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 PCB3B problems programming 27C801

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T O P I C    R E V I E W
necro_nemesis Posted - 02/05/2008 : 20:20:37
I have a PCB3B of the design type that has the pot for adjusting Vpp voltages. It is still sold, even as recently as this week I saw it on Epay. If required I can post a pic of the board and it's current settings.

I have been trying to program 27c801 with no success.

From left to right on board setup is:

I have are the 8 pin 6&7 jumpered (P1 -> A19)
Nothing on the 18/p1/Vcc jumper left of the dips
Dips as per program (PCB3)
Default on the jumper blocks right of the ZIF
6.2V on the Vcc (metered at ZIF)
12.75 on the Vpp (metered at ZIF)

I have tested all ZIF points including A-19 (pin 1) for logic and Vcc/Vpp voltages. All appear to be good and in the correct locations for a 27C801.

I am running a 12Vdc 1.2amp power supply.

My PC is Windows XP Sp2 and I have installed the port polling registry fix.

I have set EPP in my BIOS settings and confirmed my printer port settings in device manager.

My cable is less than 18 inches long and is of good quality (supplied with unit).

I have attempted to program with 0.97a, 0.97b+, 0.97g, and 0.97ja.
I have tried various values of tWp and tWc (increased and decreased)after having failure with default settings.

Depending on software I get mixed results. The immediate verification following program usually fails at the first byte. On subsequent verification it will go further, the best case get I 49% verified and then corrupt data a location 0x80000. I suspected A19 as a result of this but on test page it does show a value of around 4 volts when ticked off on the box and measured.

I have done my homework and am out of ideas at this juncture.
1   L A T E S T    R E P L I E S    (Newest First)
ZLM Posted - 02/06/2008 : 17:06:15

1. measure the Vpp during the programming see if it is too low.
2. change to another EPROM see if works.
3. put back the Vcc to 5V see if it is making difference.

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