Yamaha A-1000 Repair and Info Thread

Discussion in 'Yamaha' started by tmsears, Apr 13, 2017.

  1. tmsears

    tmsears Active Member

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    Another victim of "the glue"..

    Hi folks,

    I've been a longtime lurker and seldom post, as I have very little I am able to add to this excellent forum! :D

    I have a background in IT hardware and networking but little electronic repair experience outside of turntables. I am in the process of learning, and I have learned so much from this forum! My sole amp is a Yamaha M-4 that is acting up and needs new caps most likely due to age among other things I am sure; it has sadly become unusable in it's current condition.

    In my infinite wisdom I decided to get a "substitute" integrated amp while I learned how to work on the M-4 at a leisurely pace. I wanted tot take my time so as to not risk messing it up. I sold off a turntable and used the funds to by an A-1000 off of the 'bay'. I corresponded with the seller and found out that he had bought it new, always babied it, and didn't want to part with it but the wife.., etc.

    Believe it or not, it all was true! The amp arrived packed extremely well, in immaculate condition, complete with manual. I blew the dust out of it, hooked it up to a dim-bulb tester I made, plugged in a pair of MonoPrice headphones, and played Huey Lewis on my old crappy phone through it. At first I only got one channel, but I was able to get both going by tapping on the relay.

    The amp sounded wonderful, for exactly 38 minutes. That's when I heard a 'brrrrrtttt' sound in the headphones as I watched the bulb in the DBT lite up full strength.:(

    I opened it up and well, a pictures at this point will save me from boring readers anymore than I have already. I apologize for the picture quality in advance:
    IMG_20170319_164919326.jpg IMG_20170319_164955045.jpg IMG_20170319_164928967.jpg IMG_20170319_165526423.jpg IMG_20170319_165558804.jpg IMG_20170319_165554870.jpg

    Thanks to this site I know that this is the dreaded "glue" and not the capacitors simply leaking. I found more glue on the "equalizer" and tone boards but the glue there has not gone bad...yet.

    So it looks like I am going to have to repair my substitute amp so that I can repair my M-4. I have been wanting to get into repairing vintage amps as a hobby but I didn't know my initiation was going to be a trial by fire :eek:.

    So the first two questions that I know to ask is, 1) on the blue resistor that has the corroded leg: there is only one other resistor colored blue like that in the amp, it is the same value, so I assume it is the "twin". They are R133, 134. 820 Ohm:
    IMG_20170319_165027335.jpg

    2) The 680uf caps, and I guess the 330uf's next to them, are they signal path or power? I have the service manual but I am still learning how to read schematics, so apologies for this and future ignorance.

    Oh, and the obligatory 'resistor bbq' that is equalizer board 14 (thanks go to @avionic for the replacement tip!):
    IMG_20170319_164746960.jpg

    I have a used 100 Mhz oscilloscope, two crappy home depot DMMs, a Chinese component checker and a Weller magnastat (don't laugh) and I ain't scared, but not foolish (I hope).

    Any advice would be greatly appreciated. :bowdown:
     
    Last edited: Apr 17, 2017
  2. zaibatsu

    zaibatsu Active Member

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    393
    Congratulations on the purchase, the A-1000 (in Class-A mode) is up there with Yamaha's best sounding amps IMO, though a bit of a sleeper as it doesn't have the fame (or fancy looks) of some of the more popular ones. Only those who've heard know. :D

    The downside is that they run hot and should be restored pretty carefully before going for the next 30 year run.
    Listening only with the DBT was a smart call for sure. Has the relay stopped clicking on when you power it on with the DBT?

    1) Not sure what your question is about those resistors? Probably wise to replace but I doubt it's the issue.
    2) The 330uF and 680uF are power filtering caps from my understanding. It's good to desolder them and clean off all that glue (acetone helps soften it) + replace any corroded jumpers or resistors affected by the glue (sometimes hidden under the caps). You'll probably find they are reduced in capacitance (and it's not a bad idea to replace them) but if it's within -15% IMO it's not going to cause the amp trouble provided the corrosion and glue situation is sorted. The ~$10 Mega328 component tester off ebay is quite handy for this.

