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

Solid State Talk all about solid state amplification.

output transistors are dead?
output transistors are dead?
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 26th August 2010, 09:06 AM   #1
mdm102 is offline mdm102  Russian Federation
diyAudio Member
 
Join Date: Jan 2010
Default output transistors are dead?

Hi,

Could you help me to understand, I tried to bias amplifier module, but overturned VR at some moment, it is single turn VR, and seems that I burned output transistors. I measured 42-50 DC voltage on the speaker terminals. Is this mean that output mosfets 2xIRFP240 and 2xIRFP9240 are dead?

Thank you!

MD
  Reply With Quote
Old 26th August 2010, 10:19 AM   #2
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
output transistors are dead?
Do they read short circuit Drain to Source ? and what's the amp ?
  Reply With Quote
Old 26th August 2010, 12:21 PM   #3
east electronics is offline east electronics  Greece
diyAudio Member
 
east electronics's Avatar
 
Join Date: Jan 2006
Location: Athens GREECE
yeap .... post a circuit ...that behaviour rings a bell ...that could be fun to see !!!
__________________
SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
  Reply With Quote
Old 26th August 2010, 03:09 PM   #4
mdm102 is offline mdm102  Russian Federation
diyAudio Member
 
Join Date: Jan 2010
Thank you for reply, guys! Drain to Source opened in both directions. The model of the module is HPA-nxV300se by Anthony
  Reply With Quote
Old 26th August 2010, 03:25 PM   #5
AndrewT is offline AndrewT  Scotland
R.I.P.
 
Join Date: Jul 2004
Location: Scottish Borders
what does "opened" mean.

Open to the free flow of test current?
or
Open circuit when tested?
__________________
regards Andrew T.
  Reply With Quote
Old 26th August 2010, 03:59 PM   #6
nigelwright7557 is offline nigelwright7557  United Kingdom
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
If the bias became too great you would turn on both sets of transistors at the same time and short out the power supply.

Thye usualy go short Drain to Source although i have sometimes seen MOSFETs go int all sorts of weird states. I even had one with a partial short from gate to drain.

To be safe I would replace all the MOSFET's not forgetting to wind the bias back to zero before you power up again.
__________________
PCBCAD51 pcb design software. 2018 version out now with lower prices >> http://www.murtonpikesystems.co.uk
  Reply With Quote
Old 26th August 2010, 04:28 PM   #7
mdm102 is offline mdm102  Russian Federation
diyAudio Member
 
Join Date: Jan 2010
Quote:
Originally Posted by AndrewT View Post
what does "opened" mean.

Open to the free flow of test current?
or
Open circuit when tested?
I meant current can flow in both directions, seems diode between Drain and Source allow to flow current in both directions. http://www.vishay.com/docs/91210/91210.pdf
  Reply With Quote
Old 26th August 2010, 04:34 PM   #8
mdm102 is offline mdm102  Russian Federation
diyAudio Member
 
Join Date: Jan 2010
Quote:
Originally Posted by nigelwright7557 View Post
If the bias became too great you would turn on both sets of transistors at the same time and short out the power supply.

Thye usualy go short Drain to Source although i have sometimes seen MOSFETs go int all sorts of weird states. I even had one with a partial short from gate to drain.

To be safe I would replace all the MOSFET's not forgetting to wind the bias back to zero before you power up again.
Yes, I measured all 4 power transistors, they allow to flow current from Drain to Source in both directions, seems they all are dead. I don't know should I change also small biasing bipolar transistor MJE340, could you advice how to check it? Thank you!
  Reply With Quote
Old 26th August 2010, 05:12 PM   #9
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
output transistors are dead?
If they are short they will read 0.00 on DVM on diode check.

The MJE340 needs to be tested out of circuit to fully check. If you are unsure how to interpret readings then it might be wiser to replace it... that said a FET amp shouldn't do much damage to drivers etc when the FET's fail.

When you power up use a 100 watt bulb in series with the mains supply until you are sure the amp is OK.
  Reply With Quote
Old 26th August 2010, 07:16 PM   #10
mdm102 is offline mdm102  Russian Federation
diyAudio Member
 
Join Date: Jan 2010
Quote:
Originally Posted by nigelwright7557 View Post
To be safe I would replace all the MOSFET's not forgetting to wind the bias back to zero before you power up again.
Anthony said in his manual to set VR to 450-500ohm (VR is 0-500ohm single turn), strange

I just desoldered all mosfets and checked these with DMM, 1 of 9240s is dead for sure, the second 9240 is alive, 240s are alive also.
  Reply With Quote

Reply


output transistors are dead?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Alesis Power Amp Transistors Dead what else to check? 777funk Solid State 7 14th March 2008 04:35 PM
dead output fets? traw Pass Labs 2 23rd December 2006 08:47 PM
My Lm3886, Dead or not? DC at OUTPUT! mathieujohnson Chip Amps 8 29th June 2006 09:19 PM
Long output lead or long output transistors leads? which one to pick? chris ma Everything Else 3 6th June 2003 12:06 PM


New To Site? Need Help?

All times are GMT. The time now is 09:44 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki