Salas hotrodded blue DCB1 build - Page 112 - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

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

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 9th June 2011, 04:45 PM   #1111
Tea-Bag is offline Tea-Bag  United States
not politcally affiliated
diyAudio Member
 
Tea-Bag's Avatar
 
Join Date: Feb 2006
Location: Kennebunk
Blog Entries: 7
The LED thing is was counterintuitive to me at first. But, have to put the LEDs in reverse polarity, because of the nature of other stuff in PS.
__________________
Last 2014 Salas GB, ends Nov 30th Here to Sign Up! |F5TC Boards and power supplies available PM| Hot-Rod DCB1 boards and kits available PM |Mesmerize kits available (no boards)
  Reply With Quote
Old 11th June 2011, 02:49 AM   #1112
nezbleu is online now nezbleu  Canada
diyAudio Member
 
nezbleu's Avatar
 
Join Date: Dec 2009
Location: Halifax, Nova Scotia, Canada
I don't understand that comment. The LED's are forward-biased, that's why we care about their Vf. When I look at the schematic I don't see the LED's "in reverse polarity".
  Reply With Quote
Old 16th June 2011, 09:21 PM   #1113
diyAudio Member
 
Join Date: Jan 2006
Location: Kent, UK
just swapped out the current limiting resistors for 2.7 ohm wirewound ceramics. Measured 1.1v scross the negative side, which yields about 400ma. feeling the heat now. not sure if my dmm reading is really accurate as I need to change its battery - could be nearer to 600ma


for some reason I have lost the + side. the bank of 3 resistors is still lit but the bank of 5 are not lit. the relay still works. any ideas on what has blown?

its getting warmer here in the UK, so I want to see how far I can push the B1. the - side is not getting especially warm with the 2.7 ohm resistors. I have 1 ohm on standby once I sort out the + rail problem, still sounds good on 1/2 of its potential though.



Brad
  Reply With Quote
Old 16th June 2011, 09:27 PM   #1114
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Either one led of 5 (or more) or the jfet underneath, or the output Mosfet. See if there is Vgs in output Mosfet. Then turn it off and check if every led can alight with a 1.5V battery one by one, or with diode checker on dmm.
  Reply With Quote
Old 18th June 2011, 07:43 AM   #1115
diyAudio Member
 
Join Date: Jan 2006
Location: Kent, UK
Hi Salas,

all the LEDS are ok.

looks like either the MOSFET, of the 1st JFET. on the working side from the input end of the PCB I measure -21v,-9.5v and -24.5v the non working side gives 26.9, 26.9 and 21.6. the 1st SK170 reads -21.2, -21.2 and -0.7. the non working one gives 21.8, 0.7, and 0.7.

best Guess? I say JFET! what do you think?

Brad
  Reply With Quote
Old 18th June 2011, 07:49 AM   #1116
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Well, its the easiest to replace first and see anyway.
  Reply With Quote
Old 18th June 2011, 11:27 PM   #1117
diyAudio Member
 
Join Date: Jan 2006
Location: Kent, UK
just replaced the SK170 JFET - no difference.

wonder if I should look to change the 1st or 2nd stage MOSFET next?
  Reply With Quote
Old 18th June 2011, 11:52 PM   #1118
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Look if there is about 3.5-4V between their G,S first. If there is not, its a problem.
  Reply With Quote
Old 19th June 2011, 02:38 AM   #1119
diyAudio Member
 
Join Date: Jan 2006
Location: Kent, UK
cheers Salas,

here are the readings working MOSFET on negative side -21v,-9.5v and -24.5v the non working side gives 26.9, 26.9 and 21.6

Brad
  Reply With Quote
Old 19th June 2011, 02:42 AM   #1120
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Measure Vgs on each non working side MOS individually. Pins 1,3 on each.
  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
dcb1 buffer with shunt reg. merlin2069er Swap Meet 0 3rd August 2010 06:25 PM
F2 and DCB1 parts selection - please advice! DQ Pass Labs 6 25th November 2009 04:20 PM
Y B Blue - how blue LED improves the CD playback Peter Daniel Digital Source 176 25th September 2003 08:40 AM


New To Site? Need Help?

All times are GMT. The time now is 05:37 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