Fried my THCAD-10

Pretty Sure the thcad is dead, just have not tested the 7i76e yet

PCW wrote:

Probably the easiest way to check the 7I76E encoder inputs is to jumper the 7I76e encoder for TTL mode, "watch" the encoder A,B,Index inputs and ground them (TB3 pins 7,10,13) one at a time (to TB3.9) and see if the hal pin changes

Sorry, its been a long time and I finally got back to this.
I checked that W10, W11, W13 were already set to TTL mode.
In halshow, by default A input was on, B input was Off, and Index input was On
Both B input and Index Input changed state when shorted to ground

A input did not change.

So does that sound like its working or is there a problem on the A input? (which is where the THCAD was connected to - eg pins 7 & 8).
If its blown, could I just use the B inputs instead?

The ISL32273 device used for the encoder interface has a maximum +-13V input range so it looks like the
THCAD frequency output that goes to pin A somehow got shorted to a 24V or other signal greater than 13V

You can not use B because B is count direction in counter mode, but I can make firmware that rewires the A input to the 7I76E B pin (or you could replace the ISL32273)

freeby.mesanet.com/7i76e_76x1dbea.bit

Puts the encoder A input on the 7I76E B pin

Depending on the previous state of the B input in your system, the count direction might change
(so you may need to change the sign of the encoder scale)

Peter, thank yo very much. A very nice surprise to wake up to downunder. Very much appreciated!

So now I just need to order a replacement thcad board.

Since the input part of the THCAD works (LED blinks) you could probably fix it by replacing U4 (The output RS-422 driver)
with either a ISL32174 (5V swing) or DS26LS31 (TTL swing)

Peter, thanks.

What would be more reliable? Non TTL? Does that mean I just move the W10,11,13 links?

Peter, I've located U2 on the THCAD board. Its an 8 pin IC and both those part numbers quoted resolve to a 16 pin IC. From what I can see the one on the board is a 272C55M but I can't find that one either.

Is there another part number I should be searching for?

Dunno where I got U2 from. Sorry about that. You said U4. Looks like it will be TTL as thats the only one I can find here
au.rs-online.com/web/p/line-transmitters/5361186/

26LS31 is fine, its still RS-422 differential so no jumper changes
the 26LS31 just has a bit lower voltage swings (but is much easier to find)