74196 chip in Frequency counter

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april

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I have come across one of these and pin 1 being a "NOT LOAD" pin has a wire soldered to it which has come loose. I am trying to find where to re-attach it but it is not easily found .

It would help if I had an idea of what I am looking for. A positive voltage point or an earth point or otherwise. The data sheet says " when taken low" etc etc.

Can someone explain what a "NOT LOAD " is ? Not toooo technical please
 
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hi,
The NOT LOAD pin , means that to load into into the counter the state of the input pins [ABCD], the LOAD pin must be pulsed low ie: to approx 0V.
 
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The "NOT" means that the pin is active when it is grounded (Zero volts )
"LOAD" makes the output pins Qa, Qb, Qc , Qd have the same data as the input pins A,B,C,D.
So when the "NOT LOAD" pin is grounded, the counter output is the same as the data input. This is used to preset the counter to a given number.
Pictures of the board would help.
Timescope
 
Thanks Ill attach some pics here shortly

I take it then that I am looking for a pin on a chip which will pulse low at a certain designed point in the count and pass that pulse to the "NOT LOAD" pin.
 
Not neccessarily, if your counter has a switch to adjust the gate (probably marked 'gate'), to measure different frequency ranges then the load pin might go here, or possibly to another ic, maybe a one shot.
 
dr pepper said:
Not neccessarily, if your counter has a switch to adjust the gate (probably marked 'gate'), to measure different frequency ranges then the load pin might go here, or possibly to another ic, maybe a one shot.
Click to expand...

One shot being a 555 timer ? or what others might it be ?
 
74121, 74122, 74123 spring to mind, repairing something by proxy isnt very accurate
 
No Probs , come on over !
Should only take you 17 hours each way plus waiting and other travel time .
But you pay ! OK?
 
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Are there not bunches of 74196 counters in a line? If so, I'd think that all of those "pin 1" inputs would be connected to the same electrical point. Now, that's a stab in the dark, not knowing anything at all about the frequency counter.
 
Thanks I'll have a look at that

Here are pics-The wire is midway up on left side white red heat shrink on end -hard to see on first pic --is from bottom board- see next pic but may or may not come up the back , probably attaches back on to the same bottom board somewhere but I can't detect any plausible solder residues on pins as yet . Thats why I tried it up the back to the top board somewher

Oh Freq counter is a Yaesu YC-7B and I think I have a circuit but hav'nt found that yet either.
 

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OK. In the second pic, the column on the left are the cascaded 74196 chips, five of them and five 7-segment LED displays. That makes the middle column the decoder/drivers for the display and the right column are resistor packs for current limiting of the display LEDs. I can't make out the decoder/driver type numbers -- I don't see 7447 or anything like that on them. Having five D/D chips tells me that the display is not multiplexed.
 
The white wire in your picture is connected to pin1 of Q01 and it should be connected to pin10 of Q15 on the other board (74LS04). I suspect that this wire was added to bypass a defective connection in the plug and socket that connects the two boards or a broken pcb trace. To cross check, you could clean the tip of your soldering iron and check for pieces of the wire in the solder.

Timescope
 
Careful examination of that pin shows no additional soldering that I can find on the top of the pin . On the bottom is a possibility so I will check that carefully for wire in the solder as you suggest. I have one other problem with it too . I have lost the display for thousands altogether and am investigating this so I wondered if this could go to the 5th bank of counters.
 
I would not worry about the lost digits yet until after the "load" wire is connected. It was probably soldered under the board.

Timescope
 
I tested that wire on that pin to no effect.
Now as I cleaned and lubricated the plug pins a week ago ,if it was to jump the pin , then the pin is fixed anyway it seems .

So the lost digit is my only concern now
 
I had power problems. Let's start with the display, part number 5082-7740. It is a common cathode display and I have attached the internal connections taken from the datasheet
.

I'm assuming that the defective display is the second one from the bottom of your pictures, D505 and the other digits are working.
With power removed, check that pin 1 of the display has continuity to ground. Here are the pin connections viewed from the front
.

The display circuit board is soldered directly to the main counter board. It is possible that there is a break where the solder connects to the display board ( the connections for this display are under the circuit board from the resistor array R806 ). Check for continuity between the display pins and the resistor array R806. The value of the resistors in R806 are not indicated but should be about 330 ohms.

If all the connections are ok, switch the counter on and measure the voltages at the display pins and the decoder ic MSM561RS (Q12). Post the results.

The circuit is configured as a ripple carry counter ( the output of each counter goes to the input of the next one ). Since the first digit (tens of thousand) is working, the 74LS196 (Q06) is probably ok.

Timescope
 
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