Ah,

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Thanks Mark – that makes more sense.? Now, I just have to figure out why 2^nd_VCO_Vcc is showing as 0 volts.? Sounds like something in the local power supply for the 2^nd VCO.? I’ll do some more probing in that area tonight.

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One thing that has made this more difficult for me is that there is a discrepancy in the labeling of the test points between the schematics in the CLIP and the silkscreen on the RF module PCB.? The schematic will reference a test point of “TN215” for example, but the PCB will have a label of “TNQA3” (these are two randomly picked test points – unlikely that they are the same one).? Is there a way to correlate the two?? Is it something as simple as the PCB silkscreen being a hexadecimal version of the TN in the schematic?? Until I figure out the naming system, I have to find the nearest component to the test point, find it on the pcb using the component map, and then find that on the pcb itself – very time consuming.

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I have the service manual, and the CLIP for this device.? While the CLIP is invaluable, it is a bit frustrating at times – schematics that are not clearly labeled, component placement diagrams without an index, etc.? I guess I’ve been spoiled by the old-school Tektronix service manuals that had all the indexes, and a theory of operation as well.

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Thanks again for your help, I should have more info after tonight.

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-- Mike

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Michael,

I see what you are talking about but you are misunderstanding the purpose of that (analog) MUX. It is selecting various analog signals (Vcc, temp, etc) and checking their levels, most likely with a DAC.
(not sure where ANA_TEST goes) So it is not supplying power to anything... it is reading it. Most likely during a self test. (maybe this gets enabled during the power-on sequence?)

You might also try the SERVICE MENU (password is "-2010") but I have not really used it before so be cautious!

Do you have the service manual? (E4401-90474)