Toshiba HX-10 Black Screen: What To Check?

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By Rink

Rookie (25)

Rink's picture

11-07-2012, 13:50

Hi there,

I've just got my first real MSX and am having a little bit of a problem getting video from it. With power on, I can only find a black screen (whether by using the composite video out or the RF out). I've tried it on three different TVs with the same result each time; and am hoping you can help me get this thing working.

  • The Caps-Lock LED comes on when the key is pressed, and goes off when it is pressed again. As normal basically.
  • Pressing Ctrl+G outputs a beep as it's supposed to (I believe).

So I guess the ROM and CPU are ok?

I haven't yet had a chance to unscrew the casing and make sure all chips are properly seated - that's next on my list. And I have a replacement LVA-510 on order as I've heard they can be a common source of this problem.

Is there anything else I should be looking at while I have the unit in pieces?

Cheers guys.

Edit: BTW This unit and all cables etc. are spotless - like it's never been used... but I believe it may have sat unloved for a while.

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By Manuel

Ascended (15680)

Manuel's picture

11-07-2012, 15:06

Cool, where did you get it?

By Rink

Rookie (25)

Rink's picture

11-07-2012, 15:20

Just on eBay - I would say I got lucky but if there's a problem I can't fix then maybe not so lucky Smile . On the other hand, it wasn't expensive and I got an excellent tape recorder (which I've been needing for ages) so life isn't all bad.

Obviously I'd still like to get the MSX working though. LOL!

By RetroTechie

Paragon (1563)

RetroTechie's picture

11-07-2012, 16:16

  1. Check supply voltages: +5V (likely okay), +12V (??), -12V (often not used / only for cartridges), sometimes there's an intermediate supply like +9V in video circuit. Or filtered versions of 5V/12V.
  2. Check clock signal(s) if possible. CPU seems to be working, so looks like at least Z80 clock is present.
  3. Put a cartridge in the machine that is known to auto-run a sound-producing demo, and check sound output. If you can hear that, chances are the problem is confined to the video output circuitry (like +12V power, or that PAL encoder IC).
  4. If you have an external RAM cartridge, try that. Possibly RAM is damaged such that machine can't initialize normally.

3 & 4 Can be tried simultaneous. Results from above checks should make it much more clear what you're looking at. Don't try 3) or 4) until supply voltages are known to be OK.

By Manuel

Ascended (15680)

Manuel's picture

11-07-2012, 16:28

RetroTechie: he already reported to have sound with CTRL-G. So, it gets into basic normally. This also means that RAM is OK, I think. So I guess it's in the video circuit.

By Rink

Rookie (25)

Rink's picture

11-07-2012, 17:03

@Retro, you're not the same RetroTechie currently helping me out with a ZX81 issue are you?

If so, small world. Smile

By RetroTechie

Paragon (1563)

RetroTechie's picture

11-07-2012, 17:48

@Manuel: agree, I think so too. So next step would be check +12V & see if there's other supply voltages in video circuit. Of that's okay, maybe a burned output transistor or that PAL encoder IC.

@Rink: yup, this one. Using the same nick on a couple of sites (retrotechie70 on eBay) but beware there's other RetroTechies around... ;) Loaded anything in that ZX81 already?

Btw what's up with these smilies randomly turning into text? :-?

By mars2000you

Enlighted (5495)

mars2000you's picture

11-07-2012, 18:16

RetroTechie wrote:

Btw what's up with these smilies randomly turning into text? Question

It's a random feature of MRC ! Hannibal

By Miguel_Noe

Champion (442)

Miguel_Noe's picture

11-07-2012, 18:20

Quiet! We are going to wait for that "EXCUAJARINGUE" the MSX. And we'll see...
Big smile

By Manuel

Ascended (15680)

Manuel's picture

11-07-2012, 18:33

Posting here solely to get rid of the notification mails!

By Rink

Rookie (25)

Rink's picture

11-07-2012, 19:03

RetroTechie wrote:

Using the same nick on a couple of sites (retrotechie70 on eBay) but beware there's other RetroTechies around... Wink Loaded anything in that ZX81 already?

Hahahahah cool. Nice to speak to you again.

I haven't had a chance to try it with the files you sent me and was hoping to do it tonight (as well as fiddling with this MSX). At least I now have a tape recorder so can try a different audio source and actual ZX81 tapes too. Fingers crossed.

Cheers mate.

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