Is there more than one hardware version of the T'bolt?
Mine has U18 (right behind the RS-232 connector) as an Intersil
ICL232IBE. This is a dual RS-232 transceiver that includes a doubler
and inverter to generate plus and minus 9 to 10 volts from the +5
input. It appears to have the required capacitors on the bottom of the
board. The open circuit RS-232 voltages on mine are just under 10 volts
which seems a little low for a 12 volt source.
I didn't try to run mine without -12, but the presence of that chip and
messages on this list made me think that the -12 was only used for the DAC.
Ed
WarrenS wrote:
I've run test of the effect of the Neg supply on a Tbolt's operation and the effect on it's noise. (It would seem I'm one of few nuts that actually test things)
The Neg supply effects the RS232 neg swing and the neg output of the DAC.
As long as the Dac out (OSC EFC input) is > than a couple of volts above the
neg supply (or the EFC is positive) all worked fine at any Neg supply down to -3
volts.
This is because most RS232 receivers don't need their input to swing negative.
Your -7 volts statement agrees well with my test. You can go even lower on the
neg supply with no ill effects IF you do not need the DAC output to go all the
way to neg -5Volts.
ws
PS I did not test for the effects with a Neg supply less than -3 volts, It may
of been able to go even lower, I just wanted to insure it was reliable with -5
volts for my application.
******************
[time-nuts] Thunderbolt no usable sats.
Arthur Dent golgarfrincham at yahoo.com
"It may or may not be used for tuning voltage but what I said is
100% correct. The Andrew/Grayson units these T-Bolts were
used in provided -7 VDC for this negative supply and the same
T-Bolts work properly on -12 VDC. If this voltage is missing, the
com port will not work."
+++++++++++++++
Please read what I actually said. Do you disagree that these
units will not run on -7 VDC or that the com port will not work
if the negative supply is missing?
-Arthur
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