Yamaha B-2 restoration journey

As usual, very nice work! You are definitely inspiring changes in my own restoration efforts.

As to how tight, here is the Sil-Pad thermal performance data sheet from Bergquist showing thermal effectiveness vs mounting pressure for it's products. How that translates to how much you tighten the mounting screws. I would assume that you would mount the same as with mica and grease - tight enough to give a reasonable amount of pressure and keeping the hardware from loosening but not so tight as to distort the transistor case.
http://www.bergquistcompany.com/pdfs/techLibrary/Sil Pad Overview.pdf

I am curious as to which silpad you are using - I was planning on a K10, but looking at those charts there may be some better options from a thermal perspective, though not sure if the difference is meaningful.
Thanks. The silpads I have are from Aavid Thermalloy: https://www.aavid.com/products/thermal-interface/thermalsil/53-03-2g

They can be ordered at Mouser.

My biggest problem at the moment is the power switch. Which is unrepairable. The solder legs were so brittle that at first during other works one leg broke off. So it was still usable for a Triac power switch upgrade. When I went on that journey today two other legs broke off like they were made of cookie crumbles. Then I tried to dismantle it in order to check whether I could make new legs myself and a few parts flew across the kitchen. Very unfortunate and most likely not my day today :no:

I was even tearing down my CT-600 and CT-810 to see whether they had similair switches, but they are quite different and can't be mounted in the same frame holes as the original.

So, I'm in desperate need of a power switch. Searched the net and the Bay, no luck so far...

The brand is Petrick and type 285/5. They tend to be used in different brands of audio equipment in the 70'ies and even other Yamaha's. Mostly CR-X00 receivers. By the looks of it, very crappy switch. Can you imagine 230V going through that thing for almost 40 years? :crazy: I really think those switches were not made for 40 years +. My B-2 seems to have been used occasionally, but it has had a 'new' switch which was connected with thermoplastic connector blocks.
 
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I spent some years working in the sil-pad industry. Normally best practice is not to compress the sil-pad more than 20% of it's free air thickness. So as an overly thick example, if you had a 1mm thick pad you wouldn't want to compress it to less than 0.8mm thickness.

More compression generally won't bring you any extra thermal benefits and will start to damage the material.

Cheers,
James
 
My biggest problem at the moment is the power switch. Which is unrepairable. The solder legs were so brittle that at first during other works one leg broke off. So it was still usable for a Triac power switch upgrade. When I went on that journey today two other legs broke off like they were made of cookie crumbles. Then I tried to dismantle it in order to check whether I could make new legs myself and a few parts flew across the kitchen. Very unfortunate and most likely not my day today :no:

Eventually a switch will pop up either through eBay or a forum member with a parts unit. In the mean time I'd reinstall the switch for cosmetics and wire it as if the switch was on, then use a switched power strip to turn it on and off.
 
Sorry Mr Yamaha but you should use mica insultators on THIS kind of heatsink NOT silpads . Those heatsink did exist in 3 versions :
-1) anodized black aluminium with no epoxy paint
- 2) anodized black aluminium with black epoxy paint
- 3) anodized black aluminium with blue epoxy paint
Micas should be used in case 2 and 3
Silpads may be used in type 1 and only this one
Power disspation is critical and if you use the wrong insulator you play with your V-FET !
 
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Sorry Mr Yamaha but you should use mica insultators on THIS kind of heatsink NOT silpads . Those heatsink did exist in 3 versions :
-1) anodized black aluminium with no epoxy paint
- 2) anodized black aluminium with black epoxy paint
- 3) anodized black aluminium with blue epoxy paint
Micas should be used in case 2 and 3
Silpads may be used in type 1 and only this one
Power disspation is critical and if you use the wrong insulator you play with you V-FET !

Thanks Clinic, but your advise does always seems to come afterwards :rflmao:

Can you explain why this is not the right thermal insulator for this type of heatsink? It was advised by a very respectable B-2 restorer :naughty: Although I did not tell him that my heatsinks had a blue coating.

Btw, the VFET's in my unit were originally greased without mica sheets. 100% the first time they were taken out.
 
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Somewhere in this forum there is a thread that goes into the epoxy heat sins, and as I recall the blue epoxy acted as an insulator. Yamaha dropped the practice as it was non standard. Here is a thread that at least mentions the three types - blue epoxy, black epoxy, and no epoxy. http://audiokarma.org/forums/index.php?threads/b2.439559/page-5#post-8029847

My second B-2 has blue epoxy, but it will be a while before I start work on it. I will use an insulator if one is already present. Adding an insulator if it isn't needed lowers power dissipation needlessly.
 
