Which chip is the most likely to be a fuse?

[+karri]

Hi,

 

I have a few Lynx I units where the voltage refuses to rise above 4.2V. Obviously some chip is eating up the power.

 

So far the metal casing hides Mikey, Suzy and RAM. I did already replace the caps, MOSFET and zener.

 

Most likely I could just try to push enough power in to see from where the magic smoke escapes. But I wonder if someone has good experience of what chip is the most likely corpse.

[+karri]

I opened up the metal cover and there is one chip getting REALLY hot. U3 the RAM chip.

[+karri]

By removing the bad chip the voltages got back to normal. I found the same chip on ebay for €5 for 10 chips.

[Level42]

I like monologues, especially when you come up with the solution

 

Seriously, great info !

 

I bet Utsource might have even been cheaper.....but also slower....

What type of RAMs are they ? (sorry too lazy to check schematics.....LOL)

 

 

I have a feeling RAMs may die first on over-voltage situations....or maybe in general.... see how mT RAMs die on A8's....

Edited April 16, 2018 by Level42

[+karri]

The RAM is of the type D41464C.

 

Easy to find on ebay.

 

I also had another Lynx I that was on all the time. The broken chip was U6 a hex inverter. After I replaced it from another broken Lynx the on/off buttons started to work.

 

Perhaps documenting broken parts could help me next time I have to fix some Lynxes.

[+karri]

Continuing on my monologue...

 

I also have a Lynx that says "INSERT GAME".

 

As the text turns up I assume that Mikey works. RAM works. Suzy works at least partly.

 

The cart port could have a cold joint (it did not).

 

The voltage is at 4.85V. So it appears to be ok.

 

Perhaps re-capping could be done first. These are the logical parts that turn bad at old age.

[+karri]

This is so weird. The problem was in the wear of the cart connector itself. Some carts like Slime World refused to start so I got the diagnose wrong. The cart connector just needs a little work-over with some dentist tools.

 

And re-capping I assume.

[+karri]

The next broken Lynx started nicely when given 5V to the poles of capacitor C39. But the normal start/stop and power adaptor was broken.

 

The first thing was to get a barrel socket from another broken Lynx.

 

The transistor Q13 was burned. Transferred a good one from another broken Lynx.

 

So now I have still one more "good" Lynx.

 

(The whole idea with this exercise was to find a few broken Lynxes so I could get the cart connectors for my programmer. I bought a bunch of broken Lynxes and 4 seems to be badly broken. For the resurrected Lynxes I do some re-capping and let them back in the wild.)