Model Paint Tool - Painting new spice models

[MarekH]

I just had a go at downloading Dmitry's paint kit and painted a model for a 3b7 using the datasheet as a model.

It is very easy to get straight into the right ball park but deceptively difficult to decide on the best parameters for a good plot.

For a 3b7 (I couldn't find a spice model here or elsewhere online) I have come up with

MU 19.53
KG1 1885
KP 664.85
KVB 234.06
VCT -0.6372
EX 1.194

This looks like a good fit between 0 and -6v grid lines but diverges at +2v and -8v

Can someone with more experience of painting curves cast an eye on this and suggest strategies for improving this or is this attempt typical of what is achievable?

kind regards
Marek

 

[mashaffer]

Is this software for triodes only? It would be extremely useful if it worked with pentodes.

 

[bOTL]

I just had a go at downloading Dimitri's paint kit and painted a model for a 3b7 using the datasheet as a model.

It is very easy to get straight into the right ball park but deceptively difficult to decide on the best parameters for a good plot.

For a 3b7 (I couldn't find a spice model here or elsewhere online) I have come up with

MU 19.53
KG1 1885
KP 664.85
KVB 234.06
VCT -0.6372
EX 1.194

This looks like a good fit between 0 and -6v grid lines but diverges at +2v and -8v

Can someone with more experience of painting curves cast an eye on this and suggest strategies for improving this or is this attempt typical of what is achievable?

kind regards
Marek

Where can I download the Paint Kit ?
Thanks

 

[MarekH]

The web page is at Model Paint Tools: Trace Tube Parameters over Plate Curves, Interactively

Another attempt:-
MU 20.48
KG1 2661.75
KP 288
KVB 45 to 59
VCT -0.225
EX 1.316

kind regards
Marek

 

[Koonw]

Very close to mine. I usually adjust Mu so that the lowest and highest curve is mostly coincides with data curve. Adjust Ex for interspacing between plots, KG1 for angle, these 3 are mostly used to make the curve fit, I get the following:

**** 3B7 ******************************************
* Created on 07/12/2018 05:08 using paint_kit.jar 3.0 
* [url=http://www.dmitrynizh.com/tubeparams_image.htm]Model Paint Tools: Trace Tube Parameters over Plate Curves, Interactively[/url]
* Plate Curves image file: 3b7.png
* Data source link: 
*----------------------------------------------------------------------------------
.SUBCKT TRIODE_3B7 1 2 3 ; Plate Grid Cathode
+ PARAMS: CCG=1.4P  CGP=2.6P CCP=1.8P RGI=2000
+ MU=20.8 KG1=3037.2 KP=370.8 KVB=210 VCT=0 EX=1.37 
* Vp_MAX=300 Ip_MAX=15 Vg_step=1 Vg_start=2 Vg_count=11
* Rp=4000 Vg_ac=55 P_max=2.7 Vg_qui=-48 Vp_qui=300
* X_MIN=142 Y_MIN=51 X_SIZE=575 Y_SIZE=575 FSZ_X=1295 FSZ_Y=735 XYGrid=false
* showLoadLine=n showIp=y isDHT=n isPP=n isAsymPP=n showDissipLimit=y 
* showIg1=n gridLevel2=n isInputSnapped=n  
* XYProjections=n harmonicPlot=n harmonics=y
*----------------------------------------------------------------------------------
E1 7 0 VALUE={V(1,3)/KP*LOG(1+EXP(KP*(1/MU+(VCT+V(2,3))/SQRT(KVB+V(1,3)*V(1,3)))))} 
RE1 7 0 1G  ; TO AVOID FLOATING NODES
G1 1 3 VALUE={(PWR(V(7),EX)+PWRS(V(7),EX))/KG1} 
RCP 1 3 1G   ; TO AVOID FLOATING NODES
C1 2 3 {CCG} ; CATHODE-GRID 
C2 2 1 {CGP} ; GRID=PLATE 
C3 1 3 {CCP} ; CATHODE-PLATE 
D3 5 3 DX ; POSITIVE GRID CURRENT 
R1 2 5 {RGI} ; POSITIVE GRID CURRENT 
.MODEL DX D(IS=1N RS=1 CJO=10PF TT=1N) 
.ENDS 
*$