75 volts AC on chassis - 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 8th September 2002, 08:41 AM   #1
diyAudio Member
 
Join Date: Aug 2002
Location: CA USA
Unhappy 75 volts AC on chassis

My hafler DH 500 has 75 volts AC between the frame and neutral or ground. I discovered this when it gave me a couple shocks.

Any ideas what might cause this and why it doesnt fuse?

Ive checked for continuity between the frame and trans. secondaries and there is none. Seems to me the AC means it has to be before the bridge rectifier?

Any suggestions?

thanks,

Fritz
  Reply With Quote
Old 8th September 2002, 08:52 AM   #2
skaara is offline skaara  Slovenia
diyAudio Member
 
Join Date: Jun 2002
Location: Europe, Slovenia
How does you PS look? Post pics, schematics..
  Reply With Quote
Old 8th September 2002, 02:58 PM   #3
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Default Did you try checking the caps?

Check to see if there is a cap (or pair of caps) on the AC line into the power switch -- -- could be dirty (or blown) in which case you could get some leakage, also check the filter caps -- (do you have a half-cycle of AC?) I just replaced one of the filter caps in a receiver -- but I would think you would blow fuses first. Lastly, check if there are any ceramic caps across the rectifiers --
  Reply With Quote
Old 8th September 2002, 03:53 PM   #4
diyAudio Member
 
Join Date: Jun 2002
Location: Germany
Default DH500 PS

Check C406
Attached Images
File Type: jpg dh500.jpg (27.2 KB, 419 views)
  Reply With Quote
Old 8th September 2002, 05:47 PM   #5
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
So did you check for any resistance between the frame and transformer primary? If that's OK see below.

The fact that you got no resistance between the frame and the transformer secondary means you have a very early DH500. There is a 0R5 0W5 resistor on each circuit card between the speaker output ground and the input jack ground. Check for continuity between the black speaker binding posts the ground shell of the RCA jacks. This resistor acts like a fuse when the amplifier is hooked up to a piece with a hot chassis.
  Reply With Quote
Old 8th September 2002, 06:08 PM   #6
diyAudio Member
 
Join Date: Aug 2002
Location: CA USA
Great advice,

I checked c406 and it was ok but then saw that the next possible short was the fan and transformer, when I clipped the fan lead the voltage on the frame disappeared! Now where to find a haffler sort of fan.
  Reply With Quote
Old 8th September 2002, 07:39 PM   #7
diyAudio Member
 
Join Date: Aug 2002
Location: CA USA
Great advice,

I checked c406 and it was ok but then saw that the next possible short was the fan and transformer, when I clipped the fan lead the voltage on the frame disappeared! Now where to find a hafler sort of fan.

However

Now when I flip the AC plug I get either 0 volts on frame used to be 75 or, when I flip the plug, 120 on frame relative to ground.

Now Ive isolated the transformer by disconnecting all three secondary wires and also removed one of the two primary wires.
When I apply current to the one remaining primary wire I get about 90 volts on the frame relative to ground. Is this a sick transformer?

Thanks

Fritz
  Reply With Quote
Old 8th September 2002, 08:05 PM   #8
diyAudio Member
 
Join Date: Aug 2002
Location: CA USA
DJK

I did have resistance between the secondaries and frame my diode check indicated there was no continuity. I checked reistance between the RCA neutral and neg speaker and I measure about 1500 ohms on both sides so i think that resistance is intact.

The resistance between all three secondary leads and frame is infinite. And the resistance between the primaries and frame is infinite.

Now I have removed all leads from the trasnformer and the frame voltage is gone. When I hook the black transformer primary to the 120 wall voltage 80 volts comes back on the frame.

Bad transformer?

Thanks,

Fritz
  Reply With Quote
Old 8th September 2002, 08:06 PM   #9
skaara is offline skaara  Slovenia
diyAudio Member
 
Join Date: Jun 2002
Location: Europe, Slovenia
Maybe bad isolation between chasis and transformer?
  Reply With Quote
Old 9th September 2002, 05:13 AM   #10
diyAudio Member
 
Join Date: Aug 2002
Location: CA USA
Do you think this is enough evidence to spend the money for a new transformer or are there other checks I could do?

The transformer case shouldnt have voltage should it?


Thanks,

Fritz
  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
12 volts to 6 Dan2 Car Audio 36 23rd November 2007 07:35 AM
power transformers 220 volts to 110 volts garydmd Chip Amps 3 7th April 2007 03:52 PM
How to star ground to Chassis without a Chassis?? Minion Chip Amps 10 5th November 2006 05:28 PM
Gainclone is on 120 volts will it be fine at 220 volts? Jimmy154 Chip Amps 7 29th June 2005 01:10 AM
Where to get chassis or chassis parts in Vancouver? Prune Parts 1 7th July 2004 06:37 PM


New To Site? Need Help?

All times are GMT. The time now is 11:26 AM.


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