lynx 2 weird issue

[bdoi]

Hi everyone

 

I have an issue on an atari lynx 2. The lynx works perfectly sound, display, control... but if you played for like 25 min and you switch off the lynx and try directly to re switch on, you will have a blank screen. You can try this many times but same issue. But if you wait like 10 minutes and try to switch on again, it works!

So the lynx seems to works only if it's cold.

I will try to change mosfet, zener and caps and see if it's better after.

Is anyone have seen this kind of issue before?

 

[Krip316]

Hi everyone

 

I have an issue on an atari lynx 2. The lynx works perfectly sound, display, control... but if you played for like 25 min and you switch off the lynx and try directly to re switch on, you will have a blank screen. You can try this many times but same issue. But if you wait like 10 minutes and try to switch on again, it works!

So the lynx seems to works only if it's cold.

I will try to change mosfet, zener and caps and see if it's better after.

Is anyone have seen this kind of issue before?

 

If my memory serves me right, I had the same problem and replacing those components solved it.

[bdoi]

Thanks! I will try that and let you know

[sage]

This happens if you replace zener setup with a cheap DCDC and have to much input voltage, too. Just as side remark.

[bdoi]

This happens if you replace zener setup with a cheap DCDC and have to much input voltage, too. Just as side remark.

 

What do you mean exactly? If I take a cheap zener diode it may cause this issue? or if I take a cheap Power supply?

 

Because here it 's a lynx ith no change for the moment.

[+Stephen Moss]

Hi everyone

 

I have an issue on an atari lynx 2. The lynx works perfectly sound, display, control... but if you played for like 25 min and you switch off the lynx and try directly to re switch on, you will have a blank screen. You can try this many times but same issue. But if you wait like 10 minutes and try to switch on again, it works!

So the lynx seems to works only if it's cold.

I will try to change mosfet, zener and caps and see if it's better after.

Is anyone have seen this kind of issue before?

 

 

Sounds like it could be a thermal issue creating a bad joint or incorrect component operation.

When you say you have a blank screen do you mean the lynx does not power on (power LED unlit & no sound) or that the lynx powers on (power LED lit & sound) just a blank screen. If the latter the first thing that springs to mind would be a problem with the High voltage power circuit for the LCD backlight. If the Lynx is powering on with the blank screen does pressing the Backlight button have any effect?

[bdoi]

 

Sounds like it could be a thermal issue creating a bad joint or incorrect component operation.

When you say you have a blank screen do you mean the lynx does not power on (power LED unlit & no sound) or that the lynx powers on (power LED lit & sound) just a blank screen. If the latter the first thing that springs to mind would be a problem with the High voltage power circuit for the LCD backlight. If the Lynx is powering on with the blank screen does pressing the Backlight button have any effect?

thanks for your help;)

I tried it again and same result:

after 20-30min of perfect working play, i switch off. Wait 2s and switch on:

blanck screen with no sound but power led ok and backlight ok. I mean I heard the pop of the speacker when I switched on and the backlight is ok but the brigthness wheel didn't do anything. And I tried to press backlight button , and it didn't work.

Do you think like Krip316 that a recap and zener diode and mosfet change could solve this isue?

Edited April 27, 2018 by bdoi

[+Stephen Moss]

How do you know the backlight was ok?

When you mentioned a blank screen I was thinking of a black screen or do you mean you are getting a white blank screen, the latter would suggest the backlight is working, that former that it may not.

 

When you say you are not getting video or sound have your pressed a button to begin play or waited long enough for the attract screen to run? I just want to be certain to you are getting neither and it is not just a video problem but audio is ok.

Assuming for now that as you say both Audio & Video and not working and the backlight is initially OK, then looking at the schematic Mikey appears to be the source of both the Audio and Video output and Backlight On/Off control signal. Consequently, the absence of both would lead me to initially investigate Mikey and the Reset circuit which may be keeping Suzi and Mikey in reset as being the source of the problem.

 

As it works fine initially a recap may not work, for a start you do not know if a cap is the problem in which case it may be a waste of time,and if it is a cap you would have to replace them all if you wanted to take that route without pin pointing the problem.

The fact that it appears to turn On/Off OK tells me that the MOSFET and On/Off circuits are OK, it does not indicate either way if the Zenner is faulty, the only way to be certain of that would be to measure the internal voltages.

 

 

[bdoi]

How do you know the backlight was ok?

When you mentioned a blank screen I was thinking of a black screen or do you mean you are getting a white blank screen, the latter would suggest the backlight is working, that former that it may not.

 

When you say you are not getting video or sound have your pressed a button to begin play or waited long enough for the attract screen to run? I just want to be certain to you are getting neither and it is not just a video problem but audio is ok.

Assuming for now that as you say both Audio & Video and not working and the backlight is initially OK, then looking at the schematic Mikey appears to be the source of both the Audio and Video output and Backlight On/Off control signal. Consequently, the absence of both would lead me to initially investigate Mikey and the Reset circuit which may be keeping Suzi and Mikey in reset as being the source of the problem.

 

As it works fine initially a recap may not work, for a start you do not know if a cap is the problem in which case it may be a waste of time,and if it is a cap you would have to replace them all if you wanted to take that route without pin pointing the problem.

The fact that it appears to turn On/Off OK tells me that the MOSFET and On/Off circuits are OK, it does not indicate either way if the Zenner is faulty, the only way to be certain of that would be to measure the internal voltages.

