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AU-719 recap

M

MrLupin

New Member
Good day,

i just picked up a Sansui AU-719 and since everything is original, I will be doing a full recap. I have been reading multiple articles, threads and DIY websites in order to determine the type of capacitors I should be using. I still have to make a decision.

Now I know that there no magical combinations but I am looking to find a decent cost quality balance.

Here are some of the sites I have been looking to to find capacitor comparisons:
http://www.laventure.net/tourist/caps.htm
http://www.humblehomemadehifi.com/Cap.html
http://tech.juaneda.com/en/articles/electrolyticcapacitors.html

For the larger capacitors, the AU-719 used Elna 12000uf caps. Do I need audio grade capacitors to replace those? What happens if I use a non audio cap? I have no trouble spending for good capacitors but since I lack the experience in recapping, I figured I would ask my question here. What about cap size, is it better to increase cap size? I have also noticed that some caps have life of 2000,3000 and even 18000 hrs. Is it better to go with a longer life cap?

Thanks for the help,

Lupin
 
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I've rebuilt a couple AU-717's and have two waiting. I think they are the best sounding I've heard yet. I just finished a BA-3000 and CA-3000 and they aren't as sweet sounding as the 717 yet. Perhaps when they get broken in.

I used Panasonic THA and TUP on mine for the big caps. I got them from DIGIKEY. I used Nichicon KL and PW series for the rest, oh, and VP series for the bipolars. As a general rule of thumb I replace orange caps with KL and the rest with PW and bipolars with VP. I did run across a place in the others that looked like it needed a better bipolar so I used a Panasonic that had less leakage. I generally get the smaller ones from MOUSER. If the 919 uses the same glue like the 717, you'll need to replace more than just caps. You need to replace everything the glue touches. On one of mine the leads were so corroded they stayed on the board when I removed the component. Good Luck.

Regards,

Ron.
 
More parts

Thanks Ron, that is exactly the information I was looking for.

Are there any other parts that are recommended replacement while I am recapping? I would like to replace the units that are most likely to fail while I am taking everything apart.

Another question...

When I bought the amp, I was hearing some static while doing volume changes and/or playing with the balance adjustment. I opened the unit and cleaned the balance knob without problem. The main volume was split (as much as possible without removing the small lock ring in the back) and cleaned (no more static) but I was wondering if the small lock ring can be sourced anywhere? We have small rings that are similar on various aircraft parts and those are notorious for not being easily re-usable. They easily damage when they are removed due to their one way lock feature... Does anyone know where these can be sourced?

Thanks for the help,

Lupin
 
I'm not sure on the 719, but on the 717, I usually put a hole in the volume pot to shoot deoxit in it. On the 717 I usually change the caps of course, but also clean the glue and replace everything it touches. I replace the fusible resistors and the vd-1212 diodes. I replace the trimmer resistors, and the zener diodes. Some advocate replacing certain known troublesome transistors. There are a lot of recapping threads on here. A lot of good information in them. Click the google search above and look for 719 recap. It should come up with good reply's. I also throw a three prong plug on mine, I know a lot of people say not to, but I feel better doing it and haven't had a problem yet. I guess it depends on how your house is wired. I would recommend getting a magnifying glass and checking all the solder joints over. Especially in the hot areas. Reflow as necessary. I don't think you can find the lock for your switch anymore. I usually clean them three times. Once before I start, sometime in the middle and at the end. After all that they usually are silent. Read the threads for the 719 and 717 and you should get the part numbers and procedures for it all. That's where I got it from. If you have more questions or are confused just ask and we'll try to help. Good Luck.

Regards,

Ron.
 
I've recently completed a full recap/resto of my AU-719 with some parts of the work outlined in this thread.

http://www.audiokarma.org/forums/showthread.php?t=404022

A few things to look at:

Replace the 22pf 'black flag' capacitors with silver micas

Filter caps depend upon your budget. Panasonic 15000uf 80V caps can be had in 40mm x 80mm size which matches the original filter caps exactly. You can also look at Nichicon KG Gold Tune 15000uf 63V 40mm x 100mm, or Epcos B41456 15000uf 63V 35mm x 105mm (with sleeves) as I've done (pics in my thread linked above). 'Audio-grade' caps are not a must for the filter caps.

Change the bias and offset trimpots (this is the only thing I have yet to change on mine)
 
MrLupin said:
Are audio grade caps desirable for the filter caps?
Click to expand...

Not necessarily... a high quality, long life cap with screw terminals will perform just as well. This is the exact reason why I ended up going for the Epcos. These were the same price as the Nichicon Gold Tunes and the Epcos had better specs. Having said that, the Gold Tunes are a direct fit (correct diameter) so they would be easier to install for most people.
 
The Nichicon Gold Tunes, and even more expensive Epcos are 'Audio Grade" caps in every sense to me.

