All tubes red plating - Page 2 - 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 2nd May 2012, 04:39 PM   #11
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Confirmed here too..
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 2nd May 2012, 05:11 PM   #12
diyAudio Member
 
Osvaldo de Banfield's Avatar
 
Join Date: Dec 2011
Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina
Quote:
Originally Posted by Frank Berry View Post
A schematic would certainly help.
It sounds like this is some kind of linear amplifier. If it's a linear, it's not class C.
Sometimes the term "linear" is misunderstood. A power amplifier for FM can be class C, and also called "linear" when in true it isnīt.
__________________
LW1DSE
  Reply With Quote
Old 2nd May 2012, 05:31 PM   #13
diyAudio Member
 
Frank Berry's Avatar
 
Join Date: Sep 2003
Location: Midland, Michigan
I found the schematic and published specs.
This is an 11 meter linear amplifier. Suitable for AM, SSB, FM.
Looks like it might operate in class AB mode.
Illegal in the United States.
__________________
Frank
  Reply With Quote
Old 2nd May 2012, 05:31 PM   #14
diyAudio Member
 
artosalo's Avatar
 
Join Date: Feb 2010
This link works:

http://www.google.fi/url?q=http://ww...XzoF_ZJxwiVyPQ
  Reply With Quote
Old 2nd May 2012, 05:42 PM   #15
diyAudio Member
 
HollowState's Avatar
 
Join Date: Aug 2006
Location: Taxland, New Jersey
The PDF can be accessed by goint to www.rmitaly.com then >download >download manuals >KLV1000-manual_rel_210.pdf
__________________
"It is hard to imagine a more stupid or more dangerous way of making decisions than by putting those decisions in the hands of people who pay no price for being wrong." ~Thomas Sowell
  Reply With Quote
Old 2nd May 2012, 05:49 PM   #16
diyAudio Member
 
artosalo's Avatar
 
Join Date: Feb 2010
According to manual the original tubes are PL509 having 40 V heater voltage, which is also used to generate the bias voltage.

Now it seems that tubes have been changed to 6P45S, which has 6,3 V heater voltage. So what has happened to bias voltage, which should be much more than just rectified 6,3 VAC can form.

The simple fact is that if tubes are redplating they are dissipating too much power/heat. This reguires high quiescent current which in turn can take place if the bias voltage is too low.
  Reply With Quote
Old 2nd May 2012, 06:46 PM   #17
diyAudio Member
 
Osvaldo de Banfield's Avatar
 
Join Date: Dec 2011
Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina
Artosalo: You are right. It is a biamp (RX and TX), and the values of bias are too low. He must add a 48V trafo and rewire the bias supply.
__________________
LW1DSE
  Reply With Quote
Old 3rd May 2012, 03:36 AM   #18
loopy is offline loopy  Australia
diyAudio Member
 
Join Date: Apr 2012
Quote:
Originally Posted by Osvaldo de Banfield View Post
Artosalo: You are right. It is a biamp (RX and TX), and the values of bias are too low. He must add a 48V trafo and rewire the bias supply.
Thanks for the responses. I understand about the bias voltage being too low, so I removed one end of the diode(s) and applied the 40 volts AC direct (leaving the 6.3 volts AC intact for the heater), which read about 50 volts DC on the other end of the diode, for the bias.

The same thing still occurs. I can turn the drive right down to the point where there is very little output, and they all still red plate. They take a little longer to do so, but it still happens.
  Reply With Quote
Old 3rd May 2012, 12:21 PM   #19
diyAudio Member
 
Osvaldo de Banfield's Avatar
 
Join Date: Dec 2011
Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina
Default Neutralizing.

Does the driver also gets hot plates?. May be that the problem is a VHF self oscillation, at a frequency where the plate circuit canīt absorb it. Make an easy RF power meter: a Hertz ring. Take a small incandescent lamp, the less power as possible will result in a higher sensitivity. Make a wire loop of about 50 mm (2"), (1 turn coil) and solder both ends to each pin of the lamp. Carefully, put the loop near the output LC tank, and see if with no input, the lamp brights. If this is the case, try to re-neutralize all set. Search in the web how to neutralize it, or post me and I try to explain it. Itīs easy.

Also, tell me if the trouble started from a tube replacement. It points to a neutralizing trouble.
__________________
LW1DSE
  Reply With Quote
Old 3rd May 2012, 02:06 PM   #20
loopy is offline loopy  Australia
diyAudio Member
 
Join Date: Apr 2012
Quote:
Originally Posted by Osvaldo de Banfield View Post
Does the driver also gets hot plates?. May be that the problem is a VHF self oscillation, at a frequency where the plate circuit canīt absorb it. Make an easy RF power meter: a Hertz ring. Take a small incandescent lamp, the less power as possible will result in a higher sensitivity. Make a wire loop of about 50 mm (2"), (1 turn coil) and solder both ends to each pin of the lamp. Carefully, put the loop near the output LC tank, and see if with no input, the lamp brights. If this is the case, try to re-neutralize all set. Search in the web how to neutralize it, or post me and I try to explain it. Itīs easy.

Also, tell me if the trouble started from a tube replacement. It points to a neutralizing trouble.
Yes. I just noticed today that the driver also gets hot plates. Another thing I've noticed is the output is always slowly rising. Say for example with about 3 watts in I get about 300 out, after about 30 seconds or so that might rise to ~350, and keep rising.

I'm not sure if I've always had this trouble, as I was unaware of red plating until the first time I had seen it a while ago. I have several of these tubes and they all respond the same way.

I don't think I have a low voltage incandescent lamp on hand, but if neutralizing is an easy task, I can try that if you can explain.

Thanks.
  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
6bq5 red plating maciek Tubes / Valves 9 4th October 2011 05:06 PM
For sale : 6384 Red Bank tubes jean-paul Swap Meet 0 6th March 2011 01:02 PM
Blue Tube Red Plating = Help! wushuliu Tubes / Valves 24 26th January 2011 11:15 PM
Vox tubes glowing red hot Franconio Tubes / Valves 10 4th April 2006 01:13 PM


New To Site? Need Help?

All times are GMT. The time now is 12:56 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright Đ1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2