Can anyone explain this circuit.. - 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 1st August 2004, 09:39 PM   #1
pflodin is offline pflodin  Sweden
diyAudio Member
 
pflodin's Avatar
 
Join Date: Jul 2004
Location: Alnö
Default Can anyone explain this circuit..

Hello again

As some of you might have seen, I have had a broken amp that I now have repaired sucsessfully much tanks to the friendly people here on this forum. Now when that amp is back in buisness again, I can move on to the next project.

I recently bought a couple of pro power amplifiers on a flea market (!), Two complete 2x500W (they are labeled "JBN PA1000 Power Amplifier", JBN was a swedish brand that disappeared some time ago) amplifiers and a LOT of parts.
The aplifiers are ofcourse not working, but it seems like it's just the output transistors that are blown. I have taked with a guy that was a little familliar with these amps and he said "these amps blows output transistors all the time, ans sometime even the driver trannies..".
Maybe that's the reason I got a box with 50 new power transistors with them....

The question is, Why does it blow out the transistors all the time ?

Is it something espesially strange with the power circuit of this amp ?

I have attached a verry quick drawing of the power section of this amp, Its werry rough an a lot of the components are left out, but I wonder, why all these resistors ? in other "NPN only" circuits I'w seen there has been only one per transistor..

What output power is realistic to expect from this circuit ?

/Peter
Attached Images
File Type: jpg save0124.jpg (57.2 KB, 369 views)
  Reply With Quote
Old 1st August 2004, 11:11 PM   #2
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
This amp has the same kind of ±V as the Hill, but with fewer outputs. If it has enough VA in the transformer it should be able to swing 500W/ch/4R.

The 'extra' resistors in the negative half outputs are probably there for a current limiting circuit.

I would consider using the MJ15024 in this amp as well as it will handle over twice the power that the 2SD types will. If you pull the spec sheet on the 2SD you will find that the maximum junction temperature is only 150*C vs 200*C on the MJ part.
  Reply With Quote
Old 1st August 2004, 11:19 PM   #3
diyAudio Member
 
Join Date: Aug 2003
Location: Prague,Czech Republic
It's old qasicomplementary s..t, get it to the ashcan .
  Reply With Quote
Old 1st August 2004, 11:28 PM   #4
OliverD is offline OliverD  Germany
diyAudio Member
 
OliverD's Avatar
 
Join Date: Nov 2002
Location: Germany
Re-use the case, heatsinks and power supply to build something nice
  Reply With Quote
Old 2nd August 2004, 07:25 AM   #5
pflodin is offline pflodin  Sweden
diyAudio Member
 
pflodin's Avatar
 
Join Date: Jul 2004
Location: Alnö
yes, there is a lot of nice components to be used in future projects, like 1kVA 2x55V toriodal transformers, large heatsinks, 10000uf 100V caps , 19" cases etc.

But still, I have at least 8 more or less complete amplifier modules
(heatsink with 6 transistors and PCB mounted direct on it), most of them will only need two or tree new transistors. The modules are intended for +-80V rail, but I was thinkig that I might try to run them on +-60V rail (have transformers for that) and use them to convert some old monitor speaker boxes to active types. I dont want to mount a 1kva transformer in the speaker box , but a nice little 250VA torioid should fit perfect, and I don't need 500W @4R in a monitor box.

/Peter
  Reply With Quote
Old 2nd August 2004, 07:56 AM   #6
diyAudio Member
 
Join Date: Jul 2001
Location: The Netherlands
Quote:
It's old qasicomplementary s..t, get it to the ashcan .
Upupa Epops, I only see NPN devices....you see something I don't see?
  Reply With Quote
Old 2nd August 2004, 08:08 AM   #7
diyAudio Member
 
Join Date: Aug 2003
Location: Prague,Czech Republic
We both see the same, but we have different opinions about sense of this work - I mean, that it is lost time with not guaranted results.
  Reply With Quote
Old 2nd August 2004, 08:31 AM   #8
diyAudio Member
 
Join Date: Jul 2001
Location: The Netherlands
Hi Upupa Epops,

I didn't mean I disagree with you, I just didn't see the quasi-complimentary topology... Maybe it was a quasi-complimentary design, but there are other options, don't you agree?

I would love to see a bit more of the complete schematic

greetz,

Thijs


PS
I think it would be a far more atractive chakkence to repair the amp, find out why it blows up so much and improve it...I get the impression that these a BIG amps...
  Reply With Quote
Old 2nd August 2004, 10:05 AM   #9
diyAudio Member
 
Join Date: May 2002
Location: Switzerland
O.K. quasi-complementary is not the last word in terms of audio quality admittedly.

But as far as I understand he wants to use them for sound-reinforcement. So this might be the smaller problem compared to the reliability issue.

So if he can prevent them from going up in smoke, he might be more than just content with them.

Regards

Charles
  Reply With Quote
Old 2nd August 2004, 11:08 AM   #10
diyAudio Member
 
Circlotron's Avatar
 
Join Date: Jun 2002
Location: Melbourne, Australia
Quote:
Originally posted by Upupa Epops
It's old qasicomplementary s..t, get it to the ashcan .
Quote:
Originally posted by phase_accurate
O.K. quasi-complementary is not the last word in terms of audio quality admittedly.
The GainClone crowd seems to like it well enough.
__________________
Best-ever T/S parameter spreadsheet.
http://www.diyaudio.com/forums/multi...tml#post353269
  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
Who can explain this preamp circuit to me? joe Solid State 4 5th June 2009 03:10 AM
can anybody here explain this audio circuit ankan Chip Amps 5 29th April 2009 03:03 PM
Help can some explain this circuit Amagic Parts 10 23rd July 2007 10:50 AM
Please explain a servo circuit ppcblaster Chip Amps 6 18th June 2007 12:02 PM
Could somebody explain this circuit to me? leadbelly Everything Else 21 9th February 2006 02:33 PM


New To Site? Need Help?

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