Mosfet breakdown - Page 5 - diyAudio
Go Back   Home > Forums > Commercial Sector > Vendor Forums > Tubelab

Tubelab Discussion and support of Tubelab products, prototypes and experiments

Reply
 
Thread Tools Search this Thread
Old 20th March 2013, 08:03 PM   #41
rknize is offline rknize  United States
diyAudio Member
 
rknize's Avatar
 
Join Date: Feb 2009
Location: Chicagoland
Send a message via AIM to rknize Send a message via Yahoo to rknize
Well, the tube is open until it warms up. Something is tugging on the plate until the tube is warm. You have tried a different input tube, yes?
  Reply With Quote
Old 20th March 2013, 08:31 PM   #42
RuiR is offline RuiR  Portugal
diyAudio Member
 
Join Date: Dec 2011
Quote:
Originally Posted by rknize View Post
Well, the tube is open until it warms up. Something is tugging on the plate until the tube is warm. You have tried a different input tube, yes?
Yes, i have several 12AT7's and it's the same behavior

Thank's
  Reply With Quote
Old 21st March 2013, 04:31 AM   #43
rknize is offline rknize  United States
diyAudio Member
 
rknize's Avatar
 
Join Date: Feb 2009
Location: Chicagoland
Send a message via AIM to rknize Send a message via Yahoo to rknize
If my shooting-from-the-hip calculations are right, a 10k resistor (same as R14/24) in place of the CCS should give you something that roughly works. The gain will be down quite a bit, but at least it would serve as a useful test. The resistor would go across the pads for the A and K terminals. Nothing would connect to where the G terminal was.

http://ixdev.ixys.com/DataSheet/98704.pdf
  Reply With Quote
Old 21st March 2013, 08:09 PM   #44
RuiR is offline RuiR  Portugal
diyAudio Member
 
Join Date: Dec 2011
Quote:
Originally Posted by rknize View Post
If my shooting-from-the-hip calculations are right, a 10k resistor (same as R14/24) in place of the CCS should give you something that roughly works. The gain will be down quite a bit, but at least it would serve as a useful test. The resistor would go across the pads for the A and K terminals. Nothing would connect to where the G terminal was.

Thanks

Can i test it only in one channel? I have a 1,1 and a 9,1Kohms resistors which will gave in series 10.2Kohms

One question though, how the 12AT7 will be feed? B+ will at R14/R24

http://ixdev.ixys.com/DataSheet/98704.pdf
  Reply With Quote
Old 21st March 2013, 10:19 PM   #45
rknize is offline rknize  United States
diyAudio Member
 
rknize's Avatar
 
Join Date: Feb 2009
Location: Chicagoland
Send a message via AIM to rknize Send a message via Yahoo to rknize
That's what the new resistor is for. It will go between R14/24 and R13/23 in place of the CCS. The plate will be fed by the chain of 3 resistors now in series.
  Reply With Quote
Old 22nd March 2013, 08:50 AM   #46
RuiR is offline RuiR  Portugal
diyAudio Member
 
Join Date: Dec 2011
Quote:
Originally Posted by rknize View Post
That's what the new resistor is for. It will go between R14/24 and R13/23 in place of the CCS. The plate will be fed by the chain of 3 resistors now in series.
Ohhh "A" and "K" Yes i understand it. I will do it soon and post the results.

Once again thank you
  Reply With Quote
Old 22nd March 2013, 04:13 PM   #47
RuiR is offline RuiR  Portugal
diyAudio Member
 
Join Date: Dec 2011
Quote:
Originally Posted by rknize View Post
If my shooting-from-the-hip calculations are right, a 10k resistor (same as R14/24) in place of the CCS should give you something that roughly works. The gain will be down quite a bit, but at least it would serve as a useful test. The resistor would go across the pads for the A and K terminals. Nothing would connect to where the G terminal was.

http://ixdev.ixys.com/DataSheet/98704.pdf
Done it Russ.

