Dreaded Two Beeps...

Hardware questions and modifications

Dreaded Two Beeps...

Postby VampireSlug » Fri Sep 06, 2019 8:37 am

I bought a PCjr years ago and finally found the time to play with it and... no display, two beeps. It's the floppy version with the 64Kb RAM expansion, a parallel sidecar, the newer keyboard, and it's using the PCjr display. I tried to boot with everything disconnected except the power card and the display but no change. I saw somewhere online that if the keyboard isn't recognized this could happen... I have fresh batteries but the contacts might need cleaning; I'd use a cable to connect but I don't have one. The fan spins up, the display changes from white to black and *BEEP* *BEEP*. What should my next step be? Thanks,
"The earth starts to rumble
World powers fall
A'warring for the heavens
A peaceful man stands tall"
Megadeth - Symphony of Destruction © Warner Chappell Music, Inc
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Re: Dreaded Two Beeps...

Postby Chuckphd53 » Sun Sep 08, 2019 8:09 am

I know the system will beep during boot is the floppy drive board or disk drive has issues
Do yo have a basic cartridge to plug in and test the system ie. key board..

You can also try CTRL/ALT/INS to see if the keyboard works..

keep us in the loop if you find anything..
chuck
(PCJR/JR-IDE-512DOM,TandyMod,V20-10Chip,BiDir,LPT2,3FlopBrd,
USBEmulator,ZIP100,PS2Keybrd,MouseSysMouse,InternalSwitcherPS)
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Re: Dreaded Two Beeps...

Postby ZiggyTheHamster » Thu Sep 12, 2019 7:27 pm

Try using composite video to another monitor.
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Re: Dreaded Two Beeps...

Postby geoffdaddy » Tue Oct 15, 2019 7:58 am

When I first got a PCjr I had the two beep thing as well, no display. In my case I tried reflowing a bunch of solder joints to no avail. Then I discovered poking around in the BIOS listing that there's some post codes that can be outputted to the serial port when joystick buttons are held down that would indicate where in the self-test sequence it was dying. That eventually narrowed it down to a bad CAS delay line. At that time I was able to find a replacement part on eBay, but that might be problematic now as I have seen either here for vcfed where someone tried to find one and couldn't.

Now, I've got the two beep thing happening again. I don't think it's the delay line this time though... I think it may be the power supply not holding the system in reset long enough... as I can power it down/up repeatedly quickly and it will eventually start normally.
PCjr: 10MB RACore 01 hard drive expansion, Hotshot 640kB RAM expander, optical mouse, Xircom PE3, speech sidecar.
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Re: Dreaded Two Beeps...

Postby Chuckphd53 » Tue Oct 15, 2019 2:19 pm

Sounds like you done some good investigation.
Just curious, have you recapped the Power Supply board?
I have had to,do this on a couple of mine, they are noisy...
(PCJR/JR-IDE-512DOM,TandyMod,V20-10Chip,BiDir,LPT2,3FlopBrd,
USBEmulator,ZIP100,PS2Keybrd,MouseSysMouse,InternalSwitcherPS)
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Location: Florida, USA

Re: Dreaded Two Beeps...

Postby Chuckphd53 » Wed Oct 16, 2019 12:48 pm

Also...
Had you tried booting with a Basic Cart installed ?
(PCJR/JR-IDE-512DOM,TandyMod,V20-10Chip,BiDir,LPT2,3FlopBrd,
USBEmulator,ZIP100,PS2Keybrd,MouseSysMouse,InternalSwitcherPS)
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Posts: 364
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Location: Florida, USA

Re: Dreaded Two Beeps...

Postby VampireSlug » Tue Jan 19, 2021 9:11 am

I have finally fixed the "Two Beep" problem! I obtained a box of stuff from Computer Reset recently and there were several PCjr items inside, including a boxed NOS PCjr motherboard with an AMD 8088 CPU. I swapped out my Intel 8088 mother board, popped in the new motherboard, hooked up everything and BAM, up came the color boot screen! I now have a fully functioning 128KB PCjr with floppy, parallel sidecar, new keyboard with cable, and a boxed NOS joystick! Next is the process of digging through all of my old 360Kb floppies to see what I have that will run with 128Kb of RAM.

Thanks everyone for the suggestions and troubleshooting, it's much appreciated!
"The earth starts to rumble
World powers fall
A'warring for the heavens
A peaceful man stands tall"
Megadeth - Symphony of Destruction © Warner Chappell Music, Inc
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