Some progress.
Just now (in Italy it's 9.40 p.m.) I carefully measured the parallel R65/R68 with my Fluke 8040A, with a reading of 3.3 ohms. No good.
I carefully soldered a 3.9 ohm resistor, the only value I have, in parallel with the other two. Not a carbon composition but a metal film one, for a quick test it's enough.
Result: with +15V and the trim R90 fully clockwise the pulse appears and seems good. At +15.1 V disappears again. Sgrunt.
I think there are some other resistors out of tolerance. I'll check the whole "thing" quietly tomorrow night with great patience.
If other resistor's values are needed I will make a single order, the only place near Italy where I can buy them (carbon composition, 5% 1/4 W) at decent price is in G.B....
Otherwise I can get SMD resistors but I don't know if they are suitable. The seller (in Italy) guarantees them up to 1GHz only.
Max
