Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Hi!

I am using a paper phenol PCB for my model railway booster project
(which has to handle signals at about 36000 baud). I have developed,
etched, drilled and soldered the components onto the board. Then I
sprayed a lacquer clear coat (for automobiles repairs) onto the PCB
(on the track side) as an attempt to prevent oxidation.

I have tested the functions of transistors by using a 9V battery to
pass a voltage of 9V and then -9V to the signal input and the booster
responded correctly by producing voltages at the correct polarity.
This means that all transistors were functioning correctly. However
when I plug the booster to the computer RS232 interface and attempt
to run the Directrain program, the trains fail to respond. When I
use the program to stop the trains (In digital control, a continuous
negative voltage signals all trains on the track to stop), the
booster DID respond correctly by producing a constant negative
voltage! (I measured it on the track with a digital multimeter)

Therefore do you think the lacquer clearcoat have produced the
distortion in the signal so that it cannot be picked up by the train
decoders? If this is the case, how can I fix this problem? Can I
fix this problem by using two-part thinner to strip the lacquer
clearcoat away from the booster?

Mark