    The biggest cause of problems in these is dried/cracked solder joints. Often it's not visible but I'd personally go through and redo all solder joints. I find reflowing alone isn't the best long term solution, retouching with fresh 60/40 solder is good. At the bare minimum I'd do it for all transistors. Careful not to create solder bridges or shorts, the legs/joints are obviously very close together on the small transistors.

    My advice would be:
    - Remove the big caps, clean all the glue, replace all corroded jumpers/resistors (use a solder sucker and try not to push the terminals down when removing, as it can damage the PCB tracks).
    - Redo all solder joints, at least all transistors
    - Probably no dire need to recap until you fix the problem, unless something you remove is over 20% down from spec. Do measure all the 680s and 330s to get an idea, you'll have to remove them anyway for the glue.
    - Don't take it off the DBT until absolutely sure everything is good - work double checked, relay clicks, bulb dim

    You can also pop the cover off the relay and give the terminals a careful clean with some paper or something if desired. Again, not a bad idea to replace, but I don't think it needs to be done until you find/fix the problem.
     
    Last edited: Apr 13, 2017
    Archguy likes this.
  3. tmsears

    tmsears Active Member

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    Thanks for the advice and cap info Zaibatsu !

    I pretty much had the same train of thought on how to proceed; I was going to go ahead and at least replace the caps shown in the pictures, that way they would be done with and I could use the left over leads from the new caps as replacement jumpers.

    I have two of those little component testers you mentioned, they seem pretty handy so far. :thumbsup:

    As to the resistor question. The blue one you see in the pic has a leg corroded off and separated by the glue-o-doom, maybe this angle will show what I mean better:
    IMG_20170319_165633097.jpg

    I tested it and it is a 820 ohm resistor. The service manual says that "Carbon resistors of the amplifier are 1/4W. There is no description about them in this parts list". The resistor in question, R-133, is not in the parts list, so I am assuming that it is a carbon film, like the majority of them. What sticks out to me about this particular resistor and it's "twin" -R 134, is that they are the only resistors in the amp that have a blue base color instead of the usual tan color that all the rest of the regular resistors have. That and both of the blue body resistors are installed about 1/4 of an inch higher away from the board.. All of the others are close to the board, if that makes any sense.

    Because those two resistors seem peculiar and because they make no mention of them in the service manual, I was wondering if anyone knew anything about them before I put in my order to mouser/digi-key.

    Thanks again!

    Edit: Forgot to say, yes the relay stopped clicking after it stopped working,it is stuck in protection mode. I have not turned it back on since it stopped working. With that resistor lifted off the board I didn't want to risk damaging anything.:) I have checked the main output transistors (while powered off) and non of them are shorted, so that's a plus.
     
    Last edited: Apr 13, 2017
  4. tmsears

    tmsears Active Member

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    I notice that Zaibastu and others like the Wilma film caps that look like the little red legos in place of low value electrolytics. I have a few questions about them:

    1) are they OK to use in place of both bi-polar and polarized electrolytic caps?

    2) Are there any downsides to using them?

    3) do they make the amp sound "bright" (I know many do not think caps can affect sound).


    Thanks in advance!
     
  5. zaibatsu

    zaibatsu Active Member

    Messages:
    393
    I get it now. Is that resistor the same aqua-ish colour and physical size as the vertical standing flameproof resistors?
    I'd replace it with a flameproof 1/4W as the safest bet - Yageo make a flameproof series which should cover that. Make sure you stand it off the board like the original. The color code matches your 820Ω reading so that's good. The other blue (actual blue) resistors mounted like your 820Ω are metal films, but those are listed in the manual, so I can't say for sure what these are.

