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

help with "bruce heran" el84 amp S2
help with "bruce heran" el84 amp S2
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 17th November 2010, 11:01 PM   #1
kawasaki99 is offline kawasaki99  United States
diyAudio Member
 
Join Date: Nov 2010
Default help with "bruce heran" el84 amp S2

Hello,
My first project is finished Heran EL84 PP (Oddwatt S2) amp. I'm only getting a half wave amplification on the output. I tried switching the output leads as suggested with no change. Looking at the schematic the upper EL84 is conducting while the lower one is not. Pin #2 on the upper tube has the input from the 5751 @16vac to ground, pin #2 on the lower tube has no voltage. All other voltage measurements appear to be the same. I tried alternate tubes, no change. Any assistance would be appreciated. I'm very new to this hobby.

Regards, Richard
  Reply With Quote
Old 18th November 2010, 01:36 AM   #2
gingertube is offline gingertube  Australia
diyAudio Member
 
Join Date: Oct 2004
Location: Adelaide South Oz
OK - from your description it seems that one side (bottom) is not working.
The odd watt design drives this side from the cathode.
Check:
1) That the pin 2 (grid 1) is definitely tied to signal ground (0V) via the resistor.
2) That you have high voltage to the anode of that tube.
3) That you have high voltage to the screen (pin 9) of that tube (from the Ultralinear tap).
4) That the cathode of that tube is sitting at approximately the same DC voltage as the upper tube cathode.
I think you will find one of the above is not correct and that will point you in the right direction for fixing the amp.
CAUTION: If the bottom tube is not conducting current then the top one will conduct twice its normal current to compensate - that could cause over heating of that to tube.

Also check the balance pot in the cathodes is not open circuit at one end. Checking that the 2 cathodes are sitting at close to the same DC voltage (with no signal applied) will check this.

Just some quick notes - hope it helps.

Cheers,
Ian
  Reply With Quote

Reply


help with "bruce heran" el84 amp S2Hide 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
FS: NOS TDA1541A S2 "Double Crown" adhoc Swap Meet 14 14th March 2009 07:50 PM
"it is just SO hard to get bad sound from EL84 PP amp" rick57 Tubes / Valves 34 25th March 2005 04:32 PM
Bruce Moore "Companion" - Schematic ruangrit Tubes / Valves 2 28th December 2004 04:01 PM
Using Telefunken "Tank" transfomers for a single ended el84 amp? ark Tubes / Valves 13 8th March 2004 11:32 PM


New To Site? Need Help?

All times are GMT. The time now is 10:51 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio
Wiki