[TenTec] Omni 6 Logic Board Failure

[Dr. Gerald N. Johnson]

According to the schematics in the downloaded Omni VI manual, the 
processor is an 80C32 using external memory and ROM. The memory chip is 
not very common, but Jameco has some. The CPU chip is available from 
standard distributors, its still a production item. Ditto the EPROM 
which is the same as used in thousands of Tapr and MJF packet TNCs, 
27C256, content of course is specific to the Omni VI but it HAS to be 
socketed, because there's no provision for programming it on board. That 
socket is suspect, still good sockets are distributor items. The real 
time clock chip a DS1285 is no longer made, but Dallas Semi (owned by 
Maxim) says the DS12885+ or DS12885N+ (wider temperature range) is a 
direct replacement. There is a lithium cell in a holder to hold up the 
static RAM which if never replaced is about twice as old as its expected 
shelf life. Then there are assorted TTL or HC parallel port chips and an 
82C55 which is probably commonly available yet. The DSP has its own 
dedicated A/D and D/A chips which I didn't chase down, but the DSP chip 
itself (which I think runs from external ROM) is available at 
distributors. In any case the audio cables to and from the DSP could be 
connected to work without the DSP for debugging purposes.

Its entirely possible that the later Omni VI+ control board has more 
surface mount chips, but remembering how well the control boards for the 
Paragon have responded to resoldering, after I replaced the battery, the 
sockets, and the on board electrolytics I would attack the board 
soldering, whether surface mount or not. When there are multiple 
symptoms, sometimes a shotgun attack is more effective than proving each 
problem by detailed troubleshooting. Remembering how bad electrolytics 
mess up Corsair and Corsair II displays...

73, Jerry, K0CQ

On 1/17/2011 3:45 PM, mike bryce wrote:
> I've been reading this thread here and there and I'm sure I've missed some of the finer details
>
> So, my question is simple. The logic board failure. Is it due to the microprocessor failure or the
> entire pcb? If it's the actual uP, then that's one problem that going to be very hard to solve other
> than having a second rig for parts.
>
> but if it's the failure of the pcb, then one could be manufactured  and improvements made.
>
> Since I don't have one to compare, and unless there are specialized components such as
> transformer or coils, it doesn't seem to be  a insurmountable problem.
>
> Provided that the uP is not the problem.
>
> someone, steer me in the right direction
>
>
>
>
>