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

[RedoX <ad...@re...>]

 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.