No Tim. If you look at the schematic of the 'Passband Tuning
Board', you will see that the 1.8kc position has a diode at the filters
input (and two diodes at the filters output). On my schematic (81781),
the diodes are labeled D9 and D10/D11 respectively. However, next locate
connector 41 and put your voltmeter on the pin for 1.8KHz. See if you
have voltage there when you press the button.
The connector 41 1.8KHz pin ONLY feeds the 1.8kc filter
position, through R30, R31, R32, and R33. You MUST have voltage at the
junction of R32 and R33 to get a signal into the filter. AND you MUST
have voltage at the junction of L12 and D10 to get a signal out of the
filter.
In case you do NOT have voltage at connector 41, 1.8KHz pin,
then you MUST have a broken wire between connector 41 on the Logic Board
and the Pass Band Tuning board. I say this because the voltage required
to turn on the 1.8KHz filter comes from U22/pin 13, to connector 41 and
also to connector 95. Connector 95 goes to your keypad, so if your 1.8
filter light turns on, that means the voltage coming from U22 is
good...it's just not getting to your Pass Band Tuning board connector
41.
Before getting too excited, try what someone has already
suggested. That is to pull the filter board almost out of the socket on
the PBT board. I, too, have had one filter where the pins on the filter
board were a tad too long and when I pushed the filter board all the way
down, it shorted out the filter.
But since you say your 1.8kc light on the front panel turns on
when you push the 1.8 button, the ONLY place you can have a problem is
the above mentioned diodes, resistors, and inductor, and possibly a
broken wire in the wiring harness if you are not getting voltage at the
PBT board connector 41.
Good hunting....but don't give up!!
Tom/W4BQF
calderman AT cox.net
-----Original Message-----
From: tentec-bounces@contesting.com
[mailto:tentec-bounces@contesting.com] On Behalf Of tlogan7@cox.net
Sent: Saturday, March 01, 2003 5:22 PM
To: tentec reflector
Subject: [TenTec] no voltage to 1.8 filter?
Hi folks -
I've determined that the 1.8 slot on my PTB board has no voltage
coming
through the three pin connector 41 on the rear left corner of the
board.
When the 250 and 500Hz filters are engaged voltage will run through
their
respective pin on the connector - but when I turn on the 1.8 I do not
get
any voltage.
I'm a total electronics nimno - but as far as I can tell the only
components on this board are either chokes, toroids with binocular type
cores, one normal toroid and three pots. So that must mean that the
connector at 41 runs to diodes that I'm guessing are in the jungle on
the
back of the front panel - something I'm not sure I want to mess with.
Based on this info does anybody have any additional light they can
shed on
my 1.8 slot? It appears that it just plain does not get switched on even
though the panel light turns on . Thanks for any help.
73/Tim NZ7C
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