Forcing a Logic HIGH, to a low state. How can I do this?

[danny davis]

1.) When I replace an Logic IC with a NEW Logic IC , there is more problems on the circuit board than before, before had only 2 lights not working, now with the NEW IC those 2 lights that weren't working, work now but i have 5 other lights that aren't working now

It Replaces 2 problems with 5 new problems , what is this called when a circuit board does this?

2.) When I'm troubleshooting a Logic Board and I lift up a resistor leg or an IC logic pins input or output to isolate a stage or branch, The circuits that are in parallel, different channels , branches that are in parallel or in series become FLOATING

What is this called when this happens? is this common for LOGIC circuits? one you lift up an IC pin or component leg it will make the circuit FLOATING? and all the other parallel circuits , channels, branches floating too?

 

[betwixt]

I give up - what's the point in giving answers when you just keep repeating the same questions.

Brian.

 

[Audioguru]

It doesn't matter what it is called. It means before replacing the IC you probably had 7 faults and after replacing the IC you still have 5 faults or you caused 5 faults.

No it is not common to lift up a pin of an IC or component leg. It doesn't matter what it is called. Then the following circuit will be floating and you do not want DAT.
Instead you look at the inputs and output of an IC that you think is bad, while it is working.

This is silly. I answered this same thread and same questions a few hours ago on another website forum.

 

[dick_freebird]

It Replaces 2 problems with 5 new problems , what is this called when a circuit board does this?

It's called lack of debug discipline / skill / clue causing
additional damage.

Circuit board didn't "do" this. You did. Own it.

But in honor of your efforts to misunderstand every
answer to every inane question begets question ad
infinitum I do propose that we name it the "Danny
Davis" Effect.

Don't let the fame go to your head.

 

[Audioguru]

Dick, you have been here for 5 years. Don't you remember Walters? This is him back again. Today he is called Billy Mayo on another website forum with the same questions as here. In 5 years he has not learned anything.

 

[danny davis]

Here is the schematics of the problems I been talking about, look at the buss that holds all the diodes and transistors








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I lifted up CR31 diode ( circled in blue ) and the Comp fail light when OFF , why is that ? the logic gate U7A output didn't change at all , it stayed at +15 volts , so the U7A input went floating but how when there is a R110 68K pull down resistor

Even when CR31 diode is soldered in , the Logic gate U7A output is still HIGH +15 volts , so i have no idea how the Comp Fail light went OFF from me lifting up CR31 diode

Audioguru said he has never seen and you never use pull down resistor using CMOS gates , so there you go audioguru you have seen you first pull down resistor on a CMOS input

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ARID output pin#14 switches from +15volts to -13 volts back to +15 volts , does this in 3 steps less that 30 seconds when you flip a switch

ARID output pin#14 goes to the buss line that has all those diodes and transistors hooked up to , why? and what does this buss line do?

Why did they buss it like this or have a buss line?

 

[Audioguru]

R110 is the pull-down resistor for THE INPUT of U7A, not its output. D30, D31 and R110 together with the Cmos inverter U7A make a Mickey Mouse NOR gate.
But on the other website forum you did not have a clue about what the diodes do.

 

[danny davis]

Diode Logic Question:
the designer had an NAND gate, then he uses it as in inverter , and then uses diodes and a resistor as a nor gate , there is a reason why the designer did this
why didn't the designer use a nor gate ic chip? why didn't the designer use a inverter ic chip instead of using an NAND gate as an inverter

The BIG SWITCH on the front panel turned on the Enable buss to the flip flops and to that Lamp test Buss? you called it , the lamp test buss is what the diodes and transistors are connected to

The BIG SWITCH is SW1-1 that goes to CR28 and CR25 which is going to ARIC and ARID op amps that goes to that BUSS LINE

The MEMORY Enable reset switch button ( J11-39 ) , switches off and on the Enable voltage to the Flip flops , that's the Enable buss

Here is the picture again:
**broken link removed**
SW1-14 TEST Switch connects , turns on or off the BUSS LINES , the enable buss for the flip flops and the Buss line that the diodes and transistors are tied to

The Memory Reset button J11-41 turns On the RESET buss line to the flip flops

The Comp Fail INPUT J10-44 goes to CR31 diode to R110 , 68 K resistor to U7A

The Comp Fail Input is a Logic low zero volts, how does zero volts or logic low go through a Diodes Anode?
What is ARID output doing? what kind of circuit is it?

ARID op amp output pin#14 is going to that buss line, what is that buss line doing? what is it called please?
U7 is a 4011, NAND GATE
U12 is a 4017, Decade Counter
U20 is a 4043, R/S latch, tri-state output
When I Turn on TEST Switch, SW-1 14 , it does to CR28 diode which does to ARIC op amp and to ARID

When I turn on the Test switch SW- 14 , The ARID pin#14 outputs +15 first, than -13 volts , than +15 volts , it goes through this 3 step cycle really fast

I think it Turns ON and OFF those switching transistors that are all tied on that buss line

By doing 3 steps +15 , -13, +15 it turns on the CR19 diode and Q10 switching transistor i would think this is how it works

Isn't that the whole point of that buss line connected to ARID pin#14? is to switch on the diodes and switching transistors? i'm just guessing