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tf_hh

New Hardware: Atari 400 RAM-Card 48/52 KB & external OS-ROM

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I just put the 48/52K card that I have had sitting around since last spring into my 400.  Super easy to install and everything is working great.  Thanks for another great product Jürgen!  

20201122_155639.jpg

20201122_170720.jpg

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2 hours ago, Peter Rabitt said:

WOW, are there any left... the PDF has 0 but who nows LOL

Would like one if available.. 

Neat upgrade..

Peter

Send a message to @tf_hh and he can tell you. Worth waiting for !

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Hi folks,

 

today I´ve discovered a solution for a very nasty problem told be a hand full of people in the last years. Some users told me, that with my Atari 400 RAM cart the system doesn´t start every time. Some users reports 9 of 10 starts where okay, others told me, only 1-2 times from 10 the Atari 400 will boot up. With the genuine 16K RAM cart the systems work fine.

 

Of course I´ve helped all these guys as best I can. In some cases I´ve sent new boards (free of charge), but this doesn´t cure the problem. Of course I thought that my board makes the trouble, but today I test some things and... the culprit is UAV! :-D ( @MacRorie - you should add this to the manual of UAV).

 

What I didn´t recognize, what the fact, that all users complaining (...) about my RAM cart have UAV as the plug-in kit installed. With my SCCC or plain video no one has these problems. So I try my own Atari 400 with UAV and... gotcha! Same problem. I measure around with DMM and scope, but I didn´t find any issue. I change the logic terms, try other signals... nothing helps. Randomly I checked the RESET line at the CPU... What´s that? 2 volts?

 

Now I check the schematics and it´s clear... the RESET line after power-on, delayed by a R/C link, is buffered through one unused gate of the 4050 chip. This one will removed, when UAV is installed. So the RESET line is "floating". This causes some instable start-up situations of the whole bus. The old slow NMOS RAMs and circuits on the genuine 16K RAM cart may better work with this strange behaviour... how ever, it was not my fault 🙂

 

Simple solution: Make a solder-bridge between pin 14 and pin 15 at the bottom side (solder side) of the 400 mainboard where the 4050 was before (chip´s number: A111). I´ve done over 30 cold starts and every time the system boots up fine, so it seems to work without the buffer.

 

I´ve sent also emails to all users where I remember such problems.

 

 

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On 9/26/2021 at 12:42 PM, tf_hh said:

Hi folks,

 

today I´ve discovered a solution for a very nasty problem told be a hand full of people in the last years. Some users told me, that with my Atari 400 RAM cart the system doesn´t start every time. Some users reports 9 of 10 starts where okay, others told me, only 1-2 times from 10 the Atari 400 will boot up. With the genuine 16K RAM cart the systems work fine.

 

Of course I´ve helped all these guys as best I can. In some cases I´ve sent new boards (free of charge), but this doesn´t cure the problem. Of course I thought that my board makes the trouble, but today I test some things and... the culprit is UAV! :-D ( @MacRorie - you should add this to the manual of UAV).

 

What I didn´t recognize, what the fact, that all users complaining (...) about my RAM cart have UAV as the plug-in kit installed. With my SCCC or plain video no one has these problems. So I try my own Atari 400 with UAV and... gotcha! Same problem. I measure around with DMM and scope, but I didn´t find any issue. I change the logic terms, try other signals... nothing helps. Randomly I checked the RESET line at the CPU... What´s that? 2 volts?

 

Now I check the schematics and it´s clear... the RESET line after power-on, delayed by a R/C link, is buffered through one unused gate of the 4050 chip. This one will removed, when UAV is installed. So the RESET line is "floating". This causes some instable start-up situations of the whole bus. The old slow NMOS RAMs and circuits on the genuine 16K RAM cart may better work with this strange behaviour... how ever, it was not my fault 🙂

 

Simple solution: Make a solder-bridge between pin 14 and pin 15 at the bottom side (solder side) of the 400 mainboard where the 4050 was before (chip´s number: A111). I´ve done over 30 cold starts and every time the system boots up fine, so it seems to work without the buffer.

 

I´ve sent also emails to all users where I remember such problems.

 

 

this is part of why I kept saying to piggyback UAV on the 4050 and keep all Atari outputs and functions working... but I always got the 'it works for me' response... yes it works for now... but how about later... Thanks for the write up tf-hh you are once again the voice of reason with full explanations !

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