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Leestereo's Restoration and Upgrade of a Sansui AU-777A

My amp has 2SC631 at positions TR701 - TR704, TR707 - TR709, TR801-TR802.
Is that improvement or lack of supply 2SC458?
 
The substitution of the 2SC631s was most likely due to supply issues with the 2SC458s at the time of manufacturing. The advantage of the 2SC631 is that it is not as failure prone as the 2SC458 as it ages.
 
Very well done. :thumbsup:
When Echowars (where is he?) refurbished receivers or integrated amps he replaced the transistors in the phono-stage with matched pairs of Zetex devices. Results were always excellent.
 
I am working on a full restoration of an AU-777a and have found this thread to be very helpful, thank you Leestereo! I have only gotten the power board and driver amp board done so far but have not gotten the L channel to work yet, just glows the DBT super bright with the fuse in. I did some investigating and found 3 blown 2SD218 output transistors, 2 on L and one on R channel, I think that may explain why the L channel isn't working.

I am looking for the best substitute to order for the 2SD218 and have found 3 options below:
- MJ21194G (backordered on Mouser until Jan 2024)
- MJ15003G (backordered until Sept)
- MJ15024G (Backordered until Aug)

Are these the best options for the output transistors for the AU-777a, and is one recommended over the others? Also, the 4 smaller 2SD143's all tested fine but was thinking of replacing them as well since I am already in there, any ideas on their best replacements?
 

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Brad1234 said:
I am working on a full restoration of an AU-777a and have found this thread to be very helpful, thank you Leestereo! I have only gotten the power board and driver amp board done so far but have not gotten the L channel to work yet, just glows the DBT super bright with the fuse in. I did some investigating and found 3 blown 2SD218 output transistors, 2 on L and one on R channel, I think that may explain why the L channel isn't working.

I am looking for the best substitute to order for the 2SD218 and have found 3 options below:
- MJ21194G (backordered on Mouser until Jan 2024)
- MJ15003G (backordered until Sept)
- MJ15024G (Backordered until Aug)

Are these the best options for the output transistors for the AU-777a, and is one recommended over the others? Also, the 4 smaller 2SD143's all tested fine but was thinking of replacing them as well since I am already in there, any ideas on their best replacements?
Click to expand...

I'm sure @Leestereo or some other qualified folks will weigh in on your substitution inquiry.

Have you determined what caused the output transistors to go? Were they blown before your restoration work? You'll want to address the cause before plugging new outputs in, if you haven't already.

Looking forward to reading about your restoration coming together.
 
Brad1234 said:
...I am looking for the best substitute to order for the 2SD218 and have found 3 options below:
- MJ21194G (backordered on Mouser until Jan 2024)
- MJ15003G (backordered until Sept)
- MJ15024G (Backordered until Aug)
Click to expand...
I would not recommend MJ15003 as a replacement as it's fT is too low compared to the stock 2SD218. The MJ15022 can also be considered, but the MJ21194 is the preferred replacement.
 
W
Leestereo said:
I would not recommend MJ15003 as a replacement as it's fT is too low compared to the stock 2SD218. The MJ15022 can also be considered, but the MJ21194 is the preferred replacement.
Click to expand...
Please share your replacements/substitute for these also.
2sd152
2sd154
2sd143
Regards
 
JimEGR said:
I'm sure @Leestereo or some other qualified folks will weigh in on your substitution inquiry.

Have you determined what caused the output transistors to go? Were they blown before your restoration work? You'll want to address the cause before plugging new outputs in, if you haven't already.

Looking forward to reading about your restoration coming together.
Click to expand...
So I got the stereo in not working condition and have started on replacing caps/diodes and transistors on power supply and driver boards while testing on dim bulb tester after each board. After still failing the DBT, I checked the output transistors and found 3 of 4 blown, so not sure yet if they were cause or effect of the short in the stereo, but will keep replacing caps and testing after getting the new output transistors installed.
 
Leestereo said:
I would not recommend MJ15003 as a replacement as it's fT is too low compared to the stock 2SD218. The MJ15022 can also be considered, but the MJ21194 is the preferred replacement.
Click to expand...
Thanks Lee, I think I should go with the MJ21194 then if it is preferred option. Do you have any recommendations where to buy them since mouser is backordered for the rest of the yr on them?
 
Leestereo said:
I would not recommend MJ15003 as a replacement as it's fT is too low compared to the stock 2SD218. The MJ15022 can also be considered, but the MJ21194 is the preferred replacement.
Click to expand...
Please share your replacements/substitute for these also.
2sd152
2sd154
2sd143
 
raj12345 said:
Please share your replacements/substitute for these also.
2sd152
2sd154
2sd143
Click to expand...
If you have found somewhere to buy these, they are almost certainly either 'counterfeit', or 'pulls' from physically damaged units. Either source is likely to be unreliable and you are much, much better off replacing them with Leestereo's recommended replacement, On-Semi 'MJ21194G' - BUT only buy these from reputable suppliers (i.e. almost always not 'online auction' sites) as there may be counterfeit sources for these as well now. You want to be dealing with companies like Mouser, Digikey, Farnell, and companies like them, I know this can be difficult for people located in some countries, but it is worth the effort to get the genuine devices.

The site mentioned in the post above above happens to be run by an AK member so is absolutely recommended.
 
Last edited:
Hyperion said:
If you have found somewhere to buy these, they are almost certainly either 'counterfeit', or 'pulls' from physically damaged units. Either source is likely to be unreliable and you are much, much better off replacing them with Leestereo's recommended replacement, On-Semi 'MJ21194G' - BUT only buy these from reputable suppliers (i.e. almost always not 'online auction' sites) as there may be counterfeit sources for these as well now. You want to be dealing with companies like Mouser, Digikey, Farnell, and companies like them, I know this can be difficult for people located in some countries, but it is worth the effort to get the genuine devices.

The site mentioned in the post above above happens to be run by an AK member so is absolutely recommended.
Click to expand...
Yes, very true about ebay parts sellers on average that there are a lot of counterfeit parts being sold on ebay, I avoid them almost always. But I have done a lot of business with peace.love.and.music and his store Affinity for Artifacts and trust his parts, he also has a lot of kits for the DIY'ers and good descriptions of everything he sells.
 
Hyperion said:
If you have found somewhere to buy these, they are almost certainly either 'counterfeit', or 'pulls' from physically damaged units. Either source is likely to be unreliable and you are much, much better off replacing them with Leestereo's recommended replacement, On-Semi 'MJ21194G' - BUT only buy these from reputable suppliers (i.e. almost always not 'online auction' sites) as there may be counterfeit sources for these as well now. You want to be dealing with companies like Mouser, Digikey, Farnell, and companies like them, I know this can be difficult for people located in some countries, but it is worth the effort to get the genuine devices.

The site mentioned in the post above above happens to be run by an AK member so is absolutely recommended.
Click to expand...
MJ21194 is a suggested substitute for 2SD218 which are the larger output transistors in 777a. I wish to know the substitute for
2sd152
2sd154
2sd143

Which are the smaller output transistors / driver transistors in 777 & 777a Sansui amplifier.
 
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