Apple II Troubleshooting

[HunterCupp]

Hello all,

I'm breaking this case open again because I simply don't have the needed experience to do anything about this on my own.

Here's a refresher--

A couple years back while working on an Apple II I had acquired, I managed to fry something somewhere. The machine was on, and I had forgotten to turn it off before attempting to insert an expansion card of some kind. (I don't recall what card or which slot) Following that, there was a buzz, and the machine turned off, never to turn on again so far.

Nothing at all happens but a click from the power supply when I flip the switch. Power seems to get to an expansion card I have in the first slot. (An LED turns on.)

Other than that, no beep, no power light, just the expansion card's lone LED.

And no, I don't have an oscilloscope haha.

I am able to share any photos or additional information that may be needed.

Please help if you can, I'd greatly appreciate any effort.

Thanks in advance,

Hunter Cupp

 

[HunterCupp]

Bump--

Anybody?

 

[MacTech68]

First thing you need to do is measure the voltages coming from the power supply.

You do have a mulimeter, I hope?

 

[HunterCupp]

First thing you need to do is measure the voltages coming from the power supply.

You do have a mulimeter, I hope?

MacTech68,

I do indeed have a multimeter.

 

[HunterCupp]

First thing you need to do is measure the voltages coming from the power supply.

You do have a mulimeter, I hope?

MacTech68,

I forgot to mention that I know for a fact that the power supply is functional. I have previously swapped out boards with no change.

 

[daflake]

MacTech68,

I forgot to mention that I know for a fact that the power supply is functional. I have previously swapped out boards with no change.

Putting an expansion card in while the system was on probably blew the system board out. Unless you can see what was damaged, you are going to have a hard time troubleshooting this. You may have see if you can find a new system board.

 

[MacTech68]

With the revision of board you have (the one with the RAM select blocks - marked 16K) checking power isn't as easy.

Remove all cards, remove the upper case and disconnect the keyboard - set the upper case/keyboard aside.

Using the outer part of the video connector as a ground, check these pins on one slot. NOTE: be carefull not to short pins on the slot, especially pin 50 to 49 or pin 33 to 32.

Pin 50 = +12volt
Pin 34 = -5volt
Pin 33 = -12volt
Pin 25 = +5v

And yes, I'm suspecting a fair few parts on D0 on the data BUS might be fried, but first things first before you chase your tail.
[doublepost=1475683298][/doublepost]If, when you unplugged/plugged the board you inadvertently shorted pin 49 to 50, you've sent 12 volts to inputs on TTL ICs that run on 5 volts.

Pretty common for the 8T28 to fry (or the 8304 on later revisions) - but I note that you've replaced both 8T28s from your previous thread.

That leaves the following (from what I can see) as potential suspects:

ROM (ALL) PIN9

74LS257 @B6 PIN9

RAM @C3, @D3, @E3 PIN2

You may need a logic probe to get this sorted - they should be pretty cheap if you can find them.

From your old thread, it DOES appear as though you have the Integer ROMs without a Programmer's ROM.

 

[HunterCupp]

Pin 50 = +12volt
Pin 34 = -5volt
Pin 33 = -12volt
Pin 25 = +5v

View attachment 663125

And yes, I'm suspecting a fair few parts on D0 on the data BUS might be fried, but first things first before you chase your tail.

MacTech68,

I took the Apple II apart and I then tested each pin that you listed on each peripheral slot. They all tested fine.

I'm also uploading pictures of the Apple II, plus the spare board that I have.

The spare board is the one on the floral foam.

 

[MacTech68]

Ok, now, lets test the monitor. Do you have a DVD Player or VHS recorder that can output a composite video signal? If so, plug that into the monitor from the (usually) yellow RCA connector on the back of the DVD player/VHS video recorder. The picture may not look nice, but I just want to establish that it's able to amplify a signal, extract sync and get it onto the screen.

 

[HunterCupp]

Ok, now, lets test the monitor. Do you have a DVD Player or VHS recorder that can output a composite video signal? If so, plug that into the monitor from the (usually) yellow RCA connector on the back of the DVD player/VHS video recorder. The picture may not look nice, but I just want to establish that it's able to amplify a signal, extract sync and get it onto the screen.

I'll do that for you later on today.
Are you asking me if I can get anything to display on the monitor itself?
I can for sure. I have several Apple II monitors that are in working condition, along with countless IIe's.
I'll do it anyway and post pictures if that is what you were asking. But the monitors do in fact work.

 

[MacTech68]

In the meantime, you probably should grab a TTL Logic Probe. 'B&K Precision' make a model DP-21 and there is a store in Columbus that carries them, unless you can find other local stockists.

http://www.alliedelec.com/b-k-precision-dp-21/70146283/

https://www.alliedelec.com/customerservice/forms/contactus.aspx (select your state and click "Show Your Local Sales Offices")

Another cheap tool that has recently become available, are Logic IC testers coming out of Asia on eBay. They test 74, 4000, 4500 series ICs and are cheap compared to devices that were available over the years. Some were several THOUSAND dollars.

Some come as bare boards but a few dollars more gets one in a small hand-held case (my preference).

IC Tester eBay search

(LATE EDIT- In the spirit of putting my money where my mouth is, I've just bought one - it will certainly be easier than setting up the Apple II tester - see below).

Ironically, I used to use (and still have) this AppleII IC Tester card (somewhere) :

http://www.decodesystems.com/apple2-ic-card.html

 

[HunterCupp]

In the meantime, you probably should grab a TTL Logic Probe. 'B&K Precision' make a model DP-21 and there is a store in Columbus that carries them, unless you can find other local stockists.

http://www.alliedelec.com/b-k-precision-dp-21/70146283/

https://www.alliedelec.com/customerservice/forms/contactus.aspx (select your state and click "Show Your Local Sales Offices")

Another cheap tool that has recently become available, are Logic IC testers coming out of Asia on eBay. They test 74, 4000, 4500 series ICs and are cheap compared to devices that were available over the years. Some were several THOUSAND dollars.

Some come as bare boards but a few dollars more gets one in a small hand-held case (my preference).

IC Tester eBay search

(LATE EDIT- In the spirit of putting my money where my mouth is, I've just bought one - it will certainly be easier than setting up the Apple II tester - see below).

Ironically, I used to use (and still have) this AppleII IC Tester card (somewhere) :

http://www.decodesystems.com/apple2-ic-card.html

MacTech68,

I'll definitely grab the logic probe you recommended. I'll also order one of those IC testers.
I'll get back to you once I've got one or the other.

Thank you for your help so far, I've really wanted to get back to this!