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#1
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freq counter schematic
Does anyone have a schematic for a Ramsey CT-125 frequency counter? Mine
crashed and I'd like to revive it. Thanks. AL |
#2
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"Alfred Lorona" ) writes:
Does anyone have a schematic for a Ramsey CT-125 frequency counter? Mine crashed and I'd like to revive it. Thanks. AL Open it up, and see what's in side. It will likely be one of two routes. Either it's going to have a lot of TTL, a decade counter/latch/decoder for each digit (and possibly 7490/7475/7447), and a divider chain made up of a string of decade counters. Or it's going to have a large IC that does all or most of the work, something like the Intersil 7208. If it's the first case, you can look up any schematic from 20 to 30 years ago, and get the basic wiring. There may be small changes but it will be fairly constant. Or pull out a TTL databook, and you will get the functions of the pins. The real variation will be on the input circuity, ie the analog stuff before it's converted to TTL, and the reset circuitry. If it's a large IC inside, then find the datasheet and again you will have most of the schematic. There will be much less variation in this case, since the wiring is pretty fixed. Once you have this basic information, then you can trace to find out what's not working. Figure out the time base, and make sure it's outputing properly. Maybe in either case, the analog circuitry is at fault (after all, it faces an uncontrolled environment, when it's hooked up to outside circuitry), you can always feed its output with a TTL oscillator in the HF range, in effect inject a signal, and if the counter reads out the right frequency, you know where the problem lies. Michael VE2BVW |
#3
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"Alfred Lorona" ) writes:
Does anyone have a schematic for a Ramsey CT-125 frequency counter? Mine crashed and I'd like to revive it. Thanks. AL Open it up, and see what's in side. It will likely be one of two routes. Either it's going to have a lot of TTL, a decade counter/latch/decoder for each digit (and possibly 7490/7475/7447), and a divider chain made up of a string of decade counters. Or it's going to have a large IC that does all or most of the work, something like the Intersil 7208. If it's the first case, you can look up any schematic from 20 to 30 years ago, and get the basic wiring. There may be small changes but it will be fairly constant. Or pull out a TTL databook, and you will get the functions of the pins. The real variation will be on the input circuity, ie the analog stuff before it's converted to TTL, and the reset circuitry. If it's a large IC inside, then find the datasheet and again you will have most of the schematic. There will be much less variation in this case, since the wiring is pretty fixed. Once you have this basic information, then you can trace to find out what's not working. Figure out the time base, and make sure it's outputing properly. Maybe in either case, the analog circuitry is at fault (after all, it faces an uncontrolled environment, when it's hooked up to outside circuitry), you can always feed its output with a TTL oscillator in the HF range, in effect inject a signal, and if the counter reads out the right frequency, you know where the problem lies. Michael VE2BVW |
#4
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"Michael Black" wrote in message ... "Alfred Lorona" ) writes: Does anyone have a schematic for a Ramsey CT-125 frequency counter? Mine crashed and I'd like to revive it. Thanks. AL Open it up, and see what's in side. It will likely be one of two routes. Either it's going to have a lot of TTL, a decade counter/latch/decoder for each digit (and possibly 7490/7475/7447), and a divider chain made up of a string of decade counters. Or it's going to have a large IC that does all or most of the work, something like the Intersil 7208. If it's the first case, you can look up any schematic from 20 to 30 years ago, and get the basic wiring. There may be small changes but it will be fairly constant. Or pull out a TTL databook, and you will get the functions of the pins. The real variation will be on the input circuity, ie the analog stuff before it's converted to TTL, and the reset circuitry. If it's a large IC inside, then find the datasheet and again you will have most of the schematic. There will be much less variation in this case, since the wiring is pretty fixed. Once you have this basic information, then you can trace to find out what's not working. Figure out the time base, and make sure it's outputing properly. Maybe in either case, the analog circuitry is at fault (after all, it faces an uncontrolled environment, when it's hooked up to outside circuitry), you can always feed its output with a TTL oscillator in the HF range, in effect inject a signal, and if the counter reads out the right frequency, you know where the problem lies. Michael VE2BVW Of course you could always contact "RAMSEY" to get the information straight from them! I'm sure they have it on hand. They are online! C.L. |
#5
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"Michael Black" wrote in message ... "Alfred Lorona" ) writes: Does anyone have a schematic for a Ramsey CT-125 frequency counter? Mine crashed and I'd like to revive it. Thanks. AL Open it up, and see what's in side. It will likely be one of two routes. Either it's going to have a lot of TTL, a decade counter/latch/decoder for each digit (and possibly 7490/7475/7447), and a divider chain made up of a string of decade counters. Or it's going to have a large IC that does all or most of the work, something like the Intersil 7208. If it's the first case, you can look up any schematic from 20 to 30 years ago, and get the basic wiring. There may be small changes but it will be fairly constant. Or pull out a TTL databook, and you will get the functions of the pins. The real variation will be on the input circuity, ie the analog stuff before it's converted to TTL, and the reset circuitry. If it's a large IC inside, then find the datasheet and again you will have most of the schematic. There will be much less variation in this case, since the wiring is pretty fixed. Once you have this basic information, then you can trace to find out what's not working. Figure out the time base, and make sure it's outputing properly. Maybe in either case, the analog circuitry is at fault (after all, it faces an uncontrolled environment, when it's hooked up to outside circuitry), you can always feed its output with a TTL oscillator in the HF range, in effect inject a signal, and if the counter reads out the right frequency, you know where the problem lies. Michael VE2BVW Of course you could always contact "RAMSEY" to get the information straight from them! I'm sure they have it on hand. They are online! C.L. |
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