Want to salvage a Sansui 5050.

It's up to you, but I would never buy semiconductor pulls from units being parted out - you are paying a lot of money and have no guarantees you are getting good parts. The power transistors in this unit are unexceptional, so you have no need to pursue originals.

Much better to replace the OP transistors with modern equivalents, Like this to replace the 2SA765 (PNP)
https://www.mouser.co.uk/ProductDetail/ON-Semiconductor/MJ21193G?qs=/ha2pyFaduhYR/YNuos/yPrr6J3ZPw3fA%2bbv/1AROoc=

And this, to replace the 2SC1445 (NPN)
https://www.mouser.co.uk/ProductDetail/ON-Semiconductor/MJ21194G?qs=/ha2pyFadujEihMqaz/hhkq6TQqOjR1kS1vnU717vwU=

These new replacements are cheap and are very robust, if you make a mistake and accidentally destroy one, easy to get and cheap to replace.

NB: I recommend you replace all four OP transistors.



Hi,
That is an interesting idea I had not thought of. I am not sure it would physically work though. The output transistors are plugged in to a socket which is attached to the heat sink.From what I saw based on the dimensions of the cases for the old vs new, I do not think the new would physically fit? Perhaps I am missing something. Isthere a work around for the dissimilar sizes?

Thanks for your assistance. This is quite the daunting task. It has been fun though.
 
Is there a work around for the dissimilar sizes?
Aha - I had not realised that the originals were TO-66 - wait one - I'll provide some new part numbers...

For 2SA765 (PNP)
https://www.mouser.co.uk/ProductDetail/ON-Semiconductor/MJE15031G?qs=sGAEpiMZZMshyDBzk1/Wi/PUgtclNldljZTWnEBZ5vI=

For 2SC1445 (NPN)
https://www.mouser.co.uk/ProductDetail/ON-Semiconductor/MJE15030G?qs=sGAEpiMZZMshyDBzk1/Wi/PUgtclNldlrLSDWXqsht0=

These are TO-220 replacements, but this package was designed to be a mechanically friendly equivalent to the obsolete TO-66 package - you just need to bend the legs of the replacements a bit, and use a new insulating kit - which you will need to buy as a separate item. ;)
 
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Aha - I had not realised that the originals were TO-66 - wait one - I'll provide some new part numbers...

For 2SA765 (PNP)
https://www.mouser.co.uk/ProductDetail/ON-Semiconductor/MJE15031G?qs=sGAEpiMZZMshyDBzk1/Wi/PUgtclNldljZTWnEBZ5vI=

For 2SC1445 (NPN)
https://www.mouser.co.uk/ProductDetail/ON-Semiconductor/MJE15030G?qs=sGAEpiMZZMshyDBzk1/Wi/PUgtclNldlrLSDWXqsht0=

These are TO-220 replacements, but this package was designed to be a mechanically friendly equivalent to the obsolete TO-66 package - you just need to bend the legs of the replacements a bit, and use a new insulating kit - which you will need to buy as a separate item. ;)

Ah, very interesting. It took me awhile to figure out how a TO-220 cased transistor would work with the TO-66 transistor socket that is mounted on the 5050 heat's heat sink.

(This is what my TO-66 transistor sockets look like.)
https://www.ebay.com/i/162543938220?chn=ps

Then I realized the "case" of the TO-220 transistor is the collector and just screwing it on to the TO-66 socket would probably work. I'm not sure what to do with Pin 3 which is the collector also. I would guess that I would just cut it off?

Am I on the right track with this?

Thanks again.
 
Then I realized the "case" of the TO-220 transistor is the collector and just screwing it on to the TO-66 socket would probably work. I'm not sure what to do with Pin 3 which is the collector also. I would guess that I would just cut it off?


Oooopsies, my bad that should read PIN 2 is the collector.
 
I would guess that I would just cut it off? Am I on the right track with this?
Yep, that's it. ;)

If you have a search around on AK or anywhere, you should be able to find pictures of how it is done, and looks afterwards.

If you look at the pictures in this thread
http://audiokarma.org/forums/index....00-driver-boards-f-2029.841122/#post-12044902

The silk screening on the boards shows you the idea.

(I am sure there are better pictures somewhere showing the transistors in place).
 
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Good news! I ended up replacing all of the 2SA726’s on the driver board. I new one was bad for sure. Since they were on the top ten transistors to replace here on AudioKarma, I replaced them all. I also replaced all of the electrolytics on the driver board.

When I powered it on, I heard the relay click on and sure enough, one of the channels is working now. I know the output transistors on the other channel are bad so hopefully when I get some new output transistors I’ll get both channels back.

