Broken ZXpander

[sirmorris]

The CMOS chips are faster and better IMHO so I think you've done the right thing!

[1024MAK]

I don't know if you are aware of this, but the older NMOS EPROMs (like some 27128 chips) need a programming voltage of 21V. More modern CMOS EPROMS (like some 27C128, 27C256 etc) only need 12.5V for programming.
Note always check with the datasheet for the correct programming voltage. Some chips have the correct voltage printed on them. Sticking 21V in a 12.5V chip will kill it.
USB powered EPROM programmers have to include a DC to DC converter circuit to generate the 21V from the USB 5V line.
This may not work if the USB port cannot supply the current required, or on some cheaply made programmers, the inductor and capacitors used in the converter circuit are not good enough.
There are ways to overcome these problems.

• If your programmer has an external power input, use it instead of using only USB power.
• Only use 12.5V CMOS EPROMS.
• If you can work out the circuitry, modify the circuit to take an external programming voltage supply.

Also, did you blank check the EPROM before programming?

Hope this helps
Mark

[questarian]

The CMOS chips are faster and better IMHO so I think you've done the right thing!

You're very right! The 27C128's showed up today and they burned without a problem.

I don't know if you are aware of this, but the older NMOS EPROMs (like some 27128 chips) need a programming voltage of 21V. More modern CMOS EPROMS (like some 27C128, 27C256 etc) only need 12.5V for programming.
Note always check with the datasheet for the correct programming voltage. Some chips have the correct voltage printed on them. Sticking 21V in a 12.5V chip will kill it.

Yes, I'm aware of it now. I was bit too eager to have a go at the burner so I didn't think about the spec sheets till after I started having problems. The spec sheets I could find have the 27128A's I have listed as 12.5v and both Top853 the old C1 Programmer have it down as that. The old Promenade C1 got the voltage right the first time, but the Top853 was a different matter. Several of the General 27128/27128A settings I tried used 21 Volts so I may have toasted them.

USB powered EPROM programmers have to include a DC to DC converter circuit to generate the 21V from the USB 5V line.
This may not work if the USB port cannot supply the current required, or on some cheaply made programmers, the inductor and capacitors used in the converter circuit are not good enough.
There are ways to overcome these problems.

If your programmer has an external power input, use it instead of using only USB power.
Only use 12.5V CMOS EPROMS.
If you can work out the circuitry, modify the circuit to take an external programming voltage supply.

Having the same sort of power issues with USB DVD Writers, I have a USB cable with an extra power lead, but it didn't make any difference. The old C-64 promenade C1 I tried has way more then enough current and it was have the same write issues.

Also, did you blank check the EPROM before programming?

I initially checked, and then I erased the entire set of chips at least twice when I started having problem. The Top583 was reading them as blank. I forget if I checked the one chip that did appear to burn on the Promenade, but the other three failed the blank test on that burner.

Hope this helps
Mark

Yes it did, Thanks!

-John-