Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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

Amp repair help needed.
Amp repair help needed.
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 10th July 2005, 04:18 AM   #1
contaxchen is offline contaxchen  Taiwan
diyAudio Member
 
Join Date: Aug 2003
Location: Indiana USA
Talking Amp repair help needed.

Hi I need some help with my EAR amp repair.
I got one channel 's sound much relatively smaller than the other. I swithed both channel's all of tubes. The problem is still there... I measured all of working voltage, cathode, grid, and anode,etc... They are fine according to the schematics. This doesn't solve the problem.
Again, I checked out the coupling capacitors and feedback bypass caps. They are fine.
Everything is OK.
The problematic channel got some kind of hissing sound when I play the music loud. That means the problem is related to the broken components? This unknown component is not stable when strong electric current passes through it. Which one it could be?
Any idea?
Lhchen
__________________
The best way to stop rust on transformers is to power them up.
  Reply With Quote
Old 10th July 2005, 12:22 PM   #2
SHiFTY is offline SHiFTY  New Zealand
diyAudio Member
 
SHiFTY's Avatar
 
Join Date: Jul 2002
Location: New Zealand
Firstly I am guessing you have tried different sources/ preamps and interconnect and speaker cables and eliminated them as a possibility?

With the amp turned off and the caps discharged, check your solder joints, by moving the component legs around. Sounds like you may have a dodgy solder joint somwhere.

Apart from that check the resistors haven't drifted in value, and check the output transformers measure the same.
  Reply With Quote
Old 11th July 2005, 10:22 PM   #3
richwalters is offline richwalters
diyAudio Member
 
richwalters's Avatar
 
Join Date: Sep 2003
Location: Schwartzwald
Have a peep at the NFB components from sec o/p tranny to input tube. If a feedback cap is duff on this side then the HF phase response will be wild and might aggravate oscillation at certain levels. Or it may be oscillating ultrasonically without knowing about it.

Measuring Ik on each o/p tube (quies) might show minor variations but if amp is AB then it will get worse when heavy output stage currents flow. Without a scope it's awkward; a DVM may display unsteady readings.

Many tube amps aren't keen on LS cross-over networks....perhaps this is a component area to poke about with.
Have you tried swapping speakers ?

richj
  Reply With Quote

Reply


Amp repair help needed.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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
speaker repair wizzard needed limono Full Range 27 8th April 2009 02:28 AM
Schematic needed to repair CDB492 schnitzer Digital Source 0 3rd January 2009 07:50 PM
SONY TA 70, repair help needed jojospecial Solid State 2 5th November 2008 09:15 PM
Yamaha EMX3500 repair - help needed djbon Solid State 4 20th October 2008 03:05 PM
repair akai am-49 help needed pavlos Solid State 14 1st October 2007 10:18 PM


New To Site? Need Help?

All times are GMT. The time now is 09:12 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki