R2001D not locking onto frequency

[JohnDo]

Hi Guys

I have a R2001D that will not lock on to a frequency for RX or TX. The monitor has a good 10Mhz reff signal so I know its not the switch position. I have also attempted prividing a known good 10Mhz reff to the unit to no avail.

I have performed some tests from the service manual and have confirmed I have the refference frequencies generated from the A9A1 board however I noticed A9 module is not providing a LO for the reciver. The manual states the A9 Synthisiser Board is ment to provide LO for the reciver however I can not find it on the output port of A9.

any help or assistance would be greatly apriciated.

Regards
John

[DJP126]

If you have the maint. manual, look at the 60MHz loop subassembly of the A9 module.

[JohnDo]

Thanks for the reply DJP126

I had taken some measurments from the A9A4 Board a while ago. My notes show

- the output of A9A4 at R79, I get 59.45MHz 200mV P-P where the schematic states 60.5MHz 1.8v p-p
- the shematic notes at the junction of R37 & CR11 f24= 24.003MHz 7VDC, here I have nothing but at R43 & R45 I have 25.05MHz 600mV P-P with clean sinewave



Ill put the monitor on the bench tomorow and take some more measurments

[jry]

The Junction of R37 & CR11 is the VCO control voltage. This should be pretty much DC and what the manual is trying to state is that with this at 7.0 VDC the frequency should be 24.MHz at the output of Q2.

Sounds like your 60Mhz out is too low and may not be enough to clock the divider for the 60Mhz loop.
Look at the drive to the 60Mhz output tranistor and see if the output stage gain is gone.

[JohnDo]

I have taken some more measurements on the A9A4 board.

I think the Offset Loop is working and my problem is the Translation Loop. Below are my findings

Offset Loop
Q2 Base = a steady 24.003MHz clean sine wave 9.1vp-p
Q2 Collector = a steady 24.003MHz clean sine wave 10.1vp-p
R45 = a steady 24.003MHz clean sine wave 3.1vp-p

Translation Loop
Q4 Emitter 60.1MHz 1.7v p-p Clean sine wave
Q3 - Q4 Collector 60.44MHz 2.5v p-p Clean sine wave, as I adjust the VFO KHz the freq will change between 60.4MHz to 60.55MHz
Q6 Base 60.5MHz 1.8v p-p Clean sine wave, as I adjust the VFO KHz the freq will change between 60.4MHz to 60.55MHz
R78 RF 12.4MHz1.3v p-p sine wave,
Q5 Collector 60.2MHz 2v p-p clean sine wave
R79 no freq weak noisy wave
R74 - L14 60.2MHz 2v p-p clean sine wave
R79 Isolated 60.2MHz 1v p-p


- all 60.X MHz frequencies measured above where not stable. They where hunting in the KHz range
- R79 60.5MHz Output had a weak noisy wave and would not register a frequency on the meter. Scope wave was quite poor
- with R79 isolated test I isolated the output of the A9A4 60.5MHz signal from the GHz Loop Board and I got 60.2MHz 1v p-p.

- at U14 RF I see an unstable 8 to 12MHz noisy sine wave, sometimes 12.4MHz

would I be correct in saying Q6 is bad ? Should I see 60MHz on the Emitter feeding U14 to feed Q7 that will drive the 128/129 divider ?