Have an odd problem with my Aikido. - 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 February 2009, 01:47 AM   #1
JayH3 is offline JayH3  United States
diyAudio Member
 
Join Date: Mar 2008
Default Have an odd problem with my Aikido.

I built the octal Aikido setup from TubeCad.com. I am using the included Tung-Sol 6SN7 tubes and a very simple solid state power supply designed by Sy.

When the preamp is working everything sounds great. After about 30 minutes or so the left channel will about 98% shut off. If I turn off power to the amp output of the left channel will immediately return. I will flip the switch back on and listen for about another 20 minutes. At this point flipping the power switch may or may not make the output return.

Everything looks good on the equipment, all the the connections seem solid. The only thing is the tubes dont fit too firmly in the sockets.

Any ideas?
  Reply With Quote
Old 13th February 2009, 02:58 AM   #2
diyAudio Member
 
Join Date: Apr 2003
Location: Portland,Oregon
Blog Entries: 4
Send a message via AIM to DigitalJunkie
Have you tried swapping tubes between channels?
  Reply With Quote
Old 13th February 2009, 03:00 AM   #3
JayH3 is offline JayH3  United States
diyAudio Member
 
Join Date: Mar 2008
Quote:
Originally posted by DigitalJunkie
Have you tried swapping tubes between channels?

Yup, The problem always stays in the one channel.
  Reply With Quote
Old 13th February 2009, 03:09 AM   #4
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
First thing I'd do is resolder every joint in that channel.

Do you have an oscilloscope? If so, you can isolate whether the problem is from the voltage amplifier or the cathode follower.

See if you can induce the fault by turning a heat gun on the cathode resistors in the "difficult" channel right after the first turn-on and initial warm up. If that doesn't cause the problem, carefully use some freeze spray on the passive parts of that channel- don't get that on or near the tubes or you'll let in the air and let out the smoke.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 13th February 2009, 03:13 AM   #5
diyAudio Member
 
Join Date: Nov 2002
Quote:
Everything looks good on the equipment, all the the connections seem solid. The only thing is the tubes dont fit too firmly in the sockets.
Start by making the tubes fit firmly in the sockets and then go from there.
  Reply With Quote
Old 13th February 2009, 03:16 AM   #6
JayH3 is offline JayH3  United States
diyAudio Member
 
Join Date: Mar 2008
Quote:
Originally posted by SY
First thing I'd do is resolder every joint in that channel.

Do you have an oscilloscope? If so, you can isolate whether the problem is from the voltage amplifier or the cathode follower.

See if you can induce the fault by turning a heat gun on the cathode resistors in the "difficult" channel right after the first turn-on and initial warm up. If that doesn't cause the problem, carefully use some freeze spray on the passive parts of that channel- don't get that on or near the tubes or you'll let in the air and let out the smoke.

Ill try these things this weekend.

Unfortunately I dont have an o-scope. I was thinking about getting one of the USB scopes. Do you have any experience with how well they function compared to a convential one?

I havent heard of freeze spray, but could I get the same effect from holding canned air upside down?
  Reply With Quote
Old 13th February 2009, 03:18 AM   #7
JayH3 is offline JayH3  United States
diyAudio Member
 
Join Date: Mar 2008
Quote:
Originally posted by burnedfingers


Start by making the tubes fit firmly in the sockets and then go from there.

Thats not going to happen. The pins on these tung sols seem thicker than most octals. I just tried seating one in my st70 which I have a different kind of socket in and they wont seat all the way in those sockets either.
  Reply With Quote
Old 13th February 2009, 09:05 AM   #8
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Any electronics shop or mail order will have freeze spray. You want to really thermally shock the components to see which one is the culprit.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 13th February 2009, 10:22 AM   #9
protos is offline protos  Greece
diyAudio Member
 
protos's Avatar
 
Join Date: Mar 2002
Location: Athens+Addis Ababa
I think 99.9% it is a bad solder joint according to your symptoms.I had a similar problem with mine when it warmed up i would get intermittent crackling otherwise sounded great.The solder joints looked good but it turned out one cathode resistor wire was a little short and was not soldered solidly on the pad but was "floating" inside the solder joint.
__________________
``The author always assumes that when power is applied , the amplifier will explode or ,at the very least, catch fire.
Morgan Jones, Building Valve Amplifiers.
  Reply With Quote
Old 13th February 2009, 10:33 AM   #10
diyAudio Member
 
Join Date: Nov 2002
Quote:
Thats not going to happen. The pins on these tung sols seem thicker than most octals. I just tried seating one in my st70 which I have a different kind of socket in and they wont seat all the way in those sockets either
Well, for the heck of it I checked the pin size of a number of octal tubes and found variations in the neighborhood of .002 They will seat all the way into the socket with some force without breaking anything.

Quote:
Everything looks good on the equipment, all the the connections seem solid. The only thing is the tubes dont fit too firmly in the sockets.
By you comment "the tubes don't fit too firmly in the sockets" led me to believe they were sloppy. SORRY!

Resolder all connections and look at anything with a frosty appearance as being no good too cold a joint and re-do.
  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
My Aikido!! piero7 Tubes / Valves 9 31st August 2009 10:56 AM
Aikido hum kacernator Tubes / Valves 29 29th December 2008 12:45 AM
aikido problem jayme Tubes / Valves 13 20th October 2006 09:59 AM
Aikido PSU help cbutterworth Tubes / Valves 48 13th October 2006 07:54 PM
3rd Aikido? philipbarrett Tubes / Valves 6 11th October 2005 06:35 PM


New To Site? Need Help?

All times are GMT. The time now is 02:54 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