Sansui Au919 Parts

[Kale]

The 2SC2071 and 2SA939 are rated at 250V, and the B649 and D669 at only 160V. If you do not NEED the high voltage capability, I'd use the 160V-rated Sanyo 2SA1209 and 2SC2911, or going up in voltage, the 200V Sanyo 2SA1380 and 2SC3502. If you really need a rating of 250V or more, then the Sanyo 2SA1353 and 2SC3417 would do well.

Why all the Sanyo's? Seems high-voltage, wide-bandwidth TO-126 transistors are getting tough to find, and Sanyo just happens to have a lot of good ones.

Those 2SC2071 and 2SA939 I have found in one G901DB as predriver transistors, but in my G8000 as predriver transistors Sansui installed 2SA818/2SC1628 which are very rare, and they are rated as 150V, so I think that 160V for B649/D669 is quite enough. And one very important data is fT for B649/D669 is 140MHz!!
But what is strange about B649/D669; Ic is 1.5A and in peak Ic can be 3A!! I am not sure that is true data from datasheet, or yes :scratch2:
Regards!

 

[Kale]

About B649/D669 Ic

After I have found original datasheet for Hitachi, now its clear to me about Ic data, so at Vce 13.3V --> Ic is really 1.5A!!!, at Vce 40V --> Ic is 0.5A and finally at Vce 120V --> Ic is 0.038A. But it is still great for Ic data.

Regards!

 

[nikomi021]

When you change transistors from lower to higher Vce, you change internal capacity ! This is because higher voltage need thicker isolation inside!

 

[Kale]

When you change transistors from lower to higher Vce, you change internal capacity ! This is because higher voltage need thicker isolation inside!

Not always!
2SA818 --> Vce: 150V, 5pF
2SA939 --> Vce: 220V, 7pF
2SB649 --> Vce: 120V, 27pF

 

[noveltone]

When my 919 blew it also took out a few components. It mostly seemed to blow the PCB traces around the transistors off the boards, but somehow without damaging the TRs themselves to the point of failure. Anyway, when I replaced the drivers and outputs with the on-semis listed earlier on this thread, the thing has worked well for several weeks of hard loads. The sonics are great with the possible exception of intense, layered vocals. Perhaps EW's Toshiba high-speed outputs will solve that.

There was always something fishy about one channel of my unit, but after the recap and careful checking of all the joints on the driver board, it has been much more stable voltage-wise. Perhaps your unit would benefit from this? :scratch2: Either way good luck.

Collin

 

[EchoWars]

FWIW, I believe I have found a mounting method to put the TO-3P(N) devices into a location where a TO-3 device previously was in a way that is not such a kluge. My previous idea was to bend the collector lead over the top of the device and mount the lead with a ring terminal soldered onto it to make contact with the TO-3 socket through the hole. Now, I do believe I have a much better way, and one that retains a dignified look for the output transistor by using the other collector mounting hole and keeping the collector lead straight.

Ordered a bunch of parts from on online vendor. Once they show up, I'll mount a transistor and start a new thread with some pics.

If this works well, it can be a serious method to circumvent the lack of wide-bandwidth devices in the TO-3 package and can help preserve performance for aging gear. If it works as I believe it will, it oughta be very cool. First test will be on the 919...

(yes, we techs get excited over silly sh*t...):yes:

 

[nosirrah]

Ain't Silly

FWIW, I believe I have found a mounting method to put the TO-3P(N) devices into a location where a TO-3 device previously was in a way that is not such a kluge. My previous idea was to bend the collector lead over the top of the device and mount the lead with a ring terminal soldered onto it to make contact with the TO-3 socket through the hole. Now, I do believe I have a much better way, and one that retains a dignified look for the output transistor by using the other collector mounting hole and keeping the collector lead straight.

Ordered a bunch of parts from on online vendor. Once they show up, I'll mount a transistor and start a new thread with some pics.

If this works well, it can be a serious method to circumvent the lack of wide-bandwidth devices in the TO-3 package and can help preserve performance for aging gear. If it works as I believe it will, it oughta be very cool. First test will be on the 919...

(yes, we techs get excited over silly sh*t...):yes:

Hey Glenn, ain't silly at all, if I had an AU 919 I'd be watching this thread like a hawk, bet here are twice as many folks lurking as well.
It's a damn fine thing you are taking the initiative to solve an unobtainium issue on a very good piece of classic gear...
Hell, as it goes for me I will probably get one off those 919's someday, and maybe it can be repaired....
Casey

 

[EchoWars]

Well, the solution won't be limited to the 919...it'll pretty much apply to any vintage piece that used to use fast TO-3 transistors that can't be sourced anymore.

