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

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Salas hotrodded blue DCB1 build
Salas hotrodded blue DCB1 build
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 4th June 2015, 01:27 PM   #5001
saverior is offline saverior  Italy
diyAudio Member
 
Join Date: Oct 2011
Location: Rome
Hi all,
I was quite happy with my dcb1 listening for a month and over very excellent sound quality.... but now something bad is happening!
Occasionally, after some hours of power on one of the Leds string (the one on the IRFP9240 side) switch off...and quite soon they switch on again....and everything is fine again...
Of course in the middle of this switch off/on sound is distorted and noisy

Soldering is ok. I double checked.
May be too much heat? (is quite warm now-days in Italy)

Suggestion on what I can check?

Tanks,
Saveerio
  Reply With Quote
Old 4th June 2015, 01:44 PM   #5002
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Salas hotrodded blue DCB1 build
Some intermittent LED in the string?
  Reply With Quote
Old 4th June 2015, 01:51 PM   #5003
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Salas hotrodded blue DCB1 build
Disconnect it from the stereo, power up. Tap those Leds one by one with a screwdriver, tap around the PCB near them and the relative Mosfets. Watch not to short something when doing that. Do it both when cool and when warmed up again.
  Reply With Quote
Old 4th June 2015, 01:52 PM   #5004
saverior is offline saverior  Italy
diyAudio Member
 
Join Date: Oct 2011
Location: Rome
Quote:
Originally Posted by Salas View Post
Some intermittent LED in the string?
No, no.
All five LEDS switch off at same time and then after 1-2 secs they switch on again!...

(may be useful to say that last modification was adding a blue led (on the proper place) and tapping off the bridge (from the power caps) the voltage for an extra (out of the board) LM7809 intended to power a little fan (but actually still disconnected from the fan!)
  Reply With Quote
Old 4th June 2015, 02:01 PM   #5005
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Salas hotrodded blue DCB1 build
If only one is switching then all will do because in series like chain links. There is a K170 sinking them to ground. That one can be suspicious also. I would change all 5 LEDS and the K170 if I could not focus on one intermittent component or one cold joint. I would also inspect the board vias and Mosfet joints because maybe little cracked when bolting the Mosfets to sink. Rework the joints for sure.
  Reply With Quote
Old 4th June 2015, 02:16 PM   #5006
saverior is offline saverior  Italy
diyAudio Member
 
Join Date: Oct 2011
Location: Rome
Ok thanks a lot Salas.
Actually also my suspects are about joints... this is my first "solder from scratch" board!...really one of the worst DCB1 realized I think BUT I still can't believe it works so well!

I'll do my checks and test for some days to see what happens
  Reply With Quote
Old 4th June 2015, 02:50 PM   #5007
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Salas hotrodded blue DCB1 build
Very important is your iron and solder. Use leaded solder, not ROHS, and temperature controlled iron if possible. Don't stay too long on a component when soldering, especially not on 3mm Leds which are sensitive to how much heat they can take.
  Reply With Quote
Old 20th June 2015, 10:05 PM   #5008
kj123 is offline kj123  Canada
diyAudio Member
 
Join Date: Jan 2006
Location: Mtl
Default High offset on one channel, help

Hi

I just finished the DCB1 Black board (Tea bag kit) and I have a problem with the left channel offset at -85mv. Right is 2.3mv.

Vout is 9.94v and -9.95v. Voltage across the 10r is 1.8v on both channels.

Does the high dc offset mean the fets on the left channel are not closely matched? should l replace them?

Thank you

KJ
  Reply With Quote
Old 20th June 2015, 10:21 PM   #5009
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Salas hotrodded blue DCB1 build
Its the most probable cause to think of. Remove the suspect JFETs pair and confirm their IDSS if you can.
  Reply With Quote
Old 20th June 2015, 11:22 PM   #5010
kj123 is offline kj123  Canada
diyAudio Member
 
Join Date: Jan 2006
Location: Mtl
Thanks Salas... hmm, I swapped the fets. I put 2 that are perfectly matched on left channel and now I have 0.2mv offset but the right went up to 89mv. Can I just change the right pair? or do the 4 fets need to have close idss?

thank you
  Reply With Quote

Reply


Salas hotrodded blue DCB1 buildHide 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
dcb1 buffer with shunt reg. merlin2069er Swap Meet 0 3rd August 2010 05:25 PM
F2 and DCB1 parts selection - please advice! DQ Pass Labs 6 25th November 2009 03:20 PM
Y B Blue - how blue LED improves the CD playback Peter Daniel Digital Source 176 25th September 2003 07:40 AM


New To Site? Need Help?

All times are GMT. The time now is 02:33 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki