Sansui au8500 9500 transistor replacement

Ciao sansui lover ,
Some months ago I've done a partal recapping on my sansui 8500;
Everythingh were working fine .recapping has improved sound ,has open his wings letteraly...

Some days ago I've received an elettronic parts box to repair and upgrade others hifi stuff.
I begin to replace elettrolytic bipolar that i've not in hand on the first job .they were only 6-7 not a heavy work.
When tested no sound at all! The relais doesn 't switch . I 've wasted lot of time searching for a problem on 2019 board .this acts like protection &power supply regulation .
After having jump the relais ,putting a power resistor (20 ohm) in serie with speaker I've discovering that fault was on left driver board .
From this channel come out a loud scream for a second than protection goes on.
Switching 2029 board from L to R ,scream follow the board .
With multimeter seeem everything in order ,bjt are ok ,diode ok,...just a differente impedance in the tr801-3 differential input .
Out of the board these couple of 2sa726 have the right junction...searching on net some tech said that these old transistor (they were already old in 70') leaking with the age .
So ...look for a replacement. ,some said ksc1845 & KSA992 are the right replacement ;I 've placed an order ...poland.1,2weeks delivery .
In the meantime I've read about bc559 560 rep...I've tried with the corret leg exchange.but no result ....not at all...relais switch ,hear a scream for ms,than amp goes to protection .
I like to know if someone else has really replaced sa726 with bc 550...
I'm afraid these bc550 are high hfe so goes to saturation..
Title said 8500&9500 just because use same driver board (somedays ago I open same thread in wrong section.

Many thank
Gabriele

Welcome to AK Gabriele
Have you checked the output transistors on the screaming channel yet?

Ciao,
Yes I've checked , when switch 2029 driver boad from L to R the burst noise came from other channel. Yes its follow the board.
The channel with the working 2029 board sound fine .

I'm thinking abiut the replaced bc550 instead of original bjt....
I think that no one has checked on the board..

Thanks

Mounting a couple of transistor bc550c on tr1&3 ,doesn't work.
I have put these after reading on this web , would be interesting having a feedback .original replacement or maybe the most suggest ksa992 are on the way home but I'm curious .

Thanks , gabriele

Was the lead orientation the same for the transistors you changed?
Often it's not....

Yes I've crossed 2 pin , they have a different pinout.

Some days ago I've replaced 2SA726 WITH BC559/560 how someone suggest on AK .
This on my amp doesn't works ,BC transistor in my case goes to saturation .... a short scream adn protection goes ON.
My load is a speaker with 16ohm in series to limit output current to save output driver .
Small transistor 2SA726 has been replaced with FAirCHILD KSA992 like other did on AK .
KSA992 must be solder with different pin out .
OK now the AMP Sing !

Appear that lot of leakage comes out from these transistor :
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I take decision to replace them all ; I don't want to open the amp again for same trouble.
2SA726 AND 2SC1313 on every single board have been replaced by KSC1845 & KSA992 FAIRCHILD . Most of them sits on pre board F2019 but also on phono card.
Input fet 2sk30 replaced with same type ; still avalaible .
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Not easy to replace on 2019 fillfull of wiring , easy to cook ...
Resolder every spot on boards and cleaned/washed , brings like news.
Looking at final bjt seems they are a little dry .
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Put new silicon and washed .
On MAIN caps I've added in parallel other caps , due the aging some mF can be lose.
I put 2*2200uF/50V on main cap (15000uF) and a 470uF/100V on the other.
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OK ,time to let it burning for some days and than ready for happy listening.

Ciao !

Hi,

I have used the BC560 as a substitute for 2SA726 in quite a few Amps without any problems. These have been used in phono/equaliser, tone control and differential input pairs in the main amplifier circuit. There is no gain difference issue, the 2SA726 is listed as having a gain of 600 min, and the BC560C is 600 typically (450 to 900 range). The main difference is in the ft figure, the 2SA is 100Mhz, whereas the BC is 250Mhz. The BC series is listed as a replacement on a lot of Internet sites. Same for the 2SC1313 and BC550.

