Apple IIe scambler display no keyboard led

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Apple IIe scambler display no keyboard led
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hello everyone, I have this apple IIe, the power supply was completely delivered and the voltages are perfect, initially it didn't turn on there was smoke on the capacitor C17 because it was shorted and it was replaced, now it turns on but this screen appears , no sound and no light on the keyboard, the red led of the motherboard is steady and on, I tried to swap all the integrated (the removable ones) with another APPLE 2e and the situation hasn't changed

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Try with the keyboard

Try with the keyboard ribbon cable unplugged. This is what you should be seeing and hearing: https://youtu.be/igii1OIWw7Y

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No difference with no

No difference with no keyboard cable 

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Are you sure you have +5V on

Are you sure you have +5V on the motherboard under load? And if yes, why is the keyboard light bulb off? It's not a LED, it's just a regular incandescent light bulb between the +5V rail and ground.

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Yes, all the voltages are

Yes, all the voltages are present, in any case, I still tried swapping the working power supply from the other APPLE IIe perfectly working and the result is identical

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Then why is the light bulb

Then why is the light bulb not on? Is it burned? Is it missing?

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I don't know if the lamp is

I don't know if the lamp is burnt out but even if it was I don't care, I want to see it working first :)

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Look at it this way: unless

Look at it this way: unless the lamp is burned or missing, it's absolutely impossible for the computer to work, since the lamp sits directly between the +5V rail and ground. So if you want to fix the computer, the very first thing you should find out is why the lamp is not on, as it being off means that you don't have +5V.

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ICs without power?

First, I see that you replaced C17 with a 22uF. I'm not familiar with the PAL version of the IIe but you should make sure it's correct. C17 is usually a 10uF capacitor.

Also, if you have access to an oscilloscope, I would start by checking if the 6502 and the HAL has clock signal.

Also check that all ICs have +5v on their power pin. I suspect that some are unpowered since there is no sound and there is no light on the keyboard. This light is directly connected to +5v via the keybard connector pin 3:

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surely they come out from the

surely they come out from the power supply maybe it stops at some point, I try with the tester to see if the 5v reaches the bulb then, I don't have the oscilloscope, for the c17 it is a temporary solution to test it for a few seconds, I also tried an radial capacitor at 10uf but it does the exact same thing , I'll update you on the 5v voltage on the keyboard connector, thanks to all for the replies

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frozen signal wrote:First, I
frozen signal wrote:

First, I see that you replaced C17 with a 22uF. I'm not familiar with the PAL version of the IIe but you should make sure it's correct. C17 is usually a 10uF capacitor.

Also, if you have access to an oscilloscope, I would start by checking if the 6502 and the HAL has clock signal.

Also check that all ICs have +5v on their power pin. I suspect that some are unpowered since there

5.09v present on pin 3 of the keyboard, I also changed the input capacitor by 10uf, situation unchanged, all identical to before

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From what I can gather so far

C17 is on the -5V rail. Do you have a stable -5V?

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Remove the CPU.  If the

Remove the CPU.  If the screen doesn't change then I'd suspect that.

 

 

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Uh-oh.

I'm re-reading your first comment where you said you tried to swap all the removable ICs. Did you mean all those that are not soldered on? Or did you mean those you were able to pull out?

Did you swap the IOU? On your first image, we can see that color is displayed. That means that the monitor receives the color burst which should not happen after power-on since it's supposed to be in text mode. The color burst is gated by the CLRGATE' output from the IOU. Normally CLRGATE' never drops low when TEXT soft switch is reset.

 

I hope I'm wrong, but you may have a bad IOU. If you didn't swap it, please try (carefully) with the one from the other Apple IIe.

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 frozen signal wrote:On your

 

frozen signal wrote:

On your first image, we can see that color is displayed.

Yes there's color on that image because the computer is in graphics mode. The reset routine has not run which would normally set it to TEXT mode and remove colorburst. So probably not an IOU issue.

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frozen signal wrote:I'm re
frozen signal wrote:

I'm re-reading your first comment where you said you tried to swap all the removable ICs. Did you mean all those that are not soldered on? Or did you mean those you were able to pull out?

Did you swap the IOU? On your first image, we can see that color is displayed. That means that the monitor receives the color burst which should not happen after power-on since it's supposed to be i

as written in the first post I have already exchanged all the removable chips with those of the working apple IIe, nothing changes the screen is identical

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baldrick wrote:Remove the CPU
baldrick wrote:

Remove the CPU.  If the screen doesn't change then I'd suspect that.

 

 

already done as written in the first post

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It's time to invest in a

It's time to invest in a logic probe and maybe an inexpensive oscilloscope.

