Toshiba T1000 makes long beeps on startup

[hjalfi]

I got my trusty Toshiba T1000 off the shelf to do some DOS work and have discovered that it isn't working. Sad face.

When giving it 5V directly to the battery feed, it tends to make a sequence of long beeps on startup. The screen is on with a blinking cursor and the CPU is clearly running. Sometimes, it won't produce the beeps, and will go through the memory test, but then fail to boot with a NO ROM DRIVE FOUND error.

This doesn't sound like the usual power converter problems, but, still hmm. I suspect something's failing the startup test and it's some sort of error state. I have a parallel port POST reader on order, but until then, any suggestions as to what might be wrong?

 

[modem7]

I got my trusty Toshiba T1000 off the shelf to do some DOS work and have discovered that it isn't working. Sad face.

I know the feeling.
Just like pulling a toy out of the toy box, discovering it is broken, and being puzzled because you have no siblings who could have broken it since you last played with it.
I think the "It got broken" rate of my twentieth century computer 'toys' is about one toy per year.

 

[hjalfi]

I did some more fiddling.

- sometimes it does the long beep thing. Sometimes it doesn't.
- when it doesn't, sometimes it boots. Occasionally it skips the memory check.
- sometimes when it boots, it complains that it can't find the ROM disk.
- sometimes when it boots, it loads DOS and then the ROM disk vanishes. (Once it happened while executing AUTOEXEC.BAT and it got very confused.)
- once when I got it booted and DOS was present, I managed to run the diagnostics tool. It complained that the BIOS ROM was corrupt (I think, it just said SYSTEM CHECK ABORTED and a hex number) (the service manual on bitsavers is actually not referring to the same issue of machine as I have).
- the floppy drive works confidently and will read a little data but actually trying to run programs off it produces read errors.
- sometimes the cursor is shown in the wrong place.
- once when the ROM disk wasn't there and it was showing a couple of 'insert system disk' messages, the composite video output came on (I had an external monitor hooked up). That was the only time.
- I swapped the DOS and BIOS ROMs with those from a dead board I have. It did something, but it was very unhappy, and wouldn't start, instead claiming that the battery had gone flat and that I needed to set the clock --- but it wouldn't go any further. That could have been because the ROMs were from an S7 board and I have a S4 board.
- the system voltage and test point voltage both look fine.

I'm running the machine from a 5V-ish supply (I've wound it up and down by about half a volt to see what happened) connected directly to the battery terminals --- with the battery removed! --- to avoid problems with the terrible PSU circuitry in these machines.

So, basically... it's extremely unhappy. The weird glitchiness is very peculiar. I would love suggestions.

(Also, the FDDs on my IBM PC Convertible are acting up, the keyboard membrane on my ZX81 has failed, my old Vaio won't boot and the print head on my Brother word processor won't advance the ribbon.)

 

[electron55]

My Toshiba T1100 plus (actually, its soviet clone MC1504) worked the same way (unstable boot, different errors etc.) until i replaced all electrolytic capacitors first on the PSU board, than on the motherboard. After it all "unstable" problems gone. May be capacitors on your PCB have degraded too and you have crytical voltage drops when disk motor turns on, or when CPU starts massive RAM acces and so on, so it cause data corruption in the ICs.

 

[hjalfi]

Sorry for the delayed reply --- Christmas etc. Yes, it needed a recap, and now it works absolutely fine. It had never even occurred to me that was the problem, so thanks!

https://www.youtube.com/watch?v=E64hQ6R8_Uw

I hate desoldering. It's difficult and tedious and I've damaged stuff trying to do it. If only vacuum desoldering guns weren't so expensive (and loud)...