Wendy.. could you message me. I have a question about a cord adapter you helped a guy with sometime ago. Thank youI could use a critical eye on this schematic. I may have confused Not .5Hz and .5Hz
Nice.After decades in a junk box it's time for the rebirth. Cut the end off an old USB A to B cable and solder the 5vdc wires to the board. Check the power input for shorts and plug it in to a USB port for power.
It seems to know that time as passed (2001, I'm sure I built it in the early 70's) but the time-base is not working correctly (no output).
Found and fixed a few loose solder connection and adjusted the crystal trimmer for the time base.
Crystal-controlled multivibrator with series-resonant crystal.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720000155.pdf
Bingo, we have the correct frequency from the quartz crystal.
That signal goes to the first divider stage of 3 7490 counters (2 in divide by 5 mode, 1 in divide by 10 mode )
for a 1khz output that feeds into another counter stage.
That looks good. The rest of the circuit has a 7400 for the gate functions with a 7474, 7490 and 7492.
Can't remember exactly how that worked so I'll have to trace that circuit later.
Why don't you post a schematic of your complete circuit instead of just a picture in your thread. If you don't have one, now is a very good time to start. You might even find the root of your problem.Nice.
My counter also uses a crystal Time base.
I start with a 1 MHz oscillator, a divider chain for my gate signals; transfer and reset.
I’ll post a photo of my protoboard project.
I’ll post it as soon as I can.Why don't you post a schematic of your complete circuit instead of just a picture in your thread. If you don't have one, now is a very good time to start. You might even find the root of your problem.
I tried using those chips.Since someone resurrected an old thread, here's a 4 chip solution:
View attachment 199005
Where did you get your chips? I got mine in the 70's, long before counterfeiting from China became such a big problem.I tried using those chips.
Couldn’t get those to work.
We hear this so many times.Couldn’t get those to work.
I got mine from my distributor.Where did you get your chips? I got mine in the 70's, long before counterfeiting from China became such a big problem.
I breadboarded the circuit about 30 years ago and it worked fine. Instead of using 7 segment displays, I used HP 5082-7300 displays:
View attachment 199006
They cost about $20 per display if you can find them.
View attachment 199007
I study the datasheet before I purchase the chips.We hear this so many times.
A circuit may fail to work for 1, 2 , 3, ... so many reasons.
First issue is "circuit does not work" means nothing to us except perhaps DOA or "dead as a nail".
There are different states of "does not work" which when described properly can be helpful in diagnostics.
Half the time the reason for a circuit not working is because the chip is being used incorrectly and the user failing to read manufacturer's datasheet.
When a circuit does not function correctly it is important to analyze the behavior functionally. With debugging a complex system having an oscilloscope and a circuit diagram is almost mandatory.
Is the distributor reputable? Companies like Newark, Mouser, and Jameco certify the authenticity of their parts. Companies like Tayda don't, but they claim they only buy directly from manufacturers.I got mine from my distributor.
Yes.Is the distributor reputable? Companies like Newark, Mouser, and Jameco certify the authenticity of their parts. Companies like Tayda don't, but they claim they only buy directly from manufacturers.
I've done business with Jameco since around 1977. They don't have a very large selection these days, but they price match.I use Jameco most of the time.
So have I for about the same time.I've done business with Jameco since around 1977. They don't have a very large selection these days, but they price match.
That circuit appeared in an old Engineer's Notebook II sold and distributed by Radio Shack and written by Forrest M. Mims III first printing 1982 pages 34 & 35. There is a three digit, half the complete version, also. I actually used it along with a reflective photo cell (LDR) circuit involving V to F. When I used it it worked fine. The V to F was a FV9400 I think. That was a long, long time ago.Since someone resurrected an old thread, here's a 4 chip solution:
View attachment 199005
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