Sansui Au 999 Transistors

D

davethomp

New Member
Hi everyone: I have a 1970 Sansui Au 999. I need to replace the main transistors. It has (well, had!) 4 X 2SC898 Flying Saucer type on the heat sinks. I can get either Sanken 2SC1116A or Sanken 2SC2607. Any advice would be appreciated? Not much is available over here in Australia. Am I heading down the right road/path with these Sankens or not?
The smaller internal transistors are Hitachi 2 X 2SA566 and 2 X 2SC680...but these are hanging in there....I think???
Thanks
Regards: Dave
 
Firstly, welcome to AK Dave - lots of helpful people here.

Only one comment, as I am not familiar with your Sansui model - if you can get genuine Sanken 2SC1116A you have either found the vintage audio equivalent of a Gold Mine or they are Counterfeits. I would suggest you do not buy any replacement output transistors unless they are from a guaranteed reputable source - ideally these sources should be endorsed by AK members. There are acceptable equivalents for the original outputs, which can be easily obtained and are not expensive. As regards this and other issues - Flying Saucer transistors et al - someone with proper experience of these and other AU-999 issues will be along shortly.

BTW Great amp - well worth taking a lot of trouble over.

Just my 3 ha'pence worth

John
 
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Hey and further: My Sansui Au 999 has 2 X 2SA 566 & 2 X 2SC680: which are on the inside floor (and smaller than the 2SC898's). Any suggestions as to what I could replace these with would be really great help. The originals are no longer available anywhere, and few people know what to replace the originals with!
May as well do the lot as the amp is 37 years old and currently the lid is off!
Thanks: Dave
 
I replaced the flying saucers in my AU-999 with Zetex ztx694b
and ztx795a. Worked like a champ. You can get them from Digikey or Mouser.
 
It doesn't work!

Well, I replaced my 4 X 2sc 898 original flying saucer transistors in my AU 999 with 4 new Sanken 2SC1116A tranistors. And this is the quietest the amp has ever been ...too quiet...it doesn't play! Not a hum, not a note, not a whistle!!! NOTHING!
1. Should I have pumped it full of that heat sink white power..the aluminium nitrite?
2. Should I give up and stick to my Parasound!
3. Find a new interest?
Rgds: Dave
 
Ask Echowars.

He worked on my 999 a few summers ago. He discovered my unit had a different set of transistors than most others that he had seen. It seemed surprising to him. I have owned it since it was brand new. It had never even opened up prior to him. So, he might have a different factory substitution idea.
 
Davethomp, I have no idea what you have done, or why. The so-called 'flying saucer' transistors are NOT mounted to the heatsinks, so I'm at a loss to understand why you replaced them. You seem to have gleaned some info from reading old posts, and reinterpreted it in some twisted way.

Everything you need to know is here: http://audiokarma.org/forums/showthread.php?t=144862

If those original power transistors are good, there's no reason to replace them.
 
Thanks EchoWars:...but I don't think I like the tone of your response! I appologise if something in my question has reminded you of the iognorant great unwashed who read this site and attempt to learn through it! It could just be me, as I am a bit over sensitive these days trying to learn this stuff and seemingly recieving less than helpful insights from pointeers such as your response. There's lots of people with knowledge, but us lesser mortals have to bow and scrape a lot to get access to it. And it seems that 'moderators' these days are on the side of the well established guys, and not us learners. I have recieved my fare share of unhelpful comments from other sites and was hoping this to be different. Admittedly, that was referring to speakers, which seem to hold their fare share of mystery! But it seems to me that this site may as well be like the others. PLeae honour me with your esteemed opinions again! I am sorry to be a pain, and obviously ignorant!
Now, in my AU999 it has a group of 4 larger 'flying Saucer type transistors' that screw into the heat sink and have eclectrodes that poke through, with a grommet into the circuit boards mounted on the other side. Mine had 2 X NTE 28089IF in the front (one on the right anbd one on the left) and 2 X Hitachi 2SC898 on the back 2Sc898....one on the right and one on the left. On the floor inside the amp, it had 2X 2AS 586 in the front (one on the right and one on the left) and behind at the back it has 2 X 2SC680 similarly one on the right and one on the left. These smaller ones I though to be the pre-amp transistors and the larger the ones for the power amp modules.

