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

In a message dated 7/10/2003 3:29:31 AM Central Standard Time, 
farnell_mark@... writes:

> 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?
> 
If this Clearcoat really IS "clear"---that is, has no aluminum "paint" in 
it---that should have NO effect on this circuit!  I assume you cleaned all the 
solder-goop (rosin-flux) off with thinner before you sprayed it? 

You could remove it with lacquer thinner, but I doubt this will have ANY 
effect!  There is summin ELSE afoot, methinks!


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