Apple 1 voltage problem

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Apple 1 voltage problem
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Image icon The screen when starting3.18 MB

After my copy of Apple1 is started, the -12V voltage will be reduced to -11.5V in a few seconds and suddenly become 0V. Has anyone encountered this strange problem? If I do not insert AM1404APC, the voltage will be reduced to -11.6V and keep it. There is nothing about the screen after startup.

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Hi aihk!

Can I see a picture of your AM1404APC? I hope you didn't buy them from Aliexpress? There are a lot of fakes there now, at best you will get relabeled NE555s.

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IMG_4694.JPG

 

 

Is there any way to test the quality of AM1404?

 

 

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Macintosh_nik wrote:Can I see
Macintosh_nik wrote:

Can I see a picture of your AM1404APC? I hope you didn't buy them from Aliexpress? There are a lot of fakes there now, at best you will get relabeled NE555s.

Can this chip be used? I seem to have seen you have used it

 

 

 

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Some hints ...

... your AM1404 look genuine. At least they are not laser marked .... all the fake ones I ever saw were laser marked, which the originals never were. These crafty Chinese counterfeiters also sell laser marked "6502". Never saw an original 6502 being laser marked. Production of NMOS 6502 stopped long before laser marking became mainstream in the semiconductor industry.  Western Design Center of Bill Mensch still make and sell genuine 65C02 of their own design. No need to buy from Chinese counterfeiters.

 

Your power up screen indicates that your 1404 are not shifting bits. Nothing, nada, there.

 

Maybe a bad / counterfeit DS0025 ?    --- it's another "hot" and rare item and the Chinese sell lots of counterfeits which are  relabeled industry standard MOSFET gate drivers, but  in a CMOS technology, and not bipolar. Some of these CMOS drivers blow up when exposed to the 17V in the Apple-1, as they are only rated for 12V. There are others which are rated to work at these voltages but they lack the pulldown resistors on their inputs, which only the DS0025/DS0026 have. So both inputs never have  a stable operating point and both drivers may activate at the same time. If they do, the AM1404 will get shootthrough current, will get hot, and may die. This excess current on -12V may also motivate the 7912 regulator for -12V into thermal or overcurrent shutdown.

 

If you have an oscilloscope, check PHI3 and PHI4 to have +5V/-12V swings (NO AM1404 in the sockets) and that they don't overlap in the negative region (-12V).

 

To test the 7912 regulator, you can load it at the appropriate 22 uF capacitor (the one between -12V and GND) by putting a parallel resistor of  220 Ohms (or so) in parallel to that resistor. A good 7912 should be able to sustain that load and still make -12V. If it doesn't, check the voltage at the 2200uF capacitor which must be -14V or higher.

 

- Uncle Bernie

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UncleBernie wrote:... your
UncleBernie wrote:

... your AM1404 look genuine. At least they are not laser marked .... all the fake ones I ever saw were laser marked, which the originals never were. These crafty Chinese counterfeiters also sell laser marked "6502". Never saw an original 6502 being laser marked. Production of NMOS 6502 stopped long before laser marking became mainstream in the semiconductor industry.  Western Design Cente

 

 

Thank you for your answer ~ I sent a picture of DS0025. I measured the resistance of PIN3-4 220Ω.

 

I have no oscilloscope. I measured the voltage of 2200UF capacitors up to 40V. I see that the capacitor of 2200uf on the manual is only 20V. My 5600uf capacitor voltage is 11V.

 

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Hi aihk!

As respected Uncle Bernie already said, your 1404 does not look fake, but there is no assurance that they are in working condition. My friend invented a tester for these shift registers, it's an open project, you can check it out. He also sells self-assembly kits on eBay. I personally haven't tried shift registers in round metal cases, but many guys have, they work fine.

https://github.com/renatasdgt/1024bit-shift-register-ic-tester

 

 

 

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Hi aihk!