 

[Morden2004]

Modernizing a classic Sansui

Excellent, Glenn! :thmbsp:

We're all waiting for your reports to begin. :yes:

Paul

 

[nikomi021]

What do you think about new heat sink with TO-3P transistors and cooler?

 

[EchoWars]

Explain please...are you speaking of replacing the original heatsink with a new one? I'm confused...

 

[nikomi021]

Yes.There is a lot of shapes of heatsinks with TO-3P handling. It is just an idea, because you need good cooling in full load,for long time.

 

[EchoWars]

Well, there's nothing really wrong with the stock heatsink. Heatsinks are expensive, so changing them isn't too feasible.

 

[nikomi021]

I gave an order from DIGIKEY for MJ21193G and MJ21194G, 2SC2238 and 2SA968. I will try to change trans. on one channel. I am impatient to hear this!

 

[EchoWars]

Well, unfortunately my 'plan' for using the TO-3P(N) devices has collapsed with the 919.

I used a heatsink section from a trashed 9090 here for experimentation, and it all fit fine. Certainly the measurements were the same on the 919, but the style of the damn TO-3 socket did me in!.

The most common TO-3 socket has small 'cone-shaped' metal pieces to make contact with the emitter and base leads. It's round, and holds the leads in place. Well, the sockets on the 919 have two steel 'fingers' that pinch the base and emitter leads. Because the leads on the TO-3P devices are flat instead of round, if you simply shove them in the socket they make very poor connection with the fingers. So, take a pair of needle-nose pliers and turn the flat TO-3P leads 90°, and they made great contact with the fingers. Only now, they can scoot forward and back in the socket, since if you look at the socket you can see that the 'slot' that the fingers are in is quite wide. When the transistor is installed, there's little to hold the base and emitter leads in the center of the hole in the heatsink, and the leads are pushed out and make contact with the edge of the hole in the heatsink.

This idea is still quite feasible for most gear that uses a more conventional style of socket, but unless I want to change out all the sockets in this ampyikes, the 919 is going to have to make due with the dog-slow MJ21193 and '94.

Damn.

Here's a pic of the 919 socket.

 

[LBPete]

So close. I've got an AU-7900 amp where the T03 outputs are soldered in. It seemed odd that Sansui would do that but there is no worry about bad contact. Could you do something like that here?

- Pete

 

[Fhamre]

If you are patient you may come across the originals. I recently bought a pair of 2SA1116's off ebay. Also a G-9700 I saved from the dumpster came with 4- 2SA1116's and 3 working 2SC2607's. They are out there!
Good luck!

 

[EchoWars]

So close. I've got an AU-7900 amp where the T03 outputs are soldered in. It seemed odd that Sansui would do that but there is no worry about bad contact. Could you do something like that here?

Soldered changes everything. Ought to work great.

If you are patient you may come across the originals. I recently bought a pair of 2SA1116's off ebay. Also a G-9700 I saved from the dumpster came with 4- 2SA1116's and 3 working 2SC2607's. They are out there!

Fixing this for someone else, so it gets done now, or not at all.

Salvaged outputs are a fine source, but I have a hard time trusting eBay sellers with all the counterfeits around.

 

[spaceman]

EW, would it be a reasonable idea, to just jam a couple wooden toothpicks in the ends of the slots, then break them off close, to fill in the gap some? They wouldn't be conductive, & it could easily be removed, I imagine, if it didn't work. Just a thought. :scratch2:

 

[EchoWars]

No...but a clipped lead from a diode or resistor might perform the same function, jammed down into the socket. But then I'd have to worry about it coming loose and shorting something. Wood couldn't be a long-term solution, and a conductive lead has its own dangers. High-temp plastic or Nylon would be great, but I don't know where I'd find a small sliver that would do the job.

Another day, another amp, perhaps. If the driver and heatsink boards were a little easier to remove in the 919 I might consider the idea of trying to limit the movement of the leads in the socket, but in reality removing these components from this amp is a bloody nightmare.

I got it all re-assembled at the moment with the On-Semi outputs, and there are advantages to using these instead of the fast TO-3P deviced I wanted to try. Such as the difficulty in blowing these up. And although slow, they likely contribute to stability. I hope.