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Attempting to revive dead Lynx II


Passive Matrix
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Hi, I recently purchased a very nice looking Lynx II from eBay which was listed as faulty. Upon opening it I found that the ribbon cable which connects to the LCD screen was damaged and had split half way along its length. This didn't worry me so much because I had purchased it with the view to installing one of McWill's modern LCD displays, however upon further investigation it seems like there is some other problem. The unit was not powering on with either AC or DC power when a game was inserted. Seeing as this is a common problem I purchased a kit of replacement parts and proceeded to do the following:

 

- Replaced all the electrolytic capacitors,

- Added a new MOSFET transistor on Q12,

- Replaced the transistors on Q4 and Q13,

- Replaced the Zener diode

- Replaced R74 with a 30 ohm resistor

- Replaced the original power jack

 

Unfortunately even after all these steps the unit will not power up on either batteries or AC power. Is a working LCD display needed for the unit to power up? Is there any more repairs I can attempt before giving up? I have checked it with a miltimeter and power is entering the circuitry but it just doesn't seem to be enough to get it running.

 

Any suggestions as to next steps for trouble shooting? It's a very nice looking PCB with no corrosion so I was kind of surprised I could not get it running. Any help would be much appreciated. :)

 

Cheers

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I would not have thought a broken LDC flex circuit or ribbon as you call it (the big orange one) would prevent the Lynx from powering on, damage to the smaller green one which connects the buttons might. I cannot see how the LDC flex circuit would have been damaged that way other than by someone taking the Lynx apart, if someone has been poking around in there not really knowing what they were doing who knows what other damage they may have caused.

 

If the green flex circuit looks ok I would check that voltage is getting to the unit and that the on/off power latch is working in the first instance.

Try measuring the voltage across D11 or C35, if you are not getting 9volts DC then my post in this topic may help to solve the problem.

If you are getting 9V then look at the power latch, my posts here may help with that although some of the component references are different between the Lynx 1 and 2, ie D12 (the Zenner) & R56 on the Lynx 1 are D13 and R74 on the Lynx 2.

 

 

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I would not have thought a broken LDC flex circuit or ribbon as you call it (the big orange one) would prevent the Lynx from powering on, damage to the smaller green one which connects the buttons might. I cannot see how the LDC flex circuit would have been damaged that way other than by someone taking the Lynx apart, if someone has been poking around in there not really knowing what they were doing who knows what other damage they may have caused.

 

If the green flex circuit looks ok I would check that voltage is getting to the unit and that the on/off power latch is working in the first instance.

Try measuring the voltage across D11 or C35, if you are not getting 9volts DC then my post in this topic may help to solve the problem.

If you are getting 9V then look at the power latch, my posts here may help with that although some of the component references are different between the Lynx 1 and 2, ie D12 (the Zenner) & R56 on the Lynx 1 are D13 and R74 on the Lynx 2.

 

 

 

Thanks for the tips, I checked and I'm getting 9.13 V across D11 and 9.15 V across C35. Does this mean the game is completing the circuit? I ask because I noticed a bit of corrosion on the cartridge connector pins that could maybe be an issue. I will scrape them clean with a blade and see if that makes any difference. I'll also check out the link you posted and see how that goes.

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Okay I have good news and bad news. The good news is I have isolated the problem as to why it was not turning on. It was simply a lack of conductivity in the "ON" button contacts. I lifted the little piece of plastic over those buttons and gave the contacts a quick clean with a cotton tip and alcohol and then bingo! it turned on.

 

The bad news is smoke started coming from C56 and the solder around its legs began to bubble. Also while I was moving the whole button assembly around I heard a little snap and discovered part of the ribbon had split breaking one of the lines. These look like carbon or something so I don't think I will be able to bridge them with wire. So I guess I'm all out of luck.

 

Could the smoke just be from 20 years of sitting idle or is it best to give up on the motherboard too?

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I'm in a similar boat, having replaced everything that Passive Matrix has, I get a blinking red power light when I try to power it on.

As I recall it does that to indicate low supply voltage which you would normally only expect to happen then using batteries.

Have you tried measuring the voltage across the diode or capacitor I previously mentioned (D18 & C66 if a Lynx 1), you should measure around 9V DC when using the power unit or a fresh set of batteries.

If you do get 9V then you have the correct voltage going in, if not measure with the unit powered off to see if the voltage is the same.

