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Pioneer SA-7800 - Help replacing transistors!

Are the output's bad? If so, some bad and not so bad news. Fujitsu hasn't made them for at least a decade. Here's a quote from Mark from an 2006 thread about a SA8800 (same output's). Not sure on how relevant the linked thread is.
http://www.audiokarma.org/forums/showpost.php?p=899257&postcount=4

The output devices on the sa-8800 are the same as the sa-7800, which are the 2sa1075 and 2sc2525. These cases have a very unusual configuration.

IF the unit is working, leave the outputs alone, because the replacements that were found for the sa-7800 a while back wouldn't FIT, they were about 3 mm too big in every dimension, and wouldn't shoehorn in between the pc board and the other fittings mounted on the heatsink.

We eventually found some very expen$ive replacements,
which is documented in this thread, starting at post 64 ( http://audiokarma.org/forums/showthread.php?p=853771&highlight=2sa1075#post853771 )
which you will find very informative.
Click to expand...

Unless Mark and Glenn have come up with a work around for this in the last 8 years.............................................
 
Hi Larry!
Yes : both 2sa1075 and 2sc2525 (pair) are damaged on that channel...

Well, if it's absolutely mandatory to keep the "original", then I think there are still some chances to get an old/used (and probably abused) pair of 2sa1075 and 2sc2525 from somebody...

On the other hand , I'm pretty sure uncle Nick has all necessary skills to fit some On-Semi MJLs (3281 and MJL1302 ???). I saw him fitting some TOSHIBA outputs in a SA708 and the cases (TO−264 I think?) were identical to above mentioned MJLs). I still have doubts those TOSHIBA were genuine, but that's another story.
The main idea is : new transistors can be used as replacements (i.e. they will fit somehow).
I even saw an old thread were our AK fellow "leesonic" was doing this thing successfully (not able find the link right now...).

But ok, I'll wait to see what Mark will say about that.
 
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I reversed the high power dissipation resistors to the other side of the board...
Click to expand...
Maybe important to mention: on my board, some resistors are raised on ceramic insulators (at least this is the case for my amp).

BTW, some items in your list are bold-ed. Any special meaning for that?

I also noticed this : "(R=60-120, O=100/200, Y=160/320)"...
I'm 99.9% sure it's the range for transistor's beta (hfe)... right?
In this case, does mouser offer the possibility to select/buy a specific range?
 
I do have a problem here:
In the service manual that I have (a PDF file) it says: Q27, Q28 = 2SC1914A

Mark, in your list it is: q27 q28 2sa1914

?!?
 
larryderouin said:
Use the KSA992FBU. Mark's been using that to replace the 1914 in the 7800 since at least 2009 (at least the oldest thread with it is dated that.... http://www.audiokarma.org/forums/showthread.php?t=200669&highlight=2sa1914&page=2 ). The "A" is most likely a gain suffix, but I can't find a damn thing on the 1914A.
Click to expand...

Hi Larry,
Well, that's why I am worried about !
According to the service manual Q27/28 are NPN transistors...
And the KSA992FBU (replacement) transistor you indicated above is PNP !!!

Am I missing something here ? (Anyone can make mistakes...)
Please bear with me, I'm just an embedded programmer with almost no experience in electronics, but I do have the feeling something is not ok about the Q27/28 replacements...

Sigh... :sigh:
 
ok, I was beginning with the first steps in making a component-list on mouser's site.

Few remarks:
1) the problem with Q27/28 replacements (I already detailed this issue in my previous post).

2) 512-KSC1845EBU seems to be obsolete and stock is zero.
As long as it is no longer manufactured... what else should I use as replacement?

3) 512-1n4454 fast 100v .2a
All I could find at mouser is at 75v (and not fast either)... ?!?

Mark, please can you help me with the above issues?
:tears:

<<Edit>> :
PS: Uncle Nick says I also have to replace those trimmers ?!... :scratch2:
 
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groenhen said:
Hi Larry,
Well, that's why I am worried about !
According to the service manual Q27/28 are NPN transistors...
And the KSA992FBU (replacement) transistor you indicated above is PNP !!!

Am I missing something here ? (Anyone can make mistakes...)
Please bear with me, I'm just an embedded programmer with almost no experience in electronics, but I do have the feeling something is not ok about the Q27/28 replacements...

Sigh... :sigh:
Click to expand...

