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 ST M27C4002 Fail Blank test		  New Topic  Reply to Topic
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polynomial

USA
2 Posts
Posted - 03/11/2026 :  10:18:51  Show Profile  Reply with Quote
Question,

I'm wondering why my new ST M27C4002 chips (3 of them) fail a blank test at address 0 with 0x3d. All of the chips fail the blank test with the same error even after an hour under a UV light. Can read the chip data without issues though. I have had no issues with different types of ROMs, e.g., M27C256. My setup is a new GQ-4X4 (3/2026) burner with the chip in a new ADP-054 16 bit adapter (jumper on pins 1-2) and the selected device as a M27C4002. Tried different speed settings but always fails a blank test.

Any insight that people can offer is truly appreciated!

Poly
Poly Nomial
Reply #1

polynomial

USA
2 Posts
Posted - 03/11/2026 :  12:50:34  Show Profile  Reply with Quote
I figured it out and the EPROMs are fine! User error. The GQ-4x4 and the ADP-054 use 40 pin sockets for the 27C4002 EPROMs. The issue was that the ADP-054 Adapter only has 18 pins to connect to the GQ-4x4. This is hard to see because of the size of the adapter, but once I figured this out, I just needed to move the adapter down one position in the GQ-4x4 socket, and the EPROMs could be blank checked and written!
Poly Nomial
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