loud hum w/ 1st Gainclone - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 30th November 2004, 08:24 AM   #11
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Bret, you may also have a break in the negative voltage rail to that channel.
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 1st December 2004, 04:16 AM   #12
diyAudio Member
 
Join Date: Mar 2004
Location: Connecticut
First, thanks for responding--I really appreciate the help!

Well, it seems that the bottom of the board looks clean--no shorts are visible. The board is BrianGT's and the V- & IN & OUT holes are separated--I also checked V+ & IN & OUT--no visible connections. So it doesn't appear to be shorted. The voltage is actually -35VDC not +35--sorry, my bad typing.

Nuuk, I did continuity checks with the power off between the V-, V+, PG-, & PG+ of the right (bad) channel to the left (good) channel. It showed 0 Ohms for each set (e.g. V- of Right to V- of Left). I think this should have checked for any break in the power rails & it looks like they are intact.

Any other test to look at? I've gone over the wires about 50 time & they are fine. I can't see a short on the board, but I'm at a loss to figure out why they huge DC offset. It seems as if it has to be a short between V- & In or OUT. The chip is not even the slightest bit warm, but I am only turning it on for a minute or so to test. Could the chip just be bad?

TIA,
Bret Morrow
  Reply With Quote
Old 1st December 2004, 07:00 AM   #13
boholm is offline boholm  Denmark
diyAudio Member
 
boholm's Avatar
 
Join Date: Apr 2004
Location: Copenhagen
Quote:
Originally posted by JazzzSpazzz
Could the chip just be bad?
Since you have tested everything thoro'ly, it does seem that the chip is dead. So:

You should try and solder out the bad chip and measure it for a short between -V and output. If this is 0 ohms then it is dead. If not then measure between -V and output on the board. If no short there, then measure the input vs. -V. If no short there then power up the board(still without the chip) and measure voltage on the input pin. If this is not 0 volts, then measure +V and -V. If they are not + and - 35 volts, then . . . Well, the chip can still be bad, so a spare could come in handy
__________________
Best regards
Bo
  Reply With Quote
Old 1st December 2004, 08:01 AM   #14
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Do as Bo says but before you remove the chip, measure the voltages on each of the pins to check that you have both + and - 35 volts!
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 1st December 2004, 08:16 AM   #15
m@ is offline m@  Thailand
diyAudio Member
 
Join Date: Nov 2004
Location: bangkok
My 0.2$'s:

In my haste to finish my first GC, I managed to mix up the signal and signal ground (the IN on Brian's board looks like an N - my anxious little brain said SG - signal, N - neutral, which makes no sense, but hey...).

This produced a nasty DC offset/buzz, but I can't remember if it was as high as 35V.

I feel your pain... But it's well worth the effort.
  Reply With Quote
Old 2nd December 2004, 03:30 AM   #16
diyAudio Member
 
Join Date: Mar 2004
Location: Connecticut
Quote:
Originally posted by Nuuk
Do as Bo says but before you remove the chip, measure the voltages on each of the pins to check that you have both + and - 35 volts!
Will do. I disassembled the unit holding the amp boards & got them out of the box with wires attached. Man, was this a bad design--it looks really nice (IMO), but it is not user friendly! I'm going to bring home some narrow test probes that I have at work before I test, so I will test tommorrow (mainly because I'm tired & don't want to make a mistake). Oh, dispite having electronic test equipment at work & am rather clueless about it--I'm better on the biology end

Quote:
Originally posted by m@
My 0.2$'s:

In my haste to finish my first GC, I managed to mix up the signal and signal ground (the IN on Brian's board looks like an N - my anxious little brain said SG - signal, N - neutral, which makes no sense, but hey...).


This produced a nasty DC offset/buzz, but I can't remember if it was as high as 35V.

I feel your pain... But it's well worth the effort.
Thanks, I check & rechecked, but I can always find other ways to mess things up ;-) I have to remember the end product right now!

Cheers,
Bret Morrow
  Reply With Quote
Old 2nd December 2004, 04:10 AM   #17
jleaman is offline jleaman  Belgium
Banned
 
Join Date: Apr 2002
Send a message via AIM to jleaman
try and unsolder these chip would be a hard task witha dual layer board and yeah i cant see any one doing this can you ?
  Reply With Quote
Old 2nd December 2004, 08:17 AM   #18
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Quote:
Man, was this a bad design--it looks really nice (IMO), but it is not user friendly!
I still maintain that hardwiring is the best way to build a GC for beginners as it is easier to fault find, and see (and understand) where all the parts go!

I'm not saying that PCB's are no good, just in this case I would prefer to hardwire.
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 2nd December 2004, 01:26 PM   #19
diyAudio Member
 
Join Date: Mar 2004
Location: Connecticut
Quote:
Originally posted by Nuuk


I still maintain that hardwiring is the best way to build a GC for beginners as it is easier to fault find, and see (and understand) where all the parts go!

I'm not saying that PCB's are no good, just in this case I would prefer to hardwire.
Sorry, I was saying my design of the box BrianGT's boards were put in was the "bad design". I think the boards were simple & quick. I read your site before Brian set up the group buy and was going to get around to trying to build 1 "someday". The availablity of a "kit" made me actually get going on it sooner, rather than later (never?). I have hardwired speaker crossovers with no concern but those components are huge compared to the ones in a GC.

My box is too small. The boards & heatsink are on a platform that drops into the box--it is very snug & I didn't think enough about soldering lines from the tranny & input/outputs when I set it up. The goal was to use silicone adhevsive to secure the platform to small cleats on the sides of the box when everything works--I thought that it would make a real nice dampening system for the amp boards. It took me a good hour to get the platform out of the box, so I could remove the right side board to see its underside. The best thing I can say about it is that I still think that the box looks lovely on the outside and should work well, eventually.

I hope to test out the chip this PM.

Thanks again,
Bret
  Reply With Quote
Old 3rd December 2004, 10:40 PM   #20
diyAudio Member
 
Join Date: Mar 2004
Location: Connecticut
Default results from testing

Well, I measured to try & discover the problem, but I'm still a bit clueless. Here's what I know:

No continuity from chip pin 4 to pin 3 (-V to OUT).
No continuity from chip pin 4 to OUT on board.
No continuity from chip pin 4 to pin 7 (-V to IN).

I powered up the board & measured VDC:
...from V+ to PG+ I've got +35VDC
...from V- to PG- I've got -35VDC
...from pin 4 to board ground I've got -35VDC
...from IN to SG I've got 10.3VDC
& of course I've got -35VDC from pin 3 to OG.

The only thing that I can identify as odd is the chip, but there appears to be no apparent shorts in the chip. I emailed BrianGT telling him what I know & asking him what he thinks.

I'm thinking about desoldering the leads & listening to the left channel in mono! Stereo is so over-rated!

Cheers,
Bret Morrow
  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
For those that like it loud RacerXtreme Multi-Way 25 12th September 2007 04:02 AM
GainClone not Loud HouRman9 Chip Amps 5 10th September 2003 03:11 AM
For those who have hum with theyr gainclone (loud or not) Bricolo Chip Amps 6 16th July 2003 07:57 PM
My Gainclone is too Loud PaulHilgeman Chip Amps 5 16th February 2003 01:02 AM


New To Site? Need Help?

All times are GMT. The time now is 04:55 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