Rapid flashing and V-sync scrolling

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Rapid flashing and V-sync scrolling

Hello, this is my first ever Apple 1 replica build! The video in this post is showing the main issue I've run into after having an opportunity to replace the damaged +5v regulator and the +12v regulator! My initial thought was a bad crystal but after replacing it with a new one the problem persisted. I started looking through the forums here for an answer and couldn't find one. A recent post made me start pulling chips one by one to see what was wrong. The included picture is of the running board with no 74166N chip installed at D-1. Am I on the right track?

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No, sorry, you are NOT on the right track !

In post #1, AuraKSphere wrote:

 

"A recent post made me start pulling chips one by one to see what was wrong. The included picture is of the running board with no 74166N chip installed at D-1. Am I on the right track?"

 

Uncle Bernie says:

 

OK ... so there are people out there who think that pulling an IC and leaving the socket empty will actually fix the problem ?

 

This is really cool ... so if the engine in your car does not start, you start to rip out parts from the engine until it would start ?

 

A little bit of reason and logic would be in order: every IC in a system serves a purpose. If it had no purpose, the designer would have removed it from the design and the IC would not be there in the first place. If you pull ICs leaving empty sockets you cripple your system. There are very rare cases where removing an IC can give a clue what is wrong. For instance, I once recommended a builder to remove the 555 timer (and ground the logic signal it makes) to help isolate a problem associated with the cursor logic.  Only in such cases, removing ICs serve a specific and known purpose.

 

In any other case, you have to substitute the IC you have removed by a known good one before turning the power back on.

 

If you don't use a known good IC as the substitute, you may have put in another bad one. I encountered some new-old-stock ICs where half of the tube were bad. So if you don't know if your substitute ICs are good, use at least a different one from another tube, preferably another date code or even another manufacturer.

 

As far as I can see from your screen shots, your Apple-1 almost works. At least the dot pattern is there and no dots are missing. This is a known parasitic effect in the Apple-1 but believe it or not, the dot pattern tells us that the whole timing chain is OK. Which is a lot.

 

You may not have an IC issue but a monitor sync issue. Rolling picture can usually be solved by adjusting V-HOLD. Slanted lines can be solved in many cases by adjusting H-HOLD and/or the VIDEO LEVEL pot on the Apple-1 (video level too low typically causes sync issues).  The rapid blinking is normal after the Apple-1 is turned on. It should go away if you give a CLR SCREEN. After CLR SCREEN one blinking cursor ('@') should appear and the rest of the screen should be blank. RESET should then start the 6502 and Wozmon should give you a prompt. These tests can be done without a keyboard, just using a jumper wire, but for reasons of safety I recommend a GIMMICK SWITCH (search this forum for it).

 

The outcome of course depends on the story of what happened to your Apple-1 before this. If the +5V regulator and the +12V regulator were bad and did cause overvoltage, a lot of chips could have been damaged.  Or did you check all the regulated voltages before you populated the sockets with ICs, didn't you ?

 

If you did, this begs the question what really happened to kill said two regulators. Normally, they are virtually indestructible, as they have self-protecting circuits.

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What happened

The +5v regulator was dropped on concrete while looking for bolts to mount the heatsink and regulator to the board, the +12v regulator was just bad. I did populate the Terminal section and B-2 after testing all the regulated lines first, at the time of first power on the +5v and -5v were stable, the -12v line was stable and the +12v was non-reponsive. After a few power ups the +5v started oscillating rapidly while the terminal section was populated. Replacing the regulator fixed the oscillation. From there I tried out a method if troubleshooting I believe you recommended to another user about removing the 2513, 2519b and the 2504 chips to get different outputs to the tv and got positive results but nothing changed the scrolling and flashing issue, then came to the point where i pulled the 74166N and got the solid screen. At the moment, that's where I sit in the trouble shooting stage. 

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A Thanks to Uncle Bernie

So, How did I get here?  It started back in September after watching The 8Bit Guy's Apple 1 video and some encouragement from my friend, I purchased a board. My overall goal was to build a functional replica with all off the shelf componets (Ebay, Unicorn and similar places of purchase.)

I got my board in september started getting all the compents together I started and after about a month or so and ran into voltage issues on some of the lines due to bad regulators. Replaced them and had correct voltages after that. Put in the video sections chips that I had purchased earlier in and immediently ran into video issues with rapidly flashing and scrolling of the signal on the Tv I was using for it. Replaced the 74166 and it helped fix the brightness and some of the random scrolling. 

I had gotten in touch with Uncle Bernie by this point and he had helped me through the debugging of the signal that I could get during intial start when it was stable. Bad 2504v's plauged the build from these tests. At least three according to the results. Removed them from the board and the output was better no more random % and 5. The timing and cursor logic was working however. 

I was given the test to see if the 2504v's were truly bad and using this I found that three from before were for a fact bad and removed permenently.

It was this point after not getting any further my journey of all off the shelf came to and end and I ordered One of Uncle Bernie's kits. Being a hapless maverick has its down falls and mine was filled with electrical and chip problems. 

From here the kit soon arrived and I replaced all the chips on my board with the kit and adjusted the 74123 timing oneshot with the provided kit and it worked perfectly from the boot up to running the hidden diagnostics page. Which to me was a thrill to see happen. I had wanted to make my own burned-in kit and went to check how many of my chips were actually bad. I found 1 more 2504, 1 mk4027 and the two PROMs which were not programmed with anything. 7 total chips. Of which I would've never found without Uncle Bernie's kit or his expert advice and guidence. 

I wanted to make my own burn in kit with my own chips along side his kit and have started to do so along with and upgraded CCTV for a perfect signal each time.

Thanks again. 

 

 

 

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