to92 transistor replacement - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 9th February 2015, 09:42 AM   #1
Trileru is offline Trileru  Romania
diyAudio Member
 
Join Date: Dec 2010
Default to92 transistor replacement

Hello,
I started to refresh my Marantz unit, and it seems that I'm going to change almost everything inside. Only ceramic and film caps will remain. I already replaced the electrolytic caps and all resistors with metal film.
I pulled out the old transistors and measured them. While they are not leaking at all, hfe is a bit wild between them so I'd like to replace them.
I added the schematics for the boards in question. I'd like an opinion if I can replace them with low-noise BC327/BC337 as I have good access to those, for cheap. I can get lots and match hfe on pairs. Also BC550/BC560. Both pairs have different gain codes so I can match almost all transistors from the amp.
I'll list the transistors I found:
Power Supply: H802 - 2sc945p (hfe 237) in the datasheet P is 200-400
H803 - 2sc945q (hfe 189)in the datasheet Q is 135-270
Buffer Board: HD01-HD04 - 2sc1328T (measured hfe was between 481 - 595)
- datasheet specs hfe at 360-700.
Tone Board: HE01 - HE04 - 2sc1327S (measured hfe was between 338 - 486)
- datasheet specs hfe at 260-520.
HE09 - HE12 - 2sc1222 I guess. Transistors have C1222 written.
- measured hfe was 417 to 735. Datasheet lists it wrong as EBC, it's actually ECB. And has a weird code (2E51A) that doesn't match the datasheet for HFE rating.
HE05-HE08 and HE13-HE16 - 2sa733q (measured hfe 160 - 192)
- Q is a rating of 135-270.
Power Amp:
I haven't gotten to tear down the pcb but the transistor numbers are consistent with the schematic.
2sc1327 S or T hfe of 260-700.
2sc1318 Q or R hfe of 85-240.
2sc945 Q hfe 135-270
2sa641 M schematic has different letters for hfe rating. I have no idea.
2sa684 G or F schematic has different letters for hfe rating. I have no idea. this is a larger to92 package.

I'd like to replace all since working on this unit is a real pain. I don't want to go back inside for the next 10 years, I just want to enjoy it. Right now everything is teared down from the amp so while I'm reacaping, re-resistoring I'd re-transistor as well
The output transistors are 2SD315, and they seem in working order. The package is TO66 so if they fail I need to adapt TIP41. But those I can access more easy, no need to replace them now.

So, besides the larger to92. can I replace everything with low-noise BC327/BC337 or BC550/BC560 type transistors with matching HFE values?
Attached Images
File Type: png PS.png (193.6 KB, 624 views)
File Type: png Buffer.png (91.6 KB, 607 views)
File Type: png Tone.png (233.4 KB, 588 views)
File Type: png Amp.png (257.3 KB, 588 views)
  Reply With Quote
Old 9th February 2015, 10:49 AM   #2
diyAudio Member
 
Welcome's Avatar
 
Join Date: Mar 2013
2sa733 = KSA992

2sc945, 2sc1222 = KSC1845

I wouldn't use BC transistors in a japanese amp.
__________________
  Reply With Quote
Old 9th February 2015, 10:49 AM   #3
diyAudio Member
 
Join Date: Jul 2003
Location: Dona paula, Goa
hfe will always be wild even if you take the new transistors. The small signal transistors will not be damaged sometimes even for the life, anybody's.

If it ain't broken, don't fix it.

Gajanan Phadte
  Reply With Quote
Old 9th February 2015, 11:37 AM   #4
Trileru is offline Trileru  Romania
diyAudio Member
 
Join Date: Dec 2010
Quote:
Originally Posted by Welcome View Post
2sa733 = KSA992

2sc945, 2sc1222 = KSC1845

I wouldn't use BC transistors in a japanese amp.

Why is that? Aren't they compatible? I don't have access to ksa/ksc.
I could match the gain with new transistors
  Reply With Quote
Old 9th February 2015, 11:42 AM   #5
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Many Jap amps are quite critical of the transistors used, particularly in the output stages. Its not just gain, they actually differ slightly in absolute turn on volts (maybe different manufacturing techniques and doping back then) which can be a big factor where critical bias voltages are needed and generated. For example replacing the drivers and outputs may give a low or no quiescent current that is non adjustable (without altering other components in the bias network). There can also be very real stability issues due to differing inter junction capacitance.

That said, the small signal stages, while showing no benefit for swapping devices, should show no real problems either.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 9th February 2015, 12:09 PM   #6
Trileru is offline Trileru  Romania
diyAudio Member
 
Join Date: Dec 2010
Ok, thank you.
What bothers me is that the tone (preamp) transistors have a wide hfe between the same type. 400 to 700 spread in hfe seems a bit high for me.
So I could do this in the lower stages but not in the final one?
  Reply With Quote
Old 9th February 2015, 12:12 PM   #7
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
The hfe variation is a non issue thanks to the action of negative feedback. Whether you uses an hfe of a 100 or 800, the circuit would still perform essentially the same. If an hfe of 400 is the lowest of what is in there already, then I would say that was actually pretty high even by todays standards.

Honestly, you won't gain anything by replacing these.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 9th February 2015, 12:14 PM   #8
Trileru is offline Trileru  Romania
diyAudio Member
 
Join Date: Dec 2010
Quote:
Originally Posted by Welcome View Post
2sa733 = KSA992

2sc945, 2sc1222 = KSC1845

I wouldn't use BC transistors in a japanese amp.
I seem to be able to get locally 2sc1845 and 2sa992. Should be the same?
  Reply With Quote
Old 9th February 2015, 12:18 PM   #9
Trileru is offline Trileru  Romania
diyAudio Member
 
Join Date: Dec 2010
Quote:
Originally Posted by Mooly View Post
The hfe variation is a non issue thanks to the action of negative feedback. Whether you uses an hfe of a 100 or 800, the circuit would still perform essentially the same. If an hfe of 400 is the lowest of what is in there already, then I would say that was actually pretty high even by todays standards.

Honestly, you won't gain anything by replacing these.
Only for those transistors.
In the tone board I have 2sa733q with 160 lowest. But that is in spec with the datasheet as well.
I thought about replacing them as I thought they are old and might give up at some point, and then I see everyone is recommending to match transistors gain.
  Reply With Quote
Old 9th February 2015, 12:24 PM   #10
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
hfe variations will have a minimal effect at any part of the circuit. Your biggest problem is the other characteristics (not hfe) of the transistors in the power amp causing serious problems if you start swapping them for other modern types. You would need to rework and change some component values.

The preamp stages will work with pretty much anything.

There is no real reason to suspect the transistors will fail... as a general rule that doesn't happen. They should be as good as the day they were made.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Transistor replacement grandville45 Parts 30 1st April 2010 05:50 PM
identifying a to92 transistor (S107) kasra Parts 5 14th April 2006 04:39 AM
Transistor Replacement portlandlay Solid State 26 14th December 2005 07:46 PM
Transistor replacement Mlaen Solid State 3 18th February 2005 11:00 AM


New To Site? Need Help?

All times are GMT. The time now is 04:44 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.
Copyright 1999-2015 diyAudio

Content Relevant URLs by vBSEO 3.3.2