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Re: [TenTec] Need Corsair Part

To: tentec@contesting.com
Subject: Re: [TenTec] Need Corsair Part
From: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Reply-to: geraldj@weather.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Tue, 07 Dec 2010 11:32:08 -0600
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
I have a data sheet for the Corsair counter. It would reproduce well in 
a modern micro, though it might take a bit of PC board to adapt a 100 
pin surface mount chip to the original board. PIC comes to mind first 
but a glance at a Mouser catalog showed there were several makers all 
with competitive but software incompatible chips with enough I/O and 
built in counters. Though one probably would want to implement the 
counter in software if its fast enough (the MK50938N only counts to 1.5 
MHz) because you need BCD output from the counter to be converted to 7 
segment display drive in the micro. Last time I converted binary to BCD, 
I recall it took some division and division is SLOOOOOOOW with out a 
math coprocessor and its slower there than addition. Using 6 registers 
and some program logic to make a BCD counter may work well. Or even one 
32 bit register with proper bit based logic to detect BCD overflows and 
to push the carries as needed every ten ^ x counts.

One rub with doing anything like that is that there's a learning curve 
for each family and sometimes for each different chip, and with the 
thousand to choose from in the Mouser catalog one has to punt, pick one 
and live with its foibles because it takes too much time to learn 
another well enough to select smartly.

The Corsair II does use the 68705 with embedded code that includes the 
keyer as a side effect. Its custom code for Tentec and if they can't 
reproduce it, it will be difficult, though it might be more like an 
emulation of the MK50938 with keyer added. It might need to be designed 
from the circuit function. Its possible the 68705 may be set up so it 
can't be read.

There may be market niche for these and for Omni VI controller boards, 
VI+ with DSP gets tougher. I'll sleep on it many moons.

The other thing to check is that its a known failure mode in the Corsair 
II when the miniature aluminum electrolytics get too old the display 
fails. That could be true of the Corsair and a hand full of 89 cent 
electrolytics may be the root of the whole problem. Go for the highest 
temperature rating and lowest ESR rating you can buy from Mouser or 
Digikey. When a few bucks of capacitors with a history of failing can 
make a chip look bad, its important that those crappy capacitors be 
replaced first. Miniature aluminum electrolytics are not forever 
components, some won't pass my power factor test when new. They start 
out as poor and get worse with age. They age fastest when not powered. 
The electrolyte either leaks out or etches away the insulator formed on 
the aluminum foil causing severe leakage when power up again a few years 
later. For reliable circuits 2 years without power is all any of the 
best electrolytics can stand, more idle years makes a disaster in the works.

73, Jerry, K0CQ

On 12/7/2010 11:10 AM, mike bryce wrote:
> I've did some digging, too.
> for the corsair II, it looks like it's a microprocessor, and unless you have 
> the code,or can read it from a known good chip, you're sunk.
> here's the data sheet:
> http://www.alldatasheet.com/datasheet-pdf/pdf/77313/MOTOROLA/MC68705P3S.html
> you can find the part, "IF" you're willing to spend the $200 min line.
> the corsair I, the MK50398N is a bit easier to find. It's just a 'counter on 
> a chip' and there's a place in England that has them in stock for a mere $150 
> + shipping.
> Like jerry mentioned, I'd look into the receiver counter from AADE and see if 
> you couldn't the counter to use the ten tec original corsair display
> Mike, WB8VGE
> SunLight Energy Systems
> The Heathkit Shop
> http://www.theheathkitshop.com/
> J e e p
> o|||||||o
> "If you can't explain it simply then you don't understand it well enough"
> Albert Einstein
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