KEE-RIST! I missed the SA vs SC. Sorry about that. Hold on................................(did a forum search for 2SC1914A)....Just went thru some more threads. The 2SC1914A gets replaced with the KSC1845FTA See post 19 for pics.. http://www.audiokarma.org/forums/showpost.php?p=6602520&postcount=19

Q2) KSC1845FTA is the replacement for the KSC1845EBU. The suffix (EBU or FTA) is the gain component and either bulk(BU) or Tape(TA).

Q3) Can't help with the DIODE.

Yeah replace the trimmers. They get a set in them and when you adjust them they can go open or short. Best not to mess with them and just replace.
 
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Many many thanks Larry for your valuable help!

We are close to midnight here and I'm still looking to find an equivalent for that diode:
1s2076 replace: 512-1N4454 fast 100v .2a
Should I search on Mouser for "fast rectifier 100v" and just pick one that has the forward current greater than 200mA ?
Hmmm, isn't 1n4148 a good candidate ? (100v / 300mA / 4nsec)

On the other hand, what do you suggest as replacement for outputs : 2SA1075 and 2SC2525 ?
What options do I have? (I have absolutely no problem if it's TO-264 package/case).
 
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Ok, here is the status of the component list (for Mouser):

1) With Mark's help, I have the replacements for TRANSISTORS and DIODES.
TODO: - find replacements for output transistors and for that fast 100V diode (1s2076).
(Also, I thank you Larry for your help!)

2) I have also some replacements for E-CAPS, not sure if it's good or not, as I did it myself...

3) With Lee's help, I have the replacements for (burnt) RESISTORS and for TRIMMERS.
Remark: One of the original trimmer is 68k, there's no exact fit on Mouser, so shoud I will buy 50k or 100k...?

Well, what else should I order/buy from Mouser ?
Did I miss something ? If so, please tell me.
I definitely want to have only one order, because P&P to Europe is quite expensive!...

PS: I wish I can have this amp fully working before x-mas... :music:
 
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1s2076
You have to learn to get the specs, look at the data, search on Mouser for similar characteristics.
Features
• Low capacitance. (C = 3.0 pF max)
• Short reverse recovery time. (trr = 8.0 ns max)
• High reliability with glass seal.
Pkg: DO-35
Vrm=35V
If=150mA

First to try out, our favorite:
1N4148
pkg: DO-35
trr=4ns
cap=4pF
Vrm=100V
If=200mA

== Good enough for me or use the 1N4448 for the 2pF capacitance to more exact..
 
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Thanks Rick, there's a lot of info (and links) you provided!
Yes, getting the specs is a good thing :) no doubt!
Yet, even when there are only few options, question is: what should I choose?
As I see, even the case/pkg is important... DO-35. (just an example, first I didn't pay attention to that...)
And probably other things are to be taken into account...
I don't have any experience, that's why I need to ask for advice from people who have been through similar situations and have the related know-how.
It is such a stupid situation when, after ordering and receiving the replacement components, you find people saying "ohhh, but that diode is not the right choice" or "that transistor is not good at all", etc.
So, at least I'm trying to do my best to find the optimal replacement parts for this sa-7800 amp, as I have the feeling that it worth the effort.
To be honest, I am a little bit scared, as SA7800 is quite complex, but that won't stop me to fix this amp, with the help of some AKers of course :)

PS: diode you recommended is already on my mouser-list (1n4148) :thmbsp:
 
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groenhen said:
Hi Mark!
Ok, step by step, as I have plenty of time :)
I really wanna do a good job... I wanted this amp since I was 10... Now I'm 44 :(

I'm an expert in AVR microcontrollers. I made a super multi tester, so I can test all components: transistors, caps (ESR included), resistors, inductors, etc.
(project is from internet, not my idea. I just built one for myself).

I already mentioned (see first post) a list of damaged parts.
Took your advice and tested Q5 and surrounding area... It seems to be ok according to multi-tester. Q5 has a logo similar to Mitsubishi, but different somehow... Could it be former logo of Panasonic? I mention this as it seems the GWH-118 board had some intervention(s) on it... not sure yet... dust doesn't seem equal on all components ;)

Honestly, I don't trust old list of transistor replacements. That's why my initial question still stands: what should I buy for finals (2sa1075 / 2sc2525) and for those ("drivers" I think they are) 2SA913 and 2SC1913 ?
I prefer mouser as I will order e-caps from them...

Mark sorry my ignorance (bare with the SW guy) but what is it got to do with the phono stage?!

My uncle, he is about 78, an old school guy. He saw the amp and he smiled. We are in a serious competition. He is a guru of all kind of analog circuits, I am good at digital.
He said he can fix it in 1 hour but he won't do it as he wants to see me sweating :(

So, Mark I promise to follow you advices carefully just to show him I can make this amp work...

