DVP Card Problem

[Rod Greene]

Hi all,  I'm having trouble with my k1ea DVP card and hopefully the 
great wisdom of the reflector participants can shed some light on this.

Background:

The card's serial # is 213 and it shows "revision B" stamped on the card. I
purchased it in June of 1992, having placed an early order at Dayton 
that year when they were first announced. I also purchased a generic
cable as I had a Ten Tec OMNI V at that time.  

Here's the problem:  The card introduces hum into the mic circuit.

The cable's currently wired for a Kenwood. I have the diagram for how the 
Kenwood connections are made and have faithfully followed that and 
double checked everything. Even back when I had the OMNI, I couldn't 
get rid of the hum. It appears to be a ground loop, and I can reduce it
some by running a separate ground connection between the rig and the PC.

Couple of observations, the hum only starts when I execute the DVPTSR. I 
presume the TSR engages one or more of the on board relays, and that's 
when the hum starts. The four cable shields on the audio portion of 
the cable are tied together at each end of the cable and also tied to 
the hoods of the connectors.(per the diagram) At the DVP end, these 
shields are connected to pin 11 of the db15 connector. However, 
pin 11 does not connect to anything on the board.  Should there be a 
connection to the board?  On the board, edge pin B1 appears to be the
ground connection to the PC bus. It is connected to what appears 
to be a ground trace on the card. Should this bus and pin B1 be 
connected to pin 11 of the db15 and thus the shields of the cable? 
Does anyone have a circuit diagram of the DVP itself to help in tracing
this out? I have tried not connecting the shields to the hoods at either
end of the cable with no change in the problem. 

Any help or suggestions would be appreciated as the card has never been
usable. I have thought of using an isolation adaptor like I have
heard they use in automobile stereo audio systems to eliminate 
ground loop problems. I tried an audio transformer back when I was
trying to set it up with the OMNI, but that didn't work very well either.
I have used DVPs at other stations with Kenwoods similar to mine, so I 
know they can work well. Reply to me directly and I will be glad to post 
a summary.

Thanks, Rod w7zrc@micron.net
 

............................................................................
w7zrc@micron.net             Rod Greene W7ZRC             Boise ID    DN13UN
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