Should I replace the other transistors on the driver board also?

There are two 2SD438‘s, two 2SB560‘s paired and two 2SC1951‘s
 
Been awhile since I posted on this topic. I have done a lot of work on this 5050. Good news is I now have both channels working. Yay!!

Bad news is, the right channel is a touch distorted. I checked the bias on the output transistors per the service manual instructions. The left channel is perfect at 15 mv. The right channel is 0v and the trim pot has no effect.

I don’t really understand how the bias circuit works. I would take any advice or direction if anybody has any.

Thanks.
 
Just wanted to update my effort to resurrect my Dad's Sansui 5050. Goal was to replace all of the caps and of course make it work again.

Started out with no audio. Receiver would not come out of protect mode. Looked like a barn find honestly. Here is what I found.

I was checking resistance on some various components on the F-2701Power SupplyBoard and noticed that the resistance across F604 (250v, .15A) was 28 ohms and the resistance across F605 (250v, .15A) was 58 ohms. I got the same reading when I pulled them out of the holder. Replaced both.

Either TR01 or TR03 had failed. I replaced the TR01 - TR04, 2SA726's with KSA992's . After this, the receiver came out of protect mode. However I noticed a bit of distortion on the right channel. Putting the scope on the output, I saw this.

Sansui 5050 scope bad channel_edited.jpg

One of the power transistors had failed. I picked up a pair of matching output transistors, although in the end I only replaced the defective one since it seemed to match the original better. After this, both channels sounded good.

I replaced all of the electrolytic caps, board by board, checking after each one was done to make sure it was working. The receiver sounds awesome now. They are currently paired to my Pioneer HPM100's. Very happy with it.

The one question I have for anybody is about the panel lights. I replaced all the panel lights with LED's. Cool white. I like the look, but I noticed the light is not completely even across the face. It appears the LED's are a tad to directional. Anybody else notice this??

I also have a Sansui 9090DB that has no output unless I take out the jumpers and put the input straight into the Main amp. So that is my next project. Pretty sure it is the Dolby board. Pray for me please. :rolleyes: I purchased this system overseas in Japan while I was in the Navy during the 70's.

Want to thank everyone for their assistance. This place is a goldmine of information. Definitely going to become a subscriber here.
 
...The one question I have for anybody is about the panel lights. I replaced all the panel lights with LED's. Cool white. I like the look, but I noticed the light is not completely even across the face. It appears the LED's are a tad to directional. Anybody else notice this??...

For the 5050 that I restored with LEDs, it was necessary to orient the LEDs towards the back (i.e., facing the white plastic housing) to achieve a seamless even dial illumination.

5050 dial lights 2.jpg
 
For the 5050 that I restored with LEDs, it was necessary to orient the LEDs towards the back (i.e., facing the white plastic housing) to achieve a seamless even dial illumination.

View attachment 1426628


That makes sense. I will definitely try that.

My 5050 has a crappy vinyl laminate of some type. It is flaking in spots. Yours looks like real wood. Did you refinish the case?

Thanks for you response.
 
The original vinyl wrap that was on the Sansui 5050 consists of 2 layers: the outer layer is easily peeled off (due to the drying out of the adhesive). The inner layer on the wood case itself is quite robust and was left on (surface was cleaned with isopropyl alcohol to remove any adhesive residue). The outer layer was replaced with a nice cherry wood vinyl wrap, e.g., https://www.amazon.com/Tact-Brand-18-Inchx9-Feet-Creative-Self-Adhesive/dp/B00B2734LW.

5050 case top.jpg

5050 side final.jpg

Some Pioneer receivers of this same era also used this type of imitation walnut veneer, and their cases can also be similarly restored, a Pioneer SX-750 with the same cherry wood covering as the Sansui 5050 can be seen via this link.
 
The original vinyl wrap that was on the Sansui 5050 consists of 2 layers: the outer layer is easily peeled off (due to the drying out of the adhesive). The inner layer on the wood case itself is quite robust and was left on (surface was cleaned with isopropyl alcohol to remove any adhesive residue). The outer layer was replaced with a nice cherry wood vinyl wrap, e.g., https://www.amazon.com/Tact-Brand-18-Inchx9-Feet-Creative-Self-Adhesive/dp/B00B2734LW.

View attachment 1427083

View attachment 1427084

Some Pioneer receivers of this same era also used this type of imitation walnut veneer, and their cases can also be similarly restored, a Pioneer SX-750 with the same cherry wood covering as the Sansui 5050 can be seen via this link.

Oh wow, that looks so much nicer. Added that to my to do list. Thanks for the link..
 
