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 11th December 2005, 09:28 PM   #1
diyAudio Member
 
Join Date: Dec 2004
Location: Washington State
Default Transisitor Replacement

I am trying to bring my Sugden A21 (old) amp from the dead to the living.

It looks like one channel is dead and I think that a bad BFY53 transistor is the problem. The rest of the amp and the scematic only show BFY52. Since I am not a transistor guy I need help. I see that BFY52's are available and I want to use one of these instead. It looks like the h(FE) min for the BFY53 is 30 and 60 for the BFY52 otherwise they look very similar.

Is this OK?
  Reply With Quote
Old 11th December 2005, 11:00 PM   #2
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi portlandlay,
I can't find data on the BFY53 so I can't advise. If the only difference is a higher minimum gain, then maybe - yes.

Anyone else have a clue?

-Chris
  Reply With Quote
Old 11th December 2005, 11:06 PM   #3
diyAudio Member
 
Join Date: Nov 2002
Can you post a schematic of the amp?
  Reply With Quote
Old 11th December 2005, 11:26 PM   #4
diyAudio Member
 
Join Date: Dec 2004
Location: Washington State
There is no exact shematic. The one under it is very very close to the one found at http://www.tcaas.btinternet.co.uk/index-3.htm then going to Sugden.

I found both the BFY53 and BFY52 specs (not much) at http://www.americanmicrosemi.com/pro...-05-1000.phtml
  Reply With Quote
Old 11th December 2005, 11:42 PM   #5
poobah is offline poobah  United States
diyAudio Member
 
poobah's Avatar
 
Join Date: Nov 2005
Hey Portland,

Does the other channel of the amp have the same __53 transistor?

Could this be a sloppy repair?
  Reply With Quote
Old 11th December 2005, 11:57 PM   #6
poobah is offline poobah  United States
diyAudio Member
 
poobah's Avatar
 
Join Date: Nov 2005
Hey Portland,

If the schematic says BFY52 (high hfe) and you found a BFY53 (low hfe) on the board... especially if the other channel on the amp has a '52; the manufacturer may have been measuring 53's and sorting out and using the 52's with high gain... happens all the time.

Anatech is dead on the mark though... usually you can sub an otherwise equivalent transistor with another unit of higher hfe.

Hope this helps,
  Reply With Quote
Old 12th December 2005, 12:14 AM   #7
diyAudio Member
 
Join Date: Dec 2004
Location: Washington State
Both of the channels have one 53. The schematic differs from this but the shematic was really not the same amp. It was by James Sugden during the time this was made but was different in some small ways from the A21 that I have.
  Reply With Quote
Old 12th December 2005, 06:05 PM   #8
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi portlandlay,
Thanks for the link to the specs. They do appear identical except for the DC current gain.

What position in the 10W schematic is closest to where the BFY53 located in your amp?

-Chris
  Reply With Quote
Old 12th December 2005, 06:14 PM   #9
diyAudio Member
 
Join Date: Dec 2004
Location: Washington State
anatech,

No, thank you for taking the time to look at it. The 53 is the one that that is left on the schematic. It is not driectly feeding the ouput transistors.

Stephen
  Reply With Quote
Old 12th December 2005, 06:19 PM   #10
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi Stephen,
I read that as TR3, an emitter follower (buffer). The higher gain will reduce the loading on the preceding stage. Go ahead and use the BFY52 instead.

-Chris
  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 for older DEI amp whoya2350 Parts 0 29th March 2009 02:05 AM
Looking for replacement transistor kockaboy Parts 4 15th October 2008 04:51 PM
transistor replacement xcicc Solid State 0 16th August 2008 10:05 AM
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 05:29 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2