AX-500 Thread

Discussion in 'Yamaha' started by Bratwurst7s, Dec 28, 2016.

  1. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    DSC02984.jpg
    After having several AX-700's go through my hands I've been curious about the AX-500 for a while, as the 700 has proven to be a very nice amp. So when one came up on the 'bay last August for low money I snagged it. It sat on a shelf until November when I finally had tome to go through it and now I can share the experiences.

    Unusually this one has red markings on the knobs, all of the other Yamaha's that I've seen have white markings. If someone did the coloring on their own they did a good job because it loks factory to me. Cosmeticly the amp was/is in very nice condition on the outside with only a very few scratches.

    Cheers,
    James
     
  2. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    The amp worked when I got it, first start was with a dim bulb tester and then with a pair of cheap test speakers. But internally it had issues. Namely glue corrosion, and someone had been in there before me. Some of the glue was scraped away and 2 zener diodes had been replaced. But there was a lot of nasty looking glue and corroded stuff in there.

    DSC02987.jpg DSC02997.jpg DSC03000.jpg DSC03002.jpg DSC03008.jpg
     
  3. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    After a general vacuuming the speaker selector board got cleaned up first and it's solder connections re-flowed.

    DSC03115.jpg DSC03116.jpg

    The speaker posts were in good condition so they stayed as is.

    Cheers,
    James
     
  4. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    The phono board was next. It had glue on both sided that needed to be removed, and of course new caps.

    DSC03117.jpg DSC03118.jpg DSC03129.jpg DSC03130.jpg

    Cheers,
    James
     
  5. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    To deoxit the switches and pots I used something that I improvised, an infusion needle hot glued onto the end of the nozzle tube with the tip filed to a cone shape. More info and pics here...
    http://www.audiokarma.org/forums/in...a-a-500-and-a-520.631520/page-4#post-10078702

    This works really well. The needle tip fits into the small holes on the switches and plugs them at the same time. So the switch is pressurized and the deoxit is really forced through it, it comes boiling out of every crack and opening.

    Cheers,
    James
     
  6. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    For re-capping the phono board I used:
    C142, 143 (2200µF/6.3v Elna): 2200µF/6.3v Nichicon FG
    C224, 225 (220µF/25v Elna): 220µF/35v Panasonic FC
    C149 (33µF/16v): 33µF/35v Panasonic FC
    C135, 136 (10µF/16v Elna): 10µF/25v Nichicon ES Muse (BP)
    C147, 148 (22µF/16v BP): 22µF/25v Nichicon ES Muse (BP)

    I would have liked to replace the 6.3v caps with 10v but there is simply not enough room for a larger dia cap.
    C147 and 148 are in the signal path and were originally bi-polar so I replaced them with Nichicon ES Muse BP. But C135 & 136 are also in the signal path so I used ES Muse in those positions also.

    Every component that had come in contact with the glue was removed and cleaned. Luckily none showed any signs of corrosion so everything except for the caps was reinstalled. I used a 1.0mm drill bit to carefully hand clean the remaining glue from the holes in the board before reinstalling the components.
    On the back side of the board the glue was removed and after cleaning the caps, chokes and the black wire were hot-glued in place.

    DSC03131.jpg DSC03133.jpg DSC03137.jpg DSC03139.jpg DSC03140.jpg

    Cheers,
    James
     
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  7. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    The input board had one wire held in place with Sony glue. That was cleaned up and hot-glued, and the connections were re-flowed. Sorry, no pics there.
    That was the easy stuff. The main pcb involved a lot of work.

    James
     
    Last edited: Dec 28, 2016
  8. boza

    boza Super Member

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    Awesome work James it looks brand new. :thumbsup:
     
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  9. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    In the area around the main filter caps and the area around C187 in the amp section there were a number of corroded jumpers. In all I replaced 16 jumpers. Everything in these areas was removed cleaned and checked for corrosion. In the end I only had to replace 3 resistors and 2 zener diodes. More on them later. Again, I used a 1mm drill bit to hand clean the remaining glue from the pcb holes before installing/re-installing a component.

