MSR2000 Exciter Help

[BillBBB]

I picked up an MSR2000 with the hopes of converting it to amateur use (VHF), but I am having no luck tuning the exciter. I chceked out the unit completely with the original elements (I had to give them back) and everything seemed in spec on my service monitor, not too shabby for sitting amost a decade. Since I replaced the elements I sucessfully tuned the receiver (I have the manual set and a test meter), but I can't even get a blip on the meter while tuining the exciter. I am following the process and setting the coils as per the tuning guide. Does anyone have any ideas what I can look for?

It seems as though the station is not trying to key the exciter when I flip the switch on the comtrol module. Is there a way to check for this on the backplane? I tried grounding pin 5 (f1 select) and saw no changes.

The voltages on the exciter pins (all the same, TX keyed or not):
1 - 0
2 - 0
3 - 0
4 - 0
5 - 1.46
6 - 0
7 - 14.0
8 - 0
9 - 9.48
10- 0
11 - 0
12 - 2.8
13 - 0
14 - 0
15 - 5.5
16 - 0
17 - 0
18 - 0
19 - 0
20 - 14.0

[Bill_G]

I'd check the new channel element first. Just verify it's putting out the correct fundamental.

[BillBBB]

That is a fantastic idea, but how does one go about doing so? I cant find any documentation relating to the process of testing an element.

[KI4M]

I agree with Bill_G. The last VHF MSR I tuned down to 2M I ordered my crystal from Bomar and put it in my element. When I installed it I could not find it on the service monitor anywhere. Changed the crystal to another channel element and it's been playing wonderful for over 2 years.

[BillBBB]

I suppose it is a matter of applying bench power to the element and sniffing the output with the service monitor? Based on the exciter diagram and the voltage measurements on the pins perhaps 14v; however I am not certain and don't want to damage either the element or my 8920.

[BillBBB]

Strike that - 14v should be 9.4v, still rather unsure exactly how to setup the test.

[Bill_G]

Use a decoupled oscope probe, or use a length of coax cable with a small value cap soldered to the end as a probe to sniff around the tcxo at the fundamental freq. If you have access to a MSR2K test set, meter 1 will show you if the oscillator circuit is running or not.

[Astro Spectra]

Manuals and schematics can be downloaded from:

http://www.repeater-builder.com/motorol ... index.html