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By using the resistance and capacitance values for the IC5A 556 timer IC we get one-shot periods between 0.5 and 1.6 seconds for the kHz switch position, and between 0.5 and 1.6 msec in the Hz position. The trimmers would adjust these to 1.00 sec and 1.00 msec respectively. I believe the switch labels (Hz and kHz) in the schematic diagram got swapped. The 1-sec period would let the counters count 0 to 999 pulses (0-1 kHz) and the 1 msec period would open the counters to count from 0 to 999 kHz (0-1 MHz). The calculations eliminate the possibility of IC1 as a prescaler or divide-by-x counter. Thus, IC1 probably is an obsolete CD4583. Don't give up hope: A CMOS Schmitt trigger CD4093 will do the same job, although it requires some rewiring. DigiKey has many in stock for under a dollar.

According to my ancient Motorola CMOS databook, MC14583B is a dual Schmitt trigger in a 16 pin package.  Channels A and B can be used independently or there is an exclusive OR output on pin 14. The outputs are tri-state with the control on pin 13. Pin 13 is not connected which is very, very bad practice. However, channel B input (pin 15) is tied high so only channel A is being used. Therefore, you can use any garden variety Schmitt trigger in its place.

The 4583 IC in your frequency counter is a non inverting dual Schmidt trigger. I found this in an old Motorola CMOS data book from 1991 #Q4/91 DL131 REV 3 on page 6-498. The Motorola part number is actually MC14583B. Only the A Schmidt is used in your circuit, the B Schmidt is unused. The Schmidt trigger is used in front of the counter IC1 to ensure a clean input to the counter. Typically the Schmidt trigger output will transition low when the input drops below 40% of the supply voltage and the output will go high when the input goes above 60% of the supply voltage. For the MC14583B device these thresholds are adjustable via external resistors through the positive, negative and common terminals. In your circuit those three pins 5, 6 and 7 are bussed together without a resistor and this sets the thresholds to around 40% and 60% of the supply voltage.

Pin 9 is the A input
Pin 4 is the A output
Pin 15 is the B input (unused so tied high to 9V)
Pin 10 is the B output (unused)
Pin 5 is the negative A (pins 5,6 & 7 are tied together to set the A device threshold)
Pin 6 is the positive A
Pin 7 is the common A
Pins 1, 2 and 3 are common, positive and negative for the B Schmidt (unused)
Pin 16 is VDD. Supply voltage, 18volt max for this device
Pin 8 is VSS. Supply voltage return.

A replacement for the '4583' could be the MC14093B or CD4093 available from Newark, etc., although these do not have adjustable thresholds they will be close to those of the 4583. These are quad two input NAND Schmidt triggers, so all unused input pins must be tied high (to 9V in your case).

I found an MC14583B IC in a 1991 Motorola Data Book. This part is a dual Schmidt trigger IC and appears to match the pinout  shown in the schematic. The pinout is not fully legible in the electronic issue. Using a Schmidt trigger in this application makes sense. I have attached a photo of the data sheet.

If IC1 is indeed an MC14583B or equivalent it should not be powered from 9V! The logic high output from Q1 is only 5V. The data sheet for the MC14583B indicates the minimum input voltage required to guarantee a logic high to be 80% of it's supply voltage. Also the logic high output voltage from IC1 is too high for the 5V downstream logic.

It is possible that IC1 is not actually defective but is not seeing a logic high due to poor design. This theory can be tested by substituting a 7 volt power supply for the battery. If it works at the lower voltage, I would modify the circuit to power IC1 from 5V.

I also question not having a resistor between the junction R1/C1 and the base of Q1 to limit input current to a non destructive level! This might best be accomplished by cutting a 1/16" gap in the track leading to the base of Q1 and soldering a 1K surface mount resistor across the gap.

Am attaching a ZIP file with 4 scanned pages of the MC14583B data sheet for your information. MC14583B.zip

The answer to question 11151 is it is an NE556 dual timer.

The chip you are looking for is a CMOS 4583. It is a dual adjustable  schmidtt  trigger. The 556 timer clocks the 4583 like a gate. I checked the usual places and it may be obsolete.

The best match for IC1 that I found is a Dual Schmitt Trigger, TC4583BP or NTE4583B.

Because most of the other ICs in this circuit are standard 4000-series CMOS parts, that indicates the 4583 at IC1 likely is also. Using that to refine the search, the part is a dual Schmitt trigger buffer.

The unique property of a Schmitt trigger gate is that it provides hysteresis.  When a slow-rising, slow-falling, or noisy analog signal is applied to an ordinary gate, that gate may oscillate and switch several times as the input crosses its switching threshold. But because this Schmitt trigger requires a much higher input voltage to switch high than it does to switch back low, it will clean up its analog input, and its output will switch only a single time.

In this circuit, that behavior is important because the input signal is being used as a clock for the counters.  Without the Schmitt trigger, some input signals might trigger multiple clock pulses per cycle, resulting in wildly incorrect frequency numbers.

Searching for Motorola's specific version number of this part, MC14583BCP, seems to produce better search results, revealing data sheets and even a seller of the part on Amazon!  However, because the circuit does not actually take advantage of the unique programmable hysteresis feature of the 4583 (by just tying pins 5, 6, and 7 together), any other CMOS Schmitt trigger should work just as well, if you can find something cheaper and don't mind slightly modifying the circuit.

This appears to be a dual Schmitt Trigger. I found the NTE4583B data sheet at: www.nteinc.com/specs/4500to4599/pdf/nte4583B.pdf VCC, GND placement is consistent with your Fig 1 schematic. Pin 9 is "A In" and Pin 4 is "A Out". So this would appear to be a Schmitt Trigger used to clean up the input signal.

The 4583, in that design, is an obsolete dual Schmidt trigger chip, which is intended to square up the input signal so it meets the minimum rise/fall time requirements of the downstream counter chips. Probably the simplest substitution would be a 4584 / 74C14 hex Schmidt trigger chip, with two of its inverters wired in series. The remaining four inverters should have their inputs grounded, to prevent excessive current consumption.

The chip you asked about the CD4583 is what is known as a Dual Schmitt Trigger ... that chip has been discontinued but some stores still have the NTE4583B which was their substitute for it. I have attached a .pdf file of the NTE Data Sheet for this chip. Worst case is you would need to rewire the schematic to use a more current version of an equivalent chip. nte4583B.pdf

One such store that says they have them is listed below:

www.moyerelectronics.com/BVModules/ProductTemplates/MoyerProductTemp/Product.aspx?productid=1e4bffa7-6961-4e1a-82f7-8a161ab401ea

Try looking at a MC14583B dual schmitt triger with only one side used. Pin out looks correct, Pin 9 is input and Pin 4 is output. Pins 5, 6, 7 are used to adjust hysteresis.

The 4583 is this part: www.nteinc.com/specs/4500to4599/pdf/nte4583B.pdf.

According to all my old data books, the 4583 IC is a Dual Schmitt Trigger, and NTE supplied them to the service industry, part number NTE4583. You can look at their data sheet here:
www.nteinc.com/specs/4500to4599/pdf/nte4583B.pdf

Supposedly, a company called "Mountain States Electronics has one in stock. Here is their address and contact info:
2107 South College Avenue
Fort Collins, CO 80526

Since the inventory for Mountain States showed only 1 in stock, here is another supplier of the TC4583 Schmitt Trigger chip. These people have a bunch of them and the price is definitely right:
http://store.americanmicrosemiconductor.com/tc4583bp.html