Blinking Apple //c

[quote=Arths]

Replaced internal power supply

• Measured the 7905 with a voltmeter, got -5.1V as expected

[/quote]

Did you check the other voltages especially the +5V?

Regards

Ralf

[quote=Arths]

Where do I check the +5V on the logic board ?

[/quote]

Do you have the schematics of your IIc? If not, here:

https://mirrors.apple2.org.za/ftp.apple.asimov.net/documentation/hardware/schematics/Schematic%20Diagram%20of%20the%20Apple%20IIc.pdf

Look at page 5. There are the definitions of the connectors. J11 is the internal power supply.

[quote=Arths]

I need to precise that I didn't have the original power supply, so maybe the replacement is faulty ?

[/quote]

Every power supply can be faulty.

Regards

Ralf

[quote=Arths]

• C57 shows zero

[/quote]

C57 is the capacitor of the incoming voltage from your external 15V power supply. If there is "nothing" this external box is off.

[quote=Arths]

• C44 and C43 shows infinite when speaker is unplugged, .845 when it is

[/quote]

Of course. These capacitors do not belong to the power supply. See page 3 of the schematics.

The five voltages at the internal power supply connector are ok. If these values are stable ...

What do you see at pin J11-12 labelled "FFF"?

Regards

Ralf

[quote=Arths]

Pin J11-12 labeled FFF shows zero.

[/quote]

... when the power switch is ON?

[quote=Arths]

I see the trace coming from the power switch, is that where the problem is ?

[/quote]

I don't think so.

Read the "IIc Reference Manual Vol 1", chapter 1, page 6!

"Warning

If the power light flashes on and off, turn off the computer immediately. Find out what caused the condition (such as a brownout) and remedy it before turning the computer on again. Above all, do not use the disk drive when the power light is flashing; this may damage the computer."

Glad to have the Technical Manuals. But unhappy with this meaningless text. Means: go to your Apple dealer and buy a new one.

Go to the schematics of the IIc to page 4. At the bottom there is a NE555 and a LM311. They are responsible for the flashing power LED. I think the NE555 does the blinking and the LM311 watches the incoming voltage (called "+12VIN" but really accepted around 15VDC). I think there is the cause of your problem: either the LM311 is dead, the 5V supply of the internal voltage regulator,  or your external power supply is faulty.

Try your IIc with another power supply! 15VDC are good.

Regards

Ralf

[quote=Arths]

I will try to test the LM311 using the schematics.

[/quote]

Pin 7 of this LM311 must have a very low voltage, means <0.7V (or so). I just tested my IIc and I see there 0,06V. My original external European power supply delivers around 16,5V, and this IIc works with one internal disk drive.

At pin 8 of the LM311 you must see the voltage from your external power supply without any (even short) interrupts. At pin 3 you must see around 7,2V with your 15V switching power supply (external voltage * 10/21). At pin 2 there must be 4.5 to 4.6V.

If your external (switching) power supply produces even very short interrupts, I think you will see different voltages at pin 7 and also at pin 2.

Try another power supply! 1.2A @15VDC are enough. It's probably your powerful (and cheap) switching power supply.

Regards

Ralf

[quote=Arths]

So I guess this is a power supply issue ?

[/quote]

I assume that this switching power supply is not appropriate for this usage. Too strong (5A) and "confused" by the large capacity C57. You can try to remove this large capacity near the power switch. Probably this will help.

Another idea: insert a resistor into the cable from the external power supply to your IIc i.e. 1Ohm >2,5Watt, better more Watt. This resistor will be a bit more than warm (estimated upto 2,5Watt heat).

Another hint: disconnect the power cord from the external power supply if the IIc won't be used. Cheap chinese switching supplies (if used as an external replacement) don't like this mode. With the original external power supply you see a power consumption of nearly 5W if the power switch is switched off. This heats the external "brick".

Regards

Ralf

[quote=Arths]

I'll wait until I receive a new external power supply bought from RetroGameSupply which should respect the original specifications. Keeping you updated.

[/quote]

Let's hope that this is the solution. But I have another (last) idea: switch ON your IIc, connect your actual external power supply with the IIc and - last! - connect the external power supply to 230V. Probably this is a temporary solution.

Regards

Ralf

[quote=Arths]

Just received the new external power supply, unfortunately it is still not functional..[/quote]

Hm, can you use a lab power supply or something like that? This should display the actual current upto 2A. Or can you get an oscilloscope?

[quote=Arths]

I have exactly the same voltages for the LM311 (which might be faulty?), nothing going through R13, R14 and R22.

[/quote]

Of course this LM311 may be dead. With a dead LM311 the LED would blink but the IIc would start normally. So I think there is something wrong with the power supplies. And this seems to be not a static issue but a dynamic. So you should look at the incoming voltage from the exernal power supply and the 5V on the mainboard.

In your first posting you wrote that this Apple IIc was never working before. Probably there are some other issues which influence the power supply.

[quote=Arths]

One thing I don't understand is why are there IIc logic boards where these chips are completely absent ?

[/quote]

This board will never blink. The POWER LED will always be on.

Regards

Ralf

[quote=Arths]

Do you have specific points where I should check for right voltages ? (Already checked the rails)[/quote]

The connector of the internal power supply will be ok at the moment.

[quote=Arths]

Oh so these chips will never prevent my IIc from booting right, they do serve as a warning purpose ?

[/quote]

Yes. As you can see on the pict from the polish site.

[quote=Arths]

Also noticed that the 5V (instead of 0.7) coming from pin 7 of the LM311 goes to pin 4 (RESET) of the NE555 which might trigger it.

[/quote]

I don't know why the LM311 does this. I'm not an analogix :-)  So I would watch the two voltages which are reponsible for this behavior if the LM311 is not dead. A two channel oscilloscope would be good.

If you have a new LM311 you can replace this little chip and see what happens. But your IIc won't boot after this action as it does at the moment.

Regards

Ralf

[quote=Arths]

Going to go to a friend's place to see what comes out from the composite video connector.[/quote]

That's the most important action.

[quote=Arths]

Maybe I should try cleaning the board with vinegar.

[/quote]

Regards

Ralf

I had the same blinking problem but the computer worked perfectly. Replaced the L1311 and all worked right. Have you tried reseating all chips? Checked the ROM? If by any chance you have another ROM, swap it. Better if it's ROM 3 or 4, to be able to fdo the self test.

Good luck.