high voltage after cap. change - 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 13th April 2012, 12:54 AM   #1
diyAudio Member
 
Join Date: Apr 2012
Location: mn.
Default high voltage after cap. change

after recapping a fender ab165 i am finding 680 volts at pin 3 on 6l6's rechecked my work several times can't find the problem. i also changed the bias cap and resistor. need help
  Reply With Quote
Old 13th April 2012, 03:00 AM   #2
MelB is offline MelB  Canada
diyAudio Member
 
Join Date: Feb 2005
Location: BC Canada
How many volts on Pin 5? For the voltage to get that high you have NO current draw in the amp. It would appear you can measure the bias voltage WITHOUT turning on the standby switch. (Probably a good plan).
  Reply With Quote
Old 13th April 2012, 01:21 PM   #3
diyAudio Member
 
Join Date: Apr 2012
Location: mn.
33v on pin 5. these tests are without the power tubes in. with tubes in i get hissing and crackling. i could not get a 16uf- 425v cap used 20uf- 500v . could this be the problem
  Reply With Quote
Old 13th April 2012, 01:37 PM   #4
diyAudio Member
 
Tom Bavis's Avatar
 
Join Date: Jun 2002
Location: Macedon NY
Voltage will be high without output tubes, but not THAT high... cap is fine, better than original.

Is your meter set to DC? Some meters read DC voltage much higher when set to AC...
  Reply With Quote
Old 13th April 2012, 01:39 PM   #5
diyAudio Member
 
Join Date: Apr 2012
Location: mn.
with power tubes in, with speaker connected i still get 585v on pin 3. i think the noise could be from over powering the power tubes.
  Reply With Quote
Old 13th April 2012, 01:41 PM   #6
diyAudio Member
 
Join Date: Apr 2012
Location: mn.
meter is a cheap one it could be wrong but does have 2000 v scale
  Reply With Quote
Old 13th April 2012, 01:50 PM   #7
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
does your meter use 9v batteries? and when was the last time you replaced it?
__________________
the best advertisement for a good audio design is the number of diy'ers wanting to build it after all the years....never the say so of so called gurus....
  Reply With Quote
Old 13th April 2012, 02:04 PM   #8
MelB is offline MelB  Canada
diyAudio Member
 
Join Date: Feb 2005
Location: BC Canada
Looking at the schematic you need -45 volts for bias. The power tubes are crackling because they are getting warm. I also think your voltage meter is wrong. Unless you are plugging in to 220v with a 120v amp. Can you bring the bias up to spec.? Just for giggles see what your volt meter reads plugging it into your wall AC.
  Reply With Quote
Old 13th April 2012, 02:23 PM   #9
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
What are the maximum voltages that can be applied to your test probes and DMM?

AC and DC will be different.
__________________
regards Andrew T.
  Reply With Quote
Old 13th April 2012, 06:56 PM   #10
diyAudio Member
 
Join Date: Apr 2012
Location: mn.
i did'nt think about the battery, changed it out now it works! ok here i go, pin 3 has 420v dc, where do i measure -45v on the bias board. it just crackled hard enough to blow the fuse. makes it hard to test this thing when it keeps blowing fuses
  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
why this class D power supply no high voltage side electronic cap? greenamp Class D 10 29th January 2012 06:32 PM
pg ms2125 showing right clip after cap change! marko Car Audio 11 28th May 2007 07:40 AM
Cello Palette voltage change? young_pup Solid State 3 27th September 2006 11:23 PM
Change coupling cap from .47uf to 2.2uf andy2 Tubes / Valves 7 24th February 2005 05:40 PM
Voltage Change US/UK ebarker2 Solid State 5 22nd February 2004 05:24 PM


New To Site? Need Help?

All times are GMT. The time now is 07:02 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