Somewhere in this forum there is a thread that goes into the epoxy heat sins, and as I recall the blue epoxy acted as an insulator. Yamaha dropped the practice as it was non standard. Here is a thread that at least mentions the three types - blue epoxy, black epoxy, and no epoxy. http://audiokarma.org/forums/index.php?threads/b2.439559/page-5#post-8029847

My second B-2 has blue epoxy, but it will be a while before I start work on it. I will use an insulator if one is already present. Adding an insulator if it isn't needed lowers power dissipation needlessly.

Second that!
Why use insulators on the blue (painted) heatsinks?
 
Sorry Mr Yamaha but you should use mica insultators on THIS kind of heatsink NOT silpads . Those heatsink did exist in 3 versions :
-1) anodized black aluminium with no epoxy paint
- 2) anodized black aluminium with black epoxy paint
- 3) anodized black aluminium with blue epoxy paint
Micas should be used in case 2 and 3
Silpads may be used in type 1 and only this one
Power disspation is critical and if you use the wrong insulator you play with your V-FET !

Patrice, would you please elaborate on the need to use pads with the blue epoxy heatsinks?
 
Why use insulators on the blue and black (painted) heatsinks ?
Yamaha did not with painted heatsink ! it is not necessary and we all understand why !
Using insulators is necessary with no painted heatsink
I have refixed many B2 and some were touched by somebody before who over tight TO3 screws ! this way the insulator paint was dammaged and an insulator was necessary to avoid short but only in this case .
Using silpads is find if it is on recent heatsink with high precision place machined with high tolerances . Silpad should not be use on old heatsinks just because surface shape is critical .
For a good thermal conductivity less space you have better it is . Multiple insulator is not good idea (paint + insulator ) decrease efficiency
Am I clear ?
PS : regarding : Thanks Clinic, but your advise does always seems to come afterwards , sorry I don't live in front of my computer ..I have customers waiting for repair
 
Now some pictures
1) not painted heatsink
2) blue painted heatsink with marks closer to screws area

DSC05726-R.JPG DSC08191-R.JPG DSC08198-R.JPG DSC08782-R.JPG
3) Dammaged area are easy to see on this black painted heatsinkDSC05726-R.JPG DSC08191-R.JPG DSC08198-R.JPG DSC08782-R.JPG
 
Now some pictures
1) not painted heatsink
2) blue painted heatsink with marks closer to screws area

View attachment 873743 View attachment 873744 View attachment 873745 View attachment 873746
3) Dammaged area are easy to see on this black painted heatsinkView attachment 873743 View attachment 873744 View attachment 873745 View attachment 873746
So no mica plates like you stated earlier, but just thermal grease?

The blue paint of my heatsinks have no marks or damaged areas.
 
Not sure whether anybody struggled with the mirrored PCB lay-out drawings in the SM, but I did. And I think it can make you make mistakes.

So, I used my MS Paint skills to re-mirror the drawings and re-re-mirrored the component labels (not jumpers) afterwards to make it readable.

Use at own risk! :biggrin:
 
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This would've been great to have a week ago!

That is an annoying aspect of the service manual.

But this amp is so easy to work on.
 
Not sure whether anybody struggled with the mirrored PCB lay-out drawings in the SM, but I did. And I think it can make you make mistakes.

So, I used my MS Paint skills to re-mirror the drawings and re-re-mirrored the component labels (not jumpers) afterwards to make it readable.

Use at own risk! :biggrin:

B-2%20Driver%20board%20Reversed.jpeg

I did that for all the boards I'm working on (without reversing the components) and marked the values as I removed the components. It's the only way I can keep this 100% straight and no or no room for mistakes on these. I'm somewhat lysdexic so i can read backwards just as well as forwards (or mirror, or upside down, etc.). Nice job and a lot of work!
 
A small update here. Less time to spend on the B-2 as the girlfriend returned home after a 6 months lasting internship abroad. You know how it goes when the boss returns home :biggrin:

I had some time to re-mount the VFET's the proper way, with silicone (non conducting) thermal grease.

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Also found a 'new' power switch, I actually stole it from my CT-600. I combined it with the well known Triac switch solution.

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I also had to replace two components on the power board due to new insights. Replaced C222 with a PP film cap and TR216 with a new Zetex transistor.

IMG_3668.JPG

And I installed some new CMC RCA sockets with new shielded wires for direct input in the driver boards. Again, the changes made are reversible.

IMG_3462.JPG

Next up: reinstall the driver boards as is and fire the B-2 op. Exciting :naughty:
 
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