Bill, I assume you are following the instructions for complete alignment as found in LBI-3615, here: <www.repeater-builder.com/ge/lbi-library/lbi-3615d.pdf> The instructions include advice to ensure that the exciter is completely aligned first, and a reminder to allow the PA to completely warm up before starting alignment. If you have a poorly aligned exciter, the PA will be difficult to tune because its source impedance is not close to 50 ohms. Been there, done that.
One point to keep in mind is that Progress Line equipment was designed in the era of analog V-O-Ms, and a digital meter may give erroneous readings. 73, Eric Lemmon WB6FLY -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of w8wer Sent: Sunday, October 12, 2008 6:01 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] GE M/N 4EF5A1 amplifier We have used two of these amps for many years. I am trying to replace the tube (4CX250B) in one of them. This is my first time doing this. I have replaced the tube with one I think is good that was stored in the repeater. The GE instructions are typical, transmit at low power into the output of the amp, peak the grid current with Grid and Filter controls then null the grid current using the neutralizer control. The problem: after peaking the grid current with Grid and Filter, the neutralizer control will only further peak the grid current, the nulls occur at both ends of the control travel; there is a definite peak in the middle of the control range instead of a null. Any idea what would cause this condition? Bill
