CR1020 Restoration Guidance

Very nice. I'll check the two smaller ones as you've shown and focus on the polarity of the capacitor rather than the markings on the board. All great hints to increase my chance for success here. However, I'm still baffled by the amount of smaller caps on the power supply board. I'd like to not have to change all of them. At your convenience, any helpful thoughts would be immensely appreciated.
 
I was afraid you were going to say that. I was thinking the hi-temp Nichicon's (UPW, UKT, or UKA). It seems to be what most are using and recommending. I'm open to suggestions though. I'll just purchase a wide variety as I have some other projects to work as well.
 
KL's and PM's as well. I'd be leaning towards PW's myself.
 
If your still contemplating the 2020 service bulletins.
BTW Here are the correct ( exact) resistors for the service bulletin
You will need two of each..
https://www.mouser.com/ProductDetail/Ohmite/93J22RE/?qs=sGAEpiMZZMtTURnxoZnJAKfV%2by28kSnliksfpOSpVU0=
https://www.mouser.com/ProductDetail/Ohmite/93J33RE/?qs=sGAEpiMZZMtTURnxoZnJAH%2bfrh0DY3Azih2JkIbYPbw=
I can tell by the previous photo's that the ones installed are to large physically and could be a potential for shorting out other components on the electrolytic board.

When you get the new power resistors in, hereby some hints.
As Yamaha suggests, they should be kept off the board.
Well...... right..... then this would happen..... the PSU control board would clash with one or more resistors o_O

View attachment 1037304

MUCH MUCH better would be to mount those resistors on the back side of the PCB, as they get plenty of free air and the heat is kept away from that confined space on the component side, avoiding all kinds of long term issues. The longer the legs the better to reduce the stress on the PCB tracks; those resistors get hot and expand. The large number of power on-off operations cause as many thermal cycles. Also less heat is dissipated to the PCB.

View attachment 1037305

Not the nicest piece of work regarding the tracks, but my board was really fried....loosing various pieces of copper tracks in the process. I had to insert special rivets (and to get the $300 PCB riveting tool for that). I did bent the legs of the power resistors towards each other for more mechanical hook-up strength and in some case replacing the lost tracks.

View attachment 1037308

Here a view after final re-installation; it shows the space and air the power resistors have; it really works out well: the components on the other side stay nicely cool, as does the PCB. Nice warm air flowing out of the top; they really do get hot.

View attachment 1037306

Now that I am on it; I have to warn you for an important **** up by Yamaha: one of the + marks for the left 50V/1000uF capacitor is on the wrong side.
And so did I wrongly install that cap:

View attachment 1037313

So what happened.... due to power resistor in front of it, it did not explode in my face (current limiter, for once....). I had one spare, replaced it, and all starting to work fine.....ooooffff :oops: ESR value had tripled, though capacitance was still near 1000uF. When I opened up that cap 4 weeks later (for fun), it had a huge pressure inside ! Like it was boiling. No joke thus.

However, these caps are part of the power rails to the PSU control board which didn't work correctly at all (no surprise). It did afterwards, but only after the following happened as well:

Another BIG WARNING: do NOT power up the unit without the PSU control board inserted to the PSU capacitor board !!!! Because those 1000uF/50V will see ~65V in that case. In order to have the voltage below 50V, there must be a current flowing through those power resistors (i.e. the rails need to be loaded). In case the control board is not inserted, those power rails are not loaded and thus raise to the voltage upstream of the power resistors !!
 
If your still contemplating the 2020 service bulletins

Well, judging by the discoloration of the molex connector, heat definitely seems to be having an effect on this board. The SB may be for the 2020 but it appears to me that it could benefit from the same mods, especially since you've indicated that the 2020 uses the same board. Also, I know testing caps while still in circuit is very inconsistent and lacks accuracy (I know I need a good ESR meter or tester), but I've checked for simple capacitance and all of these capacitors situated along the left side of the power supply board (viewing from the front of the unit) are reading extremely low - I'll check the right side as soon as I de-solder the blue AC lines as you indicated last night.