    There are surprisingly few caps in the PSU section, only 5 including the main filter caps.
    C219, 220 (12000µF/65v Nichicon): United ChemiCon SMH 15000µF/80v
    C215, 216 (330µF/25v Elna): UCC KYB 330µF/35v
    C221 (0.22µF/50v Elna): 0.22µF/63v Wima MKS-2

    In the protection area:
    C212 (47µF/16v): Panasonic FC 47µF/50v
    C213 (22µF/16v): Panasonic FC 22µF/25v
    C214 (220µF/6.3v): Panasonic FC 220µF/10v
    Relay: Finder 24v 40.52.9.024.0000

    Zeners C125 & 126. One had been replaced and the other had corrosion. Here is where my inexperience with zeners makes for questions. I found a data sheet for MTZ zeners and for the MTZ-16C it showed 15.69 - 16.51v. I'm used to finding the center of tolerance and using that as nominal, which in this case works out to 16.1v. Being unsure if that was the correct thing to do I ordered both from Mouser.
    http://www.mouser.de/ProductDetail/NXP/NZX16B133/?qs=mSipnS5lFm90j779ap838A==
    http://www.mouser.de/ProductDetail/Microsemi/JAN1N966B-1/?qs=TXMzd3F6EymeqzVfLrjjGg==
    And in the end I used the 16v from Microsemi. I have no idea if I did the right thing, but on the other hand the amp works beautifully, so, Huh.

    Also, next to those zeners are some big 2w MOX resistors. R263 & 264 (2.7kohm) and R262 (1.8kohm). They were all corroded so I replaced them with 2.7k KOA Speer MOX 2w MO2CT631R272J and 1.8k KOA Speer MOX 2w MOS3CT52R182J.

    DSC03251.jpg DSC03252.jpg

    Cheers,
    James
     
    Last edited: Dec 28, 2016
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  10. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    The big filter caps. The original 12000µF63v caps are 4 lug with 22mm spacing on the +-. 35mm dia x 80mm H. And while I have successfully drilled the board on a few A-520's there was just no way that would work here for the 10mm snap-in caps with the pcb pad spacing. And after thinking about it a lot I just don't want to drill boards anymore in general. It just somehow doesn't feel like clean work and is irreversable.

    So after measuring I figured that there was just enough vertical space to use some 4mm pvc spacers and still have about 2mm between the top of the caps and the amp cover. I used a 1.5" holesaw to cut some disks out of 4mm pvc stock and drilled pass-through holes. Then I marked and filed relief slots to clear the jumpers that pass under the caps. For leg excentions I tightly wrapped 1.5mm² around the legs, soldered and bent, leaving a nice long leg that would be easy to get through the pcb holes. The holes around the original legs were drilled small and opened up with a rat tail file just enough to get a fit that snapped onto the cap legs. Not shown in the pics I also used a small amount of hot glue to hold the disks extra securely.

    This worked quite well, the caps mounted nice and securely. I cut some 2mm closed cell foam pads and put them on top of the caps with double stick tape as a security measure against the case getting pressed down onto the caps.

    DSC03255.jpg DSC03258.jpg DSC03260.jpg DSC03261.jpg

    Cheers,
    James
     
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  11. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    Thanks Boza! It was a fun project.

    Cheers,
    James
     
  12. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    I see now that I neglected to take enough photos and don't have any pics of the finished amp section. Nonetheless, here is how it went.

    C187 (470µF/80v Elna) was glued down and several jumpers in the area were corroded. Surprisingly no other components in the area were corroded, they all looked good after cleaning. The pcb holes were cleaned as before and everything was reinstalled.

