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 12th February 2019, 09:11 AM   #461
Zen Mod is online now 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
I know indra , solution per se (as we already know) elegant and effective , but puzzling is what is culprit of hysteric behavior of dB's amp ........ and both channels the same

for now , I found just two minor changes ocassionaly needed - increasing either R18 or P2 (will send 20K in future) for proper offset , and decrease of R3 , to lower turn on current surge in buffer when using Borbely WCF

all other problems happened, were due to operator frenzy

name it ....... whatever you can and can't imagine : rotated opto , rotated 7805, mixed places of BD critters , too much diodes mounted , Cinemag pushed in pads for Jensen , mixed trimpots....

though , Greedy Boyz are still much more clever , than I was making my 3rd , 4th or 5th amp .......
__________________
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

Last edited by Zen Mod; 12th February 2019 at 09:15 AM.
  Reply With Quote
Old 12th February 2019, 09:58 AM   #462
indra1 is offline indra1  Indonesia
diyAudio Member
 
Join Date: Nov 2010
Location: Bogor
Ookidoki.
  Reply With Quote
Old 12th February 2019, 10:03 AM   #463
Zen Mod is online now 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
forgot to say - agree about gate leakage , thought about that but somehow (silly , dumb , old?) didn't mention ........ probably looking for something "more" drastic

dB - care to measure - DVM on mVdc range - across gate resistor of SITs ?
__________________
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, 04:02 PM   #464
dBel84 is offline dBel84  United States
diyAudio Member
 
Join Date: Jul 2006
Location: midwest USA ~ WI
"dB - care to measure - DVM on mVdc range - across gate resistor of SITs ?"

will do - R21 only or include the flying resistor too ?

"puzzling is what is culprit of hysteric behavior of dB's amp ........ and both channels the same"
"all other problems happened, were due to operator frenzy"


greedy idiot I may be in the end - the symmetry is what puzzles me too , I must be a very good idiot and reliably did the same thing on both sides

Quote:
Originally Posted by indra1 View Post
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.
I will grab a bunch of measurements to help try and clarify the electrical behaviour of the amp.

Last night I was able to use P1 to crank up the bias easily to 2.4 A at 19.7V on the rails. I wanted to make sure that P1 was still functioning in one direction at least - I could then again easily lower it back down to 1.8A which is the lowest it would go with that Rail voltage.

"High line voltage? Mislabeled donuts?"

?? I have used Avel Lindberg transformers many times without issue - they are clearly well matched as both channels are the same . I will measure the line voltage but it is normally around 120VAC without much fluctuation - the grid where I live is pretty good.

Avel rates their primaries at 115V ( Primaries: 115V + 115V. Frequency: 50/60 Hz ) That might explain the slight bump



thanks for all the input to try and help me resolve this - truly appreciated.

..dB
  Reply With Quote
Old 12th February 2019, 04:47 PM   #465
indra1 is offline indra1  Indonesia
diyAudio Member
 
Join Date: Nov 2010
Location: Bogor
Quote:
Originally Posted by dBel84 View Post
...I have used Avel Lindberg transformers many times without issue - they are clearly well matched as both channels are the same ...
We were wondering for the reason you have 25.4v rail, too high for a 18V winding loaded at 2A+. On regular Mosfets and bipolars, a bit higher rail only means a bit higher dissipation, but Iq of VFET is a function of supply voltage, at a certain rail voltage the biasing opto hits minimum Vce and no longer able to regulate.
  Reply With Quote
Old 12th February 2019, 04:55 PM   #466
flocchini is online now flocchini  United States
diyAudio Member
 
Join Date: Feb 2004
Location: Davis,CA
Donald

Just checked my M2 with Toshibas - I get 21V with a 1.8A draw.

Does your M2x use the same supply? or do you have a separate supply for it?
What does it measure?

Hope that helps

Bob
  Reply With Quote
Old 12th February 2019, 06:04 PM   #467
dBel84 is offline dBel84  United States
diyAudio Member
 
Join Date: Jul 2006
Location: midwest USA ~ WI
Hi Bob - I built my M2X with SMPS supplies - so no comparison unfortunately.

I cannot recall the unloaded voltage but I think it was close to what I am getting which means that under load, the voltage is not sagging

18VAC x 1.414 = 25.4V DC = this is the exact line voltage I am getting with a full load which perhaps speaks to the quality of the regulation of the Avel transformers

- I should have gone with smaller / cheaper transformers 15+15 which would have yielded rail voltages of 21.21VDC - this might be the easier solution ultimately if we do not find the problem with my build.

..dB
  Reply With Quote
Old 12th February 2019, 06:27 PM   #468
flocchini is online now flocchini  United States
diyAudio Member
 
Join Date: Feb 2004
Location: Davis,CA
Donald

Any way to try your SMPS supply?


Best

Bob
  Reply With Quote
Old 12th February 2019, 10:13 PM   #469
Zen Mod is online now 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
Quote:
Originally Posted by dBel84 View Post
Hi Bob - I built my M2X with SMPS supplies - so no comparison unfortunately.

I cannot recall the unloaded voltage but I think it was close to what I am getting which means that under load, the voltage is not sagging

18VAC x 1.414 = 25.4V DC = this is the exact line voltage I am getting with a full load which perhaps speaks to the quality of the regulation of the Avel transformers

- I should have gone with smaller / cheaper transformers 15+15 which would have yielded rail voltages of 21.21VDC - this might be the easier solution ultimately if we do not find the problem with my build.

..dB
that's having nothing with Donut regulation

effective DC voltage is matter of rectifier and filter (cap bank ) not Donut voltage up and down

what we are interested in is - exact AC voltage at defined load and resulting DC at same defined load

so , please check that and write here

btw. silly question - your DVM is trustworthy > battery state OK and non-suspicious?

and another one - where ( on which position) you're monitoring Iq .... can't remember that you mentioned in-rail 0R1 , so it must be R in CRC ?
__________________
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 13th February 2019, 12:56 AM   #470
flocchini is online now flocchini  United States
diyAudio Member
 
Join Date: Feb 2004
Location: Davis,CA
"btw. silly question - your DVM is trustworthy > battery state OK and non-suspicious?"

not so silly - a year ago I had a old Fluke do some strange things - replaced the battery - problems continued - it wasn't worth the cost they wanted to repair it - buried the meter - using different one - all is good

point is that I went down the wrong path because of not checking the basics
  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 13 14th March 2019 02:58 AM
PCB tips and tricks - Part 4 AndersHa Construction Tips 5 28th March 2016 11:26 PM
How To Solder Tips and Tricks Eddiegnz1 Tubes / Valves 21 20th December 2013 09:52 AM
Tube Tips/Tricks for beginners SamK2012 Tubes / Valves 10 19th November 2012 12:12 PM
Couple of tips/tricks peace brainerd Everything Else 0 10th April 2006 03:57 PM


New To Site? Need Help?

All times are GMT. The time now is 01:46 PM.


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