First time boot troubleshooting

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First time boot troubleshooting

I finally got my apple-1 built! Issue now is getting it to work.

 

I luckily was able to suss out my first issue being 3 dead 74161 ICs causing no video. Those have now been replaced and I now have output.

This is my current situation:

 

I get blinking Ds and $s, I don't think that is quite right since I usually hear about blinking @s

Past that when I hit clear screen I get a screen full of &$ and a blinking F "cursor". Reset appears to do nothing. No matter how much I press clear screen it still fills up with &$'s.

 

Any thoughts where I should look next? Thank you!

 

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Quick update!

A quick update with good news after some messing about, reset now works and I can type in commands and I get output! The issue with &$ continues unfortunately. I feel like this may be an easy fix seeing how it is otherwise functional. Thank you for any input!

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Quick update! Pt2

So the screen issue is definitely at least partially related to the 2504 shift registers. I have sussed out that at least 4 of them are "good" they dont show any difference in behavior when swapped.

 

My keyboard looks to have lost a 7404 in the time I have been working with it. I tested them good earlier but it has been cooked now. I double checked voltages and found a good +5 and +12 volts, I thought the -12 was a little high at -12.4 but if anyone could say otherwise I would love to hear. Reset does appear to work at least in terms of printing a slash then moving down a line, and the clear screen still does not clear the screen other than for the time the button is pressed.

 

Thank you!

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How to investigate the problem.

In post #3, NowlasWolf wrote:

 

" I thought the -12 was a little high at -12.4 but if anyone could say otherwise I would love to hear. Reset does appear to work at least in terms of printing a slash then moving down a line, and the clear screen still does not clear the screen other than for the time the button is pressed. "

 

Uncle Bernie comments:

 

The negative voltage being only 0.4V off is OK. No worries about that.

 

You other problem - clear screen not working properly - most likely comes from bad 1404 shift register (I wonder where you bought them, Unicorn ?)

 

You can pull all six of them in Row D out and then use  a wire with a protection resistor (use ~470 Ohms, it's not critical) to inject logic "H" levels from the +5V rail on the now empty output pins (IIRC, #1 and #5 of their DIL-16 sockets, but please check this against the schematic, as it's from memory). This will allow you to exercise each individual bit of the video data path, and check the ASCII code for the characters you see if that makes sense. The full screen should be the same character.

 

Once you have verified that the video data path as such works OK, you can insert (power off !) one 1404 at a time and see if the "clear screen" command can clear that 1404. If it can't, this 1404 is suspect. Replace with another one . Based on what you wrote above, you may end up with four good 1404 and three bad ones. You should put one of the known good ones into the place for the cursor 1404 (shares the same socket with the DS0025, Row C) and the other good ones in the lower video memory bits. Leave the bad ones out (sockets empty). Then you can type stuff and see if what appears on the screen makes sense, and if the cursor and the scrolling works. If you have i.e. three good 1404 at the LSBs, you could type ABCDEFGH and you should get a sequence of eight characters, with their ASCII codes incrementing (as you have 3 good LSBs).

 

Try to get good 1404 from the vendor who sold you the bad ones as a free exchange of defective merchandize for good ones. I once bought a set of 1404 from Unicorn and IIRC, three of the seven were bad. They required a "Return Authorization Number" to send the bad ones back, and the new ones I got from them for free were OK. So I have a hunch that they do have a way to check them, but they don't check all of the ICs in their kits, and wait for the customers to complain, if bad ones are in there.

 

With my Apple-1 IC kits (now sold out) I avoided all that trouble for me and for the builders by only selling proven good ICs which ran for 4 weeks 24/7 in a burn-in rig, a special Apple-1 with burn-in PROMs which would exercise the memory and the video in a thorough way. So I never had any complaints. Only one IC died at a builder, and it was one of the early 2519N I had, which had a high infant mortality rate, hence, the long burn-in.

 

I replaced it free of charge and everybody was happy. (The later 2519B I used were much, much better, only about 1% infant mortality, and they all had a 1976 date code, very desirable).

 

I don't think that selling Apple-1 kits with no burn-in of all the ICs is commercially viable. Because due to the age of these ICs, it is very likely that 1 out of 3 builds won't work (my calculations based on actual failure rates from my burn-ins, also see may "IC graveyard" posts on Applefritter).

The hassle and loss of time to deal with the situation IMHO is simply not worth selling them at the first place. This is why I insisted on the 4 week burn-in, and made no exception. Other sellers may value their own time to be worth less may see this topic in a different way.

 

- Uncle Bernie

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Will do further testing

Thank you for the testing method! I will definitely give it a try. I actually tried the two suspect ones in the cursor position as well and was rewarded with a no cursor upon power on, this has me hopeful that only 2 of my shift registers are bad. I infact did get them from a set from unicorn, I may have to follow up with them because the 74161 4 bit counters were 3 out of 5 dead. I have since replaced the lot of them with newer replacements, (also from unicorn) while I was picking out parts needed for a gen1 and gen2 ACI since I have both of the boards.

 

I will update if have anything new come up but I am still truly excited to have something finally at least partially working after so many months.

 

I am truly disappointed not getting one of your sets when I could have uncle Bernie but I also enjoy the aspect of troubleshooting and making things work regardless. Granted I would have also enjoyed the much smaller bill haha. I read your one post about creating seeds to continue making kits or at least testing components for future builders to make use of. I think that would be really amazing for the community to do and I would also be interested in doing so, (if I can make my build rock solid in the least haha)

 

Thank you again!

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Testing done

I have followed your steps uncle Bernie and have made double sure that the two 2504 I suspected were the bad actors are infact bad. They don't allow for the screen to be cleared nor be written at all. I have some extras currently on the way. The good news is that the computer portion still looks rock solid! I can't wait to have this 100%!

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It works!!

I got in my new 2504s and the video section works perfectly now!

 

On to the next! I think I am having intermittent memory issues, values don't get written correctly sometimes or get changed, the test print program in the manual even sometimes fails to be entered in correctly. I've had the test print program freeze but at least be escapable.

 

Using the ACI (Original spec, my Ver2 is yet to be built) it fails to read programs, it seems to finish way sooner than it should, it will be halfway into a program and then print the /

 

Obviously I have some instability, anything I can do to help it along? I will say I have a DS0025 and MOS 6502B, I am hoping that would allow for a good timing window for memory errors but perhaps there could be something else I am unaware of?

 

Thank you!

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