The AM Forum

hello all :)

I'm wondering if someone that has completed the level II audio mods from K6AD can help me. I'm confused on some of the capacitors values.

1) the cap labeled 390 across the transformer driving the two 807 is this 390uf, .390uf, .390pf, or 390pf? Also no polarity is given making me think that this is a film or ceramic cap. no voltage is given. 

2) Same problem as in question one the cap labeled 62 to ground off of pin five of V2.

Thanks all  ;D     

Which Mod and which Schematic?

There are dozens out there, some good, some bad.

Phil - AC0OB

Hi Phil

This is the Level II mods in the Electric Radio magazine from k6ad. Number 110,111,112 in electric radio.

I don't have those issues of ER (I do write articles for them) but I suspect those are 390 pF ceramic rated at 1kV.

Phil - AC0OB

I'm looking at the schematic. Looks like a 390pf in series with a 330 ohm resistor across the grids/secondary of the driver transformer of the 807s.

I don't see the other cap you mentioned labelled 62 off pin5 of V2 to ground.

Al VE3AJM

Hi Al

Yeah I think is a 390pf ceramic also....The diagram your looking at is for the Level I mod however the 390 cap is the same. The .33 to ground in your diagram was changed to a 62 something in the level II mod. 

I'll have a look at the later Mod 2.

Al

Thanks Al .... its in the book #111

Looks like 62pf 1kv rated at least.

Al VE3AJM

Thanks!! should I use mica or ceramic .... probably don't matter?

Either type with the suitable voltage rating. Use what you have on hand or can get easy access to I would say. Cool mod for the Viking 2.

Al VE3AJM

Ok Great!!!!

Thank you Al and Phil!!!!

It appears the 20k resistor across the secondary is a "damper" to dampen out transients and to load the secondary.

The series 330 ohm resistor and 390 pF cap has a -3dB point at 1.2 MHz to "snub" any transients with frequencies from 1.2MHz on up.

Phil - AC0OB