A-1000/A-1020 info/repair thread

Discussion in 'Yamaha' started by OMGCat!, Aug 18, 2015.

  1. OMGCat!

    OMGCat! AK Subscriber Subscriber

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    I didn't even notice what side of the page I was reading, ha. No wonder I can't read color codes properly :scratch2:
     

     

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  2. tubed

    tubed Lunatic Member

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    Think that's bad?
    I full on am fricking color blind.
    Carry on guys.
     
  3. avionic

    avionic " Black Knights " Subscriber

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    Doesn't help matters when resistors get a little age,dust and heat on them. Colors tend to fade or change tint.
     
  4. OMGCat!

    OMGCat! AK Subscriber Subscriber

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    Well the A-1020 is in a holding pattern until I send in the new Mouser order but I did get the T-1020. Made it through the post without getting smashed to bits, looks great and even works.
    I decided to pull the lid just to make sure it wasn't full of dust and/or black widows or something and I found something familiar...

    [​IMG]

    Sigh, I've been glued again. Seems to have a smoked transistor thrown in for good measure as well.
    [​IMG]

    [​IMG]

    I could probably send it back but it's in nice cosmetic shape and they are all probably in similar mechanical shape so I'll just fix it. I'm glad I waited until this arrived to send that order in. I figure I'll do the usual glue removal, replace those diodes (I have the SM on the way for the PNs) change out the larger value caps as well as those two transistors. Then I might be able to listen to the things :)

    So, anyone know a good sub for 2SD1437?
     
  5. OMGCat!

    OMGCat! AK Subscriber Subscriber

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    Updates have been slow in coming but progress has been made. I'll blame 3, 10 hour/day work weeks and a 24 hour motorcycle endurance race for my "weekend" for not having any pics up. On a high note I did get to drive a new 918, GT3RS and Cayman GT4 in one week.
    Actually I'm pretty much done. Setting the bias with those multiturn trimmers was an absolute treat :)
    I've been listening to the A-1020 for about a week now and it's a winner. I haven't had a system with 'synergy' since I got back into audio but this finally makes it. Paired with my B&W DM620s it sounds absolutely amazing.
    I'll have to take some pictures of the finished product but suffice to say that I'm happy and think the inlay of time and money was more than worth it.

    The only sorta issue I have is that I've got around 27mA of offset on each channel. It's not really high but it is higher than I'd like. What would need to be changed to bring the offset lower?
     
  6. avionic

    avionic " Black Knights " Subscriber

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  7. OMGCat!

    OMGCat! AK Subscriber Subscriber

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    Thanks for the sub suggestion. You were right btw concerning the emmiter resistors. They tested around .4ohm on my checker and...so did the new ones. Guess the leads and/or checker error gave me the off number.
    Oh well. I put the ones I removed back in and have spare resistors for a future project.
     
  8. 39cross

    39cross AK Subscriber Subscriber

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    did the glue actually eat through the diode leads? Are you sure the transistor is gone, or is that discoloration from running super hot?

    just curious - in any case I'm sure it's worth replacing them all.
     
  9. OMGCat!

    OMGCat! AK Subscriber Subscriber

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    No, the diodes were fine. The glue pretty much fell off of them when they were pulled and they all checked very close to each other. The two transistors checked very differently with one showing very low gain. I don't think it smoked but it had been running very hot for a long time.
    I ended up reusing the diodes but replacing the big cap (because I didn't feel like trying to get the glue off even though it checked ok), the two transistors and the jumper. I added clip on heat sinks to the transistors to try and keep them a little cooler. There's not a lot of room in there but it's doable.
    I've it for a few hours already and it seems to be a very good tuner.
     
  10. OMGCat!

    OMGCat! AK Subscriber Subscriber

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    I don't want to be one of those people who abandons a thread they started, even though I am already there it seems, so here is a quick update and a few photos.
    I've been using the A-1020 in the main system for a bit over a month now and am totally pleased with it. It's probably gets 15-20 hours use a week and never misses a beat. Overall it's an excellent integrated amp that I'd recommend to anyone who doesn't mind putting in the resto work that's needed otherwise I'd suggest getting something a little newer that lacks the magical component dissolving glue.

    Here are a few pics of the final repairs. This closeup is of small heatshields I made up for the Silmics. Those resistors get HOT and these little shields dropped their temp a bit more than 10C after an hour. If you're going to use the amp a lot I'd suggest putting together something like these.
    [​IMG]


    Next, the small boards mounted to the heat sinks are easy to install improperly. If you don't fully push them into the mounting brackets they will tighten crooked with the transistors only touching the sinks at the top.
    [​IMG]

    Here's a pic of the feet I used. They are 44x18mm machined aluminum with O-rings on the bottom. Super nice for $12 shipped. I used self tapping screws that fit right into the punched holes already pushed into the bottom plate.
    [​IMG]


    The parts replaced, all in all not a bad job with the results being more than worth it.
    Thanks for all the help and info everyone :)
    [​IMG]
     
    zaibatsu, mhjmhjones and Bratwurst7s like this.
  11. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    Nice work! Please explain a bit about what material that you used for those elco heatshields. Looks like a good idea.
    I tried to buy an A-700 a few days ago but got overbid in the last 2 seconds by $0.50. :(

    Cheers,
    James
     

     

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  12. OMGCat!

    OMGCat! AK Subscriber Subscriber

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    The heat shielding is aluminum tube with a composite inner liner used to cover thermoformed plastic lines in some VAG vehicles. This one covered a vacuum line routed directly over the catalytic converter which showed it rejected heat very well. I saved it from a failed part (the unshielded connector cracked when I attempted to remove it) and cut it in half then glued it to the caps. I'm not sure it is needed but I feel better about it being there.

