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Technics SU-8077 Rebuild

Yes, I would have insulated the leads with heat shrink, but if you think it won't make much difference, then I am going to do with the film cap that Jeromach recommended. That way I can purchase them all from the same place on one order. Thanks!
 
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Mmmm..., to be honest, in my personal opinion these kind of caps may perhaps look nice, but only add to the costs, not to any noticeable improvement of sound quality. Mildly put...

As for the Wima's; I even did tests, rebuilding one amp with Wima's where they could replace electrolytics and one - the same model of course - with electrolytic capacitors only. The sound difference? None.

I just advised the Wima's here for convenience and because I know they do the job, but the capacitor you initially proposed might do it just as well, I only never used them to see how they perform.
 
MacPhantom said:
@jeromach: sorry for thread-hijacking, but now that you mention Icq: how do you adjust this with high power amps?
I have an SE-A3 in which I've aligned everything - except for the level meter (no scope at home, but nvm) and said Icq, as I don't have dummy resistors rated for 300W.
Click to expand...

Is this a MK1 or MK2? I have an SM here of the SE-A3K, presumably a MK1. To adjust this one an oscilloscope AND a distortion analyzer is needed. I wouldn't know of a way to do it differently.
 
jeromach said:
The 8077 btw uses a clamp and it might not be easy to find a proper replacement, since it needs both be wide and high enough. But I just checked what for instance Digi-Key has available and most likely all of these will be ok (I looked at 12k uF too, that would be an upgrade, although probably not really noticeable); http://www.digikey.nl/products/en/capacitors/aluminum-capacitors/58?k=&pkeyword=&pv13=63&pv13=75&FV=4038d3,fc01ac,fc01c7,fc01d1,fc01eb,fc01ed,fc01ef,fc01f2,fc01f7,fc01f8,fc01fc,fc01fe,fc026b,ffe0003a&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

If the diameter of the old caps is 40mm than it would probably be best to take one of 65mm high, then it will probably fit the clamp nicely. Then these two would be the ones to choose;
http://www.digikey.nl/product-detai...nics-cde/383LX103M080N062/338-2034-ND/2256635
http://www.digikey.nl/product-detai...nics-cde/382LX123M080N062/338-2109-ND/2295339

Please take note that all of these are "Radial, Can - Snap-In - 4 Lead" versions, these will fit the existing print without modifications. Also, please check all sizes before ordering, my recollection of sizes might be wrong!
Click to expand...

Hello Jermomach,

I checked the leads on the existing filter caps of my 8077, and I am pretty sure they are Though-Hole Solder in place type, so I cannot use the snap in 4-Lead type. So, I looked on Digi-Key and found these from Nichicon that are designed for audio and meet the specs. http://www.digikey.ca/product-detail/en/nichicon/UFW1H103MRD/493-3183-ND/1965205 What do you think of those?

Trouble is, as soon as I go to a larger can to fit the bracket, I cannot get the Through Hole connections. Would it be okay to use these without a bracket if they are soldered in? Or, maybe I should look for a different brand that has larger cans with Through Hole soldering connections. What are your thoughts on that?

Thanks
 
Can you make a picture of the back side of the print where the filter caps are soldered in? I can't imagine it is different from those I worked on, but it is possible, so let's check that out first.
 
It should look like this;

4IOlT6h.jpg
 
Yes, exactly. That is the one. Here is my photo:

Circuit Board.jpg

I put a couple of orange ovals over what appear to me to be the top and bottom solder leads of the filter caps. Is this correct?
 
Interesting, yours doesn't have the symbols printed on it...

Ok, as for the ovals, the solder lead on top and at the bottom are the leads that are used for stability, they are not electrically connected to the capacitor. When you look closely at the board you can also see there are no traces, it connects to nothing :).

So, at the left, in the middle, is the positive pole lead, at the right (outside the oval) is the negative pole lead.

You therefore need to unsolder all four leads and replace the filter cap with a snap in model with four leads (careful, they also exist with other numbers of leads), you can also refer to my earlier recommendations, but please check the sizes before you order them.

PS: The caps you mentioned are low (probably too low) on ripple current, apart from them not fitting well either.
 
Ah.... I understand! Thank you for that. Makes sense now. :)

Also, you mentioned to be careful with the thermal diodes on the power transistors, bud didn't actually mention that those power transistors should be replaced. Are they prone to failure over time?
 
No, the power transistors will last a lifetime (and longer :)) if not abused. Mostly, 99% of the cases, they either work properly or not at all.
 
That is nice to hear that the power transistors will last. May I ask you now about those double transistors, so that I can order the correct parts. I did some reading on another thread on this site that the thing to do is to use two bipolar transistors and wire the emitter legs together in the same hole. Then to shrink wrap the tops of the transistors together. The part recommended for the 2SA798 double transistor was a Fairchild KSA992 transistor. When I keyed it in to Mouser, these four possibilities came up:

http://ca.mouser.com/Search/Refine.aspx?Keyword=Fairchild+KSA992

Can you give any clarification as to which one would be the right choice, or maybe you have another choice of transistor I should order.

