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 4th June 2012, 07:17 AM   #1
diyAudio Member
 
Join Date: Jun 2012
Default Help with GZ34

I am building an AD-15 remake and am stuck on the rectification portion of the amp. When the GZ34 is soldered in there is no voltage being drawn from the secondary of my power transformer, but when I replace the gz34 with a bridge rectifier the amp works fine. The circuit is soldered up according to the schematic, so I am baffled as to why it's not working. Could i be overlooking something?
  Reply With Quote
Old 4th June 2012, 07:28 AM   #2
diyAudio Member
 
Join Date: Oct 2004
Location: Adelaide South Oz
Do you have the GZ34 heater circuit wired up correctly?
Cheers,
Ian
  Reply With Quote
Old 4th June 2012, 07:36 AM   #3
diyAudio Member
 
Join Date: Jun 2012
Yes the tubes glow up but it doesn't seem to be drawing any power from the transformer. I have 2 and 8 going to the brown wires of transformer i think its 3.15 volts not the heater though and 4 and 6 to the secondary. I am using the blues junior power transformer replacement as well. The tube isn't supposed to be grounded is it?
  Reply With Quote
Old 4th June 2012, 08:55 AM   #4
diyAudio Member
 
MellowTone's Avatar
 
Join Date: Jun 2006
The heater supply for a GZ34 should be 5V between pins 2 and 8. Said 5V tap should be rated for minimum 1.9 amps.

Is the schematic you're working off this one here (or thereabouts)? http://www.prowessamplifiers.com/sch...s/AD15main.jpg
__________________
I Reject Your Reality And Substitute My Own
- Adam Savage, Mythbuster
  Reply With Quote
Old 4th June 2012, 11:14 AM   #5
cobra is offline cobra  United Kingdom
diyAudio Member
 
Join Date: Oct 2009
The Valve Wizard this is good onfo if ..you have 2.5 0 2.5 ht from center tap if not pin 8 is h/k if you have only 6.3 volts then poss an ez81

good luck cobra
  Reply With Quote
Old 4th June 2012, 03:12 PM   #6
12E1 is offline 12E1  United Kingdom
diyAudio Member
 
12E1's Avatar
 
Join Date: May 2012
Location: Near Huntingdon, Cambridgeshire, UK
Quote:
Originally Posted by cobra View Post
The Valve Wizard this is good onfo if ..you have 2.5 0 2.5 ht from center tap if not pin 8 is h/k if you have only 6.3 volts then poss an ez81

good luck cobra
"ht from center tap" is NOT correct for a GZ34. The cathode has its connection to pin 8, the heater voltage (5 volts AC) is between pins 8 and 6. The HT current must come from pin 8. If you were to take the HT from a tap on the heater winding then you would superimpose half of the heater AC voltage on the HT output.

To the OP - you say it works with a bridge rectifier. That only tells us that there are some volts from the HT on the transformer. I assume that you do have a center tap on the HT winding on the transformer...? (should be marked for example 350 - 0 - 350, or whatever voltage it is designed to provide). Using the GZ34 as a full-wave rectifier requires that the 0 volt center-tap on the HT winding is grounded. Then you get the +HT out from the cathode (pin 8, as above). Note that the heater winding for the GZ34 is at +HT voltages and should be regarded as hazardous. It must not be connected to other valve heaters in the design.

If you do not have a center tap on the HT winding of the transform, then let us know and we can advise an alternative arrangement,
  Reply With Quote
Old 4th June 2012, 03:17 PM   #7
diyAudio Member
 
Join Date: Feb 2008
Location: Niederösterreich
[QUOTE=12E1;3047911]"ht from center tap" is NOT correct for a GZ34. The cathode has its connection to pin 8, the heater voltage (5 volts AC) is between pins 8 and 6.



Pins 4 and 6 are the PLATES for the HV secondary. Pins 2 and 8 should have 5 volts applied across them to light the heater. Rectified DC should be taken from pin 8.
  Reply With Quote
Old 4th June 2012, 03:21 PM   #8
diyAudio Member
 
Join Date: Feb 2008
Location: Niederösterreich
To use a 5AR4 rectifier your transformer MUST have a center-tapped HV secondary which should be grounded. If your secondary does not have a center tap then a hybrid Graetz-bridge is possible which utilizes two solid-state diodes alongside the 5AR4 to form a Full-Wave-Bridge.
  Reply With Quote
Old 4th June 2012, 03:48 PM   #9
12E1 is offline 12E1  United Kingdom
diyAudio Member
 
12E1's Avatar
 
Join Date: May 2012
Location: Near Huntingdon, Cambridgeshire, UK
[QUOTE=mctavish;3047914]
Quote:
Originally Posted by 12E1 View Post
"ht from center tap" is NOT correct for a GZ34. The cathode has its connection to pin 8, the heater voltage (5 volts AC) is between pins 8 and 6.



Pins 4 and 6 are the PLATES for the HV secondary. Pins 2 and 8 should have 5 volts applied across them to light the heater. Rectified DC should be taken from pin 8.
My apologies for the error re pin 6. I would correct my post, but appear to be unable to do so.
  Reply With Quote
Old 4th June 2012, 04:01 PM   #10
diyAudio Member
 
Join Date: Jun 2012
@mellowtone that is the exact schematic I am using. And my transfper does not have a center tap. Is there a schematic i can see to utilize the gratez bridge. And also would it be better to just go ahead and use bridge rectification?
  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
Why two GZ34 in this schematic? mfaughn Tubes / Valves 3 20th June 2011 09:27 PM
Toughness of GZ34? Psychobiker Power Supplies 0 8th March 2008 09:14 PM
GZ34 and temperature rossdt Tubes / Valves 2 26th October 2006 09:04 PM
Got sparks in my GZ34! HeadSh0T Tubes / Valves 29 19th March 2004 07:49 PM


New To Site? Need Help?

All times are GMT. The time now is 04:59 PM.


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