    I deviated from stock in one regard. I had some Nichicon PJ(M) 680µF/80v caps left over from an AX-700 rebuild and used one of them in place of the 470µF/80v for C187. The rest of the amp section went as follows:
    C191, 192 (220µF35v Elna): 220µF/50v Nichicon KZ
    C201, 202 (100µF/16v Nichicon Muse): 100µF/25v Nichicon FG
    C157, 158 (100µF/6.3v Elna): 100µF/16v Nichicon FG
    C159, 160 (22µF/16v Elna): 22µF/25v Nichicon FG
    C193, 194, 211 (1µF/50v): Wima MKS-2 1µF/63v

    Now here I have to apologize. Because my notes show what caps I installed in the rest of the amp section, and what they replaced, I failed to note their positions. And what the schematic shows for the remaining caps doesn't match my notes. So I'll have to open the amp back up and check this, as well as take some more photos. So rather than provide possibly wrong info the rest of the list for this are will have to wait.

    For trim pots I used Vishay 1kohm 3/8" 20 turn pots, Mouser PN 594-64Y102.

    Cheers,
    James

    edit: Corrected position numbers for the 220µF/35v and 100µF/6.3v caps. Added C193, 194 and 211. Now I just need to supply photos of the finished main amp section of the board.
     
    Last edited: Dec 29, 2016
  13. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    One thing that I forgot to mention, something that I really don't like about this amp. For the most part there are no silk screen labels for components on the PCBs. So one really has to use the pcb layout pages of the SM along with the schematic to know what/where everything is.

    Cheers,
    James
     
  14. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    The Tone board has 4 elcos.
    C169, 170 (1µF/50v Elna): 1µF/63v Wima MKS-2
    C167, 168 (4.7µF/50v Elna): 4.7µF/50v Wima MKS-2

    DSC03262.jpg DSC03265.jpg

    Cheers,
    James
     
  15. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    And the front Main board with the rest of the switches and Loudness etc also has 4 elcos...
    C119, 120 (0.1µF/50v Elna): 0.1µF/50v Wima MKS-2
    C153, 154 (10µF/16v Elna): 10µF/25v Nichicon ES Muse BP (signal path)

    DSC03263.jpg DSC03264.jpg

    Cheers,
    James
     
  16. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    Concerning the pots and switches on the front boards. The needle extention that I added to the Deoxit spray nozzle let me get pretty deep into the pots to spray, and I found that because it's soo small in dia I could also get it pretty deep into the switches through a small opening in the side. Again, like before getting the nozzle in like that forced the spray through the switches and they aren't giving me any sound problems. That's good because at first I tried disassembling the tone bypass switch for cleaning. I will never again do this of my own free will unless there is really no other choice. It took me more than 2 nerve shattering hours to get it (correctly!) back together. The parts are so small (!) and easy to lose (!), this is not for the faint of heart or someone with shakey hands. See that little z shaped hook in the 3rd pic? That's the latch. It has to go back in perfectly, mounted in the little copper frame. It's fantasticly easy to lose. And I did lose it once. After a frantic half hour of searching I found it. I'll use a CAN of Deoxit on a switch before I go through rebuilding one of these switches again.

    DSC03266.jpg DSC03284.jpg DSC03287.jpg

    Cheers,
    James
     
  17. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    Anyway, the amp is done now and in my PC system for the moment with a pair of Canton Quinto 510 speakers. I really love the A-520 that I have been using but the AX-500 is even better. Along with the Asus Xonar Essence STX sound card as a source it sounds very good indeed.

    I'll pull the amp sometime in the next week or 2 and open it up and take some more pics of the main pcb.

    DSC03292.jpg DSC03293.jpg

    Cheers,
    James
     
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  18. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    OK. So I promised some more photos, and more so I promised Maritimer that I'd supply some. So here goes...

    DSC03464.jpg DSC03465.jpg DSC03466.jpg DSC03467.jpg DSC03468.jpg

    Cheers,
    James
     
  19. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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  20. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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