MCUmall EPROM BIOS Chip Burner Forum
MCUmall EPROM BIOS Chip Burner Forum
Home | Profile | Register | Active Topics | Members | Search | FAQ
Username:
Password:
Save Password
Forgot your Password?

 All Forums
 MCUmall Forums
 Using The Enhanced/Dual power Willem Programmer
 Problems reading NMOS EPROMs
 New Topic  Reply to Topic
 Printer Friendly
Author Previous Topic Topic Next Topic  

ftvwdlt

3 Posts

Posted - 02/08/2017 :  07:43:13  Show Profile  Reply with Quote
Hi,

I'm using a dual powered Willem Programmer to read old EPROMs (M27128A, 27256).
Unfortunalety I get a lot of reading errors. Some days ago with a 27256 where I thought of a faulty IC, today a 27128 with the same problems.
Reading CMOS-EPROMs like 27C256 works.

As I read the power supply can be a problem. I use an external AC/DC adaptor instead of USB supply. On the powered IC on the willem board I can measure 4.88V between VCC and GND.

I also tried to change the timings without success.

Anyone with suggestions what could have gone wrong?

Thanks
Reply #1

anniel

625 Posts

Posted - 02/09/2017 :  03:51:02  Show Profile  Reply with Quote
Bit creep?
Go to Top of Page
Reply #2

ftvwdlt

3 Posts

Posted - 02/10/2017 :  00:01:39  Show Profile  Reply with Quote
Sorry, I'm not sure what bit creep means.
Go to Top of Page
Reply #3

anniel

625 Posts

Posted - 02/10/2017 :  04:30:17  Show Profile  Reply with Quote
In some old chips the MOS cells tend to slowly shift voltage values.
Go to Top of Page
Reply #4

emorysmith

USA
8 Posts

Posted - 02/10/2017 :  08:22:23  Show Profile  Reply with Quote
4.88V seems a bit low. The older chips draw more current and may be pulling your Vcc down.
I'm not familiar with the "dual powered" but my PCB60e is USB/External powered and I use a 12V 2A wall wart.
Does your board have a 7805 regulator? If so, does it get warm?
Go to Top of Page
Reply #5

emorysmith

USA
8 Posts

Posted - 02/10/2017 :  08:39:46  Show Profile  Reply with Quote
This may be of interest:
http://www.mcumall.com/forum/topic.asp?TOPIC_ID=1630
Go to Top of Page
Reply #6

anniel

625 Posts

Posted - 02/11/2017 :  06:44:55  Show Profile  Reply with Quote
Sorry, I am using a GQ4X, can't help you with the 7805.
When dealing with difficult chips I use an external variable power supply and isolate the voltage from the programmer to find the sweet spot.
Go to Top of Page
Reply #7

ftvwdlt

3 Posts

Posted - 02/17/2017 :  03:19:53  Show Profile  Reply with Quote
Today I took some time for it.

I took the bridge for 3V3 power and put an external 5V source on the EPROM supply.
This didn't take much time and did the job without modifications.

Thanks for helping!
Go to Top of Page
Reply #8

anniel

625 Posts

Posted - 02/17/2017 :  03:49:15  Show Profile  Reply with Quote
Good but there is no need for modifications. You can put a small V shaped piece of paper in the ZIF socket.
Go to Top of Page
Reply #9

supervizeur

315 Posts

Posted - 04/01/2017 :  12:55:58  Show Profile  Reply with Quote
Or a piece of Kapton tape folded in 4 sticky side in.
Go to Top of Page
Reply #10

anniel

625 Posts

Posted - 04/01/2017 :  16:21:44  Show Profile  Reply with Quote
Yes, that's also what I use but I suppose not everyone has Kapton on hand. Not that they shouldn't have some around.
Go to Top of Page
Reply #11

supervizeur

315 Posts

Posted - 04/11/2017 :  18:02:46  Show Profile  Reply with Quote
+1
Go to Top of Page
Reply #12

anniel

625 Posts

Posted - 04/15/2017 :  06:33:57  Show Profile  Reply with Quote
Talking about Kapton, I wonder why the cheap Chinese copies outgas that pungent smell.
Go to Top of Page
Reply #13

supervizeur

315 Posts

Posted - 04/25/2017 :  11:56:27  Show Profile  Reply with Quote
Nothing goes to waste in China, they use cat urine as colorant.
Go to Top of Page
Reply #14

anniel

625 Posts

Posted - 04/26/2017 :  10:27:49  Show Profile  Reply with Quote
+1
Go to Top of Page
Reply #15

supervizeur

315 Posts

Posted - 06/04/2017 :  03:05:56  Show Profile  Reply with Quote
Just worked on a board with a Chinese copy of Kapton and the complaint was bad smell...
Go to Top of Page
Reply #16

anniel

625 Posts

Posted - 06/09/2017 :  03:05:32  Show Profile  Reply with Quote
What kind of board?
Go to Top of Page
Reply #17

supervizeur

315 Posts

Posted - 06/12/2017 :  11:15:42  Show Profile  Reply with Quote
EICAS PCB.
Go to Top of Page
Reply #18

anniel

625 Posts

Posted - 06/15/2017 :  11:30:06  Show Profile  Reply with Quote
That must have caused some scare.
Go to Top of Page
Reply #19

supervizeur

315 Posts

Posted - 06/20/2017 :  03:09:32  Show Profile  Reply with Quote
Not really they where highly trained personnel. More of an inquiry how it got there.

Go to Top of Page
  Previous Topic Topic Next Topic  
 New Topic  Reply to Topic
 Printer Friendly
Jump To:
MCUmall EPROM BIOS Chip Burner Forum © Copyright 2003 - 2009 Mcumall Electronics Inc. Go To Top Of Page
Generated in 0.16 sec. Snitz Forums 2000