I finished K2 #4690 about a month ago..works great and meets all specs.
2 weeks ago I finshed the KAT100 which will live in an EC2 along with
a KPA100. I installed a KIO2 in the K2 and hooked up the KAT100 and my
laptop... All is well and worked perfectly.. all voltages were
correct. I am now building the KPA100. Yesterday, I had reached the
point where you ck the voltages in the KPA100 [page 23]. All voltages
were within spec EXCEPT pin 27 of U1 This voltage should be 5.8VDC and
is 3.98VDC. This is the 8R line, which comes out of the K2 at abt 7.98
VDC.
I followed this voltage back thru to the KIO2. The control lines are as
follows: KIO2 in K2 hooked to DB9 on back of K2.... This cable runs to
the DB9 on rear of KAT100. The KPA100 ribbon cable connects to P4 on
the KAT100 board.
The 8VDC [8R] line is 7.98VDC up till R1 [3.9K] on the KIO2 board.
Without the control cable attached the the voltage on pin #9 on the KIO2
DB9 is 7.98vdc....with the cable connectiong the KIO2 to the KAT100 the
voltage drops to 3.98.. Looking at this line [8R] in the KAT100, it
enters thru pin #9 on J3 runs to pin # 9 on P4 [ where the ribbon cable
for the KPA100 connects] and thenon to the gate of Q3 the FET switch.
There is a 3,9K. resistor to ground on the gate of Q3..
So, R1 in the KIO2 is in series with the 8R line and RP1 [ the 3.9K
to ground off this line] form a voltage divider. This explains the
3.98VDC on pin 27 of U1 in the KPA100. By the way the current draw on
this 8R line is 10 ma.
Is this low valtage going to cause any problems in the KPA100
operation? I assume that the reason for this is that with the KPA100
moounted in the K2 box.. the control ribbon cable would hook up direct
and avoid the KIO2. In this "normal" hookup.. the DB9 on the K2
would be used for the PC hookup only.
IM SORRY TO HAVE BEEN SO WORDY.. But just wanted to give all the info I
had. Tom, N0SS and I came to these conclusions on the phone, last
nite,,but would like to hear other input..
Is this correct? Wll it cause any problem?
Any help or thoughts would be appreciated.
Thanks,
Doc K8RR
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