Pumpkin preamp - ordered by Steen , official making thread

[Zen Mod]

Hi Tony 😉

easy peasy , for 2SJ109, matching by Idss :

source and gate to +9 (max 12V)

drain to mA meter red probe

mA meter black probe to gnd

 

[tonimxp]

Hi Tony 😉

easy peasy , for 2SJ109, matching by Idss :

source and gate to +9 (max 12V)

drain to mA meter red probe

mA meter black probe to gnd

Hi Alex i have just tried and the results with 9v power voltage are this :

1° 2sj109 91/92 mA

2° 2sj109 53,5/53,5 mA

Please what do you think about different idss betwen 1° and 2° jfet?

I also have four 2sj74 bl 6g and i tried with same idss matching method.
the results are this:

1° 2sj74 10,10mA
2° 2sj74 10,10mA
3° 2sj74 10,04mA
4° 2sj74 10,07mA

Please can you advise me what to use for your Aleph J Babbelfish?

Thanks in advance

 

[Zen Mod]

they're fakes

according to 2SJ109 datasheet , there are 3 groups of Idss for exactly same test setup :

GR , BL , and V

if you made test as I wrote ( see enclosed sketch) , they're fakes without doubts

look at 2Sj74 side , presume that Rs is zero , for your case of measuring (full) Idss

http://jm.plantefeve.pagesperso-orange.fr/2SJ109.pdf

 

[tonimxp]

they're fakes

according to 2SJ109 datasheet , there are 3 groups of Idss for exactly same test setup :

GR , BL , and V

if you made test as I wrote ( see enclosed sketch) , they're fakes without doubts

look at 2Sj74 side , presume that Rs is zero , for your case of measuring (full) Idss

http://jm.plantefeve.pagesperso-orange.fr/2SJ109.pdf

Yes my Rs is zero and my type are BL ,so...what should be the correct IDSS (if they were genuine) in my case, with 9V and without Rs?

 

[Zen Mod]

see picture above

6 to 12mA

 

[tonimxp]

see picture above

6 to 12mA

I have to open a dispute on ebay, please with what voltage value (with my set up measurement) should get from -6 mA to-12mA Idss?

 

[Zen Mod]

as I said already - in range of 9 to 12V

what you got are probably re-labelled bjt's

 

[tonimxp]

as I said already - in range of 9 to 12V

what you got are probably re-labelled bjt's

thanks Alex

 

[tonimxp]

So...about my four 2sj74 bl 6g

1° 2sj74 10,10mA
2° 2sj74 10,10mA
3° 2sj74 10,04mA
4° 2sj74 10,07mA

Are they ok to use for your Aleph J Babbelfish?

And about my post n°3420 of this tread what do you think?

For 2sj310 (Q1 and Q2) of Pumpkin i have found those values of Vgs:

180-184-(187-188)-(193-196) mV so i have match as in parenthesis.
The current draw is set to 5mA for five minutes test time.

I have to ask you your comments for results.




Thanks in advance
🙂

 

[Zen Mod]

So...about my four 2sj74 bl 6g

1° 2sj74 10,10mA
2° 2sj74 10,10mA
3° 2sj74 10,04mA
4° 2sj74 10,07mA

Are they ok to use for your Aleph J Babbelfish?

perfect 😉

just take care of pinout

......
And about my post n°3420 of this tread what do you think?

For 2sj310 (Q1 and Q2) of Pumpkin i have found those values of Vgs:

180-184-(187-188)-(193-196) mV so i have match as in parenthesis.
The current draw is set to 5mA for five minutes test time.

I have to ask you your comments for results.




