Panasonic FS-A1 Mk II - no video signal

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Par sabre470

Resident (35)

Portrait de sabre470

05-05-2015, 19:12

Hello,

Long time lurker of this site who finally has an account is looking for kind help.

I've had an MSX1 since 1985 (Yamaha) and got it out of its box a few weeks ago, still working as perfectly as on day 1.

After that I decided to source an MSX2 to (finally) play the likes of Vampire Killer on real hardware Smile

I got a machine recently, it's not a top of the range MSX2 just a Panasonic FS-A1 Mk II.

After initial testing, it powers on but no video on the screen... The funny thing is that when I put a cart in it (in my test Penguin Adventure) then I can hear the sounds (although not very high), start a game and play albeit without any image. I knew when I bought it, it wasn't tip top, so no buyers' remorse, just looking to fix it.

Any thoughts before I start operating on it?

Thank you in advance for your help

Sabre470

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Par Algorythms

Champion (285)

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05-05-2015, 22:19

Par sabre470

Resident (35)

Portrait de sabre470

06-05-2015, 00:43

Many thanks for your help Algorythms, a very helpful post.

Right now, I've tested the power supply and the multimeter says it's working fine. In fact the voltage for both the AC and DC portion shows higher voltage than on the adapter but I guess this is regulated by the computer's motherboard.

I think I found some possible culprits though. Since the audio is working but a little faint, I checked the caps and that led me to find some leaky caps on the daughterboard that (according to this article in Spanish on this very forum) is in charge of amplifying bot audio and video signals. Though my Spanish is rusty at best and Google Translate is not very accurate.

I also try to get to Basic mode (as suggested in the post you shared) to see if I can get any changes on the screen and although it might be a false positive, the up scan converter I'm using (an XRGB Framemeister) seemed to be affected as if it was trying to lock on a signal.

So far I've only tried the video via composite, I don't have an RGB21 cable yet for this MSX.

Here are some pictures I took tonight of the daughterboard:

I'm trying not to get too excited, as this isn't an easy job to extract the caps let alone solder some news ones. But could theses caps be the source of my troubles?

Par RetroTechie

Paragon (1563)

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06-05-2015, 01:35

Welcome to MSX.org, sabre470! Smile

sabre470 wrote:

Right now, I've tested the power supply and the multimeter says it's working fine. In fact the voltage for both the AC and DC portion shows higher voltage than on the adapter but I guess this is regulated by the computer's motherboard.

First & foremost, that's where you need to check voltages: on the board(s), while in operation. If there's 16V going into a 7812 regulator (just an example), that means nothing if that regulator is dead & its output reads <11V. Sounds like the board's +5V is okay, but perhaps +12V isn't (-12V normally isn't used/important).

Definitely try RGB output! Composite video goes through a lot more encoding / buffering circuitry, and composite video encoder IC's are common culprits when comp. video out is missing.

If you intend to use this machine regularly, replacing electrolytic capacitors would be good idea. In short: electrolytic capacitors are among the weakest / short-lived electronic components, right up there with mechanical parts, connectors, rubber belts, etc. If you replace them, best is to replace them ALL @ the same time.

For some, it would be fine to replace with a tantalum or ceramic capacitor (often a smaller value one). For some, it may not even change anything noticeable / measureable if you simply cut them out. Question Unfortunately, that can only be told when you know what each capacitor's function is (read: when you've got a schematic of the machine).

Quote:

I'm trying not to get too excited, as this isn't an easy job to extract the caps let alone solder some news ones.

Replacing caps is relatively easy, even for people who have no electronics skills... But (beside the replacement parts) you do need a little soldering experience. And the right tools for the job. You could practice on some 'e-waste' (boards from equipment that was thrown out earlier). Or start in the power supply, where the opportunity to do irrepairable damage is smallest.

Quote:

But could theses caps be the source of my troubles?

Most capacitors are used in the power supply and analog parts of a circuit, so yes, definitely.

Par Jipe

Paragon (1391)

Portrait de Jipe

06-05-2015, 09:48

check solder of IC's on mini-board before replace capacitors

Par sabre470

Resident (35)

Portrait de sabre470

07-05-2015, 18:42

Thanks a lot guys.

I've ordered parts to build an RGB cable, I think it differs from the one I have for my MSX1. Happy soldering job Smile

I will test the power on the board as well, if all is well there then I will proceed and change caps and see what happens Cool

I checked the solder on the mini board, everything looks fine apart from a nasty cold tobacco smell Crazy Quite tempted to chuck all the plastics shell bits in a dishwasher that thing must have lived in bar or a tobacco factory...

Par sabre470

Resident (35)

Portrait de sabre470

13-05-2015, 00:52

Hi there,

I've done some more tests...

1st I tried to build an RGB21 cable to feed my XRGB nothing came out of it not even sound, I used diagrams and Panasonic pinout found on MSXFAQ, obviously I've missed a trick. I'm a bit lost with the some of pins terminology on the pinout:

DIN 8 pins female

1 GND
2 AUDIO
3 NC?
4 C SYNC?
5 +5V?
6 R
7 G
8 B

7 6
3 8 1
5 4
2

Can I build an Scart RGB cable out of this or RGB21 the only way to go? I have multiple adapter on my XRGB to take signal from EU consoles.

2nd I tried the Scart cable I built recently for my PAL MSX Yamaha which works on that machine with the XRGB and same result as when I use the composite and sound on RCA no picture but I get sound though faint (damn caps!)

3rd I tested the regulator (I've only found one on the board?), here is a picture of it and dc voltage readings:

The radiator attached to the regulator gets really hot quickly, is that normal?

Any thoughts?

Here is a picture of the mainboard:

Finally, I'm going to replace the faulty caps but I need to remove the radiator. What paste do I need to use on the regulator to bond with the radiator, I have a feeling regular CPU thermal paste won't do the trick?

Readings from power supply for good measure ;)

Pic of the power adapter:

Thank you again in advance for your help.

Par ApolloBoy

Expert (96)

Portrait de ApolloBoy

17-05-2015, 22:39

Jipe wrote:

check solder of IC's on mini-board before replace capacitors

Those surface-mount capacitors are definitely leaky, those need to be replaced before anything else IMO.

Par sabre470

Resident (35)

Portrait de sabre470

20-05-2015, 00:16

Hello,

Many thanks for your advice. I replaced the caps but the original ones leaked so much that traces are missing, one of the caps came off on its own, another one was stilll 1/2 soldered. Only the biggest cap was still firmly on but had leaked. I stuggled to get the new caps on, solder wouldn't stick at all. I did what I could and it's not a pretty sight. Overall it seems the caps leaked on many parts of that little board.

Now the computer still turns on, keyboard is responsive, but no more bios sound, no image. All I hear is a click in the speaker when i touch any key, only F8 makes a proper key sound.

I'm gonna have another crack at it over the weekend, however I'm afraid the board might be fried completely Sad

Par ApolloBoy

Expert (96)

Portrait de ApolloBoy

21-05-2015, 19:17

Did you try cleaning off the dried electrolyte? If you don't clean it off beforehand you're gonna have a really hard time soldering in your new caps.

Par sabre470

Resident (35)

Portrait de sabre470

25-05-2015, 17:35

Yes I cleaned it up all nicely, but some of traces have gone because of the acid, so not a simple job.

I've tried again from scratch today, removing the caps and putting but no change. I'm coming to the conclusion that the IC board and/or the computer is dead. The computer powers on as does the keyboard, but nothing happens, pressing the keys on the keyboard makes a clicking sound, so I'm thinking maybe something is shorting

Unless I can find a replacement board, that poor MSX2 will end up being recycled Sad

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