Re: [Usbpicprog-technical] Help making one. Getting strange results...

[Frans S. <fra...@gm...>]

  Hello,

In case you don't get an e-mail from the mailing list, I also send it to 
your e-mail address.
The voltage on R1 should be about 13.something volt, 12V is too low. I 
still suspect your capacitors.
I am also curious what you connected as a target board, is there 
anything else besides the target microcontroller? Or did you maybe make 
other connections to the MCLR line?

Good luck!

Frans

Op 4-9-2010 23:06, RedoX schreef:
>   Hello,
>
> R13 is disconnected. That's what i though first, but because it was on
> the schematics I tried with... Now It's OK, left removed.
>
> In fact, the values I gave you were taken with a voltmeter (pretty
> accurate) and not only with the IO test program (there a difference of
> 0.20-0.30 V between the voltmeter and the software.)
>
> I tried removing the 12V Zener, without success.
>
> In fact, the voltage pump seems to work well: When I measure before Q4 I
> get a little more than 12V, but after Q4, the voltage doesn't reach more
> than 10.7-11V. This 2v loss seems common, normal with this kind of
> transistors... According to the datasheet: the Gate Threshold Voltage
> seems to be typically 2.1v. I tried to bypass Q4 but that's no good
> idea... VPP is good but no more controlled, so devices won't go in
> programming mode...
>
> I'm using 1uF 50V capacitors, it should be fine (and my getting 12v at
> R1 !), and I tried changing the transistor with a one picked from an
> other store (different serie, still BS170) without better result.
>
> When I tried to recognize the 18f, Vpp is around 10.7v, when I try with
> the 16F, VPP goes to 9.7v... According to the datasheets, theses VPP
> voltages are correct to enter programming mode, but shoudln't be
> differents and the 16f should be detected, even if it doesn't want to
> program (as the 18f is doing (but the device may be in cause, I'm not
> sure it's ok...))
>
> I'm waiting for some others 18F from Microchip, I'll try with these
> ones... And at last, I'll try an other board... Maybe I have some kind
> of bad luck with this one ^^
>
> I don't know how to reply directly to your reply, so I'm sending you
> this email. I hope I'm not wrong, I'm not quite familiar this Mailing lists.
> Moreover, I subscribed to the mailing list-archive , but got no
> notification of your answer... I'll check this.
>
> Thanks for your help.
>
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