He doesn;t need screw terminals, the original solder tabs are still found on the Nichicon Gold tunes, and I think they are an excellent cap. I second their recommendation.

Scott T.
 
scottrt said:
The Nichicon Gold Tunes, and even more expensive Epcos are 'Audio Grade" caps in every sense to me.

He doesn;t need screw terminals, the original solder tabs are still found on the Nichicon Gold tunes, and I think they are an excellent cap. I second their recommendation.

Scott T.
Click to expand...

The Epcos caps that I sourced were the same price as the Gold Tunes, plus free postage vs $25 from Partsconnexion to Australia, so this made the decision to go for the Epcos a bit easier for me. However, I would have been very happy with either of them. :)

I wasn't trying to infer that screw terminal caps were necessary... it was simply an example of a type of cap (industrial, computer grade etc) that would be more than suitable for this application. I agree that the Gold Tunes are a fantastic solution for anybody not wanting a tricky installation job.
 
pete_mac said:
Change the bias and offset trimpots (this is the only thing I have yet to change on mine)
Click to expand...

Thanks for the info Pete,
Do you know how much current goes trough the trimpots? I am looking at the Sansui service manual and while all the resistors show a set value, the trim pots (VR01 & VR02) only has ohm range and not power.

I am just concerned with putting a trim put that could not handle the current...
 
I use 3/8" Bournes single turn model 3386 in either H or P for all my trimpots. I believe they are half watt. Work like a champ.

Regards,

Ron.
 
Another Question...

I have identified all of the electrolytic capacitors on F3101, F-2926 and F-2627. I notice that F3101 has some capacitors identified as C01 and C02 which would appear to be ceramic. Is it a good idea to replace those?

Same question for C606, C15, and C16 on the same board?

What bout the tiny orange caps on F-2627, namely C02-C04,C10-C14,C18-C23 & C25? Would those normally be replaced during a recap?

Before tearing down the AU-719, I am trying to make sure I have all the parts required..

Thanks

Éric
 
Mostly you just replace the electrolytic capacitors which include tantalums since they are electrolytics as well.

On the 719 and others you have to replace the black flag as some call them. I have not done one with those caps yet but have read the threads about them.

The ceramics should be fine. They don't normally get replaced. I have replaced one that was on the back of a board only because it was physically damaged by someone in the past.

Small orange electrolytics I usually replace with low leakage KL series from Nichicon.

Regards,

Ron.
 
Thanks Ron,

How do you identify Tantalums?

Some further question...

The black flag Capacitor, I imagine it is the C03 on the two driver boards (F-2916,F2927)?

Also, I read in a few write ups that the MV12 diodes were to be replaced. Are all the diodes to be replaced? They degrade over time? Where are they sourced? I tried Mouser,Newark and digikey and can not seem to find the 1N4848 diode. If I use 1N4004 in series, it should be equivalent?

Is it recommended to replace the main transistors, TR701,702 and TR 703,704 (2SC2581,2SA1106)? If so , do you replace with same of with an equivalent? I can't seem to find a source... Woodang.net appears to be down and digikey,mouser and newark come up blank. Any recommendations for source?

As far as heat transfer paste, I imagine the paste used for CPU bonding to heat sinks would be adequate?

I see Pete_Mac added Bypass caps on the main Power caps, what are the advantages of doing so and what kind of caps are bypass caps? Bipolar electrolytics?

Thanks for your help,
 
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Tantalums are little tiny tear drop shaped capacitors. I have seen them in orange and blue. They usually have writing on them on one side. It will also have a tiny little plus sign by one leg.

The black flags I've seen pictures of are black and square. I think the value is written on them. I have no idea where they are located. You might find them with a search. I remember a thread last year discussing them. Use the google search above.

The diodes your looking for are 1n4148TA. Mouser has them as 512-1n4148TA. Lay them side by side one band up one band down. Bend two legs toward each other, solder the two legs together. Cut off the excess length. Then, cut the other end of the one with the band down a tad short to mark it, like a negative lead on a capacitor is short, and then put heat shrink over it. This makes a replacement for the Varistors or VD-1212's as they are designated by part numbers. Put the short lead in the hole the arrow points at.

I would not replace the output transistors unless they are bad. I have not had to replace any of mine yet. I just got done replacing a part I got from Mouser that was bad. A filter capacitor that caused a lot of hum and hiss. It would be better to keep as many good parts as you can. Took me a while to find that bad part. I didn't expect a new part to be bad so I went there last.

For heat sink grease I use "type z9" from gc electronics. It's specifically designed for this application. CPU grease is designed for CPU's.

As far as bypass caps go, I have never done it. I guess it might be good. I just see so many things that people say helps. I doubt my ears can tell the difference for most of it. You can try if you wish. I just keep in mind that if it was good, everyone would be doing it.

Regards,

Ron.
 
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