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JDM PIC programmer troubleshooting

Hello,
A while ago I came across a schematic for a slightly modified JDM PIC
programmer which I just finished building. Unfortunately using it with
IC Prog did not yield good results- even though Vdd and MCLR voltages
are present, I am only getting blank data when trying to read/write a
16F84A chip.

* What other signals should I be checking and what are the expected
values ?

* What are reliable settings in IC Prog ?

* Does the schematic look correct? I compared it with the original
design and noticed a 2.2k instead of 1.5k resistor and the transistors
are different, though they seem to have similar specs :
http://img218.imageshack.us/img218/633/jdmro1.png

Thank you!
 
N

none

Jan 1, 1970
0
Hello,
A while ago I came across a schematic for a slightly modified JDM PIC
programmer which I just finished building. Unfortunately using it with
IC Prog did not yield good results- even though Vdd and MCLR voltages
are present,

What are the value of those voltages?
I am only getting blank data when trying to read/write a
16F84A chip.

Another item on a 16f84a. IIRC its Vpp has to have a voltage of 13V
nominal.
* What other signals should I be checking and what are the expected
values ?

Start with Vpp and Vdd values. If Vpp isn't at least 12V it isn't going
to program.
* What are reliable settings in IC Prog ?

* Does the schematic look correct? I compared it with the original
design and noticed a 2.2k instead of 1.5k resistor and the transistors
are different, though they seem to have similar specs :
http://img218.imageshack.us/img218/633/jdmro1.png

Probably not critical. The biggest problem with the JDM programmer is
that it requires a real serial port (i.e. +/- 12V signals) to work
properly. Most modern serial ports swing at much lower voltages.

BAJ
 
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