My 610 board build.

[HOWARDHB]

I suspect that the bus drivers were (partially) damaged by the interconnect ribbon cable issue...

[ronin47]

I suspect that the bus drivers were (partially) damaged by the interconnect ribbon cable issue...

I am considering that the LS138's might be something relabelled that has different trigger voltages.

The signals are getting over to pins 1,2 & 3 of U18, but nothing happens when they get there, no output despite 4,5 & 6 being correct.

According to the datasheet the voltages I see there are sufficient to drive an LS138, but if they are relabelled IC's with different specs that might not work with the voltage it's getting.

By the bus drivers are you referring to the 8T28's or the 8T95's? I haven't looked at the 28's but the 95's do seem to be getting signals in OK and sending them back out again.

Also the 95's seem to be responsible for BA13,14 &15 which is what U18 takes in.

It's probably going to have to go on hold as I am away for a week next week.

[ronin47]

OK, so I'm going to have to park this whilst I'm away.

It seems clear that U18 isn't providing any output to U15, despite the inputs being good and the IC testing fine.

No /CE0 or /CE1 from U15 means no RAM, and since U16 and U17 require the same signals then /CE is a bust across the whole 610.

I see it as being either re-labelled LS138s that require a higher voltage to work or that the 8T95s are bad as was suggested. Either way I can't order replacements as they won't arrive before I go on holiday.

What's coming out of the 8T95s looks fine, but I have no way to test and my bad cable could have damaged them.

So I'll order some before I come home and hopefully they'll be here the week after next.

[HOWARDHB]

The 3 to 8 binary encoders that work (for me) are: Fairchild, DM74ALS138N. I was fortunate to find, at my local supplier, a tube of 20, for a buck, (which rhymes with LUCK, no less !)
I used period correct, "Dual-leaf" I.C. sockets, and in retrospect, should have used the gold plated "Turned tapered" types. A lot of head scratching could have been avoided.

You will succeed, I am certain, and "getting there" is a triumph to be remembered!

[ronin47]

The 3 to 8 binary encoders that work (for me) are: Fairchild, DM74ALS138N. I was fortunate to find, at my local supplier, a tube of 20, for a buck, (which rhymes with LUCK, no less !)
I used period correct, "Dual-leaf" I.C. sockets, and in retrospect, should have used the gold plated "Turned tapered" types. A lot of head scratching could have been avoided.

You will succeed, I am certain, and "getting there" is a triumph to be remembered!

Much appreciated Howard, your help is very much appreciated.

I used dual wipe sockets too, oddly I've had less success with turned pin sockets, but there you go

Tube of 20 for a buck is nice I'll see if I can find Fairchild parts to order that'll arrive when I get home from my holidays.