Daewoo CPC400/CPC400S old stock in South Korea

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Por Takamichi

Champion (496)

Imagen del Takamichi

10-12-2019, 15:15

I and my friends suggest several precautions with CPC-400;
1. Keyboard repair guide is here.
2. Its default FDD is a rare Panasonic BELTLESS drive that is easily rotten. You cannot simply repair it by replacing the belt. You have to replace it with more common FDD such as Mitsumi.
3. The FDD is noisy because it vibrates against the casing. It's CPC-400's inherent issue, not the FDD's.
4. CPC-400 has unique disk access interface that might fail. For instance, TAPE2CAS, that saves bit by bit, generates corrupt file.
5. If inserting a cassette causes a hangup, cleaning the connections of the belt that connects between the insertion port and the PCB might solve it.
6. My friend makes an excellent modern video board replacement, that comes with SCART output, for CPC-400 for cheap. Ask him. He speaks fluent English.

Major overhaul like replacing the PSU wasn't necessary with my case. It's in better condition than all the toxic leaks suggest.

openMSX has "CPC-400S" option so try it if you want to try screen 9 and its unique slot assignments before getting real one ;)

Por bifo

Supporter (5)

Imagen del bifo

04-01-2020, 19:21

I received my CPC400 today, the capacitors appear to be ok but the batteries (two alkaline AAAs) leaked, so I'll be cleaning up the AV board. Takamichi: are you using a step-up transformer or did you switch the power supply to 100V instead of 220V?

Por bifo

Supporter (5)

Imagen del bifo

11-01-2020, 04:28

I cleaned the leaked acid and the contacts and resoldered the battery wire, booted it up this evening with my old 1084S monitor and it works quite well. A few keys need some hard presses, but other than the battery leakage it seems to have arrived in perfect order. The transformer works well, stepping up to 230v. I'll be replacing the floppy drive with a USB emulator as soon as it arrives and I need to build an RGB cable to connect things, but it looks like a solid machine.

Por Grauw

Ascended (10159)

Imagen del Grauw

31-12-2020, 02:33

Would anyone who got their hands on one of these mind confirming whether it has stereo PSG output (if the mono / stereo switch on the back is set to stereo) and how the three PSG channels are panned?

The red plug is for the right audio channel, the white plug for the left channel. Enter the following in Basic to play a test tone on each PSG channel, and check which output they sound from:

PLAY "a1"
PLAY "","b1"
PLAY "","","c1"

See PSG wiki.

Por Takamichi

Champion (496)

Imagen del Takamichi

31-12-2020, 03:07

CPC-400 does not split PSG to R and L channels but splits PSG to one and SCC to the other. If there is no SCC you hear the same sound from both channels regardless of the switch condition. I haven't tried SCC and FM or other sound module at the same time. This person knows more details. The idea might had been similar to that FM-MUSIC + MSX AUDIO "MSX stereo".

Por Grauw

Ascended (10159)

Imagen del Grauw

31-12-2020, 03:36

Thanks for the info, that completes the missing data for the stereo PSG table Smile.

Por Takamichi

Champion (496)

Imagen del Takamichi

31-12-2020, 04:19

I tested more. When the switch is STEREO, PSG/FM MUSIC/MSX AUDIO is only heard from the R channel with the L channel being silent so I lied about "hear the same sound from both channels". I played several Konami games but couldn't tell which channel is PSG and which is SCC. Is there anything like a Moonblaster track that outputs only the SCC sound?
Edit: I played the SCC-supported Knightmare from the Konami Game Collection 1 and noticed strange thing. When there is no SCC cartridge I hear the bassline and sound effects from the L and only the melody from the R. When there is SCC I hear only the sound effects from the L and only the background music from the R. This behavior indicates it's not the simple PSG <-> SCC splitting.

Por Grauw

Ascended (10159)

Imagen del Grauw

31-12-2020, 04:25

Quote:

When there is no SCC cartridge I hear the bassline and sound effects from the L and only the melody from the R.

Hmm, this does suggest a stereo PSG after all. Have you tried these three Basic lines?

PLAY "a1"
PLAY "","b1"
PLAY "","","c1"

If the PSG output is stereo then I expect the first line should play on both channels (center), the second on the left channel, and the third on the right channel (or possibly left / right swapped).

Por Takamichi

Champion (496)

Imagen del Takamichi

31-12-2020, 04:35

Result: When there is no SCC, everything is heard only from the R.
When there is SCC,

PLAY "a1"

Only from the R.

PLAY "","b1"
PLAY "","","c1"

Only from the L.

PLAY "a1","b1","c1"

a1 from the R and b1 & c1 from the L.
I guess if you do the same thing that Konami Game Disks do, you achieve the same result without SCC.

Por Grauw

Ascended (10159)

Imagen del Grauw

31-12-2020, 04:52

Very weird behaviour! At times like these you wish a service manual was available Smile.

Maybe there are some issues with the sound mixing circuitry in these machines (similar to the Philips NMS 8250), or in your specific machine. It would be good if someone else could also perform these tests to see if the results match.

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