Something realy really wrong with my N64 RGB mod

Something realy really wrong with my N64 RGB mod , regulator overheating

Hello!

today I upgraded the RGB amp of my n64 to a TI7374 based one... at first I was happy because it produced a less blurry picture until after some 15mins of gameplay the screen started flickering...

the diagram I followed is this:



I feed the RGB lines to pins 1,2,3 and from pins 14,13,12 I get the output via 75ohm resistors.
There is a 100nf ceramic cap directly soldered in pins 5 and 10
There is a 22uf cap soldered in pin 9 and 10
Pins 5,6,9 are all grounded together and pin 10 gets +5v

here are some pics:









and here is my +5v source, the same as the previous amp that was made from transistors:



now this small regulator gets extremely hot, the n64 does not freeze but the picture is displayed like there is no sync at all... it was OK for about 15 mins of initial testing and suddenly thie screen lost it's sync.

I am sure I have made a stupid mistake somewhere , any input will be greatly appreciated! Thanks in advance

 

it seems the TI 7374 is drawing too much current? built a 2nd amp and there is no short-circuit... wtf

edit: yes, the 7374 starts overheating after a while...?!

edit2: yep, chose the +5v point from the av port, after 5-6secs you cannot touch the 7374... there is something wrong with the amp design?

 

If the chip gets hot after a few seconds, but works for several minutes before has problem, and assuming this repeats after letting the chip cool fully, then it may well be the solution might be to put on a largish heatsink and fan attached to keep it cool. Worth giving that a go anyway, might help.

Also, if your 7805 gets hot, you can always put two in parallel so they can output more amperage at less heat.

 

The 7374 can safely operate at 85c without issue. But it shouldnt really be getting hot at all.

 

I am doing either something terribly wrong or the 7374 chips are fake or something.
I kid you not: the 1st 7374 on the n64 actually made some spark+smoke, I could smell overheating components... I though OK, the 7374 was busted so I made a 2nd new amp... it behaves the same , it overheats and causes the 7805 to overheat too.
What could cause this? Bad 100nf caps? I measured the 7805 output, it is 5.04v which is OK...

I have re-installed the original amp pictured below, it has inferior image quality but does not cause the 7805 to overheat... though I would really like to use the 7374 it produces a very crisp image...

 

Not sure if this of concern, but in the digram it shows the 22uf cap connected to pins 10 and 11 but it looks like you have it connected to 9 and 10 instead.

 

yes you are right, I have the diagram wrong... the cap is at 9+10 (vcc + gnd) , will fix the pic

 

Hmm okay.. Not too sure on video electronics and having a harder than normal time reading the datasheet, but maybe try a 100uf cap instead of the 22uf?

TI Datasheet:

EDIT:

The TSH345 from ST looks like a very tempting drop in replacement from my understanding of the circuit. The application designs in the datasheet look a lot simpler.

 

That orange capacitor - the one in your pic on the first post is a tiny circle 104 you get on many boards, the large one on your photo is a different capacitor type entirely, no?

 

both are 100nf, the small one is 16v (IIRC) and the orange one is max 100v , couldn't get any more small ones here...

 

Should have said - I could have thrown you some in with the last bunch of stuff you ordered from me.

 

^ thanks Bad_Ad84 but I already grabbed some from eBay I appreciate the thought though! cheers!

 

I find that the smaller 7314 amp is used for the N64 ( http://www.mmmonkey.co.uk/ntsc-nintendo-64-rgb/ ) , will it have much difference than the 7374? I just loved the 7374 quality (for as long as it worked that is....)

 

I use the 7314 on n64's I mod