I did not find yet any part suggestions for replacement of the 2SC2291transistor, though.

Thanks!
 
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The KSA992FTA will do the job. The 2SC2291 can be replaced with KSC1845FTA. (F = DC gain factor range, TA = packing method / how the leads are bent)

Now here comes the interesting part; every two transistors that will be made into one for the purpose of replacing the old double transistors should be matched on current gain (hFE).
It's rather easy to do, but it can take some time, you'll need a tool to do it and you need to buy more transistors than actually needed to be able to get matched pairs.

So, as for the tool, check this topic; http://audiokarma.org/forums/index.php?threads/cheap-component-tester.749729/
If you buy one it might take some time to show up, if you're more in a hurry you'd probably be able to find an Atlas transistor tester, but they come at a price and are less versatile.

Please note that the pinouts for the two original double transistors are different, your home brewed replacements should reflect that too. Also, put some thermal paste between the two before they are shrink wrapped.
 
I think I get that, but just for clarification, and after reading the service manual a bit, with the two KSC1845FTA transistors, the "B" legs need to be joined in the same hole. Is that correct? Do you figure about a dozen transistors of each should get two matched pairs of each?

BTW I think I have a friend who can loan me the transistor tester. If not I will order one.
 
Exactly. The 2SC has a common base (B) leg, the 2SA a common emitter (E) leg and these need to be joined in the same hole.

Sometimes it doesn't fit, then either the hole can be widened a little, or one of the legs can be cut half way and the remaining part soldered to the other transistors leg. The latter is what I usually do.

I think you'd need something like 20 to 25 transistors to find a 100% match. With a dozen you will find a 100% match if you are lucky. Now a 99% match will also do, but these transistors come cheap and you will need them for the 8088 too to do the same trick there :)
 
Yeah, I guess I need 4 to match, not two pairs, which means I will have to get more of them from the start. Probably two dozen or more to find 4 matching. Thanks for all the help. Time to start ordering and getting to it!
 
Okay, I ordered all the parts, or at least all the we can agree on at this point. There will probably be a few more finds later on. :-)

Then I decided to get started doing a little cleaning and such. I also took out the two large filter caps, and discovered some partial messy brownish rings underneath. Does this mean that they were physically leaking? They are being replaced anyway, but I am just curious. Would they have been sealed down for some reason? Seems to me that you were right, Jermomach, and that they were not long for this world.
 
jeromach said:
Is this a MK1 or MK2? I have an SM here of the SE-A3K, presumably a MK1. To adjust this one an oscilloscope AND a distortion analyzer is needed. I wouldn't know of a way to do it differently.
Click to expand...
Thanks! It's the first version (the MK2 is too rare…). I too have the service manual for it, and I know that I'd need a scope and THD meter to align it properly. However, the SM also says I need dummy load resistors…
Anyway, I'll probably leave it as it is for the moment (heatsinks don't get even warm at 1W peak per side, and I cannot hear any distortions – I guess I'm on the safe side for now).
 
This thread makes me want to dig up my old SU-8099 and recap it. These old Technics amps are excellent sounding units. I parked mine 5 years ago because it started pumping out static out of one channel, then the next channel a few days later. Last time I tried firing it up, it never triggered the output relays. One day I'll get around to refurbing it. Honestly, the reason I never have yet is because I'm somewhat intimidated by the complexity of the guts of the thing. There's a LOT of stuff under that cover!

Ed, good luck with your rebuild/recap! Look forward to seeing your progress on this project.

p384397640-4.jpg
 
cube-tube said:
This thread makes me want to dig up my old SU-8099 and recap it.
Click to expand...

Wow. An 8099! If you are not interested, I am! I love these Technics amps. My 8088 sounds awesome in my system, and I bet the 8099 would be even more impressive. That was their top of the line at the time, I believe.
 
One more question, Jeromach. Sorry to be a pest!

I am re-thinking the trimmers I ordered. If you remember, they go right in front of the large filter caps. I ordered these:

http://ca.mouser.com/ProductDetail/...=sGAEpiMZZMvygUB3GLcD7n4W/LGLppVQILhtyxliN3I=

They are 200 ohms, 250 volt, 1/2 watt, and single turn. I chose them because the pin configuration seemed to work. I will find out for sure when they arrive.

Now I am wondering if I should have chosen a multi-turn trimmer such as this one:

http://ca.mouser.com/Search/Product...virtualkey65210000virtualkey652-3339H-1-204LF

This one only comes in a 50 pack right now, though.

Any thoughts? Thanks
 
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