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Need help with Apple II repair

Jimmy

Jimmy

Veteran Member
Joined
Feb 19, 2012
Messages
594
Location
Fort Walton Beach, Fl
I have an Apple II that makes a continuous sound when powered on, sound is like a squelch.

I have an Apple II plus motherboard and some spare chips I picked us with the sale.

Pictures of motherboards are attached. Any help would be greatly appreciated.

I really know nothing about these old apples.

Thanks,

Jimmy

Apple II
IMG_2189[1].jpg

Apple II Plus
IMG_2188[1].jpg
 
Squelch means to eliminate sound, so it likely doesn't sound like that :)

What are the spare chips?

If it were me, the first thing I'd do is take one good RAM chip and replace all the other RAM chips one at a time with it until something changes.
 
Sorry, if you adjusted the Squelch on a old CB Radio such as a white face Johnson it often made a sound that we refered to as Squelch. I am sorry I should have been clearer in my explaination.

The working Apple II I have is missing the same ram and rom chip. I have a memory expansion board that can be plugged into the missing ram chip socket.

Here is an explaination from Wikiapeadia on the sound that is similar to what it is making. Hope this is cleaner to the sound it is making.
"In devices such as two-way radios (also known as radiotelephones), the squelch can be adjusted with a knob, others have push buttons or a sequence of button presses. This setting adjusts the threshold at which signals will open (un-mute) the audio channel. Backing off the control will turn on the audio, and the operator will hear white noise (also called "static" or squelch noise)"
 
My ][+ will work without a chip in that RAM socket as well, but I've heard others say their machines will not working without either a chip or a ram card plugged in there. Maybe try taking a RAM chip off the other board and put it in that socket just to eliminate the possibility.

My memory is very foggy about this, but I think it shouldn't work without the particular ROM chip that's missing from the board in the top picture.

What are the part numbers of the ROM chips, and what sockets are they in, on both motherboards?

Which ROMs you have could determine whether a board will or won't work without a particular ROM chip.

If you do have a correct set of ROMs, I would again start by checking the RAM. That's always the first thing to go.
 
Thank you, I really had no idea of where to begin. I will replace the ram row by row and test. I picked up several of the old Apple's recently and would like to get them working. One of the Apple II's and an IIe worked. The II I am worknig on now, either of the II Plus's or the other IIe works, The IIe will power up to a prompt but other than the reseting none of the other keys appear to work.

Thanks,

Jimmy
 
It sounds like the //e has a bad AY-5-3600-PRO chip. It could be a bad connection to the keyboard too.

If you have multiple //e's, you can swap that chip with another one and see if it works.
 
Are you sure the noise isn't coming from the PSU? In my experience they can click and sometimes made odd noises...especially if there is a short on the board....particularly in those caps close to the PSU.

Tez
 
I swapped the row of chips on position "A" and the noise is now gone and the screen is showing but has the repeating Characters "@@77". I am sure I read a post about this somewhere before. Whats funny is now one of the non working II+s is working but seems to have a horizonal hold problem.

The shound was coming from the speaker. I swapped a power supply from a II+ and it was doing the same thing.

Thanks,

Jimmy
 
Jimmy said:
I swapped the row of chips on position "A" and the noise is now gone and the screen is showing but has the repeating Characters "@@77". I am sure I read a post about this somewhere before. Whats funny is now one of the non working II+s is working but seems to have a horizonal hold problem.

The shound was coming from the speaker. I swapped a power supply from a II+ and it was doing the same thing.

Thanks,

Jimmy
Click to expand...

Ok, if the ][ motherboard has the @@77 characters, it likely doesn't have the autostart ROM. Just hit reset (or ctrl-reset), then type ctrl-B at the * prompt. You should get a ">" prompt for Integer basic.

It looks like you have the programmers aid #1 ROM on the ][ board, that includes a ROM based RAM test routine, if you'd like to test the memory. Here's a manual for the PA #1 ROM: http://www.downloads.reactivemicro.com/Public/Users/Grant_Stockley/A2 Programmers Aid 1.pdf
 
Jimmy said:
I swapped the row of chips on position "A" and the noise is now gone and the screen is showing but has the repeating Characters "@@77".
Click to expand...
I wouldn't swap a whole row of chips. I'd take one good chip and "piggyback" it on each chip, one at a time, like this:

Step 1: Power off
Step 2: Put good chip over RAM chip
Step 3: Power on

Do this until you see a marked change. If something changes, try it with and without the working chip to verify that it is the chip causing the change. Then, swap that chip. If the computer isn't still working, get a second working chip and continue testing and swapping chips, one at a time.

It's very common to have multiple bad chips, and it's very hard to isolate them unless you check one at a time.

Unless there's something about the Apple that is prone to displaying @@77@@77 that I'm unaware of (there could be!) then I'd still assume there's bad RAM.

Whats funny is now one of the non working II+s is working but seems to have a horizonal hold problem.
Click to expand...

What did you do to make it start 'working'? Or, did it do this on its own? What kind of horizontal hold problem? Is the display consistent, but rolling horizontally?
 
HoJoPo said:
Ok, if the ][ motherboard has the @@77 characters, it likely doesn't have the autostart ROM. Just hit reset (or ctrl-reset), then type ctrl-B at the * prompt. You should get a ">" prompt for Integer basic.
Click to expand...
Doh! I forgot about that.
 
When I restarted this time I had "@@??" repeating characters. I tried the CTRL-Reset CTRL-B with no results. Pressing CTRL-ENTER-RESET does restart it.

On another note, the II+ is working fine now. I will try testing the Ram again.

Thanks for all the help.

Jimmy
 
Jimmy said:
When I restarted this time I had "@@??" repeating characters. I tried the CTRL-Reset CTRL-B with no results. Pressing CTRL-ENTER-RESET does restart it.

On another note, the II+ is working fine now. I will try testing the Ram again.

Thanks for all the help.

Jimmy
Click to expand...

Do you get a "*" prompt with blinking cursor after it? If so, try ctrl-B then enter... I forgot to specify that.

If you have a Disk ][ attached in slot 6, type "6", ctrl-P, enter to boot from slot 6.
 
No just the same "@@??" repeating characters. I do have a Disk ][ and a disk controller card. I will try attaching the disk and see what I get.
 
Jimmy said:
No just the same "@@??" repeating characters. I do have a Disk ][ and a disk controller card. I will try attaching the disk and see what I get.
Click to expand...

Can you screen shot the screen? Is it like looping? or a static display of those characters? What happens on reset (does it clear, etc..)?
I know garbage characters can be a good sign of bad RAM, can you piggyback or outright replace, going chip by chip till it effects a change?
 
First step before you go any further in troubleshooting is to reseat every chip on the board. Pull the chips out and re-insert them one at a time trying not to bend a pin.

These old socketed boards tend to need this every few years to remove some oxidation in the sockets.

I've had more than a couple of boards that went from dead to easily troubleshooted this way.

Good luck,
Corey
 
RW I can this evening. I will get some screen shots.

Corey thanks I will try reseating the chips, I think we talked at the Vintage Show in Atlanta last year.

Guys thank your for all the help.
 
I replaced the ram chips and reseated each chip on the board. I know have a reverse video background. I am not sure if it is displaying characters or not, if the characters are in normal white characters. The hum is now gone. I get the beep at boot and the control-enter-reset restarts.

I think if I can figure out the reverse video background the apple Ii should be back working.

Thank everyone for all the help.
 
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