Blinking Apple //c

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Blinking Apple //c

Hello,

I currently own an Apple //c with which I have issues and therefore have never been able to use it.

 

Symptoms : 

  • As soon as the computer is turned on, the "Power" light starts blinking continuously
  • Cracking noise is coming from the speaker
  • No startup beep, floppy disk drive does not try to read a disk

What I've done so far :

  • Replaced the external power supply with one from eBay (15V measured with a voltmeter)
  • Tried booting with floppy disk drive unplugged
  • Reseated DIP chips
  • Replaced internal power supply
  • Measured the 7905 with a voltmeter, got -5.1V as expected

 

Unfortunately, it is still not working. Even though the logic board seems pristine.

 

I thought I could get some help from you guys, I'm really starting to be hopeless.

 

Thanks in advance,

Cheers

 

- Arths

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Arths wrote:Replaced internal

Arths wrote:

Replaced internal power supply

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

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

 

Regards

Ralf

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Hello Ralf,

Hello Ralf,

 

Thanks for your answer!

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

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

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Arths wrote:Where do I check

Arths wrote:

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

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.

 

Arths wrote:

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

Every power supply can be faulty.

 

Regards

Ralf

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Here are my results

Here are my results

Capacitors

  • C57 shows zero
  • C44 and C43 shows infinite when speaker is unplugged, .845 when it is

Rails

 

Thanks

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Arths wrote:C57 shows zero

Arths wrote:
  • C57 shows zero

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

 

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

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

 

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Just wanted to test

Just wanted to test continuity for C57, C44 and C43.

 

Pin J11-12 labeled FFF shows zero.

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

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Arths wrote:Pin J11-12

Arths wrote:

Pin J11-12 labeled FFF shows zero.

... when the power switch is ON?

Arths wrote:

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

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

 

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Oh okay I see.

Yes when the power switch is on, is this expected ?

 

I will try to test the LM311 using the schematics.

Just purchased another external power supply online.

 

Thanks for your patience

- Arths

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Arths wrote:I will try to

Arths wrote:

I will try to test the LM311 using the schematics.

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

 

 

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There is definitely a problem

There is definitely a problem here, here are my results on testing the LM311

 

  • Pin 7 gives me 5.01 volts
  • Pin 8 gives 15.2 volts as expected
  • Pin 2 gives 4.99 volts 
  • Pin 3 is 7.20 volts

 

So I guess you were right this is a power supply issue ?

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Arths wrote:So I guess this

Arths wrote:

So I guess this is a power supply issue ?

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

 

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Well thank you a lot for your

Well thank you a lot for your help, you are really helpful as I am a total beginner in electronics.

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


Best regards

- Arths

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Arths wrote:I'll wait until I

Arths wrote:

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

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

 

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RalfK wrote:Let's hope that

RalfK wrote:

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

 

 

Unfortunately that did not work, we'll see.

 

Best regards

Arths

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Just received the new

Just received the new external power supply, unfortunately it is still not functional..

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

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

(http://appleclub.pl/wp-content/uploads/2017/04/DSCF4364.jpg)

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Arths wrote:Just received the

Arths wrote:

Just received the new external power supply, unfortunately it is still not functional..

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?

 

Arths wrote:

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

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.

 

Arths wrote:

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

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

 

Regards

Ralf

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Hi Ralf,

Hi Ralf,

Thanks for taking time to reply

 

RalfK wrote:

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?

I don't think I'll be able to get my hands on one of these and that the external power supplies are faulty.

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

 

RalfK wrote:

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.

 

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

I've checked voltages using the schematics, I'm getting 5V through R13, R14 and R12.

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.

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Arths wrote:Do you have

Arths wrote:

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

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

 

Arths wrote:

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

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

 

Arths wrote:

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.

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

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Just re-checked everything on

Just re-checked everything on J11 connector and so far so good.

 

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

 

Great, that's good to know.

 

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.

 

Well I might purchase a new one online.

Also checked the J8 internal disk connector and I get right voltages as well.

 

So that leaves us with the other symptoms :

  • Cracking noise is coming from the speaker
  • No startup beep, floppy disk drive does not try to read a disk

 

I can't determinate if something is coming up video wise as I don't have a composite adapter / cable right now.

 

Best Regards

- Arths

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Hello,

Hello,

 

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.

 

I've replaced the LM311 yesterday with a brand new one.

Flashing power light is now gone, and I get the expected voltages for the chip.

  • Pin 7 0,11V
  • Pin 8 15,15V
  • Pin 2 4,54 V
  • Pin 3 7,19V

 

I've also replaced C51 and C57 just in case, but still no startup beep.

Do you think a bad RAM chip could prevent it ? I've checked the Apple IIc Reference Manual and the startup beep is at the end of the cold boot sequence, just before checking disk drive.

 

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

Maybe I should try cleaning the board with vinegar.

Tell me what you think.

 

Best regards,

Arths

 

 

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Arths wrote:Going to go to a

Arths wrote:

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

That's the most important action.

 

Arths wrote:

Maybe I should try cleaning the board with vinegar.

On your pictures this board seems to be not very dirty. Later when optimizing the optical aspects of that action you can use glass cleaner or (Isopropyl) alcohol.
 

Regards

Ralf

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I had the same blinking

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.

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Hello guys,

Hello guys,

 

That's the most important action.

 

I'm going to receive a Composite to HDMI adapter tomorrow so I'll keep you updated.

 

On your pictures this board seems to be not very dirty. Later when optimizing the optical aspects of that action you can use glass cleaner or (Isopropyl) alcohol.

 

Alright, good to know. I don't think I will need to do it then.

 

I had the same blinking 

 

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.

 

Yup, reseated all chips twice. Still nothing.

Should I try to clean the pins on them after checking what's on video ?

 

Best Regards,

Arths

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Hi,

Hi,

 

Just plugged the Apple IIc on the Composite adapter and this is what I get.

 

And sometimes..

I'm unable to run the self-test, even with keyboard unplugged.

Although while I press CONTROL-RESET the screen freezes so CPU seems to understand that.

Any ideas ?

 

Edit : Just ordered five TMS4164 RAM chips from AliExpress to piggyback if there are faulty chips.

 

Regards,

Arths

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