I end with a B+ ~460VDC, ~350VDC after R14 and ~250VDC 12AT7 plate

It's the mosfet right?

The 10M45S have this characteristic: "Instantaneously reacting resetable
fuses" Does he shut down to protect himself from high voltages? B+ reach around 490VDC when the rectifier tube is warming up


thank you
  Reply With Quote
Old 22nd March 2013, 04:29 PM   #48
rknize is offline rknize  United States
diyAudio Member
 
rknize's Avatar
 
Join Date: Feb 2009
Location: Chicagoland
Send a message via AIM to rknize Send a message via Yahoo to rknize
Quote:
Originally Posted by RuiR View Post
Done it Russ.

I end with a B+ ~460VDC, ~350VDC after R14 and ~250VDC 12AT7 plate
~250V on the plate is about right. That channel should play music now, albeit with lower gain than it should.

Quote:
It's the mosfet right?
I don't understand this question. You are not using any MOSFETs right now, right?

Quote:
The 10M45S have this characteristic: "Instantaneously reacting resetable
fuses" Does he shut down to protect himself from high voltages? B+ reach around 490VDC when the rectifier tube is warming up
The "Instantaneously reacting resetable fuses" comment is under "applications" and not "features." They are saying that you can make a resetable fuse circuit using this part.

490VDC at startup is pretty normal. Keep in mind that at startup, the tube is cold and not drawing any current. The CCS sees no voltage across it at first because the tube is an open circuit. As the tube starts to conduct, the CCS will want to push 9mA through it so the CCS will have a very small voltage across it. As the tube reaches operating temp, the voltage across the CCS will rise until it reaches 80-100V or so.
  Reply With Quote
Old 22nd March 2013, 05:09 PM   #49
RuiR is offline RuiR  Portugal
diyAudio Member
 
Join Date: Dec 2011
Quote:
Originally Posted by rknize View Post
~250V on the plate is about right. That channel should play music now, albeit with lower gain than it should.
Yes it plays


Quote:
Originally Posted by rknize View Post
I don't understand this question. You are not using any MOSFETs right now, right?
Yes, only in one channel though. Replaced the other one with the resistor you suggested and take the readings.

I was asking if the mosfets are burn/faulty?


Quote:
Originally Posted by rknize View Post
The "Instantaneously reacting resetable fuses" comment is under "applications" and not "features." They are saying that you can make a resetable fuse circuit using this part.

490VDC at startup is pretty normal. Keep in mind that at startup, the tube is cold and not drawing any current. The CCS sees no voltage across it at first because the tube is an open circuit. As the tube starts to conduct, the CCS will want to push 9mA through it so the CCS will have a very small voltage across it. As the tube reaches operating temp, the voltage across the CCS will rise until it reaches 80-100V or so.
Ok, i understood

You are being a very good help If it play again i will baptize him with your name
  Reply With Quote
Old 22nd March 2013, 06:16 PM   #50
rknize is offline rknize  United States
diyAudio Member
 
rknize's Avatar
 
Join Date: Feb 2009
Location: Chicagoland
Send a message via AIM to rknize Send a message via Yahoo to rknize
Very simple test for a MOSFET. There are better ways using a small battery instead of the meter to charge the gate. Just Google it.

MOSFET testing

Since the resistor method is working, I am really confused about why your CCSs are failing.
  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
TO220 isolation kits breakdown tomchr Tubes / Valves 23 22nd March 2012 06:10 AM
Preventing bjt breakdown Stretto Solid State 16 27th July 2011 10:17 AM
Dynaco PAS transformer breakdown revintage Tubes / Valves 3 8th November 2010 02:15 PM
strange speaker breakdown makeb4break Multi-Way 2 29th March 2009 08:58 AM
Breakdown between solder tags? eeka chu Tubes / Valves 2 10th February 2004 09:14 PM


New To Site? Need Help?

All times are GMT. The time now is 08:47 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