That means you're only checking program margin to 5.75V. If programming VCC is 6.25V, but you get a half volt drop in the transistor switch, the device being programmed only sees 5.75V. At 50mA, Vce(sat) will be 0.5V to a couple volts and that's a problem. All Willem type programmers I've seen (except the Willem 4.1) use a transistor to switch VCC. Many devices will not require the maximum current from the specs, but the programmer should be designed for worst case so that all will program reliably. Proper programming of a 5V (10% tolerance) 27C512 requires VCC options of < 4.5V (for blank checking), 6.25V (for programming), and 5V at a minimum current of 50mA. If you buy one that can't do this, return it as it's unsuitable for use as a programmer. If they say they can program NMOS EPROMs, they need to be able to provide VCC at 100mA. For VPP, I'd check for 12.75, 21.0, 25.0 with a drop of less than 0.25V at 50mA. For VCC, I'd check for 4.2, 5.0, 6.0, 6.25 with a drop of 0.1V or less at 50mA. I would ask the Seller if the programmer can provide VCC and VPP at the required voltages and currents for reading/programming devices. It depends on whether they've improved the power supply circuitry which has been a weakness in most Willem programmers and what devices you want to program. I'd be happy to answer any questions you might have.Ĭlick to expand.Like most things, it depends. Since Willem programmers are hobbyist level, they assume you know something about programming EPROMs so you can do it reliably. All of the components needed should be readily available most of what you need is on the programmer you purchased. I sold Willem's programmers in the US and have small number of bare boards I'd sell at cost if you're interested in assembling your own.
Unfortunately it's no longer available commercially.
The only Willem variant I would consider buying is the 4.1 which has a relay to switch VCC so it can handle NMOS EPROMs (2716, 2732, etc) and higher capacity CMOS EPROMs (larger than 1Mb). That means they struggle to produce VPP > 12.5V, some even struggle to provide 12.5V. Just understand that all PCB3 variants use a step up regulator to generate VPP and they opt for an inexpensive molded inductor that saturates at a low current. Click to expand.If you're going to program enough EPROMs to justify not having someone else program them for you and you want to stay with an inexpensive Willem based programmer, any PCB3 variant, ATH3.1, or Willem 4.1 can be made to work.
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