Yamaha A-1020 Needs TLC

Bratwurst7s

In The Frying Pan
Subscriber
Last Thursday when I went to work and walked over to my corner of the workshop I saw a big silver amp sitting on a cart next to my neighbor's workbench and about messed my pants. There sat a somewhat abused A-1020!

I kinda freaked out and started babbling, "Where did this come from? Whose is it? What's going to happen with it?". Etc. So about then in walks my co-worker with a handfull of cheap caps from our benchstock. Turns out that the amp belongs to an aquantance of ours that wants to get it repaired. It has "bad sound", and a number of bulging caps in it, is plated with nicotine, and has any number od scratches and dents. 3 caps look like the have been replaced at some time in the past as they are a bright orange (2) and green (1). It made me really sad and a bit bewildered to see that this fine amp had been so obviously abused.

So I stopped my pal from attacking it with those caps until I could find out more about what the owner wanted and if he realized what he really had, and what he really wanted to have done. Then I called the owner and got an ok to look into finding 1) quality replacement caps, 2) a new protection relay, 3) quality replacement idle current pots.

So far I've found owners and service manuals from HiFi Engine, and done a google search of the forums here and found the following...

http://www.audiokarma.org/forums/showthread.php?t=450408
So now I have a cap replacement list thanks to 4seatPilot and I can start to look for those locally.

http://www.audiokarma.org/forums/showthread.php?t=279810
I'm pretty sure that we have a 24v Finder relay with gold contacts in our benchstock that will work, if not I will be able to find what is needed locally.

http://www.audiokarma.org/forums/showthread.php?t=379693
http://www.audiokarma.org/forums/showthread.php?t=455327
I don't think that I'll need output transistors (supposedly it supplies sound in both channels but with crosstalk and noise) but if so am hoping that those linked above are still valid and available.

I have Deoxit on hand as well as other localally produced cleaning agents. And we have a dim bulb tester in the shop. I'm only a passable hand at soldering but my foreman is a wonder and will be going over all of the solder points.

I remember reading on a different Yamaha thread that the fusable resistors in these amps can drift over time. Valid? Shouls I replace them? If so can someone point me to which type and brand etc that I should be looking for? A quick look on Friday showed that there are about 30 of them scattered through the amp. I'll have to make a list next week.

Thanks to Karl vd Berg I have links to and info about the trim pots.
http://www.audiokarma.org/forums/showthread.php?t=631520

I'll take some pics tomorrow and post them.

Is there anything else that I'm overlooking that I shouldn't be? It'd be nice to hear this thing sing again, even if I won't be able to take it home.

Cheers,
James

edit 24-Feb-2019: I have updated my parts list and am moving it here, as that seems to be a lot more logical than having it on post#31.

A note about the list. As a non MS or Apple user I don't have any of their Office products and use LibreOffice. I realize that this can be a pita for some people who don't want to have to download and install an extra program just to view this list.

So I also exported it to a pdf form and both that and the spreadsheet are included in the zipfile. Alas the pdf is translated to 3 pages that will have to be taped together to be usable. I'm sorry about that but it's the best that I could do at this time.

Also, you will notice that many of the parts choices in the list are now (February 2019) different than what is discussed in the following thread. This reflects what I have learned since 2015 and different choices that I make now. As with any such list treat it as a starting point and not Gospel.
 

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I'll take some pics tomorrow and post them.
:scratch2:

Front, back, insides, dank U... :D

The A-1020 is a beast. And the "little" brother A-720 was manufactured (under license) also by Blaupunkt as MA-5850 some time later.

Two large 22,000uF, excellent amp for class AB. For pure class A it might operate really hot, that heatsink doesn't seem appropriate, but who knows...

Attached, the back of Yamaha A-1020 over the Blaupunkt MA-5850 (A-720)...
 

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DSC00915.jpg DSC00916.jpg DSC00917.jpg DSC00918.jpg DSC00919.jpg
Front, back, insides, dank U... :D.

Oops. Well I didn't think to take any of the back today, but I will later. Here are the first 5. The 2 yellow/orangeish caps (in the power supply section of the main board) in the 3rd pic and the green one (protection section?) in the 4th pic aren't original so someone has been in this thing at some time. The traces on the back side also show obvious signs of resoldering on those caps.