    That sad to hear you missed an A-700 by so little. They seem to pop up fairly frequently on the auction site here but most seem to be stuck in protection. Hopefully you'll soon find a good working one to do a resto on.
    I've still got my eye out for an A-700 or A-1000 but have been hesitant due to having no real use for it. If I owned a home and planned to retire here I'd probably go ahead but eventually I'm going to have to move all of this stuff and seeing as how I've already got a C-80, T-80, M-65, M-60 and PC2602 in the spare room sitting unused I have been letting my logical side win out.
    On the other hand I do think this era of Hi-Fi will catch on once people run out of silver faced units to sell and word gets out how good these sound so may as well buy while the buying is good.
     
  13. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    Thanks for the info. I like the idea. I didn't look to see if Nichicon or Elna etc make 105° caps in the values needed for these amps but now that I think of it maybe that would be a good way to go also if available.

    The A-700 would have been quite a project most likely. Optically it looked very good (a black model) but the left channel output transistors were missing, and then of course one has to wonder why it got that way and what amount of damage was waiting to be found. So it's no big deal that I didn't get it. I did recently however pick up an RX-V3900 (now doing duty as my main amp for a while), an RX-500 (silver, blown main fuse, waiting to be looked at) an AX-300 (should arrive tomorrow, hopefully just needs deoxing), an A-520 (Hooked up to my wife's PC at the moment, deoxed, still awaiting a serious work over but sounds and looks good), an Infinity Alpha sub (blows fuse), and a pair of Canton LE-600 speakers (missing grills and non-oem tweeters but otherwise ok). And I have 2.5 Denon DCD-1290 cd players that I'm going to play around with modding. So I have plenty to do. :whip:

    Cheers,
    James
     
  14. OMGCat!

    OMGCat! AK Subscriber Subscriber

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    Sounds like that A-700 might have been a bit more of a project than it was worth unless it was super clean or super inexpensive. Definitely sounds like you've got plenty to keep you busy as it is either way. I'm jealous of the prevalence of silver models in your neck of the woods. I've never seen a single one here except pictures.
    As another update to the A-1020, it seems like I'm going to have to take apart the input selector switch and clean it manually. I've got crackly sound out of my phono and tuner inputs unless the button is pushed in and out a few times which clears it up for a little while but it always comes back. I've cleaned it several times with a few different types of 'tech in a can' and it will clear up but then start to cut in and out again after a short time. It's annoying to take the unit in and out of my rack and tear it all the way down just to temporarily clean a switch so it's going to have to come all the way apart this time.

    I'll take some pics of the (hopefully successful) project in case anyone else gets lucky enough to have to do this. I'm nervous about getting it back together and having the switch work properly but I'll try and steel myself and get into it this coming weekend.
     
  15. 39cross

    39cross AK Subscriber Subscriber

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    Interesting to see you have a problem with that switch. My A-720 has problems with the tone defeat switch, even after cleaning. It can cause a channel dropout. I had some issues with the mute and the Class A switches too but they have remained in better shape post-cleaning.
     
  16. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    I see lots of different silver Yamaha's here but unfortunately for you they all the ones that I've seen are 220/240v 50hz only. If I could find some multi voltage units I'd have to think about starting an export company.

    Cheers,
    James
     

     

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  17. OMGCat!

    OMGCat! AK Subscriber Subscriber

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    From the condition mine was in I'm pretty sure it was on the way to the dump if I hadn't checked Craigslist when I did. The thing had a major layer of filth inside and out that apparently made it into the switches.
    Unfortunately there doesn't seem to be a way to get into the selector switches that doesn't involve desoldering and then experimenting with disassembly so with the original plan a failure, I flooded them with contact cleaner and 'exercised' (or maybe exorcised) them a whole bunch of times x3 and then gave each a drop of faderlube.
    I listened to it on various inputs before putting it back together and it seems cured for now. I always got a crackle if I pushed a selector switch in even if the sound was good and I don't anymore so all is well?

    James if you could find multi voltage silver units I'm betting you could sell them over here. I don't know how I did it but every single bit a Yamaha gear I have, save for my universal player, is multi voltage. Guess that's what happens when you live in a large military town.
     
  18. 39cross

    39cross AK Subscriber Subscriber

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    920
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    Seems like all is well for now! I hope you're enjoying listening to it.

    And I like that little mod you put in place to shield the caps ;-)
     
  19. mhjmhjones

    mhjmhjones Active Member

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    Hey Bratwurst7s and OMGCat! - what transistors does the A-1020 take? Mine has a few bad ones, and I want to replace all of them. I think there are 12 or 14? I once saw a thread that had some transistors that can be used from parts express, I believe it was, but I can't find it. Thanks!
     
  20. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    If you mean the output transistors the one that I worked on had 2SA1265 (PNP) and 2SC3182 (NPN), 2 pairs per channel for a total of 8 outputs. I used ON-Semi NJW0302G and NJW0281G.
    https://www.mouser.de/ProductDetail...=sGAEpiMZZMshyDBzk1/Wi9NZvtrCxX3LQxpSknG8TRg=
    https://www.mouser.de/ProductDetail...=sGAEpiMZZMshyDBzk1/Wi9NZvtrCxX3LH9AISc2zENc=

    The driver transistors were 2SA1306A and 2SC3298A. I used ON-Semi MJE15033G and MJE15032G.
    https://www.mouser.de/ProductDetail...=sGAEpiMZZMshyDBzk1/Wi/PUgtclNldlWYDF5lWmMkM=
    https://www.mouser.de/ProductDetail...=sGAEpiMZZMshyDBzk1/Wi/PUgtclNldlIbxeXkBE6a0=

    For the other assorted transistors I'd have to look, it's been a while.

    Cheers,
    James
     
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