6GT5 distortion problem - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 14th March 2004, 04:08 AM   #1
imix500 is offline imix500  United States
diyAudio Member
 
imix500's Avatar
 
Join Date: Mar 2004
Location: Nashville, TN
Default 6GT5 distortion problem

Hi, I have a precision electronics amp with 4 6GT5 outputs that has been dormant for a year. After plugging it in I find that I can only get low volume that's mostly distortion. It appears that the B+ rail is being taxed heavily as the 0A2 regulator dims when signal is applied. All caps were replaced 1 year ago. Any ideas? Thanks!
  Reply With Quote
Old 16th March 2004, 03:52 AM   #2
imix500 is offline imix500  United States
diyAudio Member
 
imix500's Avatar
 
Join Date: Mar 2004
Location: Nashville, TN
Also, the unit seems to be drawing several solids Amps from the AC line when input signal is applied. Could the output stage be saturating way early? Thanks!
  Reply With Quote
Old 16th March 2004, 03:59 AM   #3
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,

Quote:
All caps were replaced 1 year ago. Any ideas?
Did you reform the caps when you put the unit back into service?

It sounds as if you have a considerable amount of leakage current somewhere along the PS which could be a dead cap.

Cheers,
__________________
Frank
  Reply With Quote
Old 16th March 2004, 04:15 AM   #4
imix500 is offline imix500  United States
diyAudio Member
 
imix500's Avatar
 
Join Date: Mar 2004
Location: Nashville, TN
Frank, when I recaped the amp nearly 2 years ago actually, I didn't know about cap reforming and just checked polarity and powered it back up when I was done. The amp worked well for about a year and it has sat in a closet for about a year. Could one of the caps died that quickly? Does reforming them increase thier life when put into service? Wouldn't a bad filter cap also come with some 60 cycle hum? Thanks!
Ricky
  Reply With Quote
Old 16th March 2004, 04:23 AM   #5
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,

Quote:
Could one of the caps died that quickly? Does reforming them increase thier life when put into service? Wouldn't a bad filter cap also come with some 60 cycle hum? Thanks!
It's certainly not impossible. Electrolytics need reforming after a long period of inactivity.
60 Hz or actually 120Hz hum is one indicator of a faulty cap but since you're using a regulated supply I suspect it rejects quite alot of PS hum.

Mind you, I could well be wrong in my analysis of the problem.
It just seems a good place to start looking...

Cheers,
__________________
Frank
  Reply With Quote
Old 16th March 2004, 06:58 AM   #6
imix500 is offline imix500  United States
diyAudio Member
 
imix500's Avatar
 
Join Date: Mar 2004
Location: Nashville, TN
It's a good starting point to check the caps then, hadn't suspected them. Thanks Frank.
  Reply With Quote
Old 19th April 2004, 07:20 AM   #7
imix500 is offline imix500  United States
diyAudio Member
 
imix500's Avatar
 
Join Date: Mar 2004
Location: Nashville, TN
Ok, found the problem. There was a direct short to ground in the output connector, so the distortion was the transformer saturating and possibly the output tubes as well. It's the simple things like those that are frustrating. My question now is, could I have damaged the outputs by driving them into a dead short?- through a transformer of course. They never glowed red and niether transfromer got warm during testing. It sounds ok but I won't know for sure until I put it through it's paces. Hoping I just got lucky this time. Thanks,
Ricky
  Reply With Quote
Old 19th April 2004, 07:28 AM   #8
dhaen is offline dhaen  Europe
diyAudio Moderator Emeritus
 
dhaen's Avatar
 
Join Date: Jun 2002
Location: U.K.
Quote:
could I have damaged the outputs by driving them into a dead short?
I doubt it. Not unless the anodes (plates) ran red for any length of time.
According to your description of the symptoms, the power supply sag limited dissapation.
  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
6GT5 audio amp? bereanbill Tubes / Valves 2 1st June 2009 01:37 AM
X-150 distortion problem jeffjazz Pass Labs 2 13th March 2009 10:16 PM
Precision Electronics Amp w/ 6GT5's, Convert to 6L6's? tablebeast Tubes / Valves 5 11th August 2005 09:57 PM
Odd distortion problem wintermute Solid State 16 10th October 2004 02:40 AM
Help! distortion problem Kilowatt Solid State 12 3rd January 2002 05:05 AM


New To Site? Need Help?

All times are GMT. The time now is 03:16 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