MCUmall EPROM BIOS Chip Burner Forum
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 Open Source Project Willem Programmer Hardware
 Which chip is bad?
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paulpenn

USA
8 Posts

Posted - 03/12/2007 :  14:44:39  Show Profile  Reply with Quote
Here's a puzzle for you hardware experts on the dual power Willem/PCB3B. Reading an empty EPROM socket fills the buffer with 04's. Filling the buffer with 00's and writing to the EPROM fills the chip with 7F's. (Switches are set for 2716). To me, this would indicate D2 was stuck high on reads, and D7 was stuck low on writes. Which chip(s) should I replace?
Reply #1

ZLM

2936 Posts

Posted - 03/13/2007 :  09:25:31  Show Profile  Reply with Quote
Based on H/W design, the empty ZIF reading should be all 04s.
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Reply #2

paulpenn

USA
8 Posts

Posted - 03/17/2007 :  12:12:42  Show Profile  Reply with Quote
I just replaced all the chips for $2.15. It now correctly reads an open socket as all FF's. Also reads correctly with several 2716's on hand. Loading files to the buffer and saving buffer to files works correctly. It still won't program, however. After trying to burn an EPROM, I find the whole chip contains the same value in every location, the same as the first byte of the buffer! Any ideas? I'm going to try another computer with Windows 98 instead of XP and see if that helps.
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Reply #3

paulpenn

USA
8 Posts

Posted - 03/27/2007 :  19:07:33  Show Profile  Reply with Quote
I wasn't able to find a Windows 98 computer to try. I swapped out the chips as recommended on a Russian web site to work with a laptop computer (IBM ThinkPad T23).
I now have: D1 & D2 = 74HC367; D3 = 4014; A1, A2 & A3 = 4015; C1 = 74HC14. The symptoms have changed: It will now correctly burn a 2716, but will not read. Doing a read command flashes the Vcc and Vpp LED's on and off and writes garbage in the first location of the 2716. Has anyone seen this behavior and have a suggestion for a fix? I tried swapping the 25-pin round cable for a ribbon cable but same symptoms. Computer is running Windows XP SP2, software is 0.97ja.

Has anyone ever sucessfully got this thing to work on a 2716?
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Reply #4

ZLM

2936 Posts

Posted - 03/28/2007 :  04:00:26  Show Profile  Reply with Quote
How do you know "It will now correctly burn a 2716" without a correct reading?
Check 4014 for reading problem.
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Reply #5

paulpenn

USA
8 Posts

Posted - 03/29/2007 :  16:27:15  Show Profile  Reply with Quote
Good question! I have an older EPROM programmer that plugs into a ISA slot. I was hoping this card would allow me to get rid of the 486 computer, VGA monitor, and keyboard the old programmer was plugged into!

Burning one of my disk files with the Willem and reading it on the old programmer shows good data.

I'll try the 4014.
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Reply #6

paulpenn

USA
8 Posts

Posted - 03/29/2007 :  17:01:37  Show Profile  Reply with Quote
Nope! Swapping in a new 4014 gives the same symptoms: Doing a read command flashes the Vcc (good) and Vpp (bad!) LED's.
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Reply #7

ZLM

2936 Posts

Posted - 03/30/2007 :  07:41:59  Show Profile  Reply with Quote
In this case you also need check 74HC04 too.
The reading is controled by both 74HC04 and the CD4014

See schematic :
http://www.mcumall.com/forum/topic.asp?TOPIC_ID=100

and make sure all connections are OK from/to those two chips.
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Reply #8

paulpenn

USA
8 Posts

Posted - 03/31/2007 :  07:29:24  Show Profile  Reply with Quote
OK -- I tried two different 74HC04's at C1 but no change in symptoms -- the Vpp red LED still flashes on a read command. Is there a DOS program I can try with this board to eliminate Windows XP problems?
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