replace a 5651 tube with a zener? - 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 8th June 2006, 02:14 PM   #1
jarthel is offline jarthel  Australia
diyAudio Member
 
Join Date: Jan 2002
Location: somewhere in Australia
Default replace a 5651 tube with a zener?

according to the Sylvania 5651 datasheet, the operating voltage is 92V. Does that mean I can replace the tube with a 92V zener?

The circuit I'm thinking of is in RDH chap33 figure 33.14 which is this one: http://img240.imageshack.us/my.php?i...ure33147hl.gif

ps. Do I really need R1 in this circuit? Also is there a way to compute for Vout so I can replace R9 pot with a constant resistance?

Thanks for the help
  Reply With Quote
Old 8th June 2006, 02:31 PM   #2
diyAudio Member
 
Join Date: Jan 2003
Location: Sweden
Hi,

You can change the 5651 to zener if you connect a good capacitor in parallell to remove the zener noise, but you will get less stability as a zener of this voltage has high temperature coefficient and high zener resistance and the zener knee is not that sharp.

You need R1 if you want to load the pass tube to max current when you want to make sure that each triode section carry the same current.

Regards Hans
  Reply With Quote
Old 8th June 2006, 02:44 PM   #3
jarthel is offline jarthel  Australia
diyAudio Member
 
Join Date: Jan 2002
Location: somewhere in Australia
Quote:
Originally posted by tubetvr
Hi,

You can change the 5651 to zener if you connect a good capacitor in parallell to remove the zener noise, but you will get less stability as a zener of this voltage has high temperature coefficient and high zener resistance and the zener knee is not that sharp.

You need R1 if you want to load the pass tube to max current when you want to make sure that each triode section carry the same current.

Regards Hans

Am I right in saying that a 92V zener is the the right replacement? I will be using multiple zener instead of just 1.

since it's very difficult to find a 160ohm 10W potentiometer these days, can you suggest a standard value?

thank you for the assistance.
  Reply With Quote
Old 8th June 2006, 05:28 PM   #4
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
The 5651 has much better initial tolerance and long term temperature stability than any garden variety zener, I went the other direction from Zeners to 5651 and other similar gas tube regulators/references and have been pleased with the results. (The 5651 is a reference.) The 5651 is commonly available on eBay for as little as a couple of bucks. Mullard made a beefed up equivalent, part number escapes me at the moment.

You can safely replace the 160 ohm pot with a pair of 100 ohm 10W resistors, one to each plate. I have designed and built a number of very similar regulators over the years and have not had any problems. The pot is "gilding the lily" so to speak and is overkill unless you are running very close to the tube's current and/or dissipation limits.

The pot or replacement resistors are there primarily to force reasonable current sharing between the two sections, it's not that critical unless you are running them right at their dissipation limit or need significantly more current in which case use a 6336A/B/C instead.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 8th June 2006, 09:12 PM   #5
diyAudio Member
 
cogsncogs's Avatar
 
Join Date: Jul 2003
Location: Wayne, West Virginia
Quote:
Am I right in saying that a 92V zener is the the right replacement?
Min Typ Max
82--87--92V

Yuup! Anywhere from 82-92V will be fine. That's what R9 is for!

Wayne
  Reply With Quote
Old 9th June 2006, 02:04 AM   #6
jarthel is offline jarthel  Australia
diyAudio Member
 
Join Date: Jan 2002
Location: somewhere in Australia
can I use a 1/2W pot for R9? thanks again
  Reply With Quote
Old 9th June 2006, 02:43 AM   #7
jarthel is offline jarthel  Australia
diyAudio Member
 
Join Date: Jan 2002
Location: somewhere in Australia
using this circuit, can I get 150V? it was never mention in the RDH chap33.

I only assumed I can because of R9 and the description (output voltage control).

thanks again
  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
replace attenuator on Golden Tube SEP-1SE wintermute222 Parts 2 3rd October 2011 08:37 PM
Gas Reference Tube (5651/85A1/etc) Internal Impedance kevinkr Tubes / Valves 6 3rd July 2009 10:22 PM
Pearl: replace zener D1 with voltage divider? h_a Pass Labs 14 22nd February 2007 01:43 PM
Zener Bias alexistheo Tubes / Valves 1 24th March 2006 03:43 AM
No zener ding Pass Labs 10 6th June 2001 12:11 PM


New To Site? Need Help?

All times are GMT. The time now is 08:19 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