Power amp under development - Page 345 - 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 20th January 2010, 12:40 AM   #3441
qsa is offline qsa  Germany
diyAudio Member
 
qsa's Avatar
 
Join Date: May 2007
fakes really bad luck

I dont have test with BC and 2 SC 1845 like in schematic from quasi


2 sc 2240 and MPSA 42/92 in NMOS working very good

NMOS is working with all MJE or 2SA / 2SC or 2SD / 2SB if not... then you have fakes or faults in pcb


bought last year all parts for NMOS very cheap in Shenzen/China

25 Mosfets IRFP460 in USD about 0,70 USD pcs.

Metal film 0,6W Resistors minimum is 200 pcs. in USD about 2,50 USD for 200 pcs.


provide us pictures from your PCB
  Reply With Quote
Old 20th January 2010, 12:54 AM   #3442
diyAudio Member
 
adamkaktus's Avatar
 
Join Date: Jan 2010
Location: Warsaw
so i will provide fastest i can. I think i should look up for some mje.By now my PCB is getting tired of replacing components.I will try to find good source of MJE,especially that my are isolated and may dissipate heat poorly,and this is first sign of fake.How about matching FETs? Did it anybody?or everybody has much more luck?
  Reply With Quote
Old 20th January 2010, 06:45 AM   #3443
sekhar is offline sekhar  India
diyAudio Member
 
Join Date: Jul 2009
Location: West bengal/siliguri
thanks every body for the reply...... one query can I use a single big heat sink for stereo operation.....??
  Reply With Quote
Old 20th January 2010, 07:23 AM   #3444
qsa is offline qsa  Germany
diyAudio Member
 
qsa's Avatar
 
Join Date: May 2007
Yes you can, I did take big single heat sink from 2 HE PA Amplifier

and SMPS Power Board +/- 80 V from PA Amplifier


@adamkaktus I think you have fault in PCB check all B C E Connection and HFE with Transistor tester, it can be fault in datasheet too .....

Before I did buy in germany MJE 340/350 with poor big difference HFE 15 and 120 its not a joke...


How about matching FETs? forget it, you dont need


actually Im writing this message and my NMOS producing earthquake in Bass...have 3 NMOS working now 1 for bass and 2 for stereo operation

I can hear details in music .... I did never heart before

heatsinks are about 30 degress after 2 hours

Last edited by qsa; 20th January 2010 at 07:28 AM.
  Reply With Quote
Old 20th January 2010, 07:58 PM   #3445
diyAudio Member
 
adamkaktus's Avatar
 
Join Date: Jan 2010
Location: Warsaw
I checked for differences this mje, 2sc and bc's. They're just like in their datasheets, also schematic is exactly similar to layout. Hfe of Mje 340 still about 67-76, Mje350 is ~150. I crushed 2 psc of this mje from fairchild, the same 2x2mm structure in both, soldered to copper-like collector. I'm going to find them in non-isolated to-126, from STM, it may not be a fake. Also i consider making new pcb, just like first, but on fiberglass base, not from epoksy-wire should be stronger, and i'm going to do this better. Old one is extremly exhausted of replacing parts-IRF's are difficult to unsolder. I also consider buying something from Mje 150XX series, is it possible to mach them on original PCB from Quasis project? Has anybody working PCB for 4 pairs of Fets-maybe it could be better grounded.
Thanks for any response.
A.
  Reply With Quote
Old 20th January 2010, 09:22 PM   #3446
qsa is offline qsa  Germany
diyAudio Member
 
qsa's Avatar
 
Join Date: May 2007
Mje 340 still about 67-76, Mje350 is ~150

ist not good, difference is to big use another devices

difference with my transistor in hfe between PNP and NPN is about 10

send pictures from pcb
  Reply With Quote
Old 21st January 2010, 05:55 AM   #3447
diyAudio Member
 
Join Date: Nov 2007
Location: Chennai
Hi qsa!

Thanks for sharing the equivalent or replacement transistors. I have done my Nmos with above mention replacement parts. Sounds amazing very clear crisp sound with deep punch when I use this as Sub Woofer Amp.

But when I use this as full range amp I feel missing full range especially high frequency. Is it due to 2SB 649/2Sd669 character? Also I used 2sc 1845 in place 2SC2240. Suggestions appreciated

Vijay
  Reply With Quote
Old 21st January 2010, 08:01 PM   #3448
qsa is offline qsa  Germany
diyAudio Member
 
qsa's Avatar
 
Join Date: May 2007
Hello vijay_meyou


> Is it due to 2SB 649/2Sd669 character?

I dont know is it a good idea to use MJE 340/350.... because I dont know the NMOS Sound with devices like in quasis schematic

> But when I use this as full range amp I feel missing full range especially high frequency.

I cant confirm this....Sound from my NMOS is very excellent in high frequency

...I think you should check your capacitors

have replace CLASS D Amp with NMOS, trust me NMOS is sounding better in high frequency and music details


1 pcs. working NMOS has 2SC 2240 for Input - all another small signal transistors MPSA 42 / 92 - MJE15034 and MJE15035 in VAS and Driver Stage BD 139 for VBE

and another NMOS

1 pcs. working NMOS has 2SC 2240 for Input - all another small signal transistors MPSA 42 / 92 - 2SB 649A / 2SD 669A in VAS, 2SA1837 / 2SC4793 in Driver Stage, BD 139 for VBE

I cant hear difference in Sound between this two NMOS with different devices

Replacement for BD 139 if not possibile 2SD669A OR MJE 180

all this devices are very popular by amplifier manufacturer easy to get and very very cheap

have change devices in NMOS for HIGHER VOLTAGE use about +/- 100 -130V DC

actually cant test with HIGHER VOLTAGE because have only here +/- 85 V DC SMPS Power Board

Last edited by qsa; 21st January 2010 at 08:09 PM.
  Reply With Quote
Old 21st January 2010, 08:20 PM   #3449
qsa is offline qsa  Germany
diyAudio Member
 
qsa's Avatar
 
Join Date: May 2007
Substitute for VAS MJE 340/350 should be 2SA1406/2SC3600 or BF 871/872 too

Check what you can get from dealer in your country, normally you can change devices without problems
  Reply With Quote
Old 22nd January 2010, 08:33 AM   #3450
diyAudio Member
 
Join Date: Nov 2007
Location: Chennai
Hi qsa,

Thanks for your quick reply.
May be you are right. I used capacitors form my old salvage boards. Today i will re build my NMOS with all new capacitors. Also need to check the availability of 2SA1406/2SC3600.

Can you advice any matching preamplifier with buffer or gain boost for NMOS amp? if any circuits are PCB layout available to build please send me.

Thanks
Vijay

Last edited by vijay_meyou; 22nd January 2010 at 08:36 AM.
  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 06:52 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