB has not even the resistor value printed on it as it usually does.

DSC06765mku.jpg

That is a first off!
What is the serial number of the unit?
 
What really really really surprises me is that your unit is seemingly originally missing fusible resistor FR803 !
That is where that black wire jumper is on your board.

View attachment 1248711

I think 'originally' as your PCB has not even the resistor value printed on it as it usually does.

View attachment 1248713

That is a first off!
What is the serial number of the unit?

Thanks a lot. I noticed that too while I was inspecting these boards, "hmm, weird jumper wire here." Is it advisable to add a resistor there? If so, is it a 10ohm 220ma as shown?

Serial is 02922, see attached.

Without going nuts as my skills are limited are there any other "should do" parts replacements on these boards for reliability? I found another thread that suggested another 4 capacitors:

http://audiokarma.org/forums/index.php?threads/yamaha-cr-2020-faulty-no-sound-sb-mods.291232/

"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."

Thank you!
 

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