Com120B deviation meter self test fail at boot up I calibrated both gen deviation and rec deviation meter. They both work fine when checked in gen and rec. Any insight on the deviation meter check during boot up self-test would be appreciated. I'm kinda stuck where to go when the meter is working fi...

I remember IFR days at work and I have seen the RF relays replaced but if the laser trimmed resistors were burnt then the whole unit was done. N0PXJ

You need to hook up the RS-232 port on the Com/-120B back side and look at the boot log. It my or my not give clue. IIRC a bad EL560.400 will not stop the unit from booting up . You should be able to set it up to receive a local AM radio station using the Remote command set. Substitution is how I fi...

The COM-120B and C power supply The fans get there power from the +12EL display thru cr24( +12minus a diode drop). If the unit reaches hot running, thermal SW1 will connect the fans directly to the +14 supply (they speed up and run even if the unit is put in standby.) +14v thru U7 to +12voven. Both ...

*idn?
syst:sec:stat 0
cal:stat 1
cal:eeprom:opt:IFBW1"15kHz" //15khz or 12.5kHz//
cal:eeprom:opt:IFBW2"12.5kHz
This is what I used when I upgraded to 12.5 kHz filter instead of 15kHz filter. *idn? is use to check connection to COM120B

While the options are stored in the RTC memory, the cals are store in the purple Tadiran tl-5135 battery on the CPU module. If the purple battery is dead, the cals will be retrieved from the front panel controller until replaced and the unit recalibrated. IFR never made COM-120S that went above 1ghz...

Your on the right trail. Raw dc power is summed(CR10,CR11-MR502) with ext. dc, clamped(CR34-SA33a) and applied to pin 5 of U4(LT1070ct).The switched output of U4 pin4 beats on T2. The diodes from pin 4 to pin 5 of U4(CR31-1n4751)-(CR12 11DQ03) are the snubber for t2. T2 secondary is rectify by CR14(...

The 14 volt oven supply is used to charge the battery when the oven heat up current rolls off(R56-.43shunt and Q13-2N2907).Q13 will then turn on Q3(irf9540) and apply charge current to the battery thru CR16(mbr1645) blocking diode.
Carl N0PXJ

Q1 (alc amp) to U1(1na10386) to U11(MSA1105) to 8dBpad to J2 on block -8dBm output to Attenuator
Carl N0PXJ

Anybody need a used PTA for parts? good power term resistor and det.
Carl
N0PXJ

The metallized plastic switch has lost its ability to go low enough to toggle the on/off circuit in the power supply. IFR just replaced the overlay to repair this. Base Band PCBD needs washed and all the surface mount electrolyte capacitors replaced. What am I saying- all the surface mount electroly...

Short Pins 7 and 8 on the RS-232 port and then turn on for monitor mode.
Carl N0PXJ

Com-120B or Com-120A baseband board main power supply rails are at +/- 10.5 vdc. I would use 16 volt caps
Carl NØPXJ

If your COM-120A has a power supply made by CEI in Florida then I have no data on that. When CEI could not meet the production schedule and IFR pulled the production back to Wichita, I have some parts for those supplies.
Carl NØPXJ

All, COM120A/B - At this time in its long life, to settle down the erratic performance you need to replace ALL the surface mount electrolytic caps in the test set. If they have leaked then that mess will have to be addressed too. I use multi layer ceramics in there place. Rocks don't leak anything a...

Being an older post ,Comment I would caution the use of the COM-120A or COM-120B for Ham radio repair. The COM-120A/B is a frequency locked unit-not a phase locked unit and the generated carrier will sound and look wobbly out of the product detector in upper and lower SSB of the UUT. NØPXJ Aeroflex

There was no TG for 1100S