Yamaha A-500 and A-520 Thread

That corroded R204 resistor - 3.3k (1/4W) is in the idling current adjustments circuit for the Right channel. When you replace it then you can replace the other R203 resistor of same value (in the Left channel) with new ones of 1% metal film. Not necessary for the left channel, but why not?

The A-520 is a nice amp. I had mine recapped but didn't replace the main 12,000uF / 56V ones, though.

But I replaced the relay... I think I also replaced the stock NJM4558 opamp with my fave OPA2604, and for me that was a nice replacement. I really like sound of the OPA2604 in these Yamaha amps. I installed a 8 pin socket and tried different opamps, including the NE5532 as well... Of course, you don't have to do all this, but I had fun in trying these IC's in the preamp section.

I am so happy to see this statement, OP Amp rolling is something the headphone guys swear by.
How noticeable are the effects of switching from op amp to op amp???
Did you rank the ones you like??

I have tried only 3 opamps in these amps: NE5532, OPA2134 and the OPA2604. I found the latter very open, 3-D, warmer, etc. I like the 2604.
For me: OPA2604 > OPA2134 > NE5532 >>>>> NJM4558

Very interesting stuff. Good advice about changing both resistors, I'll do it. The Finder relay I already have, got extras when I made my last order. Caps will get ordered in the next few weeks I hope.

The opamp socket is a very interesting thought. I've been wanting to buy some LME49720 and OPA2107 opamps for my pc soundcard (Asus Xonar Essence STX) as I've read a number of reccommendations for them, so why not for my amp. It would be fun.

The only thing that I find in the A-520 that looks like it could be the opamps are 2 inline 8-pin packages marked M5218L 4302V. And space is very tight. I would guess that there must be an adaptor socket to to go from inline 8 pin to a dual 4-pin chip, but I don't see how I'll find space. Or is the opamp tucked away somewhere that I'm missing?

A different question. I see that the A-520 has the same 2SA1306A and 2SC3298A transistors as the A-1020 has. With the A-1020 they are mounted on a card and clamped directly to the heat sink for cooling, whereas on the A-520 they are just standing all by theirselvs on the main pcb. Is there anything to be gained by clipping a small heat sink on them?

Cheers,
James
 

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A different question. I see that the A-520 has the same 2SA1306A and 2SC3298A transistors as the A-1020 has. With the A-1020 they are mounted on a card and clamped directly to the heat sink for cooling, whereas on the A-520 they are just standing all by theirselvs on the main pcb. Is there anything to be gained by clipping a small heat sink on them?

Cheers,
James

Yes.......reliability and less drift as it heats up
 
...

The opamp socket is a very interesting thought. I've been wanting to buy some LME49720 and OPA2107 opamps for my pc soundcard (Asus Xonar Essence STX) as I've read a number of reccommendations for them, so why not for my amp. It would be fun.

The only thing that I find in the A-520 that looks like it could be the opamps are 2 inline 8-pin packages marked M5218L 4302V. And space is very tight. I would guess that there must be an adaptor socket to to go from inline 8 pin to a dual 4-pin chip, but I don't see how I'll find space. Or is the opamp tucked away somewhere that I'm missing?

A different question. I see that the A-520 has the same 2SA1306A and 2SC3298A transistors as the A-1020 has. With the A-1020 they are mounted on a card and clamped directly to the heat sink for cooling, whereas on the A-520 they are just standing all by theirselvs on the main pcb. Is there anything to be gained by clipping a small heat sink on them?

Cheers,
James

You have 8 pins sockets in-a-row (SIL) for the M5218L opamp in your A-520. Brown Dog makes it nice... or you can DIY like leesonic did in post #3: http://www.audiokarma.org/forums/showthread.php?t=494473

You will need a DIP-8 socket anyway like in the pic, to try different opamps.

