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Help with AU-999 Redux

M

mdelrossi

Active Member
Well I go away for a few days only to find a heated argument, go to sleep and poof all info gone. At least google had a cached page or two. How come there isn't a smiley for duck? like hands covering the head?:scratch2:

Anyway, I'm missing the info regarding the 9002 transistors.
I had foolishly thought that all of those funny looking transistors were 8002's and had replaced them as such. Now I'm wondering if I should re-replace all of the transistors on the driver board in case I blew up any of the others?

Thanks for all of the help on this board.

Can we please keep the insults and accusations to a minimum?
I'm sure that all responders only have the best of intentions to help.
When the discussions start to deteriorate so does the help, and it gets quite confusing for the people who are just trying to learn and fix their gear.
thanks again for all of your time.
mdr
 
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Here's the driver schematic from an early manual:

999driverzz0.jpg


I noted in my earlier post that Sansui had begun to replace these 'Flying Saucer' transistors in the later models of the 999 with standard Japanese transistors.

XA495 > 2SA640
(CDC)8002-1 > 2SC875
(CDC)9002-1 > 2SA532

Previously, we looked at the specs for the Sansui-chosen replacements to get an idea of what might be an appropriate replacement. Here again we will do this:
Code: 
Part Number     Vceo       Ic         Pc        B        Ft
2SA640           50V      50mA       250mW     450    100MHz
2SC875           75V      200mA      500mW     100    170MHz
2SA532           50V      200mA      500mW      80     90MHz

Using these values, I recommended the Zetex ZTX795A to replace the 2SA640 and the 2SA532, and the ZTX694B to replace the 2SC875. It also occurs to me that, if you want a larger and heavier-duty package to replace the pre-driver transistors (TR811 & TR813), that the Panasonic 2SC1567A and the 2SA794A in the TO-126 package would also work well for these locations. (Edit: Panasonic transistors discontinued, sub the Fairchild KSC2609A and the KSA1220A).

So I'll sum up the changes as such:

XA495 > ZTX795A (PNP)
(CDC)8002-1 > ZTX694B [or KSC2609A for the TR811 pre-driver) (NPN)
(CDC)9002-1 > ZTX795A [or KSA1220A for the TR813 pre-driver) (PNP)

The stock 2SC281 used as a bias servo (TR09) is fine, as long as it is functional.
 
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Got confirmation that digikey shipped everything today. I will post back with images when I get it all put in.
 
EW,
Thanks a million. I was able to piece all that info back together from snipets I got.
Great heads up on the more robust parts:thmbsp:

After I jumped in before I took a close look (TR813 was not an 8002-1 :tears:)
I put it all together and fuse blows and hum out of the (now official) bad channel.
I had replaced all of the flying saucer transistors with ZTX694B's not looking close enough to read the part #:nono: (need new glasses).

Well I was able to get the bad driver board to work (works in the good channel) but I blew the outputs on the other channel :tears:

The Transistors are 2SD213 and 2SC898 I searched and could not find them.
I went to woodangs site and found 2SC1116A for the 2SD213,
and 2SC2607 for the 2SC898.
Couldn't find those either.
Then more digging and came across the new TO3p transistors, but would have to mount them in a weird way and would be concerned about heat exchange.
MY BRAIN HURTS:yikes:
Any suggestions would be greatly appreciated.
I'd really like to get this amp working because the working channel sounds great:yes:
thanks again
:ntwrthy:

BTW you rock with that schematic.
I purchased one from owner-manuals and I'm waiting for my order to be processed.:sigh:
 
The two TO-3 output transistors should be identical. Sounds like you had a mis-match from the beginning.

You'll need to pull and test the two TO-66 drivers also (TR815 & TR817)...do this one at a time, and make sure they get put back where they came from (with new heatsink grease, and after an inspection and cleaning of the mica insulator).

If the TO-66 drivers are OK, then you may only need to replace the outputs (but you need to take a very close look at the resistors on the driver board, as well as the 0.5 ohm 3W emitter resistors for the outputs, and the 220 ohm 1/2W resistor & the 15 ohm (1/4W?) emitter resistors for the drivers.