If you do get the correct voltage going in you need to measure the voltage across either C40, C41, C44 or R75 (C50, C39, C44 or R78 if a Lynx 1) which should be around 5V and double check you put the Zenner in the correct way round.

 

 

 

The bad news is smoke started coming from C56 and the solder around its legs began to bubble. Also while I was moving the whole button assembly around I heard a little snap and discovered part of the ribbon had split breaking one of the lines. These look like carbon or something so I don't think I will be able to bridge them with wire. So I guess I'm all out of luck.

 

Could the smoke just be from 20 years of sitting idle or is it best to give up on the motherboard too?

That is not good, C56 is connected to the High (2000) voltage transformer for the LDC backlight and solder should not melt or bubble until it reaches around 280 degrees C so that would be very worrying if the solder was bubbling as opposed to the contents of capacitor bubbling and leaking out.

 

If the break in the flex circuit still allows you to power the lynx on and off I would unplug the 3 pin connector for the LDC back light and try powering it on again with something like Ms PacMan that make a noise as soon as you start a game so you can tell if the rest of the Lynx is still working. Also measure the voltage at one of the component mentioned in my reply to zaneiken above to check the 5V supply is what it should be.

As for the damaged flex cable you may be able to patch across the breaks using a wire connected to each end of the line but repairing it at the break would be difficult as soldering is could melt the flex circuit, you could try super gluing a piece of wire across the break or bridging the split using conductive ink. But really the best solution is to replace it, Best Electronics or B & C computer vision may have them as I am sure I recently read a post stating one of them stocked them.

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As I recall it does that to indicate low supply voltage which you would normally only expect to happen then using batteries.

Have you tried measuring the voltage across the diode or capacitor I previously mentioned (D18 & C66 if a Lynx 1), you should measure around 9V DC when using the power unit or a fresh set of batteries.

If you do get 9V then you have the correct voltage going in, if not measure with the unit powered off to see if the voltage is the same.

If you do get the correct voltage going in you need to measure the voltage across either C40, C41, C44 or R75 (C50, C39, C44 or R78 if a Lynx 1) which should be around 5V and double check you put the Zenner in the correct way round.

 

 

I tried a regulated power supply today on my Lynx II - same issue initially, blinking red light. I was doing some continuity tests on D9, D10, and D11 and it started to smoke from the board. Couldn't pinpoint from where exactly, but it was from around the mosfet or diodes. I tried powering on again later and it started up (screen was completely dead though). I was getting 5.1V across D11 and C35. It was also 5.1V across C40, C41, C44, and R75. Zener diode orientation had the stripe towards R74 as per the instructions.

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That is not good, C56 is connected to the High (2000) voltage transformer for the LDC backlight and solder should not melt or bubble until it reaches around 280 degrees C so that would be very worrying if the solder was bubbling as opposed to the contents of capacitor bubbling and leaking out.

 

 

 

Here is where the smoke came from. A short circuit perhaps? Whatever it is I think this unit is too far gone at this point so I'll cut my losses and fork out the cash for a working one. I don't want to risk frying the new LCD when I install it!

 

Thanks again for your suggestions.

post-64752-0-61558300-1527851039.jpg

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Here is where the smoke came from. A short circuit perhaps? Whatever it is I think this unit is too far gone at this point so I'll cut my losses and fork out the cash for a working one. I don't want to risk frying the new LCD when I install it!

 

Thanks again for your suggestions.

 

It sounded like a short to me pulling that much power, either the capacitor itself or the LDC backlight. The reason I suggested trying it with the backlight cable unplugged to see if the rest of the system was that if the rest of the system appeared to work you would have t he option of keeping it for spare parts.

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I tried a regulated power supply today on my Lynx II - same issue initially, blinking red light. I was doing some continuity tests on D9, D10, and D11 and it started to smoke from the board. Couldn't pinpoint from where exactly, but it was from around the mosfet or diodes. I tried powering on again later and it started up (screen was completely dead though). I was getting 5.1V across D11 and C35. It was also 5.1V across C40, C41, C44, and R75. Zener diode orientation had the stripe towards R74 as per the instructions.

 

What voltage was the regulated power supply?

If 9V then a reading of 5.1V across D11/C35 is definitely wrong, if 5V then that sounds fine and may explain why the LDC was not working (assuming it was before).

 

If it started to smoke while you were doing continuity checks, sound like you were doing them with the power connected, not a good idea.

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