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Old 08-29-2009, 03:05 PM
TomL_12953 TomL_12953 is offline
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Default 60 Hz Line Frequency

In the manual for the Real-Time Clock, it says that unrectified +16v has to be brought to pin 55 of the motherboard to use the RTC with the 60 Hz line frequency. I seem to remember reading here somewhere that this isn't possible with the replicas because of the new power supplies used. I can't find the reference to it now. Does anyone know if this is the case or is my memory faulty? If I can't use the 60 Hz signal, can I use the crystal frequency OK?


Tom Lake
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Old 08-30-2009, 03:19 AM
marty marty is offline
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Join Date: Jun 2007
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Talking 60 hz

Hi Tom;
Before I replaced the Power supply in my Altair, with Switchers, it Did Have a line going to the Power Supply, which if I counted and rememberd right was pin 55... Since I don't plan on having and at this point don't have a use for the RTC, it was no problem getting rid of it.... Two suggestions --- 1. check what kind of an input the RTC is looking for, such as you might be able to tap on to a 6.3 volt line , which would be the center tap for a 12.6 volt transformer, if it has one, other wise go thru a SMALL Cap for the 60 hz signal. 0r 2. Yes you could possibly use something from the CPU Clock, but it has to be divisible down to 60 hz or I assume it won't work right. You could find a crystal or a ttl module type of crystal (can't think what its proper name is) that looks like a 14 pin Ic only with 4 pins, one on each corner. get something that will divide down , like 60mhz, 30mhz , maybe a 15mhz, if you can find it a 60, 30, 15 khz and keep dividing it down till you get what you need. I have used 74393's for my divide circuits... I have a board that I Wire-Wrapped with Sockets that I can put in different frequency modules and then pick how far down the divide chain I want, thru a number of sockets , and then out to a 74LS04 and to a Led and then out , for me to use as I wish..
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