    As for the caps - as much as it's fun to mess with all that stuff - I'd strongly recommend getting it working 100% in stock guise first before changing anything more than what is absolutely necessary (i.e. blown, corroded, or outside of spec). If those 680 and 330 caps are within the +/-20% spec (>540, >260), I'd clean them up and pop them right back in until you get the amp going and try it properly with some speakers.

    The reason I say that is, it will paint a clear picture of how the amp is supposed to sound. In my experience if there's any deterioration of the original sound, it's often due to flaky solder joints / corrosion creating conduction (or lack thereof). New parts definitely take a little while to settle in (in my experience - particularly electrolytics) so I think it's better to have a baseline first with the original parts, to your own ears. I could comment on the subjective differences but you'd be better off hearing any potential changes for yourself.

    The other thing that's probably wise to grab is a Bourns/Vishay sealed trimpot for the two 5kΩ (idle adjust) and one 100kΩ (class-A switching point adjust). I find 20-turns work best for idle (and use them for the switching point adjusters too), but I think a single-turn is better suited to the switching point adjustment. I've personally never had a problem with the stock items on these amps but I have read the occasional horror story so I change them to be safe. You do have to extend the middle leg to fit them which is a bit finicky. If you do change these, be sure to remove the originals carefully without changing their setting so that you can set the new pots to the same values.

    RE: The Wima questions - yes they can be used in place of both polar and BP caps, they are non-polar. Even within the film caps there are a lot of options (eg. polypropylene for smaller values, polyester for slightly larger ones) and various size/cost/performance tradeoffs between them.

    I'll share my current parts list for the 700 if you want some ideas (most of the caps are shared with the A-1000, just ignore the Cxxx numbers), but I would leave this alone until the amp is running.
    The small caveats to this list are:
    1) Ignore everything below row 38, non-electrolytics don't need to be replaced
    2) I didn't restrict budget so some parts are expensive
    3) I used 750uF UCC GPDs in place of the 680uF because I found most 680 caps measure more like 620. Works great but not required. You might need to jump up to 100V rating to cover the 85V rating on the A-1000.
    4) Using 2.2uF polypropylenes (for the 2.2uF 50V and 100V electrolytics) is a lot of cost and effort (lead bending), you can ignore that and use smaller polyester/PET (eg. Wima MKS2 and Panasonic ECQ-E instead of the larger polypropylene ECW-F).
     
    Last edited: Apr 14, 2017
  6. tmsears

    tmsears Active Member

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    The resistor is similar, but not the same color or coating as the vertical mounted metal film resistors. There is only one other resistor like it in the whole amp. and that one is the same value and it is also mounted away from the amp board.

    I agree fully about the repairing the amp first being the priority. I just figured it would be easier to get all the parts at once and not have to worry about it again (I am one of those people who likes to go grocery shopping once a month instead of every week:D).

    I was thinking the same thing on replacing the trimmer pots. I have dealt with the original type before outside of amplifiers and they are very touchy.

    Questions about the trim pots:
    1) Is it better to measure the values of the old pots in or out of circuit, or both? I want to get as close as possible to the original value as to minimize the risk.
    2) You say single turn is better for the class A switching point adjustment. Since I have no prior experience with that adjustment, can you tell me why the single turn is better for that one?

    Also, does anyone have any thoughts or experiences with Rubycon caps? Would they be a good brand for replacement of the 680uf and 330uf power filter caps? The only brands I can find that are available in the 680uf with the same lead spacing and similar or smaller dimensions are Rubycon, Panasonic FC, and Nichicons. The originals were Nichicon Muse series but they are not available in those values anymore, from what I can tell.
     
    influx likes this.
  7. zaibatsu

    zaibatsu Active Member

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    393
    Yeah, definitely measure them out of circuit - hence being careful not to bump the adjuster while removing.
    The switching point adjustment basically requires you to turn the adjuster back and forth (under a particular setup / set of conditions explained in the SM) until you find the point where the voltage reading on your DMM switches from +16v to -16v. I found it's easier to find that point with a single turn than with a multiturn. Up to you though - just my opinion in hindsight - as I've set that adjustment with multiturns and the stock single turns. The Vishay single turn blue pots are nice. Multiturns are definitely easier to set idle with though.