Now, I think it was another Yamaha amp then, other than A-450, I swapped a DIP-8 NJM4558 opamp. The AX-900 has a 9 pin SIL opamp, but I didn't change it due to space issue. Sorry for bad memory. However, if you intend to use the LME49720... well, that's an ultra fast opamp... you can try it but I don't know how it will behave inside your amplifier. I never dared to try such a monster. Other people here knows the LME49720... You could try the OPA2406 and the NE5532, if you intend to do this experiment. They don't cost that much, I have several of each model. The stock M5218L has same numbers/parameters of NJM4558.

zsuwaw.jpg


For the 2SA1306A and 2SC3298A transistors... do the get very hot standing by themselves during normal operation?

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You have 8 pins sockets in-a-row (SIL) for the M5218L opamp in your A-520. Brown Dog makes it nice...

You will need a DIP-8 socket anyway like in the pic, to try different opamps.

However, if you intend to use the LME49720... well, that's an ultra fast opamp... you can try it but I don't know how it will behave inside your amplifier. I never dared to try such a monster.

For the 2SA1306A and 2SC3298A transistors... do the get very hot standing by themselves during normal operation?
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OK! Thanks for the adaptor link, that would make it easy, got it bookmarked.

No no, I didn't explain myself very well. I didn't mean that I was considering the LME49720 etc for my A-520, only that I had already been thinking in that direction for my soundcard and that I'm open to the idea of using the opamp(s) that you suggested for the Yami.

LOL, I can't say how hot the 2SA1306A and 2SC3298A get yet, I still haven't turned on the amp yet! I want to at least change out those resistors first, and have been too busy to deox it yet.

Cheers,
James
 
I've finally had some time to make a cap list just now. It was very interesting to see how seriously reduced the quantity of caps is compared to the A-500, just 20 vs 33. I also looked through the service manual a bit for the first time and see that the M5218L opamp is interchangeable with the NJM4558 that you mentioned Karl, so that makes more sense to me now.

Cheers,
James
 
For the 2SA1306A and 2SC3298A transistors... do the get very hot standing by themselves during normal operation?

I just had a thought. We have an infrared camera at work for measuring temps on equipment. When I get ready to turn on the amp the first time I'll ask if I can borrow it. Might be interesting. And when I start the A-1020 I can do a comparrison. Just for fun.

Cheers,
James
 
I just had a thought. We have an infrared camera at work for measuring temps on equipment. When I get ready to turn on the amp the first time I'll ask if I can borrow it. Might be interesting. And when I start the A-1020 I can do a comparrison. Just for fun.

Cheers,
James

Engineers use these cameras to do a thermal evaluation of their designs, looking for hot spots prone to failure.

In a repair looking for weak components.
 
Engineers use these cameras to do a thermal evaluation of their designs, looking for hot spots prone to failure. In a repair looking for weak components.

We use it for things like that at work. Looking for hot components in circuit breaker panels, leaks in heating ducts etc. It was usefull for checking/compairing the motor temps on some of our elevator motors when one was running hot and we were troubleshooting it. On a boring day you can check out who has the hotest farts when it's freezing outside. :D Come to think of it you can save a jpg of what it shows...

Cheers,
James
 
We use it for things like that at work. Looking for hot components in circuit breaker panels, leaks in heating ducts etc. It was usefull for checking/compairing the motor temps on some of our elevator motors when one was running hot and we were troubleshooting it. On a boring day you can check out who has the hotest farts when it's freezing outside. :D Come to think of it you can save a jpg of what it shows...

Cheers,
James



Sounds like the boredom of winter is having an effect.

Hopefully the beer gardens will re-open soon.
 
It will be nice when things warm up enough to go to a beer garden. On the other hand, on Saturday I bought plane tickets to Seattle for a Sept vacation. It's usually done raining there by then. For a short time.

James
 
I just finished a parts list for the A-520.

Cheers,
James

Edit: revised parts list 13-Feb-2016. See post #66.
 

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I started work on recapping the A-500 today. Included here are some "before" pics. Tomorrow I'll take some afters. I was able to get almost all of the caps replaced today. Tomorrow the last 3 or 4 and then a reflow for all of the other solder joints. The fellow that I gave it to doesn't want me to change the trim pots to the Vishays that I now have. It's his amp now so I'm not going to argue with him.

