Need help with Sony HB-F5

By RetroFletch

Supporter (13)

RetroFletch's picture

22-07-2019, 09:32

So i recently got two japanese Sony HB-F5 computers, seems to be great machines but both have some issues.
Lets start with the one that kindof works..


https://imgur.com/a/pREM5Nd

Colors are all wrong, instead of the normal MSX Blue everything is an odd greenish tint both in menues/Basic and in game cartridges. Ive tried to change the onboard RGB potentiometers but it only makes slight changes.

Any Ideas where to start?

Then i have a second one, dosnt give any picture at all, even with the working daughterboard from the other machines, i have also verified that the socketed chips works in a chipswap with the working machine. Also i measured wrong volatage on the 5v pin of CPU ( only 2.5V ) so something is verry wrong.. So whats the Usual failures on these machines?

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By RetroTechie

Paragon (1563)

RetroTechie's picture

22-07-2019, 23:59

You're mostly there. Getting a screen like that means CPU, ROM, RAM etc are -at least mostly- working. Your monitor receives a sync signal, and (most) of what's supposed to be white, actually is. Green(ish) vs. blue suggest problem here may be in the cable you're using. So: what cable are you using? Do you know how it's wired?

On motherboard picture in the Wiki on this site I see:

  • An UV erasable EPROM. Your machine(s) have this too?
  • Quite a few socketed IC's. You could try re-socketing IC's once or twice. Sometimes this restores a poor contact & helps to bring a machine back to life.
RetroFletch wrote:

Also i measured wrong volatage on the 5v pin of CPU ( only 2.5V ) so something is verry wrong..

There's only 2 possible reasons for a low supply voltage like that:

  • Voltage regulator doesn't output enough current. And/or doesn't get enough current as input. I'm guessing there's a Sanken SI-3052V or equivalent handling the +5V rail (that would be IC with the biggest heat sink). Can you confirm? If so: can you put black pin of multimeter on GND pin of one of the 74LSxx IC's (say, pin 7 of IC39 = 74LS32), use red pin of multimeter on the SI-3052V pins, and report readings? (low voltage DC range)
  • Or something is 'shorting out' the supply rail. You'd probably notice this in the form of heat. Any of the IC's become very hot?

Also: can you check +12V and -12V internal supply voltages?

By RetroFletch

Supporter (13)

RetroFletch's picture

23-07-2019, 06:48

Hello, thank you for your response i will look into the non working one more with your suggestions.

As for the one with the green colors, that is Thru the standard RCA AV-output ( not rgb ) and ive tried the cable with other msx machines so i think there is something else going on.

My pcb does not have a UV EPROM but instead a genuine sony chip ( D23256AC )

I tried resocketing the chips it didnt help

Also where would i be able to test 12v?

By mohai

Paladin (808)

mohai's picture

24-07-2019, 10:44

Hello.

The small board is the encoder board. RGB-Sync is encoded into composite video there.
I would check the outputs from the VDP chip, the cable that connects that small board and the main board and the traces in the small board and the components in the middle. (I guess they are not too hard to follow.)
R,G and B should have similar components around, so I think it is easy to compare every one.

Curious thing about this model is that it does not have an standard engine on it.
I can see the PPI chip and PSG.
I guess the custom Sony chips a re some kind of pre-engine chips.

By RetroTechie

Paragon (1563)

RetroTechie's picture

25-07-2019, 20:11

Voltages are easiest to check on the cartridge slots. I see Sony even put the pin #s, doesn't get much easier than that. But I'll save you the lookup: pin 41/43 = GND (0V point), 45/47 = +5V, 48 = +12V, 50 = -12V. I suggest you check all these on both machines. The -12 often isn't used in MSX machines, +12V often in video circuitry. Oh and

RetroTechie wrote:

There's only 2 possible reasons for a low supply voltage like that:

I might add a 3rd one: "people holding their voltmeter wrong". Yes that happens. LOL!

You'll want the service manual for Sony HB-101/201. It has pinouts & block diagram for the CX23044 (slot select logic, DRAM control etc), CX23045 (IO address decoder), and lots of other IC's including that SI-3052V mentioned earlier. Datasheet for that part is a bit confusing, Sony manual (which are usually very good) lists pinout as COM/OUT/IN. So that's GND on the left pin, input (normally 8V or so) on right pin, 5V output on middle pin & cooling tab.

RetroFletch wrote:

As for the one with the green colors, that is Thru the standard RCA AV-output ( not rgb ) and ive tried the cable with other msx machines so i think there is something else going on.

Ah I see. If possible it would be good to try the RGB output (which is Japanese RGB21 pinout not SCART according to Wiki). It may help to tell "bad VDP output(s)" apart from "bad PAL/NTSC encoder". In case of the latter, there's a variety of reasons for poor/no output:

  • +12V missing. CHECK!
  • encoder IC (which one is used here?) gone bad. These tend to run hot, so especially in machines that see regular use they tend to be on their last legs after 30+ years.
  • Some transistor in that circuit failed
  • Last but not least: those darn ELECTROLYTIC CAPACITORS. There's some in there, when in bad shape they WILL affect signal going through them. Also saw some banding in screen photo you posted. If that's not a photography artefact then it'll be power related, most likely capacitors around the DC regulators gone bad. Poor supply voltages may affect circuit operation too.

You could try swapping the composite (video) encoder boards between the 2 machines. Unless that cable is soldered on both ends?

By PAC

Guardian (5183)

PAC's picture

27-07-2019, 11:04

Maybe an stupid comment but greenish pictures coming from a NTSC device in a PAL TV is something known. Being your HB-F5 model a Japanese unit I wouldn't exclude this. Is your TV PAL? Did you try it in another TV set? Does your TV have a hue adjustment in menu?