You need to see why the reset signals are not propagating.  Or maybe they are and they're being blocked by a logic chip on the motherboard.

I presume that you've examined the motherboard itself and found no broken or damaged traces, or ovidence that someone has been in there with a soldering iron before you.

 

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CVT wrote:C17 is on the -5V
CVT wrote:

C17 is on the -5V rail. Do you have a stable -5V?

-5.22v stable

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baldrick wrote:It's time to
baldrick wrote:

It's time to invest in a logic probe and maybe an inexpensive oscilloscope.

You need to see why the reset signals are not propagating.  Or maybe they are and they're being blocked by a logic chip on the motherboard.

I presume that you've examined the motherboard itself and found no broken or damaged traces, or ovidence that someone has been in there with a soldering iron before

No broken trace or other, visually has no previous repairs, the only problem was the capacitor C15.

 

Could it be a ram problem? if I put the expansion card these lines scroll very fast up and down

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Yes, I think it's a RAM

Yes, I think it's a RAM problem. My motherboard is identical to yours, except that all my chips are socketed. So I tried removing all your soldered chips one at a time to see if I reproduce what you see on the screen. The closest I got was by removing RAM chips (no beep as well):

 

 

There are 3 other non-RAM chips that also cause no beep and horizontal lines, but with them the lines are solid and there is no color. They are: the S02 in the middle of the motherboard and the two LS244 above the CPU.

 

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This diagnostics card might

This diagnostics card might actually prove useful in a situation like this (provided the CPU is functional):

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CVT wrote:Yes, I think it's a
CVT wrote:

Yes, I think it's a RAM problem. My motherboard is identical to yours, except that all my chips are socketed. So I tried removing all your soldered chips one at a time to see if I reproduce what you see on the screen. The closest I got was by removing RAM chips (no beep as well):

 

[[{"fid":"36744","view_mode":"teaser","fields":{"format":"teaser","alignment":"","field_file

I can put the eeprom sockets for all the chips in question very patiently and try swapping the following chips as well

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AppleWoz wrote:I can put the
AppleWoz wrote:
I can put the eeprom sockets for all the chips in question very patiently and try swapping the following chips as well

 

based on your pictures and the fact that the RAM is all MT branded RAM chips, I'd replace all 8 of them.  MT RAM has been known to fail at this age with startling regularity.

4164 chips are cheap.

You can also use 41256 chips (which are even cheaper sometimes) in place of the 4164 if you cut off pin 1.

 The two chips only differ by one extra address pin (pin 1).

And you might not even have to do that, becasue I think the IIe motherboard has no connection to pin-1 of the 4164 chips.

 

 

 

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baldrick wrote:AppleWoz wrote
baldrick wrote:
AppleWoz wrote:
I can put the eeprom sockets for all the chips in question very patiently and try swapping the following chips as well

 

based on your pictures and the fact that the RAM is all MT branded RAM chips, I'd replace all 8 of them.  MT RAM has been known to fail at this age with startling regularity.

<

I replaced all 8 ram and it works. Sound too, the only thing broken is the keyboard led

 

 

 

 

 

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Excellent.  Thanks for

Excellent.  Thanks for posting an update.  Too often people solve their problems and then never report back.

 

The lightbulb might be either burned out, or the socket that it sits in is oxidixzed.

Ususally those little bulbs have two rigid pins for leads and actually sit in a socket of sorts. 

Pull the bulb out, spray the socket with some DeOxIt or other contact cleaner and reinsert it.

That might be all it needs.

Otherwise these should work:  https://www.ebay.com/itm/115704358206

but you'd have to buy four.

 

 

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baldrick wrote:Excellent.
baldrick wrote:

Excellent.  Thanks for posting an update.  Too often people solve their problems and then never report back.

 

The lightbulb might be either burned out, or the socket that it sits in is oxidixzed.

Ususally those little bulbs have two rigid pins for leads and actually sit in a socket of sorts. 

Pull the bulb out, spray the socket with some DeOxIt or ot

Thanks I'll try to clean it first then, just in case maybe I should have something I can adapt like the ones on ebay

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AppleWoz wrote:Thanks I'll
AppleWoz wrote:
Thanks I'll try to clean it first then, just in case maybe I should have something I can adapt like the ones on ebay

 

There is a 5V LED with a built-in series resistor that is a perfect replacement for the bulb. It will outlive pretty much everything and it doesn't consume as much current as a 64K AUX memory/80 column card like the bulb does!

 

Link: https://www.technobotsonline.com/5mm-led-green-5v.html

 

 

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