On Thu, May 23, 2024 at 04:28 PM, n4buq wrote:
I tacked in some 51-ohm resistors in series with R4307 and R4309 which puts
the total resistance very close to 549 ohms. With that in place, I found
that, in addition to the horizontal compression when the BEAM FINDER is
working, the voltage at the collectors of Q4371/Q4356 and Q4395/Q4366 are now
very close to the values shown on the schematic. I didn't expect that.
Hi Barry,
Base voltage of Q4325 is fixed ~ 5.8V by the feedback through the amp driving the plate and the voltage divider R4374/R4382/R4384, source follower Q4381, and feedback resistor R4329.
Current through Q4321 is about 28.6mA with 499-ohm compared to 26mA with 549-ohm. This additional 2.6mA has to flow through R4329 causing 0.52V increase at emitter of Q4381. R4374/R4382/R4384 has an incremental division ratio of ~ 1/17.9. To keep things in balance output has to rise by 0.52*17.9=9.3V with the smaller resistor.
Same analysis applies to the other half.
Ozan
