Cbm dual drive 3040 disk - two red lights

[Desperado]

Can you now measure the logic levels on UD2 pins 11 and 10 and UE1 pin 16 please. They should all be HIGH.

Whit resistor or not?

 

[daver2]

No.

Dave

 

[Desperado]

Can you now measure the logic levels on UD2 pins 11 and 10 and UE1 pin 16 please. They should all be HIGH.

I am desperate!! LOW signal in these pins

 

[daver2]

You don't need to be desperate - either I am wrong with my testing or we have found a problem! Let's work the problem through...

Can you check UL2 (74LS04) pins 3 and 4 please.

Dave

 

[Desperado]

You don't need to be desperate - either I am wrong with my testing or we have found a problem! Let's work the problem through...

Can you check UL2 (74LS04) pins 3 and 4 please.

Dave

PIN 3 LOW
PIN 4 HIGH

 

[daver2]

That's OK.

Next are UH2 pins 4, 5 and 6 please.

Dave

 

[Desperado]

That's OK.

Next are UH2 pins 4, 5 and 6 please.

Dave

4: low
5: high
6: no signal

 

[daver2]

That's OK. Pin 6 is not connected because UE1 is removed.

Next is UJ2 pins 4, 5 and 6 please.

I think I have found a schematic drawing error on behalf of Commodore - but let's work it through logically rather than jumping to conclusions...

Dave

 

[Desperado]

Next is UJ2 pins 4, 5 and 6 please.

4: high
5: no signal
6: low

 

[daver2]

That's OK also.

Next is UJ2 pins 1, 2 and 3 please.

Dave

 

[Desperado]

That's OK also.

Next is UJ2 pins 1, 2 and 3 please.

Dave

1 no signal
2 low
3 high

 

[daver2]

That's OK.

Now we get to the gate that I think should have been drawn as a NOR gate but Commodore have drawn it as a NAND gate!

Can you now check UH2 pins 11, 12 and 13 please.

Dave

 

[Desperado]

That's OK.

Now we get to the gate that I think should have been drawn as a NOR gate but Commodore have drawn it as a NAND gate!

Can you now check UH2 pins 11, 12 and 13 please.

Dave

11 low
12 high
13 low

 

[daver2]

OK, so that makes sense with what you are seeing at the MC3446 buffer.

It looks like UH2 on the schematic (the gate associated with pins 11, 12 and 13) should have been drawn as a NOR gate instead of a NAND gate. It also appears as though pins 11 and 12 are swapped over.

OK, let's 'wing' the next test a bit...

You will need another resistor I think.

Connect UE1 pin 8 to UE1 pin 1 (LOW) via one of the resistors.

Connect UE1 pin 10 to UE1 pin 1 (LOW) via the other resistor.

Check UD2 pin 10 and UE1 pin 16 for a logic LOW.

Connect UE1 pin 10 to UE1 pin 20 (HIGH) via a resistor. Move the resistor from UE1 pin 1...

Check UD2 pin 10 and UE1 pin 16 for a logic HIGH.

Let's see if this works...

If not, we will have to do a bit more logic probing...

Dave

 

[Desperado]

Connect UE1 pin 8 to UE1 pin 1 (LOW) via one of the resistors.

Connect UE1 pin 10 to UE1 pin 1 (LOW) via the other resistor.

Check UD2 pin 10 and UE1 pin 16 for a logic LOW.

yes, low!

Connect UE1 pin 10 to UE1 pin 20 (HIGH) via a resistor. Move the resistor from UE1 pin 1...

Check UD2 pin 10 and UE1 pin 16 for a logic HIGH.

low signal

 

[daver2]

OK, so can you leave the configuration as per the unhappy face and report the logic levels of the following IC pins please. I may have got myself confused...

UH2 pins 1, 2 and 3.
UH2 pins 4, 5 and 6.
UH2 pins 11, 12 and 13.
UJ2 pins 1, 2 and 3.
UJ2 pins 4, 5 and 6.

These are largely the signals you measured last time.

I'll see from this what I got wrong with the test! Or (much less likely) what is wrong with your card...

Dave

 

[Desperado]

UH2 pins 1, 2 and 3.
UH2 pins 4, 5 and 6.
UH2 pins 11, 12 and 13.
UJ2 pins 1, 2 and 3.
UJ2 pins 4, 5 and 6.

with resistor??

 

[daver2]

With the same configuration as you should have left it from post #595 - i.e.:

Connect UE1 pin 8 to UE1 pin 1 (LOW) via one of the resistors.

Connect UE1 pin 10 to UE1 pin 20 (HIGH) via the other resistor.

Dave

 

[Desperado]

UH2 pins 1, 2 and 3

1- low
2- no signal
3- low

UH2 pins 4, 5 and 6.

4- low
5- high
6- low

UH2 pins 11, 12 and 13.

11- low
12- low
13- high

UJ2 pins 1, 2 and 3.

1- high
2- high
3- low

UJ2 pins 4, 5 and 6.

4- high
5- low
6- high

 

[daver2]

OK, so that is what I was expecting.

Can you now measure the logic levels on UD2 pins 11, 10 and 9 please.

Dave