Dangerously wrong diagram at apexjr? - 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 24th February 2008, 07:12 PM   #1
diyAudio Member
 
xiphmont's Avatar
 
Join Date: Apr 2007
Send a message via AIM to xiphmont
Exclamation Dangerously wrong diagram at apexjr?

Is it just me or is this pic at Apexjr showing how to hook a center-tapped transformer up to a BrianGT power supply board dangerously wrong?:

Click the image to open in full size.

(on the page http://www.apexjr.com/miscellaneous.html )

those instructions seem OK until PG+ and PG- are joined together somewhere on the amp board, and then the transformer is being shorted for half the cycle as the output from Yellow to Red is being dropped directly through two of the diodes...

It will seem to 'work', as in the output voltages will seem correct, but the transformer will be buzzing like Hell... until something melts...
__________________
"My name's Monty, and I break things."
"Hello, Monty!"
  Reply With Quote
Old 24th February 2008, 07:28 PM   #2
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
No it's fine. It is not the transformer that gets shorted, it's the lower two diodes in the top bridge and upper two diodes in the bottom bridge, thereby making them redundant.
__________________
www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more.
  Reply With Quote
Old 24th February 2008, 07:32 PM   #3
diyAudio Member
 
xiphmont's Avatar
 
Join Date: Apr 2007
Send a message via AIM to xiphmont
Quote:
Originally posted by richie00boy
No it's fine. It is not the transformer that gets shorted, it's the lower two diodes in the top bridge and upper two diodes in the bottom bridge, thereby making them redundant.

Uhhh.... no. You *can* use this board with a center tapped transformer, but *not* the way it's illustrated. Ie, the proper way to do it would eliminate four diodes, jumper the connections into a single bridge, and tie the CT, PG+ and PG- together.

The way it's illustrated in the pic will cause either the transformer to catch on fire, a diode to blow up or the fuse/breaker to blow.

[edit: had an extra BrianGT rectifier board and CT transformer around. Wired it as displayed and sure enough, transformer buzzed, lights on workbench dimmed, then fuse blew when I alligator-clipped PG+ and PG- together. But, multimeter read 60v across +/- as 'expected'.]

Monty
__________________
"My name's Monty, and I break things."
"Hello, Monty!"
  Reply With Quote
Old 24th February 2008, 10:40 PM   #4
Apex Jr is offline Apex Jr  United States
diyAudio Member
 
Join Date: Jun 2002
Location: Torrance, Calif
Thank You Dave and Roddy for the heads up...

I've been selling toroids for the Brian Gt's boards and
Troystq ( Troy St Geramain) sent over the picture which
he used to hook up the boards...

Looks like I'll have to take it down...
Anyone else a picture of there hookup's

Steve @ Apex Jr.
  Reply With Quote
Old 24th February 2008, 11:07 PM   #5
diyAudio Member
 
xiphmont's Avatar
 
Join Date: Apr 2007
Send a message via AIM to xiphmont
Quote:
Originally posted by Apex Jr

Anyone else a picture of there hookup's

Steve @ Apex Jr. [/B]
I can take some. All mine were originally soldered up for dual secondaries tho, and desoldered/modified later for CT transformers, so they may not be the clearest examples because there's solder all over the place :-)

Monty
__________________
"My name's Monty, and I break things."
"Hello, Monty!"
  Reply With Quote
Old 25th February 2008, 01:08 AM   #6
diyAudio Member
 
xiphmont's Avatar
 
Join Date: Apr 2007
Send a message via AIM to xiphmont
Here are pics of a CT transformer (one of the apexjr 25-0-25 100VA Avel toroids in fact) connected to a new-style snubberized rectifier board, as comes in the current chipamp 3886 kits.

The unused diode pads have solder on them because this board was sitting around assembled for a dual-secondary transformer and I unsoldered the extra diodes and added jumpers to modify it for the center tapped transformer.

Oh, and warm white LEDs are the new blue :-)

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.
__________________
"My name's Monty, and I break things."
"Hello, Monty!"
  Reply With Quote
Old 25th February 2008, 05:15 AM   #7
diyAudio Member
 
tangmonster's Avatar
 
Join Date: Jul 2007
Location: Cape Town
There is also another problem i found with a different power supply floating around on the net and used on BrianGT lm3886-manual pdf

http://www.diyaudioprojects.com/Chip...wer-supply.png


Either the CAP or the Diode bridge must change around, because i can just SEE that electrolytic exploding!!
  Reply With Quote
Old 25th February 2008, 05:38 AM   #8
diyAudio Member
 
Join Date: Jan 2004
Location: Cape Town
xiphmont's pictures are right. For reference, there is a circuit diagram I drew, and some alternative pictures in this thread:
Chipamp.com PSU with CT transformer
  Reply With Quote
Old 25th February 2008, 05:49 AM   #9
diyAudio Member
 
tangmonster's Avatar
 
Join Date: Jul 2007
Location: Cape Town
Your picture is correct, But in the one in my post the + output of the bridge is connected to the - pin of the 10000uF cap , This is INcorrect.

Or am i overlooking something stupid?
  Reply With Quote
Old 25th February 2008, 06:37 AM   #10
diyAudio Member
 
Join Date: Jan 2004
Location: Cape Town
Quote:
Originally posted by tangmonster
Your picture is correct, But in the one in my post the + output of the bridge is connected to the - pin of the 10000uF cap , This is INcorrect.

Or am i overlooking something stupid?
The diagram in your post is incorrect, but it seems as though the one up at chipamp.com now is correct.
  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
Wrong Voltage / current on BoZ... or Wrong Measuring ? gionag Pass Labs 8 14th May 2008 11:24 AM
Apexjr new transformer jaudio Power Supplies 23 19th June 2006 09:46 PM
Circuits living dangerously when powered off? Christer Solid State 9 28th November 2005 04:51 PM
ApexJr AlephX? tiroth Pass Labs 5 8th February 2004 12:58 AM
Buying from Apexjr - UK Paulr Swap Meet 4 26th June 2003 09:57 AM


New To Site? Need Help?

All times are GMT. The time now is 07:09 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