Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Pass Labs This forum is dedicated to Pass Labs discussion.

Babelfish M25, SissySIT - general building tips and tricks
Babelfish M25, SissySIT - general building tips and tricks
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 11th February 2019, 12:48 PM   #451
dBel84 is offline dBel84  United States
diyAudio Member
 
Join Date: Jul 2006
Location: midwest USA ~ WI
Quote:
Originally Posted by indra1 View Post
Can you measure supply voltages at the boards? You may have THS with a bit higher mu so that a bit higher supply voltage results in very high Iq.
Transformers are 18+18 (dual mono) and rails measure 25.4V all round

.. dB
  Reply With Quote
Old 11th February 2019, 01:46 PM   #452
indra1 is online now indra1  Indonesia
diyAudio Member
 
Join Date: Nov 2010
Location: Bogor
25.4v loaded at 2.5A is pretty high. If the THS you have are high mu, lowering supply voltage using a variac or a series resistor will allow you to set Iq to lower value. If my suspicion is verified then you have 2 options, use reduced supply voltage or use more suitable pair of THS.
  Reply With Quote
Old 11th February 2019, 02:00 PM   #453
dBel84 is offline dBel84  United States
diyAudio Member
 
Join Date: Jul 2006
Location: midwest USA ~ WI
Thanks. Will try this.. dB
  Reply With Quote
Old 11th February 2019, 04:43 PM   #454
Russellc is offline Russellc  United States
diyAudio Member
 
Join Date: Mar 2003
Location: midwest
Babelfish M25, SissySIT - general building tips and tricks
Quote:
Originally Posted by indra1 View Post
25.4v loaded at 2.5A is pretty high. If the THS you have are high mu, lowering supply voltage using a variac or a series resistor will allow you to set Iq to lower value. If my suspicion is verified then you have 2 options, use reduced supply voltage or use more suitable pair of THS.
Sorry to be thick, how does one know if they have high my SITs? Only parameter I know is that mine from Prass say 2.96 and 2.97 and I don't want to fry them!

Thanks,

Russellc
__________________
Pass B-1 preamp, Pass BA3 preamp, Pass F-5 Amp, Pass F-6 Amp, Pass BA-3 Amp, Pass M-2 amp, Pass Aleph J amp, Pass Pearl 2 Phono pre Tekton Enzo, Altec A7, Econowave JBL 2235H & B&C CD
  Reply With Quote
Old 11th February 2019, 05:08 PM   #455
chromenuts is offline chromenuts  United States
diyAudio Member
 
Join Date: Dec 2008
Quote:
Originally Posted by dBel84 View Post
I passed along my spare set , so was hoping not to have to buy again
If you need them back just let me know and weíll work something out. I still have the other two pair that I got from watanabetomoaki. Havenít measured any, just hoarded most everything Iíll need for the Sissy.

To be honest, Iím going to finish the F2J I started before I start the Sissy and play with some iron in my DCB1 while ZM puts together my Iron Pumpkin Xmas present that I bought myself.

I keep saying it...Iím almost finished with my dipole bass project and am excited to set it up with the B4 and Oris horns.
  Reply With Quote
Old 11th February 2019, 05:29 PM   #456
indra1 is online now indra1  Indonesia
diyAudio Member
 
Join Date: Nov 2010
Location: Bogor
Quote:
Originally Posted by Russellc View Post
Sorry to be thick, how does one know if they have high my SITs? Only parameter I know is that mine from Prass say 2.96 and 2.97 and I don't want to fry them!...
You'll need a curve tracer for that. But don't worry, use 22-23V supply and adequate heatsink, you won't fry them, they are tough beasts. Regulated supply is recommended for SITs when line voltage supply varies more than 5% or if you try to push things close to the limit.
  Reply With Quote
Old 12th February 2019, 04:28 AM   #457
dBel84 is offline dBel84  United States
diyAudio Member
 
Join Date: Jul 2006
Location: midwest USA ~ WI
well reducing the rail voltage does reduce the current - not unexpected BUT the control circuit is still not working , so I am not convinced replacing the SITs will solve the problem in my amp .

There must be something simple I am not understanding , the Iq potentiometer has the ability to increase the current , so logic tells me reducing R15 should reduce the current to enable the pot to increase it once again - but this is not the behaviour I saw previously.

I may end up burning some heat in series resistors to drop the rails to 20V which is what it takes to get 1.8A flowing.

more pondering but not tonight. thanks for the suggestion to try this.

..dB
  Reply With Quote
Old 12th February 2019, 05:22 AM   #458
indra1 is online now indra1  Indonesia
diyAudio Member
 
Join Date: Nov 2010
Location: Bogor
Quote:
Originally Posted by dBel84 View Post
There must be something simple I am not understanding , the Iq potentiometer has the ability to increase the current , so logic tells me reducing R15 should reduce the current to enable the pot to increase it once again - but this is not the behaviour I saw previously...
Not when the output of opto is saturated. Measure opto output voltage between R21 & R20 (pin 3 & 4) to verify, if voltage is < 0.5V then opto output has saturated and no longer able to regulate Iq.
Quote:
... I may end up burning some heat in series resistors to drop the rails to 20V which is what it takes to get 1.8A flowing. ...
When you are sure reducing rail voltage is the solution you want and since you have a 25.4V rail and only need to reduce supply to the THS, I would suggest a regulator instead. I think a cheap IRF540 or IRFP240 mounted on the heatsink will do the job nicely, off course bigger part has better thermal transfer property. Cut the leads between board and drain of THS and insert regulator so regulator is placed between the Hall chip and THS.
Attached Images
File Type: gif Positive Reg.gif (6.4 KB, 133 views)

Last edited by indra1; 12th February 2019 at 05:38 AM.
  Reply With Quote
Old 12th February 2019, 09:42 AM   #459
Zen Mod is offline Zen Mod  Serbia
Official Court Jester
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
Babelfish M25, SissySIT - general building tips and tricks
that's bad patch , not solving the problem

though , with rectifier etc. loaded , I'm expecting no more than Vac x 1.25

there are few volts more than that , how's that possible ?

only if donuts are 20Vac , not 18Vac

and one thing more is puzzling - how increasing both R18 and R19 is not working ?
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM
  Reply With Quote
Old 12th February 2019, 09:57 AM   #460
indra1 is online now indra1  Indonesia
diyAudio Member
 
Join Date: Nov 2010
Location: Bogor
Quote:
Originally Posted by Zen Mod View Post
that's bad patch , not solving the problem...
The patch is my adaptation of Sony VFET Pt2 to the Sissy.
Quote:
...there are few volts more than that , how's that possible ?...
High line voltage? Mislabeled donuts? Its made in China after all.
There is also a possibility of higher than average gate leakage.

Last edited by indra1; 12th February 2019 at 10:12 AM.
  Reply With Quote

Reply


Babelfish M25, SissySIT - general building tips and tricksHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
3D Modeling Tips and Tricks Patrick Bateman Multi-Way 7 15th July 2018 08:20 PM
PCB tips and tricks - Part 4 AndersHa Construction Tips 5 29th March 2016 12:26 AM
How To Solder Tips and Tricks Eddiegnz1 Tubes / Valves 21 20th December 2013 10:52 AM
Tube Tips/Tricks for beginners SamK2012 Tubes / Valves 10 19th November 2012 01:12 PM
Couple of tips/tricks peace brainerd Everything Else 0 10th April 2006 04:57 PM


New To Site? Need Help?

All times are GMT. The time now is 10:19 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki