Apple-1 replica problem at first boot.

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Apple-1 replica problem at first boot.

Hello all. First day here and first post for me with a kind of bad news. 

I just finished my Apple-1 replica and what i got is rolling characters. Even if i try clear the screen start from the beginning.  I will appreciate if I have some help from you please.

 

Here is the video:  https://www.veed.io/view/ac7a3362-b7f3-4c9a-bd03-03319ebd7f78

 

Thank you

 

 

 

 

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If you have no keyboard

If you have no keyboard attached, look at post #12 of this thread:

 

https://www.applefritter.com/content/half-problem-solved-74123-ic-now-i-have-one-more-minor-problem

 

If this does not help ( or known good keyboard attached) it's most likely a DRAM problem which makes Wozmon do weird things. Again, the thread above will enlighten you.

 

Seems we have caught another "maverick" builder who did not use my famous IC kit and now goes through all the agony, pain and suffering I myself went through when I built my first Apple-1. Then I proceeded to analyse it and fix the quirks / bugs / problems it has. Those builders using my IC kits always have 100% success at first turn on - if they follow my 62 page "Tips & Tricks" pdf that comes with the kit. These are 62 pages full of possible pitfalls to be avoided. Only a few of "my" builders ignore the "Tips & Tricks" and then make mistakes. But these mistakes can be corrected.

 

Oh I love these "maverick" builders like you, LanciaDelta. Because their failures and their suffering proves that my famous Apple-1 IC kits are worth their money. Every cent of it. As a sidenote, as far as Lancias are concerned I'd prefer the Lancia Stratos HF. Alas, my younger self was too much in the Maserati, Ferrari and Lamborghini collecting world to pay attention to the Lancias or Alfa Romeo sportscars. Muuuch cheaper to keep running and still a lot of fun.

 

- Uncle Bernie

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thank you so much for the

thank you so much for the reply uncle Bernie.

 

I installed the 2K resistor but I had no progress.

 

measuring the temperatures of ram's I found one that was a little warmer.

I replaced it as I had 2 spare parts, and everything seems to be working properly after CLR and RST,

except for the home screen in cold boot.

 

the screen is this:

 

I think it is not correct in cold boot.

 

next step is to make the uncle Bernie's keyboard emulator, but it will take me a few days.

 

is there any IC or something else I need to test for the wrong home screen?

 

thank you very much,

with appreciation, Pericles

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In post #3, Lancia Delta

In post #3, Lancia Delta wrote:

 

"I think it is not correct in cold boot."

 

Uncle Bernie answers:

 

Don't worry about the cold boot screen. This has been discussed in post #6 ... #9 of the thread mentioned in my previous post. Most newbies fall prey to the false cargo-cult type myth how the power up screen of an Apple-1 should look. As long as you see some rows of _@_@_ after sufficiently long power off and most of the @ blink (like the cursor) there is no need to take any action about finding a potentially bad IC.

 

The truth about the health of your terminal section can be found out with the diagnostics page in the A1, A2 PROMs which come with my kits, but you can also type in the example program from the Apple-1 manual, and then watch for wrong characters or other weird things happening on the screen. The advantage of the pattern I use is that it has been designed in such a way that any irregularity disturbs the diagonal stripe pattern in a very obvious way that can be seen at one glance. Furthermore, my diagnostics program exercises every location in the video shift registers through all possible bit patterns and so it can help to detect cross coupling sensitivities between shift register cells for which these early and primitive dynamic shift registers are infamous for. These were the first PMOS ICs to be mass produced after the silicon gate PMOS processes became available in the late 1960s. So they were far from being perfect. They were also used as "pipe cleaners" after a cleanroom mishap which explains the terrible quality of some of the production lots that are "left over" nowadays. IMHO these are reject lots which somehow made it into the warehouses of IC brokers and they "slept" there for nearly half a century waiting for unsuspecting buyers. I had terrible fallout rates with most of the 2504/1404 type ICs from many manufacturers and was very lucky to find a lot of AM2804 that was made by AMD in the early 1980s and is mostly trouble free.

 

- Uncle Bernie

 

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UncleBernie wrote:as far as
UncleBernie wrote:

as far as Lancias are concerned I'd prefer the Lancia Stratos HF.

 

I would go for an 037 personally :)

 

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Status update

after I made uncle Bernie's keyboard emulator, I run the character test and some programs and all seem to work fine, except of the home screen, which still has one and a half wrong lines.

I'm referring to a cold boot even after a whole day.

I have read that it is not important, but I would very much like to know the reason why it happens, as well as if it can be resolved so that the home screen is full with "_@".

 

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Is it so hard to kill this false _@_@_ start screen myth ?

In post #6, lancia delta wrote:

 

"but I would very much like to know the reason why it happens"

" as well as if it can be resolved so that the home screen is full with _@"

 

Uncle Bernie answers:

 

Apple-1 has no power on reset so all counters etc. come up in an uncontrolled way. During this time extraneous "cursors" found in the power up state of the dynamic shift register under the DS0025 clock driver (in the same socket, Row C) may or may not initiate scrolling operations. These can mess up the start screen. And other than that, the "wake up" state of these dynamic shift registers is not guaranteed to be all "0" or all "1" ... there are two banks of 512 shift register stages in each, and one bank wakes up as "0" while the other bank wakes up as "1", but this is the majority of the cells, not guaranteed for each one.

 

The only way to remedy this is to change the dynamic shift registers against others until you have a set which shows the mythical _@_@_ pattern that, it seems, now has turned into a religion and people start to insist on getting the "proper" pattern upon power up, but alas, this pattern is not guaranteed by anything.

 

If you run your Apple-1 from a switchmode power supply and not on transformers, you may see much, much weirder things happening on the screen before you push CLR SCREEN. Due to the different speed / sequence how the various voltages power up.

 

How about turning on the power only with CLR SCREEN and RESET being pressed ? The release CLR SCREEN and then RESET and all is good ;-)

 

- Uncle Bernie

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