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

Audio Innovations Series 300 II -red plate
Audio Innovations Series 300 II -red plate
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 27th May 2015, 08:08 AM   #1
Bas Horneman is offline Bas Horneman  Netherlands
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
Default Audio Innovations Series 300 II -red plate

I've have the abovementioned amp on my bench for repair. But I don't have a lot of experience finding the cause of problems in other amps than my own. But I'm keen to learn.

1.) Swapped the tube. The problems stays in the same socket.
2.) Nothing looks burnt.
3.) Screen resistor is good and is connected to the socket.
4.) Output transformer primary measure the same value in both output transformers.
5.) I removed coupling cap to the grid. No change. So no bad capacitor.
6.) Pulled the tube from the socket where the issue is...and measured b+ looks ok around 280.
7.) Cathode is connected to the shared cathode resistor and that checks out. 120R.
8.) Haven't measured the grid leak resistor yet...'t was too late in the AM so I went to bed.

But I'm stumped at the moment because everything checks out good so far.

I'm guessing the problem must be in the preceding stage i.e. the phase splitter?

Any other causes of red plate?
Attached Files
File Type: pdf Audio_Innovations_300_Mk2_schematic.pdf (192.3 KB, 79 views)
__________________
If you can see the speaker cone move...it's not hifi.

Last edited by Bas Horneman; 27th May 2015 at 09:54 AM.
  Reply With Quote
Old 27th May 2015, 08:14 AM   #2
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
You can work back from the symptom. Red plate means too much anode current. Too much anode current means either wrong grid bias or (possibly) strong oscillation. As you have tried removing the coupling cap, it can't be the previous stage.

An open circuit grid leak resistor will do it, or a bad connection on the grid socket of the valve holder. Surface leakage (due to solder flux or just general dirt) on the valveholder can do it too.
  Reply With Quote
Old 27th May 2015, 08:19 AM   #3
Bas Horneman is offline Bas Horneman  Netherlands
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
Thanks for the suggestions. The socket on that tube is dirtier and generally looks worse than the others. Solder flux was also not cleaned from the circuit board after the modifications the owner had done (not by me).

Wanted to clean it up but was too lazy to go downstairs to fetch the circuit board cleaning spray can.

Can't wait to clean it up tonight and measure the grid leak.

Cheers.
__________________
If you can see the speaker cone move...it's not hifi.
  Reply With Quote
Old 27th May 2015, 06:25 PM   #4
Ketje is offline Ketje  Belgium
diyAudio Member
 
Ketje's Avatar
 
Join Date: Dec 2012
Location: Flanders
Now you'r at it, perhaps some changes (for the better ?)
Mona
Attached Images
File Type: jpg AudioInno-300MK2.jpg (51.5 KB, 132 views)
  Reply With Quote
Old 27th May 2015, 07:32 PM   #5
Bas Horneman is offline Bas Horneman  Netherlands
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
Quote:
Now you'r at it, perhaps some changes (for the better ?)
Not my amp. And no requirements by the guy who brought it to me.

But thanks for the suggestion. I would probably also would have done that it if it was mine.
__________________
If you can see the speaker cone move...it's not hifi.
  Reply With Quote
Old 27th May 2015, 07:35 PM   #6
Bas Horneman is offline Bas Horneman  Netherlands
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
Fixed. Just started to check continuity from the grid leak resistor. From the coupling capacitor to the grid stopper there was no connection. I find it hard to tell what is what with a circuit board. Anyway fixed. Thanks!
Attached Images
File Type: jpg faultdetail.jpg (43.3 KB, 120 views)
File Type: jpg fixeddetail.jpg (96.0 KB, 117 views)
__________________
If you can see the speaker cone move...it's not hifi.
  Reply With Quote

Reply


Audio Innovations Series 300 II -red plateHide 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
Audio Innovations Series 500 parts Jon Bradbury Tubes / Valves 5 22nd January 2014 09:17 PM
Dead Audio Innovations Series 500 Jon Bradbury Tubes / Valves 10 17th May 2013 10:27 PM
FS Audio Innovations 300 mkII MINT doctersava Swap Meet 1 25th July 2011 02:53 PM
Audio Innovations Series 300 HenrikKronborg Tubes / Valves 8 6th April 2004 08:59 PM
Audio Innovations 800 (series 2) Mr. Triatic Tubes / Valves 5 12th February 2004 10:15 PM


New To Site? Need Help?

All times are GMT. The time now is 10:44 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio
Wiki