SX-1050 Protection transistor replacements, AWM-090 - resolved

[merlynski]

I am in the midst of rebuilding the Protection circuit and discovered I didn't order replacements for Q5, 2SA733; and Q3 & Q4, 2SC945. None of the lists I have downloaded suggest replacing these 3 transistors. Is this because they do not have a history of problems or failure?

I have replaced all the other transistors and the e-caps, including film for C1 & C2, and the relay.

I did find replacements suggestions in an older SX-1010 thread, which has the same protection circuit architecture:
2SA733 => KSA733, the KSA733 is end of life on Mouser, listed obsolete,
2SC945 => 2SD1616A,
neither of which I have on hand.

I found a newer SX-1050 post with these suggested replacements:
2SA733 => KSA992FBU,
2SC945A 512 => KSC1845FTA,
both of which I have on hand.

So my question is: Don't bother with them, order the older replacements, or use what I have?
Thanks for your inputs!

 

[markthefixer]

either don't
or (like I do to preclude callbacks)
go with the a992 and c1845's

D1616 was an OLD mistake that just NEVER goes away. NOT BAD, just not justified.

 

[merlynski]

either don't
or (like I do to preclude callbacks)
go with the a992 and c1845's

D1616 was an OLD mistake that just NEVER goes away. NOT BAD, just not justified.

Thanks for the reply!

I put a D1616 in place for Q6 (from an old list), should I switch it out for a KSC1845 while I have it open on the bench?

 

[markthefixer]

no, orig was a 2sc945

ksc2383

it is a SOA thing.

Please change the

awm-090 q6 2sc945 0 0 0 0 0 512-KSD1616AGBU
to
512-KSC2383YTA

Thank You.

markthefixer jun 13, 2014

 

[merlynski]

no, orig was a 2sc945

ksc2383

it is a SOA thing.

Got it, thanks!

 

[redk9258]

2SA733 => KSA733

If you do use KSA733 watch the pin out! KSA733C is center collector!

 

[EastPoint]

I use KSA992 on these boards, and use KSC2383 to replace all the 2SC945s and similar. Many of them can be replaced with the KSC1845 but it’s easier for me to just use the KSC2383 for all.

I do have KSA733 and KSC945 in stock but I don’t use those here.

 

[merlynski]

If you do use KSA733 watch the pin out! KSA733C is center collector!

When I pull a transistor I test it, and write down what it shows: hFE, Vbe and pin asignments, then I test the new one, and record its same information. Never the less, even triple checking, I STILL got one wrong on the AWR-103 PS regulator pcb and had to replace a 'brand new' shorted transistor.
Datasheets are my friends!

 

[merlynski]

I use KSA992 on these boards, and use KSC2383 to replace all the 2SC945s and similar. Many of them can be replaced with the KSC1845 but it’s easier for me to just use the KSC2383 for all.

I do have KSA733 and KSC945 in stock but I don’t use those here.

I don't have either of those on hand, but I have lots of KSC1845s. I knew I had some KSC2383s, but I had only bought a few, and it took me an hour to find them. They will be going in today!

 

[soundguy9]

I am in the midst of rebuilding the Protection circuit and discovered I didn't order replacements for Q5, 2SA733; and Q3 & Q4, 2SC945. None of the lists I have downloaded suggest replacing these 3 transistors. Is this because they do not have a history of problems or failure?

I have replaced all the other transistors and the e-caps, including film for C1 & C2, and the relay.

I did find replacements suggestions in an older SX-1010 thread, which has the same protection circuit architecture:
2SA733 => KSA733, the KSA733 is end of life on Mouser, listed obsolete,
2SC945 => 2SD1616A,
neither of which I have on hand.

I found a newer SX-1050 post with these suggested replacements:
2SA733 => KSA992FBU,
2SC945A 512 => KSC1845FTA,
both of which I have on hand.

So my question is: Don't bother with them, order the older replacements, or use what I have?
Thanks for your inputs!

I recently acquired an sx-1050 with lots of dust and I am planning to start a rebuild project. I wanted to ask you if you could share your experience or any information before I get started.

So far, I removed the decades old dust and cleaned the pots and it is sings nicely. I find it very different from my 737, I find the 1050 more musical, softer but reacher at the same time (if it makes any sense).