27c64 not programming - UK Vintage Radio Repair and Restoration Discussion Forum

TALKINGWITHPYE · 1st Apr 2023, 2:44 pm

I was trying to help a fourm member program a philips 914pm and I pulled an eprom from a 914 I had. I erased the 24c64 in a uv light box which worked fine but when I tried to program the chip with my Dataman Pro it would not program. Has anyone had similar problems with this eprom.

wave solder · 1st Apr 2023, 2:55 pm

What brand is the 2764, what is the programming voltage recommended for the 2764? Pulse delay settings, Vdd write voltage.....

There are so many subtle differences with different Eproms.

Mascot-22 · 1st Apr 2023, 10:48 pm

I have had this issue with Eprom programming. Sometimes the programming voltage
is on the Eprom sometimes not.
What i have done is to select the required Eprom in the programmers menu and start at
the lowest voltage and work up the list till you can burn the Eprom.
Worth a try

SiriusHardware · 1st Apr 2023, 11:40 pm

I've seen cases where 'low voltage' versions of standard EPROMs have originally been programmed as though they were the 'standard' versions meaning that they were programmed with a higher programming voltage than they should have been.

Surprisingly this works up to a point, the device accepts the programming - but - if it is erased and there is another attempt to programme it, it will never let itself be programmed again.

Your 27C64 is one of the 'low programming voltage' versions (VPP=12.5V) of the 2764. If it was originally programmed as a 'Normal' 2764 (VPP=21V) then unfortunately it may never be possible to programme it again.

wave solder · 1st Apr 2023, 11:54 pm

I bought some 2716 chips from china marked 12.5v that would not program, it was not until I got to 25v that they actually did retain the data. They have successfully been erased and then reprogrammed at 25v since too.

Interestingly the devices were marked as Intel but when examined through the window with a microscope there was an AMD logo on the die.

SiriusHardware · 2nd Apr 2023, 7:45 am

As far as I know there never was any version of the 2716 which had a VPP of less than 25V so that, plus the fact that you noticed they were really AMD devices, makes it pretty conclusive that you were sold 'disguised' devices.

I think possibly the reason for 'painting them up' as 12.5V programmable is that a lot of the popular low end USB powered programmers can not generate the 25V VPP needed by the oldest devices, so prospective buyers would be keen to buy 'unusual' 2716s with an apparent VPP of 12.5V.

Phil__G · 2nd Apr 2023, 10:15 am

Quote:

Originally Posted by TALKINGWITHPYE

I was trying to help a fourm member program a philips 914pm and I pulled an eprom from a 914 I had. I erased the 24c64 in a uv light box which worked fine but when I tried to program the chip with my Dataman Pro it would not program. Has anyone had similar problems with this eprom.

2764s are readily available (I could send you a few FoC) so dont worry about the suspect one. Assuming, that is, that you dumped it before erasing?

SiriusHardware · 2nd Apr 2023, 12:40 pm

I think TWP has the software 'suite' which is used to produce custom eprom images for these radios, because I remember him having problems with the DOS computer he originally used to run it a while back.

1st Apr 2023, 2:44 pm	#1
TALKINGWITHPYE Pentode Join Date: Oct 2018 Location: Carrickfergus, County Antrim, Northern Ireland, UK. Posts: 126	27c64 not programming I was trying to help a fourm member program a philips 914pm and I pulled an eprom from a 914 I had. I erased the 24c64 in a uv light box which worked fine but when I tried to program the chip with my Dataman Pro it would not program. Has anyone had similar problems with this eprom.

1st Apr 2023, 2:55 pm	#2
wave solder Hexode Join Date: Feb 2007 Location: Chesterfield, Derbyshire, UK. Posts: 483	Re: 27c64 not programming What brand is the 2764, what is the programming voltage recommended for the 2764? Pulse delay settings, Vdd write voltage..... There are so many subtle differences with different Eproms.

1st Apr 2023, 10:48 pm	#3
Mascot-22 Triode Join Date: Oct 2018 Location: Halesowen, West Midlands, UK. Posts: 24	Re: 27c64 not programming I have had this issue with Eprom programming. Sometimes the programming voltage is on the Eprom sometimes not. What i have done is to select the required Eprom in the programmers menu and start at the lowest voltage and work up the list till you can burn the Eprom. Worth a try

1st Apr 2023, 11:40 pm	#4
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,560	Re: 27c64 not programming I've seen cases where 'low voltage' versions of standard EPROMs have originally been programmed as though they were the 'standard' versions meaning that they were programmed with a higher programming voltage than they should have been. Surprisingly this works up to a point, the device accepts the programming - but - if it is erased and there is another attempt to programme it, it will never let itself be programmed again. Your 27C64 is one of the 'low programming voltage' versions (VPP=12.5V) of the 2764. If it was originally programmed as a 'Normal' 2764 (VPP=21V) then unfortunately it may never be possible to programme it again.

1st Apr 2023, 11:54 pm	#5
wave solder Hexode Join Date: Feb 2007 Location: Chesterfield, Derbyshire, UK. Posts: 483	Re: 27c64 not programming I bought some 2716 chips from china marked 12.5v that would not program, it was not until I got to 25v that they actually did retain the data. They have successfully been erased and then reprogrammed at 25v since too. Interestingly the devices were marked as Intel but when examined through the window with a microscope there was an AMD logo on the die.

2nd Apr 2023, 7:45 am	#6
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,560	Re: 27c64 not programming As far as I know there never was any version of the 2716 which had a VPP of less than 25V so that, plus the fact that you noticed they were really AMD devices, makes it pretty conclusive that you were sold 'disguised' devices. I think possibly the reason for 'painting them up' as 12.5V programmable is that a lot of the popular low end USB powered programmers can not generate the 25V VPP needed by the oldest devices, so prospective buyers would be keen to buy 'unusual' 2716s with an apparent VPP of 12.5V.

2nd Apr 2023, 12:40 pm	#8
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,560	Re: 27c64 not programming I think TWP has the software 'suite' which is used to produce custom eprom images for these radios, because I remember him having problems with the DOS computer he originally used to run it a while back.