 

 

Yes, my appologize, I talked about a white blanck screen in fact (with a working backlight).

You point a possible issue on mickey, it sounds not good and maybe too complicated

I will try to reccap all the lynx , and change zener, mosfet even if you think that it's not the problem, we will be sure after that

I will do it this week and let you know the result, I will cross my finger!

thanks

[bdoi]

Ok , so all capacitors changed, mosfet and zener also and same issue :(

You were right stephen!

[+Stephen Moss]

If it is an issue with either Mikey or Suzy that will be hard to diagnose, particularly without access to a Lynx Service manual and access to an oscilloscope.

 

I do have a 48 page TIFF file of the Handy specifications, I have never really looked at it but I will print it out and see if there are any clues in there, it may take me a while to read/understand it and try to find some simple tests (if there are any) that could be carried out to try and narrow down the issue.

 

In the mean time the only another couple of things I can think of trying...

1) Check the supply voltages around the system as although the Lynx is powering on the voltages may be off which is causing an issue.

2) As I mentioned previously look at the reset components (upper right of schematic, on mine R1,D1 & C3 maybe different on other revisions) as they my be keeping Mikey and Suzy in reset and ensure the same voltage are on Mikey & Suzy Reset Pins, compare the voltage to when the unit is working and not working.

3) Check GND & power is connected to all the appropriate pins on Mikey & Suzy.

 

Unfortunately 2, & 3 will involve removing the metal screening. And watch out for the HV transformer, particularly when holding the Lynx with back off as it is right where your fingers curl around the back, that will give you a bit of a nip as I found out the other day.

 

I can't remember off hand what prevents the Lynx from powering up without a cartridge in, it is a power pass through similar to that of the Jag (possibly pins 33 & 34 of the cart port)?

If it is a pass through shorting the necessary pins out with solder or a piece of wire and then seeing what happens when you remove the cartridge and power on once the fault occurs might give a clue. If the "Insert Cartridge" message is displayed I would speculate (without reading the Lynx documentation) that it is a good indication that Mikey, Suzy and the BIOS are working at least to some extent and a bad cart ROM read could be jamming things up.

 

 

[+karri]

To make a Lynx turn on without a cart you need to solder a wire between the pins 31 and 33. You can leave the wire there. There is no reason to remove it. It is actually nice to see the text INSERT CART instead of not getting the Lynx on at all.

 

 

I would start by measuring the +5V line at the cart connector. Is it +5V or something much lower.

[bdoi]

If it is an issue with either Mikey or Suzy that will be hard to diagnose, particularly without access to a Lynx Service manual and access to an oscilloscope.

 

I do have a 48 page TIFF file of the Handy specifications, I have never really looked at it but I will print it out and see if there are any clues in there, it may take me a while to read/understand it and try to find some simple tests (if there are any) that could be carried out to try and narrow down the issue.

 

In the mean time the only another couple of things I can think of trying...

1) Check the supply voltages around the system as although the Lynx is powering on the voltages may be off which is causing an issue.

2) As I mentioned previously look at the reset components (upper right of schematic, on mine R1,D1 & C3 maybe different on other revisions) as they my be keeping Mikey and Suzy in reset and ensure the same voltage are on Mikey & Suzy Reset Pins, compare the voltage to when the unit is working and not working.

3) Check GND & power is connected to all the appropriate pins on Mikey & Suzy.

 

Unfortunately 2, & 3 will involve removing the metal screening. And watch out for the HV transformer, particularly when holding the Lynx with back off as it is right where your fingers curl around the back, that will give you a bit of a nip as I found out the other day.

 

I can't remember off hand what prevents the Lynx from powering up without a cartridge in, it is a power pass through similar to that of the Jag (possibly pins 33 & 34 of the cart port)?

If it is a pass through shorting the necessary pins out with solder or a piece of wire and then seeing what happens when you remove the cartridge and power on once the fault occurs might give a clue. If the "Insert Cartridge" message is displayed I would speculate (without reading the Lynx documentation) that it is a good indication that Mikey, Suzy and the BIOS are working at least to some extent and a bad cart ROM read could be jamming things up.

 

 

thanks stephen, I haven't got an oscilloscope and it may be really difficult to check all mikey and suzy connection. I think I will let it like that (half working )

[+Stephen Moss]

Did you try linking the supply pass through pins on the cartridge connector to see if it powered up without a cartridge in and displayed the insert cart message?

 

If you tried that and it did not work did you check the status of the Reset voltage at TP1 and if so what was it?

If you tried that and it worked, although the document I was looking at was probably of more interest to programmers it did lead me to this...

 

If you look at the circuit diagram where the cartridge port is to the right of it is two ICs, a 74HC164 & a 74CH4040. Check those out of you can, you really need an Oscilloscope for this but a basic operation could be indicated with a multi-meter.

 

74HC4040, with the COM lead of your multi-meter on pin 8 and the Lynx powered on you should measure the following voltages...
Pin 16 = 5V
Pins 11 & 10 probably somewhere between 1 and 4 volts depending on how fast they are switching.

 

74HC165, with the COM lead of your multi-meter on pin 7 and the Lynx powered on you should measure the following voltages...
Pin 14 = 5V
Pin 1 = 5V
Pin 9 = 5V
Pins 2 & 8 probably somewhere between 1 and 4 volts depending on how fast they are switching.

 

Also measure the switched cartridge supply voltage at TP20, again you will probably read somewhere between 1 and 4 volts depending on how fast they are switching.