Now as for your supportive advice. Well mate, I asked the question. I got little return, except for the really helpful attitude!. Some loverly person suggested that the larger flying saucer type should all be the same : the original Hitachi 2SC898. I had a mixed bunch as I stated above. He suggested replacing them all with Sanken 2SC1116A or Sanken 2SC2607. I bought the first option. In fitting these I may have neglected to replace the grommets which would mean it would arch, short out and not play. This is what seems to be happening. Anyway, the other Sanken are on their way to me the SC2607, as are replacement gromets. I shall then take the poor old amp to a techitian.

So, you are suggesting I do what???????
Don't worry, I shall not be back.
 
davethomp said:
So, you are suggesting I do what???????
Don't worry, I shall not be back.
Click to expand...
So which is it? You looking for assistance, or are you going to your room to slam the door (and you know how that pisses mom off).

I have no idea why you felt the need to post that rant, but if you feel better now and would like to focus on the issues at hand, give us a head's up, and we'll be here to help.
 
Op

The OP PM'd me stating he had left the rant to you Glenn.
To my eye it's a simple miscommunication, I read the thread and links.
Davethomp, In my opinion you were offered valid help, with no show of disrespect, typed communications can lead to misunderstood messages.
If you need help with that amp, we can help you here.
Casey
 
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Flying saucer transistors (post #2): http://www.audiokarma.org/forums/showthread.php?t=138176 They are all small-signal transistors, not power transistors.

The transistors in the steel case mounted to the heatsinks are a legitimate TO-3 industry standard case. The chassis-mounted driver transistors are an industry standard TO-66 case style. In the original post, it is stated that you have four 2SC898 transistors. These are fine outputs, and I can't think of a reason to replace them. The 2SC1116's are also good, but the 2SC2607 are superfast outputs designed for high slew-rate amplifiers, and may very well cause the 999 to go into uncontrolled oscillation...I would NOT use them.

If the 2SC1116's were installed without the mica insulators, this would not necessarilly destroy them, as current would only be passing through the case and not through the transistor die. They should be removed and tested.
 
I have an AU-999 with bad output transistors - Looking at the specs, I believe I may be able to sub with MJ15015G's that I have on hand but would like confirmation as I can't find a filament, grid or plate on any of them.

Here are the basic specs on the 15015G:

120V, 15A, 180W, B=70, Ft 2.2-18Mhz
 
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DingusBoy said:
I have an AU-999 with bad output transistors - Looking at the specs, I believe I may be able to sub with MJ15015G's that I have on hand but would like confirmation as I can't find a filament, grid or plate on any of them.

Here are the basic specs on the 15015G:

120V, 15A, 180W, B=70, Ft 2.2-18Mhz
Click to expand...

Im using MJ10524 in mine simply because I have them on hand for servicing other amplifiers.....they are way overkill......
Im in the middle of a major re-fit on my AU-999.....

It looks like you can use those in there, you need to look at gain as well, but I think those will work.....dont forget to use the thermal paste on both sides of the mica insulators......unlike tubes, transistors dont like to be hot...

Is that a little joke in the end about the filament ....etc ...etc .... one would hope so......
 
When I was about 12 I took a course at the local ham radio club about electronics. Of course, it was all about tubes. I really got it, I UNDERSTOOD. Then within just a few years it all was changing to transistors.

I been looking for filaments, grids, plates, you know, all that stuff, ever since. What's all this crap with carriers, holes, doping, beta, hfe, and on and on?????

:boring:
 
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