Help with K2 Q7 collector resistance test

[Neal Campbell and Sarah Ferrell]

Hi all,

I have been through the archives so I know this has been asked and
answered a few times but I still am not making much progress on this.

The problem is that my resistance test for Q7 collecter is not correct.
With the common probe on ground and the positive probe of my DVM
measuring resistance, its abt 280 ohms. If I reverse the leads, its
around 408 ohms. All other measurements seem okay.

I have the heat sinks unscrewed and point in the air, not touching
anything. I have remove T4 (as it looked like it could be a source of
problems) and the measurements are not changing. I have magnifying
glass inspected things, blown the top and bottom of rf board with
compressed air, etc with no real movement.

Prior to the alignment in part two, the resistance reading on the 12v
line was 788. I did not realize that the polarity of the DVMs could
change the reading so I have no idea if I had the common probe grounded
or vice versa. The alignment and test of the part 2 instructions went
as expected.


Any ideas to unblock me?

Thanks es 73
Neal

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[Don Wilhelm-3]

Neal,

Try removing the Control board to see if the resistance moves up
substantially - if it does, look for the problem on the Control Board or its
connectors, oterwise look for the problem on the RF Board.

The best advice I can offer is to look at the schematic and find all the
points marked '12V' and then carefully examine each component (correct
component, good soldering, etc.)that is connected to that 12 volt line -
there are several on the RF Board (and don't overlook the connectors).  On
the control Board, the 12V line connects to U3 pin 2, the 2 voltage
regulators U4 and U5, and to one end of R16 (to feed the AF Amp).

> -----Original Message-----
>
> I have been through the archives so I know this has been asked and
> answered a few times but I still am not making much progress on this.
>
> The problem is that my resistance test for Q7 collecter is not correct.
> With the common probe on ground and the positive probe of my DVM
> measuring resistance, its abt 280 ohms. If I reverse the leads, its
> around 408 ohms. All other measurements seem okay.
>
> I have the heat sinks unscrewed and point in the air, not touching
> anything. I have remove T4 (as it looked like it could be a source of
> problems) and the measurements are not changing. I have magnifying
> glass inspected things, blown the top and bottom of rf board with
> compressed air, etc with no real movement.
>
> Prior to the alignment in part two, the resistance reading on the 12v
> line was 788. I did not realize that the polarity of the DVMs could
> change the reading so I have no idea if I had the common probe grounded
> or vice versa. The alignment and test of the part 2 instructions went
> as expected.
>

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