There's an ugly coating of nicotine and dust trhough the whole amp. We discussed that today and since the owner smokes indoors, and will be doing so in the future, we see little point in even trying to spotlessly clean the insides. I'll try to get it reasonably clean with a small brush, air and perhaps a little alchohol but not more. It's just going to get more of the same in the near future.

Full disclosure - I'm not running this project. I kinda insinuated myself into it to help, have some fun, and hopefully learn something.

Cheers,
James
 
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DSC00920.jpg DSC00924.jpg DSC00925.jpg DSC00928.jpg DSC00931.jpg And more...

Some of the front panel switches, output transistors, ugly signs of corrosion coming out of the rec-out selector switch, one of the idle current trim pots, and the back side of the volume pot.

James
 
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DSC00935.jpg DSC00937.jpg DSC00938.jpg DSC00941.jpg And that's it for now...

The exposed front panel switches are starting to show spots through the chrome, the power switch has taken a pounding, a shot of those big power supply caps, and it looks like the stereo/mono mode switch got stuck at some time and suffered for it. Kinda makes me sad to see such abuse on such a fine amp.

Cheers,
James
 
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Overall it's not that bad. :thmbsp:

For sure need a really good cleaning. Better, a DEEP cleaning (water, soap and Deoxit :D) before starting any resto.

Some switches in Yamaha amps for that era get really stuck. For some, you need to open and cleaning inside it, only "deoxing" it won't cure it.

How does it sound (with a headphone)?
 
Overall it's not that bad. :thmbsp:

For sure need a really good cleaning. Better, a DEEP cleaning (water, soap and Deoxit :D) before starting any resto.

Some switches in Yamaha amps for that era get really stuck. For some, you need to open and cleaning inside it, only "deoxing" it won't cure it.

How does it sound (with a headphone)?

Yes, it's even more dirty in person than the pics show. I will be doing as much cleaning as time and desire allow but will be saving my Deoxit for the pots and switches, that little can was expensive. But we have some other reasonably good circuit cleaners at work for the overall work.

2 things that I didn't mention before. The rear feet are missing. And today I had the bad feeling that the volume pot was broken. It didn't index correctly on the lower stop, and would turn even further with light pressure. Turns out that the outer alluminum portion of the knob has seperated from the inner plastic part and just needs to be cleaned and reglued together.

I haven't gotten as far as turning it on. We were fairly busy fixing elevators and other stuff that we get paid for and I didn't have much time. And I really want to talk to the owner at length and find a bit more about it's history before turning it on. I got as far as finding out that he is the original owner and the amp has been sitting in storage for 5 years waiting for some attention. This may take some weeks to move very far forward as it's strictly something that will get done in quiet moments between the other stuff.

I'll bring my headphones and an mp3 player to work later this week and make a first test. And I still have to find some actual caps that match the ones in that capacitor pdf list.

Cheers,
James
 
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I have an A-1000, I believe it is the previous model.

By comparison, the A-1000 heat sinks are much larger and cast metal.

A shop that did some work for me mentioned removing boards and cleaning them with mineral spirits (alcohol) and a paint brush to get the tobacco resin off of the boards. I can't speak to the safety of doing this, but the resin can't be good.

As far as caps go, a lot of people like the Nichicon FGs and Muse, they are widely available in the US, I'm sure any quality cap is better than 30 year old ones.

Someone should be able to give you the part number for a drop in replacement relays. I think there are two in the unit, one for Class A, and one for the speakers.

If the plastic is dried and brittle on the RCA jacks, it can turn into a bigger project if there are no drop in replacements.

Mine will require a complete overhaul in the not too distant future as most of it is original, still a great sounding amp.
 
I have an A-1000, I believe it is the previous model.

By comparison, the A-1000 heat sinks are much larger and cast metal.

A shop that did some work for me mentioned removing boards and cleaning them with mineral spirits (alcohol) and a paint brush to get the tobacco resin off of the boards. I can't speak to the safety of doing this, but the resin can't be good.

As far as caps go, a lot of people like the Nichicon FGs and Muse, they are widely available in the US, I'm sure any quality cap is better than 30 year old ones.

