Corcomp MOD Question and just saying hello

[TI99GUY]

Hello

Its been many years that my TI has been in storage. My family is doing some very late Spring Cleaning and I just came across my TI which collected a lot of dust. After going through all of my parts I decided to tear down my expansion box and clean it up as good as possible. I also thought that I might have to re-cap some of my boards as they have sat a long time. I opened my Corcomp disk controller casing and to my surprise it is unlike any that I have seen before. Their is some type of add on board or modification where the Western Digital chip goes. Any ideas on what this mod is or does? I would also like to get some advice as if I should re-cap my boards or leave them until I run into a problem. They all seem to work but I have OCD and like to normally fix/repair things just due to age.

[Stuart]

The add-in board is replacing the original WD1771 floppy controller with a WD1773?

[+mizapf]

The original chip was a WD2793A, at least on those boards that I saw.

 

Edit: There is a version from Miller's Graphics which uses the WD1773. So this looks as if here, the MG ROMs are used in a 2793-board, and the adapter board turns it into the actual MG version from the hardware point of view.

Edited September 19, 2017 by mizapf

[+Schmitzi]

wow, nice

[+Ksarul]

Those daughter boards were put onto the original 2793 boards to modify them to use with the 1773, as already noted. CorComp did this because the 2793 chips in circulation at that time were really unreliable (a bad lot of chips hit the channel that had something like an 80% failure rate) CorComp tested the chips they had, put the good ones into boards, and rethought their design to avoid the 2793 chip in the future. The daughter boards were made to allow them to actually use the boards they already had on hand, since they didn't have anywhere near enough good 2793 chips to fill them. This was all published at some point back in the day--either by CorComp directly or by MG. . .IIRC

[RickyDean]

Be good to have a schematic of the conversion, or good board level picture of both sides. I just bought a Corcomp off of Ebay to see if it will help me get mine operational. To see if the Pal's will work on mine. What would that chip be under the rubber bumper?

Edited September 19, 2017 by RickyDean

[atrax27407]

Here are the docs for the MG upgrade.

mg eprom for corcomp controller manual.pdf

[TI99GUY]

What a wealth of information! I guess I asked in the right place. What is the socket right in the middle that is un-populated for? Is that just where the board is soldered down to the main board? So I assume from what you are saying is that a 2793 is hiding underneath that daughter board?

 

I already put it back in the casing but I can remove it again to take pictures of the back side if you would like them.

[RickyDean]

There is probably a socket under the daughter board, that would have originally contained the 2793. The empty space on top is where the pins have been placed to correspond to the socket under there. This might be a possible way to recover some Corcomps' that it is getting harder to find 2793's for.

[+Ksarul]

The main board socket for the 2793 has the daughter board plugged into it, using the pins that are sticking down from the "empty" 40-pin socket space on the daughter board. There is no longer a 2793 installed in the original socket--the 1773 on the daughter board replaces it.

[TI99GUY]

That makes perfect sense. What are the advantages of the 2793 over the 1771 and 1773 as long as you get a good working 2793?

[+Ksarul]

The 1773 and the 2793 are pretty much interchangeable, from the standpoint of functionality.

[johnph3]

On 9/18/2017 at 9:20 PM, TI99GUY said:

Hello

Its been many years that my TI has been in storage. My family is doing some very late Spring Cleaning and I just came across my TI which collected a lot of dust. After going through all of my parts I decided to tear down my expansion box and clean it up as good as possible. I also thought that I might have to re-cap some of my boards as they have sat a long time. I opened my Corcomp disk controller casing and to my surprise it is unlike any that I have seen before. Their is some type of add on board or modification where the Western Digital chip goes. Any ideas on what this mod is or does? I would also like to get some advice as if I should re-cap my boards or leave them until I run into a problem. They all seem to work but I have OCD and like to normally fix/repair things just due to age.