[Boatanchors] SB-303 Calibrator Part Needed

[J. Forster]

The logic levels may well be incompatible. You can often mix DTL (930,
946,..) and TTL as they are both current sinking logic, but RTL is a
different kettle of fish.

You MIGHT be able to use the Fairchild 900, 914, 923 as they are early RTL
also. They came in little plastic thingies like transistors.

-John

==============


> The MC724P was a Motorola RTL logic IC that ran on 3.6 volts, not like the
> TTL family of parts (7400 series) that ran on 5 volts.  You might be able
> to
> sub some 7400 series parts, but you would have to check the signal and
> loading requirements, not just the pin connections.
>
> Mike Tallent  W6MXV
> ----- Original Message -----
> From: "Walt - WB2VSJ" <wb2vsj at earthlink.net>
> To: "'Boatanchor List'" <Boatanchors at mailman.qth.net>
> Sent: Monday, February 15, 2010 9:44 PM
> Subject: Re: [Boatanchors] SB-303 Calibrator Part Needed
>
>
>> Of course NTE had to be different than TI (or vice-versa) and the other
>> DTL
>> chip makers :) I'll never understand why NTE put Vcc on pin 11 and GND
>> on
>> pin 4...
>>
>> The NTE9924 is a quad 2 input NOR gate.  A 74LS02 or 7402 is the same in
>> function but NOT in pinout.
>>
>> You can still find the NTE9924 on the web for $11-$15 each. Or you could
>> make NTE9924 out of a 7402 by moving the pinouts around using an IC
>> socket.
>> It wouldn't be pretty, but it *may* work. I do don't know about the
>> loading
>> of a 7402 as compared to the NTE9924.
>>
>> Got an oscilloscope?  Check the signals going into and out of the NOR
>> gates
>> on the 25KHz side & also check the voltages on Q602. Q602 is the 25KHz
>> amplifier (I have a schematic if you need one).
>>
>> I'm guessing the 100KHz section works just fine?
>>
>> Good Luck,
>>
>> Walt - WB2VSJ
>>
>>
>> -----Original Message-----
>> From: boatanchors-bounces at mailman.qth.net
>> [mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of Mark Johnson
>> Sent: Monday, February 15, 2010 7:46 PM
>> To: Boatanchor List
>> Subject: [Boatanchors] SB-303 Calibrator Part Needed
>>
>> Team;
>>
>> I'm in need of IC-601 for the SB-303 Calibrator. This is Heath PN 443-8,
>> or
>> a Motorola MC724P or NTE9924.
>>
>> The 25khz output is not working and I believe that my IC is shorted.
>> Anyone
>> have one of these? I'll buy an entire BFO/Power Supply board from a
>> scrap
>> SB-303 if required.
>>
>> Thanks!
>>
>>
>> Mark V Johnson VE3DJU/VE3DDI
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