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 27th April 2005, 12:56 PM   #1
diyAudio Member
 
darkfenriz's Avatar
 
Join Date: Jun 2004
Location: Warsaw
Default HELP with an amp please!

well
it is not working as you may have supposed
simple, maybe a bit experimental mosfet one burns one resistor and I don't know why
can this be caused by output mosfets failure??
output voltage is ~3V
please help me wiser ones

best regards
Attached Images
File Type: jpg 1.jpg (51.9 KB, 380 views)
  Reply With Quote
Old 27th April 2005, 01:03 PM   #2
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
Put a very high value resistor across C5 to reset the integrator when power is off.

If the 470R resistor is burning then both upper and lower driver transistors must be conducting, try and trace what could be causing this.
__________________
www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more.
  Reply With Quote
Old 27th April 2005, 08:39 PM   #3
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
try shorting across Q7 and see if the 90 volts is still there.
  Reply With Quote
Old 27th April 2005, 09:37 PM   #4
diyAudio Member
 
darkfenriz's Avatar
 
Join Date: Jun 2004
Location: Warsaw
thank you
is the whole project 'acceptable' ?
  Reply With Quote
Old 27th April 2005, 10:40 PM   #5
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
Quote:
Originally posted by darkfenriz
is the whole project 'acceptable' ?
That is a metaphysical question.

  Reply With Quote
Old 28th April 2005, 12:06 AM   #6
fab is offline fab  Canada
diyAudio Member
 
fab's Avatar
 
Join Date: Mar 2004
Location: Canada
Default over voltage at mosfets gates

if you want to avoid wasting money in destructed mosfets, use Zener protection diodes. One between emitter of Q10 and output. Another onebetwwen the output and the emitter of Q? (PNP complementary to Q10). You can use Zener voltage about 2 volts lower than the max rated VGS of the IRF mosfets.
If you destroy zener diodes it costs less than the IRF...
  Reply With Quote
Old 28th April 2005, 01:42 AM   #7
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi darkfenriz,
Check R24, R25 for open as well as the 0.22R resistors. If you have that much across the 470R resistor, Q10 and it's compliment are either on or could be in reverse E-B breakdown. I'm fairly sure you will find a few transistors shorted. An open PCB connection could change things though.
-Chris
  Reply With Quote
Old 2nd May 2005, 03:33 PM   #8
diyAudio Member
 
darkfenriz's Avatar
 
Join Date: Jun 2004
Location: Warsaw
thanks all
one more question: what will be minimal zener current thru 0.5W 47V zener diode? I have less than 1mA I'm affraid.

BTW: all I wanted from this project was to keep output at low feedback with minimal number of stages. I used inverting mode making summing junction the slowest part of everything by means of pole-zero compensation.
This should work nice in terms of low TIM and little interference with speaker back EMF, especially HF component of this signal. What do you think?

regards
  Reply With Quote
Old 2nd May 2005, 05:01 PM   #9
diyAudio Member
 
Ultima Thule's Avatar
 
Join Date: Jan 2004
Location: Koskenkorva Land
Mr darkfenriz,

you have shown such a "guru" approach on this board when answering other posts, and now you need help?

Anyhow, your design is going to have an awfull PSRR

Redesign it and then we can think about the "problems"!

Regards Michael

PS. the "other issue" is somewhere between U4 and Q1//Q3 stages, and is also part of the "problem" you mentioned!
__________________
"If transistors are blueberries and FETs are strawberries, then tubes must be.. pears"
Michael 29th January 2010
  Reply With Quote
Old 2nd May 2005, 05:12 PM   #10
diyAudio Member
 
darkfenriz's Avatar
 
Join Date: Jun 2004
Location: Warsaw
thank you Ultima Thule
Quote:
Originally posted by Ultima Thule
Anyhow, your design is going to have an awfull PSRR

that's why I use for VAS separate transformer, 2x1000u caps filtering +-74V rail, regulated down to +-53 by lm317/337 and filterd by 2x10u caps.
Making it is so inexpensive and simple, and makes amplifier "don't worry" about PSRR aside from efficiency issue.
Thank you for suggestion, time will tell if it is going to have low noise or not.

best regards
  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



New To Site? Need Help?

All times are GMT. The time now is 03:11 PM.


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