Repair a Sony HB-F9S MSX 2

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Por cdpopolon

Supporter (15)

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09-12-2015, 17:43

Hello, I have a Sony HB-F9S and when I connect it the green light works but there is no signal on the TV (i've bought a new computer to TV cable last week). I don't know which is the problem, i've noticed that it does not make noise. Do you know if there is someone who can repair or take a look at it? Thanks in advance. I am from Barcelona.

Regards,
Carlos.

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Por zPasi

Champion (499)

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09-12-2015, 21:28

Many things can do that. Is there absolutely no signal at all, or does it display a black screen?

What kind of cable is that? Composite or RGB? Can you check the cable with some other equipment?

Por RetroTechie

Paragon (1563)

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09-12-2015, 22:21

Things that would come in handy:

  • multimeter
  • logic probe (or even oscilloscope?)
  • external RAM cartridge
  • a game cartridge (specifically: one that produces sound when inserted with no keys pressed)
  • soldering iron
  • RGB (SCART) cable + monitor/TV

Which of those things do you have? Fault finding isn't always easy, but there's quite a few things you can check yourself that are fairly easy to do.

Por cdpopolon

Supporter (15)

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11-12-2015, 11:12

The cable is a RGB-SCART cable and i've checked with another MSX and it works fine.

Regarding the other tests, i've tested with different game cartridges and it does not work. I've not tested with an external RAM cartridge. The other tests i don' t know how to do them.

Thanks.

Por RetroTechie

Paragon (1563)

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11-12-2015, 18:42

It would help if you answered my previous question, that is: which items you have available (or could borrow / use from someone).

First thing to do would be open up machine and check supply voltages. This requires multimeter (voltmeter). Power LED suggests that at least one of those is present, but doesn't say anything about other voltages or whether they're in normal range.

Next up are clock signals. Checking presence of those requires an oscilloscope, or at least a logic probe.

External RAM cartridge can be used to boot machine if internal RAM is broken. External RAM has a good chance of allowing the MSX to run in that case. Quick checks at that point are CAPS LOCK response, and pressing CTRL-G (should produce a short beep). Of course this requires a working keyboard. Smile

Using a combination of external RAM cartridge + game cartridge kind of tests the same thing, but better. Game serves to produce -continuous- sound that you may listen to on TV/amplifier. And thus tell that that is working, even in case the video output is missing.

Depending on outcome of those tests, it's often possible to pinpoint a problem in terms of "main RAM failure", "+12V supply missing", "VDP / VRAM issue", "composite video encoder broken" etc. And thus determine what to try next.

Por Wild_Penguin

Hero (644)

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11-12-2015, 19:03

I agree with all that RetroTechie said! If your MSX has a CAPS LOCK led, that would be obviously the first thing to check.

What was the other MSX you tried the cable on? Make sure your cable has the right pinout. There are several MSXs with the same connector but different pinout, according to the FAQ I've linked above!

Try different outputs if possible (RGB, CVBS and RF out). I have a Sony HB-75P here which has a broken RGB output (or my TV doesn't like sync over composite video), but composite video works fine here.

There's a service manual for your model availabe online here.

Por cdpopolon

Supporter (15)

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19-12-2015, 16:09

Hi guys, I've checked that the CAPS LOCK led doesn't work and CTRL+G does not produce any beep either. I have not multimeter or external RAM cartridge (I have only some cartridge games) and i don't have electronic knowledge. I suppose the only way is to bring it to an electronic repair shop to see if they can do something.

Por RetroTechie

Paragon (1563)

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19-12-2015, 20:21

You could start with buying a basic digital multimeter. They can be found for what, € 10 these days? A cheapo model will suffice to check power supply voltages, check some wiring, IC socket contacts, etc. And can be used for jobs around the house too (like check battery voltages, measure if a fuse is blown, etc, etc).

Electronics knowledge needed to use one of these is virtually 0. People on this forum (including me Wink ) could easily guide you through a few basic checks.

Next up, a (working) RAM cartridge would be really useful. Any people you know (or in your area) that you could borrow one from? Question Size not important, anything >=64K will do (smaller ones may not have their RAM in C000-FFFFh area).

Por cdpopolon

Supporter (15)

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24-12-2015, 16:19

Hi, I've already buyed a multimeter. Can you guide me next steps to do? which supply voltages do I have to check?

Regards,
Carlos.

Por cdpopolon

Supporter (15)

Imagen del cdpopolon

24-12-2015, 16:32

Do you need any images from the inside of the computer?

Por Jipe

Paragon (1594)

Imagen del Jipe

24-12-2015, 16:56

i help you but warning is 220V on supply transformer

on the board you have 3 x IC (regulator)

see page 18 of shematic

IC1 SI-3052V
IC3 UPC78M12H
IC2 NJM79L12A

you have arrow with IN and OUT voltage

IC1 in 9,9 out 5,0
IC3 in 20 out 12
IC2 in -23,3 out -12

turn the multimeter on DC=
put the black probe on main board ground
put the red probe on the pin you want to mesure

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