I remain extremely concerned about the transistors on the power supply board. I've observed a lot of threads and seen various repair videos where many are identifying very small transistors in other units that are known to cause problems. I'd like to purchase one of those Peak Atlas DCA testers but dam they're expensive. I was thinking of trying a $20 inexpensive DIY kit on Amazon and try before I invest $100.

IMG_0352.JPG
 
Main Power Supply Board - Disconnection
Ok, transformer AC wires (blue) landing at both BE terminals and the black wire from center of speaker protect relay to the e.cap board "E3" terminal desoldered. This definitely provided the much needed access as you indicated (many thanks Avionic). I had a rough go of it though; the black wire twisted and soldered to terminal E3 on the e.cap board was extremely difficult to heat and remove. I used a 3mm square tip and set the iron to 850 but it was still difficult to get the solder to "flow" enough to easily remove the leads. Conscience of overheating, it still required more dwell time than I was comfortable with. I butchered the blue leads to the amp a bit and will likely have to "re-flow" the "E3" terminal underneath the e.cap board. If anyone can share some tricks to disconnecting these large solder joints (i.e. filter caps, etc) without too much difficulty, I'd really appreciate any info provided.

CIG_IMG023_1.jpg
CIG_IMG024_1.jpg

E.Cap Board Inspection
The good news is that all the solder joints on the underneath side of the e.cap board look good, especially where the 6-pin molex connector is soldered; I'm told those can release over time due to heating. I did a simple cap test with my DMM and found the filter caps at 10.8 and 13.4ufs, the (2) 1000/50V both @ 620uf, the 220/63v @ 193uf, and the 100/63v @ 110uf. I know I need a good ESR meter to better understand their status but this is what's available at the moment.

Main Power Supply Board Inspection
I found what I believe to be a crack in the trace at one of the legs of TR715 (it may just be released from the board but not seperated). Hopefully "p2p" to the next connection will resolve this. I need a transistor tester to determine if any of the multitude of transistors are bad. As previously indicated, I'm going to order an inexpensive one before investing over $100 in a good one; hopefully it will get me by.

CR1020_TR715 SD880 BTrace 11-27-17.jpg
 
Clean those boards up with acetone or alcohol.Be able to better access the integrity of the traces.
 
P2P may be required. What is your method for removing solder ?
 
...oops, I spoke to quick. While inspecting the solder joints around the molex pins for connection to the main power supply board, I noticed they had cracks; I moved one ever so gently and BAM, it cracked and fell out!

Ecap Molex Solder Joints.JPG
 
I just heated the terminal and tried to use a solder sucker. Maybe some good solder wick would have been better.
Thats what I use 99.95% of the time.A sodapullt solder sucker. What are you using for the soldering ?
 
Thats what I use 99.95% of the time. What are you using for the soldering ?

I'm using a Hakko FX888D along with Kester 44 (63/37) solder, however, I did not put much solder on the end of my tip - thinking there was plenty on the terminal already.
 
I'm using a Hakko FX888D along with Kester 44 (63/37) solder, however, I did not put much solder on the end of my tip - thinking there was plenty on the terminal already.
Looks like your set..I usually run my solder tip around 700° F.
 
I cleaned the board and snapped some photos of the trace connections for TR715 - cleaned the trace back a bit and it looks to me like it's broken. Maybe I can jumper a wire across the trace. The leg to the right looks like it may have released from the pcb but not broken.

CR1020_MainPwrSup_TR715 traces.JPG CR1020_MainPwrSup_TR715 traces 2.JPG
 
Desoldering some of the old solder on these boards sometimes requires flowing a bit of fresh solder first before using the solder sucker....And frequently clearing the sucker tube of solder.
 
I cleaned the board and snapped some photos of the trace connections for TR715 - cleaned the trace back a bit and it looks to me like it's broken. Maybe I can jumper a wire across the trace. The leg to the right looks like it may have released from the pcb but not broken.

View attachment 1053903 View attachment 1053905
Do the traces still show continuity with your multimeter from point 2 point ?
 
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