Cheers,
James
 

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Should go much faster than the last one.

It took me about 1 1/2 hours to swap out 30 caps this time, including cleaning the pcb with acitone after removing each cap. I'm starting to get the feel for soldering again and am having fun.

James
 
It took me about 1 1/2 hours to swap out 30 caps this time, including cleaning the pcb with acitone after removing each cap. I'm starting to get the feel for soldering again and am having fun.

James

You may have a future in electronics repair :yes:
 
Today I finished the A-500. Interesting point. After replacing almost all of the caps yesterday, including the 220µF 6.3v (used 10v) C111 & C112 I was stumped to find another 220µF 6.3v cap that isn't in the service manual parts list (at least I can't find it). It is in the schematic, C226 in the protection circuit. In the photo it is the larger of the 2 caps next to the protection relay. I've updated my parts list and will upload it.

Luckilly I had an extra one of those (again, 10v) that I had ordered for my 1st AX-700 amp. So that got replaced today. It also turns out that the protection relay has a wider lead spacing than the Finder that I found for the A-1020 project so I'm back to finding a replacement for that again.

After that we turned it on, let it warm up for 15 minutes or so and adjusted the idle pots again. The left had risen to almost 18mV and the right had dropped to around 13mV. Closed her up and done till I find a new relay. (the old one is working, but for how long?) Also, another mistake discovered, and good that we didn't install the trimpots that I had ordered. This amp needs 3k trimmers and not 1k that the A-520 needs.

After that I recapped the Grungig 650's with Jantzen electrolytics. Then we hooked them up + a cd player and tested the setup with some Poppa Chubby. Darn thing sounds great. Really great. I'm going to buy a pair of those speakers for my A-520 in my pc/workshop room. I like them a lot and they come up on the auction site pretty regularly for €50-75.

It was really great to finally send this setup on it's way to it's new home. My friend was glowing as we loaded it in his car and that makes it another project sucessfully finished. :music:

Cheers,
James
 

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Ha ha. I just realized that I haven't uploaded the A-500 parts list at all yet. Here it is...

When I get a part number for 3k Vishay trimmers and find a replacement relay I'll update it.

Cheers,
James

Edit: Avionic linked to these Bourns trim pots in Acetate's "Fixing a Yamaha M-65 For a Friend" thread (thanks Avionic!)...

http://www.mouser.de/Search/Product...virtualkey65210000virtualkey652-3386G-1-102LF

The lead spacing looks a lot better than the Vishay trimmers that I bought.
 

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It was a totally unessicary and spontainous thing, but I saw another black A-520 on the auction site and I couldn't resist. It has one channel not working, which makes it a project, but I got it for only €23.50 plus €7.50 for shipping, so €31. In the worst case it will supply me with parts for other projects, in the best case it will be easy to fix. We'll see when it gets here, haha I haven't even started working on the 1st 520 and now another one is on the way.

Since I have absolutely no need for it if it can be fixed I'll probably victomize some poor soul with it.

But since I'll be making a Mouser order this week for my AX-700 projects I'll probably add a set of caps for this one too and see what happens.

Cheers,
James
 
I got a little work done on my first A-520 today, replaced all of the caps that were on hand (the 220µF, 100µF & 22µF are on back order) as well as the 3.3kohm R204 & 203. I also replaced 2 jumpers near the filter caps that had been corroded.

I preperation for the 2nd 520 I started to look at the parts list and was happy to see that if it needs any transistors replaced I have almost every single one on hand in quantitys to do both channels if need be, thanks to the extras left over from repairing that A-1020. It looks like I'm only missing the 2SK117 FETs. Reichelt has them for €0.39.

If I'm looking at the data sheets correctly it looks like the Toshiba 2SK170 would be a usable replacement for the 2SK117 with even lower noise, and if that's correct Reichelt has them also for €1.05. If that is incorrect someone please let me know!

Cheers,
James
 

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