    For the 330uF I can definitely recommend the Panasonic OS-CON as per my list, it has better specs than most "audio grade" caps and I've used them in a bunch of builds now.
    Edit - Nichicon Muse KZ also always a good bet.

    For the 680uF you could use the Nichicon LKG if you want the best direct replacement for the Muse series. You'll have to be a little creative with the leads to mount them, I've used them before in Yamaha amps though so just ask if you need details. Check the diameter to make sure they'll fit though.

    Nichicon UPJ also comes in 680uF/100V and I've used it with success. Normal leads and same profile as stock so easy fit from memory. I've never used new Rubycons but I'm sure they'd be good too, the old Rubycon black gates I've pulled out of Yamaha amps have been the best measuring caps I've pulled so I respect the brand. These are power storage/filtering caps so anything with high-ish ripple current is fine. Also don't worry about mixing, no harm in my experience.

    As for those resistors, I'd probably replace both with whatever you get for L/R consistency, just mount them up off the board and I'm sure it'll be fine.
     
    Last edited: Apr 15, 2017
  8. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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  9. tmsears

    tmsears Active Member

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  10. zaibatsu

    zaibatsu Active Member

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    Did you see the caps I linked? Blue text = mouser link.

    Your link doesn't work for me but Panasonic FC is fine too.
     
  11. tmsears

    tmsears Active Member

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    Yes, I saw the blue links. Excluding the snap-in cap (not feeling that adventurous), they all looked good, I am just looking at all options. Sorry about my link, I don't know why it is not working for you :dunno:.
    I live in the states, so digi-key is a viable option for me, unless you know of a reason for me not to look there. :)
     
  12. zaibatsu

    zaibatsu Active Member

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    https://www.digikey.com/product-detail/en/nichicon/UPJ2A681MHD/493-11106-ND/2599382

    https://www.digikey.com/product-detail/en/united-chemi-con/EKZN101ELL681ML40S/565-4150-ND/4843960

    I think we just use mouser since we're overseas (cheaper post), digikey is grand otherwise.
    I'd probably go for the Nichicon/UCC option over the FC, slightly higher ripple current and I find the ESR is a bit lower in practice.

    Edit - careful using digikey's ripple data though, they are providing the 120Hz measurement instead of the regular/mouser 100kHz measurement (if you check the datasheet for the KZN it's 3.5A). Neither are wrong, just inconsistent with each other it seems.

    Also a good Rubycon option if you wanted that:
    https://www.digikey.com/product-detail/en/rubycon/100ZLJ680M16X40/1189-1047-ND/3133975

    All three of those caps have pretty much identical specs, ~3.5A ripple and 18/16x40mm leaded construction.
     
    Last edited: Apr 16, 2017
  13. tmsears

    tmsears Active Member

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    Thanks for the heads up on the ripple data discrepancy; as luck would have it, I been using mouser as my main source, then I will go over to digi-key if mouser is out of stock:D.
     
  14. Nashou66

    Nashou66 AK Subscriber Subscriber

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    I prefer Digikey when possible as they have cheaper shipping option for anything under 11oz 3.99 vs Mousers standard 7
     
  15. tmsears

    tmsears Active Member

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    Thanks, that is good to keep in mind going forward. Since I can't get everything I need from a single supplier I am splitting my shopping list between Mouser and Digi-Key this go around.
     