Someone should be able to give you the part number for a drop in replacement relays. I think there are two in the unit, one for Class A, and one for the speakers.

If the plastic is dried and brittle on the RCA jacks, it can turn into a bigger project if there are no drop in replacements.

Mine will require a complete overhaul in the not too distant future as most of it is original, still a great sounding amp.

I'll bet you love that A-1000. I've seen pics of the innards and it looks like a much better build quality that the A-1020. The 3 large heat sinks alone speak of better quality.

I did some cleaning today using Rivolita-50, an industrial cleaner we use a lot where I work. It does (did) a pretty good job of removing basic crud (and nicotine) without leaving a film or residue. I have the extererior, faceplate, and inside of the cover nice and clean now.

I found a Finder replacement relay also, P/N 40.52 8A 24v DPDT with gold contacts. Conrad.de has them for €6.25.

I also learned this morning that Mouser sells here in Munich and downloaded Nichicon data sheets from them. Spent this evening so far matching FG's and making a part nr list. If time allows tomorrow I'll measure the lead distance, dia, and available space on the original caps and compere to the replacements just to be sure.

Cheers,
James
 
I'll bet you love that A-1000. I've seen pics of the innards and it looks like a much better build quality that the A-1020. The 3 large heat sinks alone speak of better quality.
I have an A-720, I see from the pictures of your A-1020 that it's almost the same interior layout. The heatsinks look inferior to the previous generation, but they do a good job.

Good luck with your restore!
 
I'll bet you love that A-1000. I've seen pics of the innards and it looks like a much better build quality that the A-1020. The 3 large heat sinks alone speak of better quality.

I did some cleaning today using Rivolita-50, an industrial cleaner we use a lot where I work. It does (did) a pretty good job of removing basic crud (and nicotine) without leaving a film or residue. I have the extererior, faceplate, and inside of the cover nice and clean now.

I found a Finder replacement relay also, P/N 40.52 8A 24v DPDT with gold contacts. Conrad.de has them for €6.25.

I also learned this morning that Mouser sells here in Munich and downloaded Nichicon data sheets from them. Spent this evening so far matching FG's and making a part nr list. If time allows tomorrow I'll measure the lead distance, dia, and available space on the original caps and compere to the replacements just to be sure.

Cheers,
James

Gold relays, sounds like a must have, send me a link. :yes:

On the Nichicons, I combined the same capacitance mf, and used the higher voltage ratings, sometimes higher than either original cap, in the MX-600 there was plenty of room for the slightly larger caps.

The large filter caps seem to present a challenge on the Yamaha amps, direct replacements are apparently hard to come by. So the question becomes where to drill the holes, and what shape holes. I haven't tried them, but the Chemicons have a following for the large caps, smaller footprint and low cost relative to the others, you would have to compare the performance specs on ripple current etc. Going a little over like 10-20% on the capacitance shouldn't hurt anything. Going up to 105C temp rating gets you different aka better materials, but may limit choices.

Higher efficiency bridge rectifiers can be had that drop in, less heat. My EE friend laughs at the idea that anyone can hear the difference.

On mine all the caps will go along with the relays, I also hear the fusisters need to go too. Probably worth testing and replacing as many components as is practical. I don't like the speaker connectors on mine, possibly mini banana posts, so I will look at them while I am at it. Gold plated 2 way posts on Amazon are something like $3 each.

I retouched the connectors on a Yamaha tuner the other day, problem went away, good cheap fix.
 
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Just noticed A-Dam and Munich, so many good memories.......

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
might make a good before and after compare.

If you have a decent pair of headphone or speakers in the shop, this is the first thing I play on any system, female voice is hard to reproduce accurately for a lot of systems. Sounds pretty good off of a CD.

It's old school, but what can I say....Tucson AZs gift to the world.

https://www.youtube.com/watch?v=dzNmG_lpNw8

A couple of test tunes from your neighborhood, dare I say between Germany and the Netherlands. Wolfs, a reason to visit Brussels.

https://www.youtube.com/watch?v=v2Bs09twUmg&index=6&list=PLgugWBANrQyU39SWyIM6sCIJWo-A3GBlD

https://www.youtube.com/watch?v=7Oox5S-HM74&index=1&list=PLgugWBANrQyU39SWyIM6sCIJWo-A3GBlD
 
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Gold relays, sounds like a must have, send me a link. :yes:

On the Nichicons, I combined the same capacitance mf, and used the higher voltage ratings, sometimes higher than either original cap, in the MX-600 there was plenty of room for the slightly larger caps.

The large filter caps seem to present a challenge on the Yamaha amps, direct replacements are apparently hard to come by. So the question becomes where to drill the holes, and what shape holes. I haven't tried them, but the Chemicons have a following for the large caps, smaller footprint and low cost relative to the others, you would have to compare the performance specs on ripple current etc. Going a little over like 10-20% on the capacitance shouldn't hurt anything. Going up to 105F temp rating gets you different aka better materials, but may limit choices.
.

My apologies, I was wrong the relay is actually silver-nickle, which should actually have less DCR than gold.
http://gfinder.findernet.com/assets/Series/353/S40EN.pdf
http://www.newark.com/finder/40-52-9-024-0000/relay-power-dpdt-24vdc-15a-tht/dp/08X7115
http://www.conrad.com/ce/en/product/502882/Finder-405290240000-Miniature-PCB-Relay-24Vdc-DPDT-CO
Funny, when I looked earlier today that relay was listed at €6.25.
http://www.amazon.com/FINDER-40-52-9-024-5000-RELAY-POWER-24VDC/dp/B00HPLOCYC

If this amp was going to come to me I would most likely go with caps rated for a higher voltage where they fit. But that decision will be handled by the owner and how much he wants to spend. The PS filter caps probably won't get changed, but I'll look up their sizes and price anyway.

I still need have to find the correct trim pots, that'll be later in the week.

Cheers,
James

Cheers,
James
 
22,000uF

...

The large filter caps seem to present a challenge on the Yamaha amps, direct replacements are apparently hard to come by..

Yes, I believe the A-1020's caps have the same type of "flat" lugs as the ones used in the AX-900, so it might be hard indeed to find a drop in replacement. But one can make it possible by drilling the board for a snap-in type like this (40mm x 80mm). The Nichicon KG type is 63x100mm and a bit pricey.

Or, with the plastic clamps, this - downside up mounting - is also possible if stock ones are ~50mm diameter.

...
A couple of test tunes from your neighborhood, dare I say between Germany and the Netherlands. Wolfs, a reason to visit Brussels.

https://www.youtube.com/watch?v=v2Bs09twUmg

Live now! http://www.3fm.nl/
 
Just noticed A-Dam and Munich, so many good memories.......

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
might make a good before and after compare.

If you have a decent pair of headphone or speakers in the shop, this is the first thing I play on any system, female voice is hard to reproduce accurately for a lot of systems. Sounds pretty good off of a CD.

It's old school, but what can I say....Tucson AZs gift to the world.

https://www.youtube.com/watch?v=dzNmG_lpNw8

A couple of test tunes from your neighborhood, dare I say between Germany and the Netherlands. Wolfs, a reason to visit Brussels.

https://www.youtube.com/watch?v=v2Bs09twUmg&index=6&list=PLgugWBANrQyU39SWyIM6sCIJWo-A3GBlD

https://www.youtube.com/watch?v=7Oox5S-HM74&index=1&list=PLgugWBANrQyU39SWyIM6sCIJWo-A3GBlD

I only have a pair of Sennheiser HD 280 pro headhhones. OK, but certainly not great. I'll be bringing them into work for the first time we start the amp.

I generally prefer Linda's earlier work, but I do like to listen to her, especially her Warren Zevon covers.

Those 2nd and 3rd links. I haven't heard of Hooverphonic before. Damn that woman has a great voice. I'll probably have to add them to my buy list now. Thanks very much.

Cheers,
James
 
Those 2nd and 3rd links. I haven't heard of Hooverphonic before. Damn that woman has a great voice. I'll probably have to add them to my buy list now. Thanks very much.

Cheers,
James

Buy the CD-DVD combo of Hooverphonic With Symphony Live, worth every penny.

The next time I am headed to Europe, use to be once a month now once a decade, I may write ahead to determine Noemie's availability for lunch with fans that have little hair and less money......

Ciao for now

Mark
 
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