Unsolved problem EL34/12AT7/5AR4 - 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 4th October 2008, 04:26 PM   #1
diyAudio Member
 
Join Date: Oct 2007
Default Unsolved problem EL34/12AT7/5AR4

Hi guys,

(I'm a real newbie, so please be indulgent with me )

Someone gave me a SE EL34/12A*7/5AR4 amp.
It sounds quite good but one channel is louder than the other, particularly in the mid-range.

I swapped tubes, swapped and changed the 12A*7; the only one I didn't change is the rectifier.

I interchanged my speakers; I tried the amp with another pair of speakers. I swapped wires and changed them.

I checked soldering, resistors and caps. Everything seems OK. But obviously, there is something wrong. Because one channel is always louder than the other.

The next step I should do is checking transfos. Gosh. I'm not really sure what to do about that...

Before this step, do you think I could do something else, that is obvious for an old DIY pro but unevident for a rookie ?

I know I should have done the schematic, but I didn't

Thanks a lot
  Reply With Quote
Old 4th October 2008, 08:55 PM   #2
diyAudio Member
 
TubeHead Johnny's Avatar
 
Join Date: Jan 2005
Location: The emerald city, Seattle, WA.
How old is the amp? Sounds to me like a resistor or cap has drifted in value, making the channels sound uneven.

Do you have knowledge working with high voltage electronics? If not get a qualified tech to check it out. Voltages inside an amp are deadly!
  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
bad 5ar4? sturmj Tubes / Valves 2 11th February 2009 08:09 PM
Funny bias problem in PP EL34. Please help OzMikeH Tubes / Valves 9 14th July 2008 11:22 PM
Tubes for Sale - Link to List 12AX7,5AR4,6550,EL34 and More baileyler Vendor's Bazaar 3 22nd April 2008 02:20 PM
a 5ar4 problem contaxchen Tubes / Valves 23 17th February 2005 01:00 AM


New To Site? Need Help?

All times are GMT. The time now is 10:28 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