Your DS0025 is not suspicious, it is genuine. Try one simple trick, change 1404 in position D11B under DS0025 to any other position. From my notes a non working shift register in that position will produce a blank screen, in other positions it will be a "corrupted" start grid. Check out the ko nata of horrors topic, I've added pics of the symptoms there.

https://www.applefritter.com/content/horror-room-symptoms-bad-cis 

What kind of board do you have? I'm a bit puzzled by the silkscreened ICC11A above DS0025. It shouldn't be there.

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Macintosh_nik wrote:Your
Macintosh_nik wrote:

Your DS0025 is not suspicious, it is genuine. Try one simple trick, change 1404 in position D11B under DS0025 to any other position. From my notes a non working shift register in that position will produce a blank screen, in other positions it will be a "corrupted" start grid. Check out the ko nata of horrors topic, I've added pics of the symptoms there.

That silk print was not available ~ I show it.I should now insert all 1404 in 5 seconds,-12V is reduced to 0.

 

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Hi aihk!

I think we can assume for now that your 1404 and DS0025 are in working order. Can you measure the voltage across the three large capacitors? There should be on the left pins of the capacitors:

Top - I have +11.3V

Middle - I have -19,7V (here "minus").

Bottom - I have +19.9V.

Are the other voltages on the board normal? I can add a photo of the power supply circuits, very handy when debugging. What is the power supply for your replica?

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Hi aihk!
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Macintosh_nik wrote:I think
Macintosh_nik wrote:

I think we can assume for now that your 1404 and DS0025 are in working order. Can you measure the voltage across the three large capacitors? There should be on the left pins of the capacitors:

Top - I have +11.3V

Middle - I have -19,7V (here "minus").

Bottom - I have +19.9V.

Are the other voltages on the board normal? I can add a photo of the power supply circuits, very

 

I just made the simulation of the transformer. I wondered if I was misunderstood. Should the transformer of 28V should be a dual 14 transformer or a dual 28V transformer. So my capacitor voltage is very high, reaching 42V, I am a 7912 manual, and the extreme voltage is 35V. Want to ask if it is a double 14V transformer?

 

 

It should be a transformer like T2 or a transformer output like T3. Thank you for your answer

 

 

 

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Hi aihk!

42V is a lot. Something is wrong, it should be around 20V. Measure the voltages between the pins of the 6-pin power connector. It should be:

 

1-2 - ~10V (I have 10,9V)

 

3-4 - ~28V (I have 30,9V)

 

4-5 - ~14V (I have 15,3V).

 

1 pin is the one closer to the heatsink and LM323K. 

 

Let someone else comment on the scheme, I collected my power supply by photo, without schematics. Unfortunately, I am not good at circuit diagrams.

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Macintosh_nik wrote:42V is a
Macintosh_nik wrote:

42V is a lot. Something is wrong, it should be around 20V. Measure the voltages between the pins of the 6-pin power connector. It should be:

 

1-2 - ~10V (I have 10,9V)

 

3-4 - ~28V (I have 30,9V)

 

4-5 - ~14V (I have 15,3V).

 

1 pin is the one closer to the heatsink and LM323K. 

 

Let someone else comment

Thank you very much. Through your answer, I know the reason for my transformer. I bought a new transformer and tested the feedback result after receiving it

 

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Macintosh_nik wrote:Your
Macintosh_nik wrote:

Your DS0025 is not suspicious, it is genuine. Try one simple trick, change 1404 in position D11B under DS0025 to any other position. From my notes a non working shift register in that position will produce a blank screen, in other positions it will be a "corrupted" start grid. Check out the ko nata of horrors topic, I've added pics of the symptoms there.

 

My voltage is normal, and I read your article carefully. Now my boot is like this. Where will it be? Thank you for your answer

 

 

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aihk wrote:Macintosh_nik
aihk wrote:
Macintosh_nik wrote:

Your DS0025 is not suspicious, it is genuine. Try one simple trick, change 1404 in position D11B under DS0025 to any other position. From my notes a non working shift register in that position will produce a blank screen, in other positions it will be a "corrupted" start grid. Check out the ko nata of horrors topic, I've added pics of the symptom

 

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