Cheers

John

Hello Sebalele

So ...look for a replacement. ,some said ksc1845 & KSA992 are the right replacement

2SA726 perfect sub is 2SA1015(Toshiba)

As I already said in another thread :
KSC1845 is in fact 100% identical to 2SC1845
Same for KSA990 = 2SA990

Sub for 2SC1313 is 2SC2320L

Usually I never mix 2S Japanese TR with BC transistors

:thmbsp:

Will be usefull having a replacement list for these old amp , based on experience not reading in a replacement database . I 've useb bc transistor on tandberg receiver succesfully but I've tried twice in these amp but they don't work.
What can I say for sure is that this 992 & 1845 sing right for the whole 9500&8500 series.
Happen sometimes that replacement do the amp work but I 'm in trouble for adjust the right bias and dc offset. In this case i use to change the variable resistance a little and measure sometimes this works but not always.
Happy to list a replacement parts for our beloved Sansui,I'll try maybe soon on other amps cons from clinic audio and skippy if they are easily avaible.
Yes cause is not easy having this sort of replacement , china is full but shipment is very long so work become boring...
ciao

Hi,

I've also used (good quality) BC550B/C and BC560B/C in sansui amps, no problems what so ever. I even compared the HFE between the original and the replacement transistors, and I was able to match that. Tested with 1,10 and 100mA collector current. The adjustment of bias and DC offset gave no trouble, and was 100% stable. The pinout is different off course, I think you made a mistake there. The suggested 100% replacements are not easy available in Europe.

Reg,

Nico.

Ciao Nico , I've experience only on sansui 8500 and I've used bc550b with no positive result .
Same bc etc used in vintage amp like tandberg , philips , revox really works (tandberg use bc transistor like most european) .
I've crossed pin cause base is not in the middle in sc/sa type .I tried twice with new bc part..but doesn't work.
Nico do you replace 2sa726 with bc type ?
what sansui do you have restored ?

Regards,Gabriele

Hi Gabriele,

I've done quite a lot of Sansui in the past years, but have to admit the 8500 or 9500 wasn't one of them. I've done 717,719, the QRX5500, the eight and a BA2000,3000, and a BA5000. Not all of them complete restoration works. Also a couple of AU70's, and a AU111. Also the more humble units like a AU3900 and a 4900. The last amp I did was a AU666, which is a very good, underestimated little amp. Now I'm currently working on a TU70, a TU666, and a TU555.

I'm pretty sure I used BC560B, and matched the HFE as good as possible. This can be important in some circuits.
Don't use the C version, as the HFE of that type is pretty high. You could try and find a japanese replacement.
Farnell is a great source for Europe...

Nico.

A 2 years old topic indeed

Now for me, Farnell is not a great source for Europe at all, as they state they do not deliver to consumers, but to companies only.
The same applies to RS.

So I am grateful the Mouser company does, individual consumers can order.

At work there is about 5 techs ordering stuff for themselves regularly, sometimes together so order is big enough to avoid shipping costs.


Now what happened in the meantime, also for work, instead of RS and Farnell, nowadays we look at Mouser first.
This involves more money than for us individuals.


Over here in Holland we have some saying which is alike "if you do not appreciate the small things, you are not worth the big things", but I guess the Element14 and RS marketing care less.

Guess some marketing people at Mouser do understand this, we consumers can buy our small things, but because of that they get the bigger orders, too.

(just opinion, no affiliation)

gslikker said:

Now for me, Farnell is not a great source for Europe at all, as they state they do not deliver to consumers, but to companies only. The same applies to RS.

Click to expand...

I have accounts with both of those companies, I am not a business, just a private individual - no problem ordering parts from either.

Same here in Australia, and RS will ship any order for free, no matter what the value.

Hyperion said:

I have accounts with both of those companies, I am not a business, just a private individual - no problem ordering parts from either.

Click to expand...

hmmmmmmm then I have to try again, one of them, next time I need something.