As far as replacing the outputs, I'd replace them all if you have a bunch of mixed and matched units. MJ21194G from On-Semi will do fine, but is way overkill for this amp. If you are interested in replacing with some original Japanese devices, I have a quartet of Hitachi 2SD675's that would do a fine job.
 
EW,
Yeah I had a mismatch on both channels I guess on side went out and they decided to split the outputs????
The two TO-66 drivers test fine, as do the concrete resistors.
I'll be ordering the MJ21194G's from Digikey as I need to order some more caps (are Panasonic FC caps a good choice?). Plus I'd rather not deplete your supply in case I mess up.:tongue:
BTW I just looked at the PS Caps and I guess that they have shrunk in the past 30 or so years
http://www.studio6r.com/Stereo/99%20ps%20caps2.jpg
http://www.studio6r.com/Stereo/999%20PS%20caps.jpg
Should I figure out a way of mounting them or should I up the the capacity to 100000 uf to get them to fit??? ( just kidding about upping the capacity):D
thanks again
mdr
 
The new caps there are only 1000uf 50V, or about 1/5 the size of the originals.

Yes, a 10,000uf 50V cap is fine. Michael Percy sells some nice Nichicon solder-tab caps that would do a great job. I think the stock caps are 40mm (check this), and you need to try hard to match that diameter.
 
Do you need to add or update any parts to handle more than doubling the power supply caps? I see a post where quadbob says 6800uf is OK, but 10,000?
 
That is a 10,000uf cap. My eyes are not what they used to be so I double and tripple checked, even got the wife to read it to me:D

When I saw the size it made me wonder. are they mislabeled?
Digikey #493-1350-ND
mdr
 
No...I read it wrong. Too many zeros, and messed me up.

You obviously need something that'll fit the clamp. Check Michael Percy Audio.
 
If you check out what quadbob does while he is restoring, if he has a smaller diameter cap he will use the foam weatherstripping around it to create a gasket.

When I cant find caps of the appropriate diameter I have done this trick as well and it worked for me.

If you check out his QRX-999, QRX-9001 threads you can see what he did.
 
I've been cutting the clamps down to size. This gets it to wrap around the cap and hold it tightly but the mounting tabs no longer line up with the original holes in the chassis. I drill one new hole in the chassis and it's all set.

EW, I haven't found a good source for 35mm cap clamps. Do you change the clamp or buy fat caps?

- Pete
 
Mouser sells a clamp that works with 35mm caps, #539-VR3, but I just use the bigger caps from Michael Percy.
 
Parts in hand, ready to dive in and replace these puppies. Exciting evening! I will post back with results.
 
Echo - on my one driver board, TR813 is a 2SA537A with a funky square heat sink attached to it around the "saucer".

TR811 is a 2SC708A with a similar heatsink.

On the other driver board these are a 8002 and 9002 like in the schematic.

Question is, should I still replace these with zetex???
 
If you want both boards to be the same...

I also doubt that these transistors need heatsinking, but because they are pre-drivers, and a TO-126-style traditionally performs these duties, I changed my original recommendation to the Panasonic 2SC1567A and the 2SA794A for these two transistors. But in reality the little Zetex transistors are mighty tough, and will work fine.

Edit: Panasonic transistors discontinued, sub the Fairchild KSC2609A and the KSA1220A.
 
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One more question - on the two tone control boards, C737 is a .1uf mylar cap - would there be any noticible difference replacing this for a different one, say, one of the panasonics you mention to replace the .47uf caps?

Also would it be horrible to replace a 33uf 6.3V cap with a 33uf 35V cap? Digikey sent me the wrong caps (330uf 6.3V)
 
C737 is just a bypass for the 33uf electrolytic anyway. Not much to gain here.

33uf 6.3V? You must be talking about C609 in the phono stage. The 'µf' rating of the cap isn't terribly important, but you do want a low voltage cap here. If Digikey sent you the wrong cap (330µf 6.3V):

1. Call them. They'll make it right immediately.
2. If a 330uf 6.3V cap will fit there, where the 33µf 3.6V cap came out, put it in. It'll work fine.
 
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