Bombjack ram location

[Retroman839]

Mm on ground pin reads


Coming out the psu like that too
A diffrent psu’s ground

 

[Lurch666]

They look shot. But your GND pins don't seem right (to me) either ... unless maybe pins 6 and 7 are internally shorted ... check those GND pins with your oscilloscope to make sure those readings are right.

Don't understand what you mean about the GND pins. Green on slice means GND so pin 8 on both look fine to me. And why do you think pins 6and 7 might be shorted?Pin 7 is the output for pin 6.

 

[Jacmar]

He's edited the post and added more pictures now I think. and started talking about LS174;s I was looking at the 2 attachment pictures for the LS74;s which have signals on the GND pins

 

[Retroman839]

He's edited the post and added more pictures now I think. and started talking about LS174;s I was looking at the 2 attachment pictures for the LS74;s which have signals on the GND pins

Sorry had to delete first pics as I had selected the wrong chip.

 

[Retroman839]

Colour genaration here 3x
2114’s
Colour pallet rams @ 6a,b,c

Só I will go here to slice tonight

 

[bones]

Keep it going man, probably nothing to do with your current investigations but what's going on with that ls17 just above the 2114s is that trace ok ? I got one of those cheapy bench digital microscopes from temu as my eyes are pretty bad nowadays.

 

[Retroman839]

Yeh almost looks like it has had a drop of xenomorph blood on it .

And that trace seems to turn and go under ..
174’s sliced good last night só I think it’s ok

 

[bones]

Yeah it's pin 6 on that 174 and it should buzz to pin 13 of the 2114 at 6B, worth a check I'd say.

 

[Retroman839]

Yeah it's pin 6 on that 174 and it should buzz to pin 13 of the 2114 at 6B, worth a check I'd say.

Thanks for tracing that 1 for me
I most definatly will do that shortly.

Can report good trace between these two legs 👍

 

[bones]

Pin 6 on the 174 is an input so if the slice says its ok then it should be good, just looked sussy

 

[Retroman839]

Pin 6 on the 174 is an input so if the slice says its ok then it should be good, just looked sussy

I think that poc made it look worse I can see a good trace now ..
Will try to add pic shortly
Mean time these are the 2114’s
I’m looking at

UPD2114LC -2. Nec
Pin 6 on scope has square wave

 

[Retroman839]

First 2114 static pallet ram @6a


No floating pins 👍

Next one @ 6b

Last one at 6 c



No address inputs at pin 5 ,15,16 ?
Chip select inactive which I guess is normal ?
No errors reporting at all
Sooo. These look all ok ?

Write enable high numbers in the red ?

 

[Retroman839]

Ok just started slicing all way along row 6 top board. From the 6a,b,c etc …. All checked out
Until
21 percent error states @ 6 h
Quad 2 input multi plexer ?
I will continue slicing .
6 H fails cycle 1 .


At 6 k

Pins 2,3,4 total out ?

 

[Jacmar]

schematics say you should have a signal on A8 (pin16) of your 2114's coming from the LS157 (pin9) at 6D

 

[Retroman839]

schematics say you should have a signal on A8 (pin16) of your 2114's coming from the LS157 (pin9) at 6D

Is that on all the three 2114’s ?
U sure pin 9 = vcc ?

Dip 16 ic ?

 

[Jacmar]

Is that on all the three 2114’s ?

yes the address lines of those three 2114 rams are all connected

 

[Retroman839]

Nice square on all 3 pin 16’s
Of the 2114’s

 

[Jacmar]

your pictures of your slice tests of the 3 2114 rams all show a solid green bar on pin 16 (A8) - you even commented on it yourself after the pics
the schematics say this should have a signal (A8) - and this should come from the LS157 (output pin9) at 6D

 

[Retroman839]

Yes I have signal
Above pic is the scope signal 👍

 

[Retroman839]

Just moved to row 5 F through to k
And I got floating pins on all the 75ls153