Got sparks in my GZ34! - 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 3rd March 2004, 04:42 AM   #1
diyAudio Member
 
HeadSh0T's Avatar
 
Join Date: Sep 2002
Location: Toronto, Canada
Default Got sparks in my GZ34!

I just finished building one channel of my 300b amp. I switched it on I had my DVM monitoring the DC coming out of it. As the tube heated up, the DC increased and then after a few seconds more purple sparks then my DVM showed 0V due to the 6A fuse blowing ..

The DC on the cathode of the GZ34 reaches about 100V before this happens.

The amp has a 300b, SV83 pentode, and GZ34 rectifier.

I also have a 100K, 2W bleeder resistor.

GZ34 datasheet says max input cap is 60uF and I only have 5.6uF so it can't be that..

Any suggestions?

my PS schematic is shown below:
Attached Images
File Type: jpg 300bpsu.jpg (25.8 KB, 605 views)
  Reply With Quote
Old 3rd March 2004, 05:48 AM   #2
diyAudio Member
 
Join Date: Jan 2004
Location: nowhere
Well you're most certianly taking far too much current for an amp of this magnitude...

You've got the PSUD simulation all wrong.

I ran the PSUD simulation here and checked current on the transformer, you're drawing 5amps! all of the time!

Voltage across the current sink is 0.012v! this should be 375volts!

You should see 0.50 amps across those GZ34's at maximum especially in real life...

Okay heres your problem, take away L2 & C3.

Replace C2 with 100uF on the 1st choke and leave C1 as is..

Try it like that..

The problem is according to PSUD is that your final voltage comes out as 500+ volts whereas the original transformer voltage was only 375... which is expected.

Try drawing more current to get the voltage down or decrease your transformer ohmage so it supplies less current.
  Reply With Quote
Old 3rd March 2004, 06:09 AM   #3
arnoldc is offline arnoldc  Philippines
diyAudio Member
 
Join Date: Apr 2003
Location: Makati
Send a message via Yahoo to arnoldc
hi HeadSh0T, Layberinthius

i ran the simulation and PSUD did not complain. at the end of the simulation he's getting 450V with a hardly visible ripple (zoom on it).

i may be missing something too, and it is also my interest how the simulation went wrong.

cheers.
Attached Images
File Type: jpg ps.jpg (90.5 KB, 555 views)
  Reply With Quote
Old 3rd March 2004, 06:15 AM   #4
diyAudio Member
 
Join Date: Jan 2004
Location: nowhere
What the hell!

It was telling me that it was morbidly unsafe, now if I re-build the simulation it's perfectly fine!?

Okay here we go, try 50hz against 60hz...

With 60hz the simulation draws far too much current while under 50hz it runs 'fine'

That still doesn't produce the 0v supply I seen earlier tho.
  Reply With Quote
Old 3rd March 2004, 07:35 AM   #5
SHiFTY is offline SHiFTY  New Zealand
diyAudio Member
 
SHiFTY's Avatar
 
Join Date: Jul 2002
Location: New Zealand
I would seriously doubt your power tranny has a secondary resistance of 0.5 ohms. Disconnect it, and measure the resistance with a multimeter. Use this actual number in your simulation.

However I believe you may have a short somewhere. Double and triple check your HT connections and your capacitors. **With the amp disconnected and discharged**, what is the resistance between B+ and ground?
  Reply With Quote
Old 3rd March 2004, 08:25 AM   #6
diyAudio Member
 
djmiddelkoop's Avatar
 
Join Date: Feb 2003
Location: Noord-Holland
There are 2 possibilities here :

1) one of the capacitors is bad. Try connecting one at a time to findout.

2) one of the chokes internally shorts to ground when voltage is ramping up. Isolate them from the groundplane to find out.

Dick.
__________________
“Information is not knowledge.Knowledge is not wisdom.
Wisdom is not truth.Truth is not beauty.Beauty is not love.Love is not music.Music is THE BEST.”
  Reply With Quote
Old 3rd March 2004, 10:00 AM   #7
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
You didn't make the mistake of connecting one side of the 5V heater supply to the GZ34 to ground, did you? GZ34 is a directly heated rectifier...
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 3rd March 2004, 10:14 PM   #8
diyAudio Member
 
HeadSh0T's Avatar
 
Join Date: Sep 2002
Location: Toronto, Canada
Thanks for the replies but I didn't have access at work today...

I created this simulation again and there were no complaints. The correct secondary resistance on the PT is 120R.

Our electricity here in Canada is at 60Hz.

Resistance from B+ to ground is around 22K.

djmiddelkoop: I'll try what you've suggested..
  Reply With Quote
Old 5th March 2004, 01:28 AM   #9
diyAudio Member
 
HeadSh0T's Avatar
 
Join Date: Sep 2002
Location: Toronto, Canada
Ok i've been kind of busy but now, i've found that when I don't have the 300B plugged in, the voltage goes up pretty high (>420V) and there are no sparks in the gz34.. but when it's in, then as the voltage ramps up to about 70V only, then i get sparks and I have to shut the amp off..

  Reply With Quote
Old 5th March 2004, 03:20 AM   #10
arnoldc is offline arnoldc  Philippines
diyAudio Member
 
Join Date: Apr 2003
Location: Makati
Send a message via Yahoo to arnoldc
something is drawing too much current. your 300B, is it cathode biased? what is the value of the cathode resistor?
  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
Sparks inside GZ34 rossdt Tubes / Valves 8 5th November 2006 11:43 PM
Sparks from amp chewy04 Car Audio 25 25th October 2004 12:19 AM


New To Site? Need Help?

All times are GMT. The time now is 10:15 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