Jay Forbes's Page

"Use of a meter for aligning the IF amplifier is good for peak alignment at the narrow bandwidth position. Balancing the bandpass aprons to prevent the need to retune can be accomplished with a meter but will be difficult and time consuming. Sweep…"

"Link does not work.  Click this one:www.youtube.com/watch?v=hhyE6YBH8ws"

"Norm, I had been doing the alignment with the control in CW position instead of CCW position....  I had my customer send this pic to verify the Selective position. I realigned in the CCW position and now the control works as it should, except…"

"Retuning from broad to sharp is expected.  Vise-versa is not normal.  It is an indication that the aprons of the IF bandpass characteristic are not balanced.  However, minor retuning is not an indication of the problem you are…"

"Yes, I have to retune just a bit from broad to sharp, and vise versa.  That gain adjustment was set to max gain."

"I haven't.  There is a bias potentiometer to compensate for change in gain when adjusting selectivity although it normally reduces gain when bandwidth is increased.  Check it.  After tuning in a station in the narrow bandwidth…"

"Mike, Norm, Thanks for all the input.  I have a DC 0-50 microamp meter on order.   All IF tuner plates are secure. Due to previous repair, I still am not sure if position of the IF tuners (open/closed) is correct as I have nothing to…"

"Yes, a DC meter is required.  Make sure the meter is working (connect to 1.5-volt battery through a 100,000-ohm resistor for 15uA), make sure the meter is connected with positive to chassis, and make sure the negative side of the meter is…"

"I have tried both alignment with a wobbulator and the method posted by Norman both work. The meter needs to be dc as you are looking at the signal after the detectors and the signal here is dc, over here in the UK the nearest I could get to a 30ua…"

"This is what I was looking at for the alignment.  I used a DC mA current meter and meter did not deflect at all.  Are you SURE that a DC uA meter will work?  Or at that low current, it will also measure AC current?"

"A DC microamp meter is identified in Scott literature for monitoring AGC voltage.  At the time the service data was prepared, a microamp meter was more accessible to service shops than a vacuum tube volt meter.  A vacuum tube volt meter…"

"That's the place, it is "Early Phil sch - clean": https://drive.google.com/file/d/1pDEzCZvbTF0x-9SCse6J5Qzc-wvtrKWm/view?usp=drive_link"

"Kent, Where exactly is it located?  I looked under Scott Info Archive/Philharmonic and did not see it there..."

"I posted the early (1937) diagram this evening. Kent"