  16. tmsears

    tmsears Active Member

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    Well, I am about to place my part orders. I will try to make a spreadsheet of the parts and their replacements. Once I get that done I will post it up here. @zaibatsu I found that I will only be able to replace the (4) 2.2uf/25v electrolytic caps in the DC servo section and (1) 1uf/50v in the auto class A section with the Wima film type. The A-1000 seems to be more "crowded" in those areas on the amp board than on the A-700. The low value caps I was not able to replace with the Wima's will be replaced with long life, low impedance electrolytics. Slowly but surely.:D
     
  17. zaibatsu

    zaibatsu Active Member

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    Good luck!

    Don't think it will matter hugely regarding the films - but out of curiosity were you comparing MKP (polypropylene) or MKS2 (polyester) sizing? I only ask because the polyester caps are pretty small, usually the same size as the electrolytics if not slightly smaller, so it seems strange they wouldn't fit. I used mostly polypropylene through my amps just because I could, but the polyester MKS2 should fit within factory footprint allocations for everything up to 4.7uF (0.47, 1, 2.2uF MKS2 are very small).

    Let us know how you go with the repair, hopefully it gets going again without much hassle.
     
  18. tmsears

    tmsears Active Member

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    On the Wima films, I looked at both, but the polypropylene would have definitely not worked. The A-1000 doesn't have any 0.47uf@50V. The only values on the board that were candidates for films were:

    C163: 1uf@50V (looks like a wima will fit, ordered one)
    C105-106,171-172: 2.2uf@25V (looks like a wima will fit, ordered 4)
    C191-194: 2.2uf@100V (looks too tight to fit a film)
    C162-164,169-170: 10uf@25v (looks way too tight to fit a film that size)

    Just for clarification, when I say those locations looked too tight to fit - I pulled up the dimensions for corresponding wimas on mouser, then dialed those numbers into a little digital caliper to see if they would fit on the amp board. In all of those cases it seemed too crowded for the wima's rectangular shape; half the time the wimas would have thoretically pushed on a neighboring transistor. I could have tried to force them to fit, but I am not feeling that adventurous since this will be my first re-cap job, assuming that all goes well with the repairs.

    Case in point: a wima 2.2uf@100V polyester, mouser p/n: 505-MKS2D042201N00K, is 11mm wide and 7.2mm long, the electrolytic equivalent is 5mm in diameter. So in that scenario, C191 and 192 would have fit ok, but 193 may not have, and 194 looked iffy. Again, I probably could have cajoled them into those locations, but the wimas, from what I have seen , have really short leads unless you get the cut tape style, and none of those were available at the time of ordering.

    If everything turns out OK, I will probably go back in and try to replace those 4 mentioned above, but for now I am just trying to keep my brain straight just keeping track of everything I have ordered and need to order (should've used a spreadsheet).


    Will post updates as soon as they happen.:biggrin:
     
    Last edited: Apr 20, 2017
  19. tmsears

    tmsears Active Member

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    Question: in regards to re-doing the solder joints, do you mean remove the solder with a solder sucker and replace with new solder, or just reflow and to touch up the joints with new solder as needed? Sorry, my metallurgy isn't very strong today XD.
     
  20. zaibatsu

    zaibatsu Active Member

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    Yep all good on the films, I do remember now that the 2.2uF 100V was a lot bigger than the 2.2uF 50Vs.
    Been a while since I looked at this stuff but sounds like you've sussed it out accurately.

    Yeah just retouch with new solder (as if you were adding a little solder to each joint), you'll see the new solder (and flux) flow into the joint when you use fresh stuff. If a joint gets particularly big or looks messy I use the sucker and redo it properly but usually they behave fine. If the new surface is round and shiny it's a good joint in my book.

    What I wouldn't do is *only* remelt the original solder, I find it has a tendency to still look cold/dry and be prone to cracking later - I figure if you're going to the trouble it's worth knowing it'll be good for the next 30 years. This applies particularly on transistors (heat stress), and occasionally caps (mechanical stress).
     

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