SemiSouth power Jfets .......... FW J2

[sp300b]

Ma nist ti ne verujem...dok to Sloba ne sastavi i protrese.

Tek onda pravim.

Sinc(o), hvala na poverenju, i da ti kaže Sinc(o), pravi slobodno.

[Sync]

Hocu..Tek sam prosli vikend prepravio babela na dual mono. Znao sam da ce biti bolje...al bas ovoliko. Milina je povuci prekidac a da to proprati apsolutna tisina. Za klasu bolji uredjaj u zvuku...pogotovo kad nema zujkana koji probija do zvucnika.

[sp300b]

Hocu..

Tek sam prosli vikend prepravio babela na dual mono. Znao sam da ce biti bolje...al bas ovoliko.

Milina je povuci prekidac a da to proprati apsolutna tisina. Za klasu bolji uredjaj u zvuku...pogotovo kad nema zujkana koji probija do zvucnika.

Milo mi jako, dakle Dual Mono

[Tea-Bag]

So after soldering out all transistors, replacing all new one's - using a brand name solder - swapped out all the caps - the second channel runs ! I have to blame Gerd for slapping me around off thread to get me moving on this.I suspect that the components were fine, just a marginal solder joint somewhere.With default resistors, 470R runs 9.4 , Source resistors run about .86v like channel one. offset is below .03v R12 and R25 like to run near 0R to keep offset the best. I will play with this more tommorow to bring the juice up if possible, although it did not seem to budge much after several turns.It looks sp300b has changed at least one of the 12k resistors to 4.7k. I also have to re-read a bit here as I believe swapping 220R resistors for 180R (I may have done that in other channel, it's been so long), may benefit bias procedure.Anyways, I am happy it's playing music. I will do my best to get it presentable in a chassis soon for some main speaker listening.

[Zen Mod]

[sp300b]

:cheers:p.s. I've changed all Three 12K resistors to 4K7.

[Zen Mod]

nice ....

[Zen Mod]

so - Generg - ...... what's up , Dude ?working on something interesting now ?

[Zen Mod]

so - let change of 3 resistor values from 12K to 4K7 be official

just in case - quote from one of previous posts - first power up procedure :

PSU - biggie Donut via Variac ,Graetz , 2x33mF Spragues

R9 in ( factory preset) mid position , R12 and R25 on min/short position

voltmeter on output for offset ; goal is zero

voltmeter across any 1R source(drain) resistor ; goal is 1V for 2A Iq

both inputs grounded

fired up , due to cascodes in front LTP everything came to life at approx +/-15Vdc

Iq around 1A5 , offset around 350mV

up with PSU at approx +/-18Vdc

check and set voltage across R3 to 9V4 ( that's 20mA through LTP)

fiddle with R12 - offset to zero

Variac - full PSU voltage +/-22V5

again R12 - offset zero

R25 - fiddle .. go to (preferably )1V across 1R ; everything in range of 750-1000mV is fine

done;

edit : schm deleted by ZM

[generg]

Hi Zen Mod, :Viannen_loungelizard: I feel fine, I build up very slowly Babelshark J2 boards you sent me in your generosity......! I am building very slowly to make no faults and to enjoy this building with the feeling to have something extraordinary......why should I change to 4,7k ? Is there less heat in Q7/8?? I have to do it now, because I just do these part. As to the preamp problem, I tried Aleph P with Semisouth R550 but there was no significant change.... but ZVN3310 did a good job! He could stay! The buffers must wait, first Babelfish!You suggested to change J103 in Pumpkin for a complementary pair?Hi tea-bag, happy to hear you are ready with the second channel, so I am eagerly waiting for hearing impressions from you and sp300b! :baklja:

[Zen Mod]

....... in your generosity......!

.....

wakoo Schwäb ......

why should I change to 4,7k ? Is there less heat in Q7/8?? I have to do it now, because I just do these part.

.....

more control current for both CCS-es ( input one and one for biasing of upper Jfet )

I have proper parameters with 12K triple and BC556B-s , but seems that sp300b have problem using BC560-s

so - this way - every control bjt is having ~3,3mA through ; that means - plenty of control current , what means more stability

You suggested to change J103 in Pumpkin for a complementary pair?

.....

your typo

I presume that you have few 2SK170BL around ?

try them instead of J310-s , as core LTP in Pumpkin

or 2SK369BL ...... if you have them ....

[Zen Mod]

motor city is burning ......... MF!!!!630 posts/43 pages !

[Tea-Bag]

I am able to bias it up to .910v no problem, and offset seems approachable.I am using BC560c - all I can seem to find @ digikey, I get around .61-62v there, okay, but 4.7k won't be big change.I put on the 13v protection diodes as well, mounted them on top. Have surgery next week (gall bladder gone ) hopefully I will be able to crap normally after that. :bathroom: So I don't think it will move into full system soon. Unless I get some duct tape and plywood like sp300. Which is a solid possibility.Still lots of work outside to do --- Snow is coming! Got all kinds of crap outside my house lying around, keeping up the white trash persona. Got to move it in to keep wife happy.

[Zen Mod]

.......

good luck with health issues ;get back soon , able to sit down

[sp300b]

Very nice. Glad to hear some other J2 ongoing well.I'll wait some MOX resistors 1/3W to come (santa claus have promised) and then it will go to Babel box instead the babel PCBs.And then will be totally and time for me to and

[Zen Mod]

spwill ya send me eagle files for ( if I remember correctly that you started something ) our Babelfish UGS ?

[Daudio]

Very nice. ........

Today I looked into a SP cellar....short beautiful.I wait for the final court finals.

[Zen Mod]

[sp300b]

spwill ya send me eagle files for ( if I remember correctly that you started something ) our Babelfish UGS ?

No

[sp300b]

Today I looked into a SP cellar....short beautiful.I wait for the final court finals.

Thanks for the Test loudspeakers

[Zen Mod]

No

[Zen Mod]

Thanks for the Test loudspeakers

any listening today ?