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 15th October 2005, 04:39 PM   #1
diyAudio Member
 
philipbarrett's Avatar
 
Join Date: Feb 2005
Location: Dallas, Texas
Send a message via AIM to philipbarrett
Default Tube PSU Question

Does anyone know of a data sheet comparing various tube rectifiers? So far, everyone I've found has an output voltage around 380 (assuming a high enough input), is this typical or are there other types with less or more voltage loss?

This is my first foray off a SS PSU design.

Thanks in advance for any help.

PB
  Reply With Quote
Old 16th October 2005, 01:58 PM   #2
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
TDSL is a GREAT resource for tube data.
TDSL

The forward voltage drop is low in the 5AR4/GZ34 and damper diodes, like the 6AU4. The forward voltage drop is large in the 5Y3 and 5R4.

A 650 V. B+ rail is within a 5AR4's capability. KV. rails can be done with damper diodes.
__________________
Eli D.
  Reply With Quote
Old 16th October 2005, 02:22 PM   #3
Joel is offline Joel  United States
diyAudio Member
 
Joel's Avatar
 
Join Date: Oct 2002
Location: Brooklyn, NY
Default PSUD2

The PSUD2 program is the standard power supply sim for the DIY'er.

http://www.duncanamps.com/psud2/index.html

I routinely get within 0.5V of the predicted value with it. The key is measuring the DCR of your power transformer primary + secondary, and your line and off-load voltages. You then enter these into the program. It's a great tool.

Joel
  Reply With Quote
Old 16th October 2005, 05:22 PM   #4
diyAudio Member
 
Miles Prower's Avatar
 
Join Date: May 2005
Location: USA
Blog Entries: 6
Here's something else that will come in handy for this: Rectifier Applications Handbook
__________________
There are no foxes in atheistholes
www.dolphin-hsl.com
  Reply With Quote
Old 16th October 2005, 06:30 PM   #5
diyAudio Member
 
philipbarrett's Avatar
 
Join Date: Feb 2005
Location: Dallas, Texas
Send a message via AIM to philipbarrett
Thanks for the advice everyone, I downloaded the PSU designer and entered my prototype. I cannot figure out how to present the PSUD data here, however, I'm using a 250VCT transformer, 6CA4 rectifier, a C filter section at 100uF followed by an LC section at 20H/100uF supplying a load at 5K.

I meter the unloaded output of this at 385VDC which seems right inline with the 6CA4 datasheet.

However, when I run the simulator I get dire warnings about current limits and the final curve shows an output voltage of 600V !

Any ideas what I'm doing wrong?

Thanks in advance - PB
  Reply With Quote
Old 16th October 2005, 11:30 PM   #6
diyAudio Member
 
aletheian's Avatar
 
Join Date: Apr 2004
Location: Philly
Sometimes in that program, I get a nasty spike at startup, you can use a soft start or stepprd startup, or just use a report delay of a second... usually works for me.
__________________
Heghlu'meH QaQ jajvam!
  Reply With Quote
Old 17th October 2005, 12:53 AM   #7
Joel is offline Joel  United States
diyAudio Member
 
Joel's Avatar
 
Join Date: Oct 2002
Location: Brooklyn, NY
Default "Any ideas what I'm doing wrong?"

Yes, you have a 100uF input capacitor. I don't think any standard rectifier can handle that large an input cap without a lot of added resistance before it.

Joel
  Reply With Quote
Old 17th October 2005, 01:01 AM   #8
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
The 6CA4 is a GOOD tube. What you've built is proof. 100 muF. in the 1st filter cap. position is TOO big and exceeds the limits given in the data sheet. That you don't get arcing over (VERY BAD) at start up is a matter of luck. When using vacuum rectifiers, the 1st cap. in a CLC filter needs to be kept relatively small. Some tubes can tolerate only 4 muF. max. The 6CA4 is quite tolerant of capacitance for a vacuum rectifier, but it should not be over stressed. 20 muF. in the 1st position is GOOD, as it will keep the rail voltage up, without exceeding published limits. The choke protects both the rectifier and the power trafo (I^2R heating) from the 2nd filter cap. Piling up the energy storage in the 2nd position is OK.
__________________
Eli D.
  Reply With Quote
Old 17th October 2005, 05:28 AM   #9
Jay is offline Jay  Indonesia
diyAudio Member
 
Join Date: Feb 2003
Location: Jakarta
100uF is too big??? 4uF???
  Reply With Quote
Old 17th October 2005, 06:06 AM   #10
diyAudio Member
 
Miles Prower's Avatar
 
Join Date: May 2005
Location: USA
Blog Entries: 6
"100uF is too big???"

Yes it is. Unlike solid state, you're dealing with high voltage, low current devices. A VT power diode doesn't have the ability to source the charging current a 100uF filter capacitor will demand. Back in the bad ol' days, some cheap equipment did have filter capacitors that big. This would overly stress the power diodes, however, it was assumed that you could just hop on down to the corner 7 - 11 and get a new one, and hope that the untech savvy customer wouldn't notice that his PS diodes were going bad too soon.

Since VTs aren't so easy to get, it pays to work them within the specs. Can't do that running them into such big filter capacitors.

Either go solid state, or use a ripple filter to clean up the AC mess.
__________________
There are no foxes in atheistholes
www.dolphin-hsl.com
  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
Tube PSU question Greyskale Power Supplies 8 27th February 2008 09:06 AM
What can I do with these? (tube and OPT question) needtubes Tubes / Valves 7 8th March 2005 01:01 PM
WE old tube question filippo22 Tubes / Valves 6 26th December 2003 07:26 PM
Tube Question, what the....? Rino odorico Tubes / Valves 15 11th November 2002 09:14 PM
Tube CAD Question Aud_Mot Tubes / Valves 0 6th October 2002 03:53 AM


New To Site? Need Help?

All times are GMT. The time now is 03:36 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