testing 1541 logic boards.

[bradhig1]

I swapped the boards in my 1541s when one kept returning a file not found error and the other kept spinning. After switching they had the opposite problems. I keep getting negative values from the 6522 chips but I think I was putting the leads for my volt meter on the wrong pins. How do I test all the chips to see if they are bad?

[SignGuy81]

When I worked on industrial electronics we had a plug in tester that tested most logic chips. The other way to do it is to use a breadboard and wire, some LEDs, resistors. Get the datasheet to see the pinout, and test the chips. Like for example, on the breadboard take the 4001 NOR chip for example. The output of the NOR gates on the chip will be high whenever neither of the inputs are high. So for the test you would hook up a resistor(330 ohm would be a good choice, higher than needed but will still light) to to the outputs, other end of resistor goes to anode of LED, cathodes to ground. Then hook all inputs to ground to start off with. Hook up 5V to pin 14 on the chip and ground to 7. In the beginning all of your LEDs should be lit. Next take one wire for each gate and place it at 5V instead. Do the test again. Now all four outputs should be off. Then swap for the other input of each gate putting the last one back on GND and the other one on 5V. Again each output should be off. Now put all inputs on 5V. Again each output should be off, as with the NOR gate the output is only high when neither input is high. You can use the same setup to test a bunch of 4000 series chips as the gates are oriented same, the only difference will be the outputs will not be lit the same because it will be different gates, for example an AND chip you do the test the same but each LED will be lit only when both inputs of the gate are high. The 7400 series are oriented differently so the wires would have to be set up differently for testing those. If you are going to be testing a bunch of those you could actually instead make your own tester with an IC ZIF socket, and some switches, I would use dip switches probably(and pullup resistors) for the inputs. That would be the easiest method if you wanted to have a way to do it all the time. Make one for 7400 series chips and one for 4000 series chips. But always look at datasheets because there are some that will not work for.

 

This might make things a lot simpler though

https://www.ebay.com/itm/IC-Tester-74-40-45-Series-lC-Logic-Gate-Tester-Digital-Detection-IC-Series-Mete/272875253601?hash=item3f88a1ef61:g:9HQAAOSwE7FZ1j9g

Edited December 8, 2017 by SignGuy81

[SignGuy81]

I just realized I overlooked the post. I thought you meant like basic logic chips, then I reread the post and saw 6522. I decided to keep my above post up there because it still may come in handy but it would take a more sophisticated setup to test the 6522 chips.

[bradhig1]

I couldn't do that. I was just testing voltages.

[bradhig1]

I just got a copy of racing destruction set today that won't load\ on my 1571. Kayaking the last event on my summer games ii disk won't load on my 1571 either. I want a working reliable 1541 and I only have a voltmeter and don't know how to test the chips on my 1541s.

[SignGuy81]

This may help for the drive that keeps spinning

 

 

 

 

A post by Soijai at http://www.lemon64.com/forum/viewtopic.php?t=26487&sid=8f56be3b6fcc50cf9925e04c015dcc6f

 

 

 

 

I had this same issue with a drive I pulled out of storage. I also had a drive that gave me no lights. I found this in the COMP.SYS.CBM FAQ:

--------------------------------------
11. Troubleshooting


11.1. What do I do for my ill disk drive?

If the drive spins and the LEDs are off:

At the back of the 1541 circuit board are two bridge rectifiers - stout
epoxy packages with 4 leads each. The innermost one is defective

If both LEDs are dim:

The 5VDC regulator is bad.

If both LEDS are on:

Drive did not make it through the power-on reset sequence. Kernal ROM
(901229-05) is susepct, as is (in order of expectation): VIA (6522),
CPU (6502), RAM (6116 or equivalent), or a "glue" chip in the reset logic

If your drive won't even accept input from the computer, and the drive
light is making some blinking pattern, then the drive may be telling you
what is wrong.
--------------------------------------

The FAQ pointed to a chip problem and sure enough, when I opened the case, there was an obvious chip issue. I had apparently cannabilized this drive 11-12 years earlier and took the CPU from it. I just took the CPU from the other dysfunctional drive and used it in the one missing the CPU and the drive works fine now.

I am not sure of the chip differences between a 1541 and the 1541-II though as I haven't opened up a 1541-II model. But the same concepts as far as a chip being at fault may apply.

-Steve

Edited December 12, 2017 by SignGuy81

[R.Cade]

There is no simple way to test it. It's a complicated, entire computer on a board.

[bradhig1]

Maybe I outta get another 1541. 1571 sometimes doesn't read disks until I turn it off and on again.

[SignGuy81]

That would probably be the best option unless somewhere repairs them at reasonable prices you could take those to.

[bradhig1]

ordered another one.