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IBM PCjr won't boot

alexkerhead

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I have an original IBM PCjr with the 4863 color display and chicklet keyboard. It was never used, but not in plastic wrap.
I plugged the monitor into the computer, plugged the power into the monitor, and plugged the power into the computer, then installed 4x AA batteries into the keyboard.
I turned the monitor power on and then turned the computer on.
It beeped twice and nothing is happening, I have tried turning on with the stock boot disk in the drive, nothing happens, just beeps twice when I turn on the power.
Any ideas?
 

modem7

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According to Scott Mueller's 'Upgrading and Repairing PCs' book (5th edition), on IBM's, two beeps is a video related problem.

But going through the listing of the XT's BIOS, two short beeps occurs on failure of the enabling of the timer/keyboard interrupts. By then, video has been initialised, and one also sees an "ERROR (RESUME=F1 KEY)" message.

I dont know why there's a discrepancy there.
I know the XT is not a PCjr, but I would have expected some similarity.

I would suggest a video problem, but Mbbrutman knows a lot about PCjr's. Hopefully he'll comment.
 

mbbrutman

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Just to be absolutely certain, you said 'two beeps' and no other activity? Can you confirm that he diskette drive didn't seek and that nothing showed up on the monitor?

According to the Guide To Operations, two beeps is bad news. When things are find you get a splash screen and one beep.

According to the Hardware Maintenance and Service manual two beeps and no image on the screen is a Power problem. Here is the diagnostic procedure:

Remove all external devices from the ports on the back of the machine. This includes the monitor. The only cable going to the machine should be the power cable. Power on and try again. If you get one beep then power off, connect the monitor, and try again.

If that does not clear it up, remove the 64KB memory card and try again.

If removing the memory card does not clear it up, remove the diskette controller. Disconnect the diskette drive power connector from the power card, but do not attempt to remove the diskette drive. There is a separate set of wires for the fan - remove those as well. Removing the diskette drive is a pain in the arse and it results in broken plastic if it is forced.

At this point it is a stripped machine - 64K and no diskette drive connected. If it doesn't work then we will need to whip out the multimeter.
 

mbbrutman

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modem7 said:
I would suggest a video problem, but Mbbrutman knows a lot about PCjr's. Hopefully he'll comment.

Besides being the local PCjr Technical God and Moderator Deluxe, I have claimed the title of Holder of Useless Knowledge.
 

alexkerhead

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Darned PCjr.
Tried everything in all configurations.
Still two beeps, nothing else.
Could the cap on the psu be bad because it sat up for 23 years?
 

mbbrutman

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Could be. The other possibility is that memory in the first 128K is bad. You removed the 64K card, so that limits it to the memory on the motherboard, or a power supply problem.

I have the wrap plugs necessary to run advanced diagnostics on it and get a better answer. If it is a bad memory chip soldered on that's a pain, but not deadly. I've never had a memory problem with the 64Kx1 bit chips or the 256Kx1 chips from that era, but the way your machine is behaving it probably is memory.

(Two beeps is a sign of intelligence. It's getting at least the 5V that it needs to run the CPU.)
 

alexkerhead

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Interesting. I can't see any discoloration or burning, so it would have had to be bad from factory?. I did have everything out, I even cleaned the prongs where the power card plugs in with rubbing alchohol, still two beeps.
 

mbbrutman

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I doubt it is power. Usually if the power brick or card fails, it's just plain dead. The way to check it is to measure the outputs from the power card. The tech ref has the exact voltages and tolerances in it. There is a bug in the tech ref, and one of the outputs is listed incorrectly. (I have to look it up.)
 

mbbrutman

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Atari,

Seach google for PCjr. Look at what the power supply looks like. Then you'll understand why you can't use a generic power supply.
 

alexkerhead

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Atari, IBM making it fully proprietary was one of the things that made is not sell so well. Even serial and parallel ports were proprietary, along with monitor connections, although you can use a composite out.
 

mbbrutman

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Let's have a terminology discussions.

Proprietary means that it was a design that nobody else could use because it was not licensed.

I think the better term for the PCjr connectors is non-standard. The serial port was a standard RS232 port - it just had a non-standard connector. The parallel port is the same as on a PC. The video connector had to be different because the PCjr supports audio through the monitor, which the other IBM monitors did not.

In retrospect, the serial port and the joystick ports are the only two connectors that were designed wrong. Those should have been standard parts. The other ports wouldn't have been compatible with a PC anyway because of signal differences. Those included the keyboard and display ports.
 
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