Trying to repair a Sony HB-F1 (MSX 2)

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By Apocalypse

Supporter (5)

Apocalypse's picture

08-12-2017, 21:09

Hi,
I'm a console and arcade PCB repairer but from time to time people send me other things like vintage computers.
So I received a Sony HB-F1 MSX 2 for a repair.
Hardware is quite simple but sill I haven't found much information about it.
The machine does nothing when powered up: power led is on but it's stuck on a black screen.
While probing the basics (CPU, RAM, BIOS ROM) I found the BIOS ROM was fried (IC14). It's a device from Fujitsu (MB831124 - 128k * 8bit mask ROM - 28 pin) I tried to replace it with a 27C010 (adapting pinout indeed cause it's a 32 pin device). With the help of MAME I found this:

Quote:

/* MSX2 - Sony HB-F1 */

ROM_START (hbf1)
ROM_REGION (0x20000, "maincpu",0)
ROM_LOAD ("f1bios.rom", 0x0000, 0x8000, CRC(9b3e7b97) SHA1(0081ea0d25bc5cd8d70b60ad8cfdc7307812c0fd))
ROM_LOAD ("f1ext.rom", 0x8000, 0x4000, CRC(4a48779c) SHA1(b8e30d604d319d511cbfbc61e5d8c38fbb9c5a33))
ROM_LOAD ("f1note1.rom", 0xc000, 0x4000, CRC(84810ea8) SHA1(9db72bb78792595a12499c821048504dc96ef848))
ROM_LOAD ("f1note2.rom", 0x10000, 0x8000, CRC(e32e5ee0) SHA1(aa78fc9bcd2343f84cf790310a768ee47f90c841))
ROM_LOAD ("f1note3.rom", 0x18000, 0x8000, CRC(73eb9329) SHA1(58accf41a90693874b86ce98d8d43c27beb8b6dc))
ROM_END

Not sure it means certain models use 5 different ROM chips. In my case I simply merged all the files in the order given by MAME. Still no luck: black screen.
I've also ruled out the CPU, work RAMs and connections in between them.
Voltages are fine (double +5V regulators, 12V regulator).
Clock is present on the main CPU, reset isn't stuck low, there's activity on all data an address pins.

That brings many questions to me:
- Does this model of MSX 2 emit any sound on start up?
- Does it require the keyboard to be plugged to be able to boot?
- Does it require the "speed controller "(a simple sliding potentiometer) in order to boot?
- Did I burn the replacement EPROM correctly (in other words is MAME file mapping relevant)?

Thanks for your help.

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By gdx

Prophet (2088)

gdx's picture

10-12-2017, 11:01

Apocalypse wrote:

The machine does nothing when powered up: power led is on but it's stuck on a black screen.
While probing the basics (CPU, RAM, BIOS ROM) I found the BIOS ROM was fried (IC14). It's a device from Fujitsu (MB831124 - 128k * 8bit mask ROM - 28 pin) I tried to replace it with a 27C010 (adapting pinout indeed cause it's a 32 pin device).

I think the better is replace the MB831124 with a eeprom of 64kB (eg W27C512). The pinout is probably the same. I did that on my FS-A1. You only need to remove the unnecessary firmware. Just leave the Bios (32k) and the Sub-ROM (16k).

By sd_snatcher

Prophet (2734)

sd_snatcher's picture

10-12-2017, 12:34

Hi, Apocalypse! Be welcome to the MSX community!

Quote:

Not sure it means certain models use 5 different ROM chips.

This machine always has a single maskROM. The 5-ROM set exists only because some dumps were made by software using the MSX itself and not an EPROM burner. This way the maskROM blocks will be split in many files. It was intended for emulation and is indeed clumsy for hardware maintenance.

Quote:

In my case I simply merged all the files in the order given by MAME. Still no luck: black screen.

It should have worked this way. So there must be another problem somewhere. If you have a RAM cartridge (can be a memory mapper), try to insert it in one of the slots. This will allow the machine to boot if the internal RAM is damaged.

This machine features a speed controller. IIRC, when the slider isn't connected to the mainboard, it will boot very slowly, and this might affect your tests. If you place a simple jumper on the slider connector will allow you to boot it at normal speed.

BTW, I second gdx tip about removing the internal "F1 Note" software. He called it a "firmware", but it's more like an internal cartridge. Very similar to the preloaded software that Sony ships into their Android phones nowadays. And it's also similarly annoying and bugged.

Most people remove these internal softwares from the machines that have it, as the MSX will boot faster and will get rid of the bugs they have. But it's better to focus on making the machine boot first, then you deal with the internal software removal.

By sd_snatcher

Prophet (2734)

sd_snatcher's picture

10-12-2017, 12:42

Try to search for the other "black screen" topics existing here on MRC, like this one. Many of the tips given there will apply to you.

By Meits

Scribe (4989)

Meits's picture

10-12-2017, 12:48

This machine does not generate audio on start up, unless you have a game cartridge inserted. In stead it boots quite useless pre-installed software which is, like gdx says, best to remove.
It does not need the keyboard to be connected but you'll be stuck in the silent firmware if you don't have a keyboard.

By Jipe

Paragon (1308)

Jipe's picture

10-12-2017, 18:18

on main board have a little board HIC-1
is the same on page 12 of this doc http://msx.hansotten.com/uploads/files/sonyhbf1xdsm.pdf
capacitors leaks and video and sound break

By Jipe

Paragon (1308)

Jipe's picture

10-12-2017, 18:20

By Jipe

Paragon (1308)

Jipe's picture

10-12-2017, 18:25

oups is not the same mini board Sad

By Apocalypse

Supporter (5)

Apocalypse's picture

10-12-2017, 22:29

Thanks you all for your help and for welcoming me here.

I've put the CPU and work RAMs on sockets and installed new ones for the peace of mind (Z80 CPUs and 41464 RAMs are very common in the arcade world so I've plenty of them in my stock of new parts).
Still the pulled parts work absolutely fine on an arcade PCB so they're probably not a problem.

@sd_snatcher: I once left the machine powered for few minutes and I could see the screen changing colours. Might be the machine initialising very slowly. I will install a jumper on the slider connector and see. Maybe the machine is repaired now, just extremely slow and I didn't give it a chance to boot.

@Jipe: There's a small daughterboard named "EX-1" with only one ceramic capacitor so no risk of leak.

I will also try to install a 27C512 with only the BIOS and EXT files. Pinout is almost identical: pin 22 has a different assignment as it's the /G signal on the 27C512 not an address line, I'll simply tie it to pin 20 = /CE.

Oh and one new question: what are the AA batteries used for? RTC? Are they needed in order to boot?

By gdx

Prophet (2088)

gdx's picture

10-12-2017, 23:25

Batteries are not needed to boot but bad values in the RTC can prevent booting. You must either replace the batteries when they are too weak or remove them.

By Apocalypse

Supporter (5)

Apocalypse's picture

12-12-2017, 02:08

Ok, so I've tried the Philips diagnostic BIOS for MSX2 and it threw me a 711 error (RTC):

At least we're getting somewhere.
According to the document mentioned in an other thread it's RTC RAM related.
I had a look and to me on this machine everything is embedded in an ASIC named MSX S1985 (Yamaha branded).
I've checked solders on that chip and they're all fine.
I guess if the chip is really faulty that's the end of the repair.
Unless I modify the OG BIOS to bypass that stupid RTC check (it's probably needed only to date wording documents you'd type on the machine, if someone has more info about it he's more than welcome here).

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