Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Pass Labs This forum is dedicated to Pass Labs discussion.

help to set dc offset to threshold s450
help to set dc offset to threshold s450
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 30th January 2016, 09:49 AM   #41
Zen Mod is offline Zen Mod  Serbia
Official Court Jester
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
help to set dc offset to threshold s450
offset is not good , but you have bigger problems if amp is not making music on output

yes , connect cap in series with speaker (to protect it from DC) and it must make music

if that's not the case , your amplifier needs proper repairs , which I'm afraid you are not capable of

so , make test again

just to make it clear - without proper repair procedure , you can't declare what's wrong - output transistors , front end , or both
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM
  Reply With Quote
Old 30th January 2016, 10:01 AM   #42
alfalf1 is offline alfalf1
diyAudio Member
 
Join Date: Feb 2013
yes confim it, with cup in serial to speaker not make music but spike like transistor burned.

but when i remove the cap the make music but i cannot increase he volume more

so the my consideration abut problems also in the output stage was valid.

is there just one output stransistor burned can it work in the manner indicated above ?
  Reply With Quote
Old 30th January 2016, 10:14 AM   #43
Zen Mod is offline Zen Mod  Serbia
Official Court Jester
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
help to set dc offset to threshold s450
no , you can't make assumptions like that

troubleshooting broken amplifier is complex process

I'm usually working backwards , from output stage - short circuit test for each element, diode test for each transistor , checking for shorted or damaged resistors etc.

without at least some experience in that , it's best to leave repair of such complex amp to someone who knows more - that way possible damage and final cost is always smaller
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM
  Reply With Quote
Old 31st January 2016, 07:38 PM   #44
alfalf1 is offline alfalf1
diyAudio Member
 
Join Date: Feb 2013
Default perhaps I have found the problem

hi Zen perhaps I have found the problem

i have dismount the output stage to check all 22 power transistor

and if i test whit the test in posistion test diode between the pont incicated B and EIi see an short circuit also if i change + and - tester tip, see folloging picture:

help to set dc offset to threshold s450-transistor-jpg


B shold be the base of transistor and

E shold be the emitter of transistor

but betwhen b end e i see an short

si i think the transitor is damaged confirm my idea ?

or i make an error ?

so it is true for all 20 thansistors indicated in the schemaindicated
q4 q6 q8 q10 q12 q14 q16 q18 q20 q22
and
q3 q5 q7 q9 q11 q13 q15 q17 q19 q21

i wait your answer
Attached Images
File Type: jpg transistor.JPG (161.6 KB, 113 views)
File Type: jpg finali_tr.JPG (159.8 KB, 51 views)
File Type: jpg stadio_finale.jpg (666.0 KB, 52 views)
  Reply With Quote
Old 31st January 2016, 08:59 PM   #45
Zen Mod is offline Zen Mod  Serbia
Official Court Jester
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
help to set dc offset to threshold s450
all upper ones are in parallel , same as all lower ones

so , you can't be sure which one is shorted , without unmounting them from pcb

in fact , for B-E and C-E measurement you can , desoldering emiter resistor of transistor you're measuring , but for B-C measurement , you need to pull out one by one
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM
  Reply With Quote
Old 31st January 2016, 10:27 PM   #46
alfalf1 is offline alfalf1
diyAudio Member
 
Join Date: Feb 2013
ok thanks very much
  Reply With Quote
Old 13th August 2019, 07:41 PM   #47
miguelnoda is offline miguelnoda  Spain
diyAudio Member
 
Join Date: Oct 2009
hello I have a Threshold 450e stage and it has two bad transistors and they have no reference anyone can help me[IMG]Click the image to open in full size.[/IMG]

Last edited by miguelnoda; 13th August 2019 at 07:43 PM.
  Reply With Quote

Reply


help to set dc offset to threshold s450Hide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Dc Offset set jbl 1201.1 mk1 stefanv Car Audio 1 15th March 2012 11:45 PM
DH-220 Clone (SMART TA-242) can't adjust DC offset using offset bias pot? beady Solid State 6 17th March 2011 10:53 AM
Threshold S300 offset issues FootFungus Pass Labs 5 15th December 2009 12:58 AM
DC Offset on the input of a Threshold SL10 hifi-hospital Solid State 10 25th February 2007 08:26 AM
DC Offset circuit for Threshold deafbykhorns Solid State 15 27th September 2004 02:49 PM


New To Site? Need Help?

All times are GMT. The time now is 09:28 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki