Resurrecting old tubes - 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 1st February 2012, 05:36 AM   #1
diyAudio Member
 
Join Date: Oct 2004
Location: Adelaide South Oz
Default Resurrecting old tubes

Hi,
I was given a box of old tubes sometime back and over the last day or 2 I've been running them thru' the tube tester (AVO MKIII) to see what were bin jobs and what should go on the shelf.

There were about 20 807s in the box. Of these about 12 tested good except for bad heater/cathode leakage. It was suggested to me that this was probably due to moisture and dirt ingress into the bases. I tried cleaning up the exterior of bases with Isopropyl Alchohol. That did'nt help.

Is the suggested problem just wrong or would I need to remove the bases and clean inside them to get any noticable improvement. This seems a lot of work so I'm asking advice before I try.

Not worried about doing irreversable damage while doing this, the tubes are'nt usable as is.

Cheers,
Ian
  Reply With Quote
Old 1st February 2012, 05:54 AM   #2
Enzo is offline Enzo  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Lansing, Michigan
Moisture in the bases? perhaps putting them in a heated environment for a time. In a very slow oven maybe or just heaters energized while sirring in an enclosed space. Cook the moisture out.
  Reply With Quote
Old 1st February 2012, 12:34 PM   #3
ryuji is offline ryuji  United States
diyAudio Member
 
Join Date: Feb 2011
Location: massachusetts
running the tubes for a few hours at higher then running voltage on just filament to keep them really warm could probably get most of the 20 tubes in workable condition, gives the getters a chance to soak up the gas
  Reply With Quote
Old 1st February 2012, 01:33 PM   #4
Doz is offline Doz  United Kingdom
diyAudio Member
 
Doz's Avatar
 
Join Date: Jul 2010
Location: Sat Down
I had 1625's the same. Oven sorted them out.
__________________
"To err is human.. to make a real balls-up requires a computer"
  Reply With Quote
Old 1st February 2012, 02:00 PM   #5
diyAudio Member
 
the_manta's Avatar
 
Join Date: Nov 2006
Location: Munich, Bavaria
807 has a 5-Pin Base. If we count the two heater Pins as one (because they aren't insulated from each other), then we have 4 Pins. These can be permutated in the following ways: ∑ 1 to 4 = 1+2+3 = 6 ways.
Heater Cathode failure is one of these possibilities (probability = 1/6)
All your 12 Tubes have that problem. 1/(12*6) ~1.4%
Seems a bit strange, doesn't it ? Would be much more likely when there would be some other insulation failures, too.
Maybe some kind of intelligent moisture (Creationism !) which only looks for the heater and cathode pins.

Well, what I want say. It is very likely that these tubes were sorted out because of f-c insulation failure. Furthermore when you already had sorted out the other 8 which tested bad.
So, either you throw them aways or use fixed bias or use seperated/insulted heater supplies.
__________________
Терпенье и труд все перетрут
  Reply With Quote
Old 1st February 2012, 07:59 PM   #6
diyAudio Member
 
Join Date: Jul 2008
and certainly....check the calibration of the test equip if everything is testing with leaks or shorts.
  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
Resurrecting a Crown DC300A TomWaits Solid State 473 23rd February 2014 07:18 AM
Resurrecting weak tubes astouffer Tubes / Valves 10 15th May 2011 12:33 PM
Resurrecting a Crest LA2210 Courtec Solid State 4 15th March 2011 03:17 PM
Resurrecting 70's audio components Stuey Parts 27 28th September 2008 04:55 PM
Resurrecting Old Speakers Brushpilot Multi-Way 5 4th July 2004 03:12 PM


New To Site? Need Help?

All times are GMT. The time now is 09:50 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