Been awhile since I posted on this topic. I have done a lot of work on this 5050. Good news is I now have both channels working. Yay!!

Bad news is, the right channel is a touch distorted. I checked the bias on the output transistors per the service manual instructions. The left channel is perfect at 15 mv. The right channel is 0v and the trim pot has no effect.

I don’t really understand how the bias circuit works. I would take any advice or direction if anybody has any.

Thanks.

Hi,
I am also currently repairing my Sansui 5050 as one channel went bad and fried the output transistors. I ordered the MJE... equivalents as suggested and put them in for one channel. It seems that i now have the same problem as you! I can adjust the bias on the channel with the original transistors to a perfect 15mV, but the other channel with the MJEs is about 0V no matter what i do :/ I also do have a lot of distortion on this channel.

how did you solve your problem with the bias adjust?

I also tried to switch the transistor pair to the other channel and then this channel lets me adjust the bias. So I am guessing that the output transistors are the cause.

I hope someone has an idea :)

PS: I also attached two pitures of the waveforms. (Yellow = Input, Magents = right channel, Blue = left channel). The clean waveform is the one with the original output transistors and the distorted waveform the one with the MJEs as output transistors. This only happens once I connect a load. With no load the output of the MJEs is also a perfect sine wave. It is also strange that on one channel the upper half is distorted and on the other channel the lower half. maybe it is because of the bias adjust,but who knows! :dunno:

y4m7C2HT0efbQU_EBqNGqkHKLXtu_Me-8kXXK0Zh1G2itUupCCiZpLRF2lH0kudFjcQTF1SxEMXdSaqNzY3QvtA0nFAD5GI-tg7jj3_MN7_RuiHZpM7QjPE2XDVmN_gVLmOGzwyFBdLEePlP48k_J0bCddFB4ItCpoE2ZBdLjyqPIi8HqFyYoPECfD2tLe6QY4E
y4mUDRNzwQSogVT5S4fVLdmUv40694hDFmEfxUUZCOOKVR1m80sktoUApQDimPVkizzvWrvfJbkNhb_v_hje73ZI9arJlU1F-FSo4LPjiGue1wpUARWJz3IYyiCVt2AAHNp41AJK9wI_cfoI3S_PEFx6ELHmCLPeeSHVCKKpWWdyOKQnMREO0J8BfWd0yYwXP8L
 
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Clearly you still have faulty or out of spec components in the originally faulty channel, the inability to adjust bias and the sensitivity to load are both clues to what is wrong. Note that when output transistors fail they often take other components with them - like driver transistors, or resistors - start by checking these. For inability to set bias also check TR05 on F-2648 and the associated trimmer VR01.
 
Claramente, todavía tiene componentes defectuosos o fuera de lo mejor en el canal original defectuoso, la incapacidad para ajustar el sesgo y la sensibilidad a la carga son pistas de lo que está mal . Tenga en cuenta que cuando los transistores de salida fallan, a menudo se llevan otros componentes, como transistores de control o resistencias, comience por verificarlos. Si no se puede establecer el sesgo, compruebe también TR05 en F-2648 y el recortador asociado VR01.
you're right
 
Reviving an old thread , I read trough this thread as I have a 5050 where one 2SA765 is bad.

Just wanted to update my effort to resurrect my Dad's Sansui 5050. Goal was to replace all of the caps and of course make it work again.

Started out with no audio. Receiver would not come out of protect mode. Looked like a barn find honestly. Here is what I found.

I was checking resistance on some various components on the F-2701Power Supply Board and noticed that the resistance across F604 (250v, .15A) was 28 ohms and the resistance across F605 (250v, .15A) was 58 ohms. I got the same reading when I pulled them out of the holder. Replaced both.

Either TR01 or TR03 had failed. I replaced the TR01 - TR04, 2SA726's with KSA992's . After this, the receiver came out of protect mode. However I noticed a bit of distortion on the right channel. Putting the scope on the output, I saw this.

View attachment 1426350

One of the power transistors had failed. I picked up a pair of matching output transistors, although in the end I only replaced the defective one since it seemed to match the original better. After this, both channels sounded good.

You state you replaced one of the power transistors . Did you use the TO-220-3 or did you find originals
somewhere? If you did can you PM me a link?

Also found some on the bay, yeah I know don't trust the bay , but these are USA suppliers so I might trust them a little more.

These have a similar curved printing of the ends of the part "upwards" as my originals do, but its the numbering under the Part number I am concerned about. Mine are all 730 .

Is that just a date code?

EDIT: Found a USA seller that had original type TO-66 that worked out.

Athanasios
 
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