BTW, I tried to search the forum... Results were from 2 years ago, something like:
2SA1930 pnp AND 2SC5171 npn for "drivers" ... but not sure it's the best choice...?

Regards,
Stanley.
Click to expand...

Sankens from digikey

2SA1075 use 2SA1216
2SC2525 Use 2SC2922
 
glen65 said:
Sankens from digikey
2SA1075 use 2SA1216
2SC2525 Use 2SC2922
Click to expand...

Hmmm, $28 + $60 = about $90
NO WAY! NO WAY !!!

I will stick to mouser, as I don't wanna spread orders...

I found 2SA1216 in Europe, but his brother 2SC2922 is not on stock :(
Pity... these Sankens looked like good candidates for replacements!

<EDIT>
I think it would be nice to have a sticky (or something) for Pioneer part replacement equivalents...
that could be updated from time to time...
For the huge benefit of all AKers.

I agree, getting the specs and searching on Mouser for replacement is ok for few items.
But what if you need a full list of items (50-100) ? Wouldn't it be better to have a data-base at hand?
Thus we can save time & energy each time when we need a replacement :)
 
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groenhen said:
Hmmm, $28 + $60 = about $90
NO WAY! NO WAY !!!
Click to expand...
I didn't know where you were located. Its not indicated in your profile.

I will stick to mouser, as I don't wanna spread orders...
Click to expand...

Its your call, but with drop in devices available, it doesn't make much sense to try and convert it to something else.
I found 2SA1216 in Europe, but his brother 2SC2922 is not on stock :(
Pity... these Sankens looked like good candidates for replacements!
Click to expand...

Those aren't the only ones that would work. Below is the link to the original Fujitsu 1075 datasheet.
Then there is another to Sanken's website. Look at some of the other MT-200 case devices and see if the European distributor you deal with has them instead.
http://pdf1.alldatasheet.com/datasheet-pdf/view/87025/FUJITSU/2SA1075.html

http://www.semicon.sanken-ele.co.jp/ctrl/en/product/list/Audio/


<EDIT>
I think it would be nice to have a sticky (or something) for Pioneer part replacement equivalents...
that could be updated from time to time...
For the huge benefit of all AKers.

I agree, getting the specs and searching on Mouser for replacement is ok for few items.
But what if you need a full list of items (50-100) ? Wouldn't it be better to have a data-base at hand?
Thus we can save time & energy each time when we need a replacement :)
Click to expand...

Maybe, but the people spitting out these lists aren't being paid to do it. It takes time, and many of the techs are up to their eyeballs in work. The lists are done on the fly as needed, and not difficult to find if one just takes a bit of time to search.
 
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2sa1216 x 2 and 2sc2922 x 2

http://ampslab.com/trans_2sc2922.htm

40 bucks (plus shipping) for the set...


Data base? The transistor cross referencing does NOT just go by the the transistor part number, it DEPENDS upon the DESIGN of the circuit it is intended for. Is that part being pushed too hard in that position, was it overkill? WHAT are the critical parameters of THAT particular part in THAT particular circuit position.

That's why guys who look up previous transistor number substitution in non-similar circuits (and use them) are asking for problems. And I have to look DOUBLE hard in MY records to be sure I didn't generate that ill conceived recommendation. Luckily some of my worse choices in the past have been eradicated by the part going obsolete, or is easily spotted with a distinctive number (a certain protection transistor - the 100uf cap discharge transistor - had a marginal SOA in the original, and the d1616 wasn't much better, thus upgrading to the c2383)

ALL of the lists were the work product of MY repairs that I did. I did do a few later that were preemptive because I knew I eventually would encounter some of that model to repair, thus I was "putting work in the bank for the future".



YOU see a list - and maybe are starting to appreciate the DAYS and possibly WEEKS of work and sweat behind each one.
 
Hi Mark,

First, sorry my proposal was probably a bad idea (just wished people can benefit from threads like this without browsing many many pages).

Second, I do have a question about those Sankens from ampslab:
As I see on their webpage, they offer 2SC2922-G + 2SA1216-Y...
But, according to data-sheet, first transistor has hfe=90 and its complementary has hfe=50.
Is it ok?! I thought the outputs should match hfe for better sound quality/fidelity or something like that...
I'm not expert, I may be wrong, so I think I better ask :scratch2: .

Thank you and be sure I appreciate the time and effort you put in this!
Stanley.
 
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