Babelfish ᄅſ....or FW J2 on Steroids .... or Not your Father's J2!

[coolnose]

Late to the party as usual, but the boards are finally soldered up and waiting.

I'd like to put to use a 500VA 2x22V transformer, any issues other than maybe having to lower the bias depending on heatsinks ?

Thanks

 

[Zen Mod]

exactly as you wrote

 

[ItsAllInMyHead]

Late to the party as usual, but the boards are finally soldered up and waiting.

Thanks

Fantastic! 😀

 

[Zen Mod]

this J2 is for Sissies

 

[coolnose]

Fantastic! 😀

Yeah... I wonder if "procrastination" is recognized as a mental disease in my country....

 

[bajjisw]

It has been a while since I got the boards (Thanks ZM). Iron Pre is singing joyfully, this is next.

Looking at boards, am I understanding the NTC board correctly? If used for 2 transformers (with a single primary each), It seems to be setup for 1 NTC per transformer.

My transformers have 2 parallel 110V primaries each. I have 2 of these (antek AS-1218), to use one per channel. I am familiar with 2 NTC per transformer (1 per primary). By (functionally) renaming terminals I can use this for 1 transformer.

Is there a more elegant solution ?

Thanks

 

[Zen Mod]

that's obviously my omission - making them for my neck of wood, for 2 Donuts, and not counting on fact that in your neck of wood it's good for just one

send me an e-mail , reminding me what's in question, and I'll send you another small NTC pcb, so you'll have it neat

 

[bajjisw]

that's obviously my omission - making them for my neck of wood, for 2 Donuts, and not counting on fact that in your neck of wood it's good for just one

send me an e-mail , reminding me what's in question, and I'll send you another small NTC pcb, so you'll have it neat

Thank you, and also for the quick reply.

 

[jwjarch]

Mighty ZM. When matching 2sk2145 devices do you only match fet to fet or does each side of each fet need to be matched?

 

[Zen Mod]

as you see from schematic, I'm using each 2SK2145BL as single JFet

so , testing one tiny bugger as simple device, two of them inside being connected in parallel

so, 4 of them in LTP, nice quartet , practically being octet

as seen in second picture in post #3

 

[jwjarch]

Thanks ZM. I won’t pull what’s left of my hair out trying to match both sides on top of every package. 😱

 

[Zen Mod]

my hair grew of constant pulling

 

[bajjisw]

LEDs

In the spirit of asking first before doing, how do I orient LEDs? I tried looking here and elsewhere.

Is the small mark - or + ?

Thanks

 

[jwjarch]

Bajjisw, I believe the small mark on the board is a C for cathode, is it not ZM?

 

[Zen Mod]

oh yeaah

'twas my attempt to be smarter than Eagle, which is not having C mark for Cathode

so, there it is ..... it took me just few years to finally understand how to edit existing and make new packages

Whoa, Blue Car! .......... I even made my own for 2SK77B and for Mos-pucks

 

[bajjisw]

Many thanks

 

[mattattnet]

chart of voltages for Babelfish J2

I am trying to fire up my amp, but am not able to get current through the power fets.

Rails are about 24 VDC plus and minus, separate dual mono supplies.

I am using IRFP150 in both the M102 and M103 positions.

All parts are as called out by ZM.

The led's all light fine, the offset can be adjusted no problem.

When I adjust P102, however, nothing happens, with only about 20 mV across either R133 or R136, and minimal current across any of the power resistors.

It is acting the same in both the right and left channel when they were tested separately.

Does anyone have schematics with expected voltages, so I can do some trouble shooting in the optoisolator CCS, bias and emiter follower areas, especially.

thanks

 

[Zen Mod]

it's late now in my neck of wood and I'm sleepy

will be back to you tomorrow

in a meantime , check notes in schematic , what appropriate values of few resistor positions are for all IRFP iteration

 

[mattattnet]

thanks, ZM

I have the jumpers where they are supposed to be, the correct value R110 and R114 for the 4 jefts, and confirmed the 1R0, 0r47, and 0R68 power resistors are in the right places for IRFP150 power mosfets.

 

[Zen Mod]

here is , some guidance for you