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TRC 449. Forgot how to do a truth chart Help.

Low_Boy

Low_Boy

Sr. Member
Jan 21, 2010
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Rochester N.Y.
I have a TRC-449 that has some odd behaviors I think it is a problem with the PLL. I was going to do a truth or logic test to further trace the problem. I forgot how to do this. I am pretty sure I am checking program pins on IC7, PLL for highs and lows. 1' and 0'. do not remember. It's been years.
 

Low_Boy,
You are correct. Program pins (13-22) should be of particular interest. Pins 19 & 22 are fixed low- 0 volts or very close to it. Pin 23 is also low but it is the DC ground for IC-7.

73
David
 
Last edited:
Dmans said:
Low_Boy,
You are correct. Program pins (13-22) should be of particular interest. Pins 19 & 22 are fixed low- 0 volts or very close to it. Pin 23 is also low but it is the DC ground for IC-7.

73
David
Click to expand...
Thank You. I just found it in the manual and was going to post that I found it. You beat me to it. Thanks
 
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This one is good until channel 7. Then a few channels drop out. All the rest are. 26 mhz.from around channel 11 to 40. Ch 19 for example is 26.1850 and 40 is 26.4050 lol.
 
NZ8N said:
uPD858 is a BCD (Binary Coded Decimal) programmed PLL chip. Check Pin 21, if it is "low", then your radio is 100 channels down below Channel 1.

http://malzev.tripod.com/comp/upd858.htm
Click to expand...
I will be getting back to this after coffee. Funny thing is channel 1 thru 7 are correct. but the code on the PLL is wrong on I believe the last pin or two pins. I have to go over this and write down the codes.
 
1-2-4-8 so far so good , but , 10-20-40-80 then 100-200
The SSB radios start at "91" CH 1, and end at "135".
The AM radios start at "182" CH 1, and end at "226"
There are exceptions but these two counts are the most common.
 

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  • realistic_trc_449_sm_sch.pdf
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    realistic_trc_449_sm_sch.png
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Fixed....... Thanks all. everything checked out good except the binary codes. I got looking at the schematic and figured the only thing it could be was that crappy plastic ribbon cable going down to the PLL. I started pushing around with a wet finger and it started working in the 27.000 range where it was supposed to. One little plastic trace was bad. Jumped the bad trace aligned it and what a nice radio.:)
 
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