Thanks in advance
🙂

they're good , of course

attached pic - view from top (as a bird ....... or Batman 😉 )

 

[tonimxp]

perfect 😉

just take care of pinout




they're good , of course

attached pic - view from top (as a bird ....... or Batman 😉 )

Good Morning Alex and...many...many thanks,also for Batman and his view on from the sky😀

 

[tonimxp]

Shunty little poblem/curiosity

Hi for everybody and merry chrystmas!
I need to know if this 25Mhz 7Vrms (see pictures attached) found out from my shunty is normal or not.
Have you tried to do an analysis of the output voltage of your shunty?
I believe however that should not be a problem ,but it would be interesting to ask what can be generated by this high frequency and if is possible somehow solve this little problem..🙄
Thanks

Antonio

 

[Zen Mod]

my specimens were dead silent , also confirmed in AR2's small DIY lab

what type of output (final) caps are you having ?

for test - try snubber RC cell across them

say 1uF and 15R in series

 

[Zen Mod]

put 1nF between B and C on BDX

one of "problems" is that mine (BDX-es) are genuine from yore times

 

[tonimxp]

I have a BC Philips brand,so... i have to put a 1uF and 15R in series between the legs of C14 and C14A?
Or a have to

put 1nF between B and C on BDX-es

Or both?

Your quote:

"one of "problems" is that mine (BDX-es) are genuine from yore times"

Sorry i didn't understand🙁 which means!🙂

But....this spurious frequency may cause problems or not on the quality sound of the preamp?

Thanks!

Sorry my mistake the spurious is 25Mhz 7mVrms [/B]and NOT 7Vrms

my specimens were dead silent , also confirmed in AR2's small DIY lab

what type of output (final) caps are you having ?

for test - try snubber RC cell across them

say 1uF and 15R in series

 

[Zen Mod]

I have a BC Philips brand,so... i have to put a 1uF and 15R in series between the legs of C14 and C14A?
Or a have to

put 1nF between B and C on BDX-es

Or both?

....[/COLOR]

both

........
Your quote:

"one of "problems" is that mine (BDX-es) are genuine from yore times"

Sorry i didn't understand🙁 which means!🙂

.......[/COLOR]

that means - during development and in first specimens I had genuine parts from old stash ; especially BDX transistors - being darlington , their quality is crucial ; problem is "problem" , meaning that I didn't checked functionality of Shunty with less than optimal parts ; less optimal - meaning not so good BDX ( fluffy production or even fake)

.......

But....this spurious frequency may cause problems or not on the quality sound of the preamp?

Thanks!

Sorry my mistake the spurious is 25Mhz 7mVrms [/B]and NOT 7Vrms

7mV is big difference from 7V

it will probably not change much in preamp function , but there is also possibility that oscillation is result of dirty surround (regarding RF) and suboptimal test setup

those dummy load resistors are pretty big ; try to connect satellite dish to them .....

 

[tonimxp]

Alex as you know i'm a policeman and i have to find the rot in everything I do but I must say that you are a great man!🙂
I solved putting 1nF between B and C on BDX-es only!
Now the shunty is ok on all range of frequency, absolutly silent as a grave!
Alex please,have you tell me that i need to change the BDX yet or it is irrilevante now ,and have you some other advice for me?

Thanks again Alex!

 

[tonimxp]

Other Mistake😡sorry i'm tired

Solved putting 1uF end not 1nF between B and C on BDX-es only!

Thanks!

 

[Zen Mod]

Other Mistake😡sorry i'm tired

Solved putting 1uF end not 1nF between B and C on BDX-es only!

Thanks!

please - try decreasing that ....... leave smallest value which is curing oscillation
1uF is way too much

........ is irrilevante now ,and have you some other advice for me?

......

if cap cures that , of course that is irrilevante (oh , boy ,Io adoro lingua italiana 😉 ) .........

advice - turn of that soldering tool , and start with Vino ......

 

[tonimxp]

Alex as I said now shunty is perfect! Why to change again, in my city there is a proverb "Never change a winning team." But you are the "Boss"......so . if you want ,please tell me what value and type of capacitor i should use and I will do.🙂

About Vino.........

Barolo..Montepulciano....Nebbiolo....or my prefered NEGRAMARO (land of Puglia where i'm born).Don't forget that if you come at Malpensa aerport ,let me know,becouse i work here and i will pleasure to meet you and give you a bottle di Negramaro.🙂

please - try decreasing that ....... leave smallest value which is curing oscillation
1uF is way too much






if cap cures that , of course that is irrilevante (oh , boy ,Io adoro lingua italiana 😉 ) .........

advice - turn of that soldering tool , and start with Vino ......