Lynx II blank screen issue - not booting up

[GTretro87]

Hey all,

 

Ok so my lynx is currently not booting up - I just received it from ebay recently as a non-working unit - thinking that I *could* possibly fix it.

 

 

Like I said, the Lynx boots up, but it's a blank screen with a few dead pixels and I don't even have any sound either. I thought at first the 3055 transistor wasn't working, but the unit boots up, it can't be that.

 

I've looked into the regulator mods, and this is what I've attempted and results:

 

 

1) removed D9 and D11, placed a 7805 there for now.

2) removed 3055 and added another 7805 there

3) results, system turns on once all batteries are in place - REGARDLESS if the 31 and 33 are jumped or not - it just turns on - but still no gameplay.

 

4) swapped 7805 for 3055 (same one removed) - same results

5) removed D13 - actually I can't remember if the unit powered on, but I DO remember the positive side batteries getting HOT at this point.. or maybe it was negative - one or the other side - I will retest this

 

 

So after all this, I believe that the power regulation circuit might be fine for now - BUT something is keeping the CPU from booting up correctly. I think it may be the copper shielding or something is being grounded that is not supposed to be. I do have a full set of replacement caps, I'm not sure if that's the cause of this, but I guess it's worth a shot trying.

 

 

 

What do you all think? Btw, here a the first few pics of my board, I'll send pics of the back later on.

 

 

I appreciate your help!!

 

[GTretro87]

Ok I guess there's nothing I can do about this little lemon :/

 

Best Electronics said that it could possibly be a bad RAM.. Oh well

[GadgetUK]

It could be loads of things... If you've made sure the voltage provided by the zener diode was 5v, and you've bypassed the MOSFET then I guess there's something wrong with the RAM, CPU, or maybe the clock. It's not out of the question for Crystals to stop working, especially in portable / hand held units where they get dropped etc. I would start by checking 5v line (which it sounds like you've done), check the clock (on a scope if you've got it, or perhaps get a logic probe on there). Also check RAM on logic probe as well to see if you've got any activity on data and address lines. I seriously doubt recapping it will fix it.

[GTretro87]

It could be loads of things... If you've made sure the voltage provided by the zener diode was 5v, and you've bypassed the MOSFET then I guess there's something wrong with the RAM, CPU, or maybe the clock. It's not out of the question for Crystals to stop working, especially in portable / hand held units where they get dropped etc. I would start by checking 5v line (which it sounds like you've done), check the clock (on a scope if you've got it, or perhaps get a logic probe on there). Also check RAM on logic probe as well to see if you've got any activity on data and address lines. I seriously doubt recapping it will fix it.

 

 

hmm.. I do have a logic probe - I'll check it out and I'll check all the voltages to make sure everything is 5v or less... this will take some time..

 

I don't have a oscilloscope though (which I should get one day).. so that's out of the question - the only option for that is to get another crystal should that be the case..

 

 

What is the probability of the RAM, CPU, or clock failing on these things??

[GadgetUK]

Crystal - possible from a drop, but very rare. RAM more probable than CPU. If voltage was over 5v due failed Zener it could have faulty CPU, Suzie, or RAM. Have you checked the cart connection is good? It's amazing how many black screen type problems a dirty slot will give.

[+karri]

Solder a wire between 29 and 31. Then you need no cart. At power up you get the text INSERT CART.

[GadgetUK]

Or EMAG TRESNI on an early Lynx 1!

[+karri]

Solder a wire between 29 and 31. Then you need no cart. At power up you get the text INSERT CART.

 

The pins are 31 to 33. I typed it on the bus from my memory and got it wrong.

 

You can leave the wire in place. It will not affect operations of the Lynx. The only effect is that the Lynx turns on without a cart.

 

I usually first measure the voltages on the board. Then the clock. After this look to see if there is any life on the data and address lines when you apply power.

[GTretro87]

 

The pins are 31 to 33. I typed it on the bus from my memory and got it wrong.

 

You can leave the wire in place. It will not affect operations of the Lynx. The only effect is that the Lynx turns on without a cart.

 

 

This I've done, the system actually booted up with all the batteries in place - without pressing the power button.. not even the Insert Game screen (which i used to get with my former lynx years ago when the cart was pressed "too far" down in the slot"... so it's neither of those

 

 

 

 

I usually first measure the voltages on the board. Then the clock. After this look to see if there is any life on the data and address lines when you apply power.

 

how do I check for that on the data and address lines exactly? or do you mean the typical logic probing? Also, which IC is which on the board??

[GTretro87]

http://atariage.com/forums/topic/238372-help-regulator-mod-gone-wrong/

 

 

 

Fixed!