Apple 1 Boot Up Tests

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RussellSpeight1967's picture
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Apple 1 Boot Up Tests

I'm still trying to get my Apple 1 Terminal Circuit working correclty.

https://www.applefritter.com/content/apple-1-replica-bootupdisplay-problem

My Apple 1 does not complete Point 3 below, the "@" do not flash.I've ordered 74161, to replace the 74161A, used in Row D, as I read about the need to mkae sure D8 is 74161, not 74161A.

 

Post #21

Remove all the chips from rows A and B.  Remove  D2 (2513), C3 (2519) and D4a, D4b, D5a, D5b, D14a, D14b and C11b (2504). ICs removed.

 Power on.

 

 1) Video section displays 40 x 24 fixed "" symbols (with no 25xx parts present) Russ >>Tested, it works.

 

 2) Video section displays 40 x 24 fixed "@" symbols (with only 2513 present)

Russ >> Tested, it works.

 

 3) Video section displays 40 x 24 flashing "@" symbols (with 2513 and 2519 present)

Russ >> Tested, does not flash.  The clear screen key board press, clears the screen while the clear screen button is pressed, once the key is released the "@" reappear, but do not flash.

 

 4) Video section displays full screen of flashing "_@" symbols (with all 25xx parts present) and can be cleared with CLR line

 Once you reach step 4, use your scope to observe pins 1 and 5.  They should be very similar.

 

 Once the videop is working properly, then populate rows A abd B.

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Uncle Bernie recommends to fully populate the motherboard

In post #1, RussellSpeight1967 wrote:

 

" Once the video is working properly, then populate rows A and B".

 

Uncle Bernie advises:

 

I have always recommended to fully populate the Apple-1 motherboard and not do the half-half approach in Mike Willegal's building instructions.

 

The reasoning behind this is as follows:

 

1. If you have checked all the regulated voltages to be correct before populating the IC sockets, there is no higher  risk for IC damage regardless of whether the motherboard is half or fully populated.

 

2. A missing CPU section can cause bizarre behaviour of the terminal section. Builders have wasted countless hours chasing down these "bugs" which just would go away if the motherboard is fully populated.

 

3. You get an earlier feedback if the CPU section works, too. This takes a lot of anxiety out and leads to a more relaxed work.

 

4. The really expensive and rare ICs are in the terminal section. The ICs in the CPU section are cheap and easy to get. So why try to protect the less valuable ICs in the CPU section and start with the terminal section ? If somebody wants to split the risks of damaging ICs, it should be the other way around. Alas, in the Apple-1, this can't be done easily as the CPU section lives on many signals coming from the terminal section.

 

- Uncle Bernie

 

 

 

 

RussellSpeight1967's picture
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I will add all ICs and see

I will add all ICs and see how I go.All voltages have been checked, even though my soldering looks poor, I've checked for "dry joints" and continuity seems good.

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