[Kat Manton]

A Bit of Testing

I powered the programmer from a bench supply set to 9V rather than a wall-wart so I could monitor supply current.

I set the VPP supply to 12.6V (off-load, as per the manual.)

Then I stuck a 510 ohm resistor in the ZIF socket, between pin 16 (Gnd) and pin 1 (Vpp) and hung a 'scope and a DMM across it.

Turning Vpp on (via the 'Test H/W' panel in the software), the voltage dropped by 0.1V. The supply was very noisy, featuring 100mV positive-going spikes and ramps and nasty 600mV negative-going spikes.

After less than a minute, the waveform changed, the voltage started falling and I could smell something. The MC34063A and the 100uH inductor were quite hot and I burnt my finger on the 7805!

The current reading on the bench supply was over 300mA (and climbing slowly) when I switched off before any magic smoke escaped.

12.6V across 510 ohm is 25mA. 25mA appears in the "typical" column for Vpp current in several EPROM datasheets I checked.

As expected, the VPP supply is rubbish and this programmer is currently quite incapable of programming older EPROMs.

Kat