CPC-464 freezes on start-up with black background colour

[Tezz]

Last test ic112 before desolder.
Pin 37 expansion port BUSRQ to ground, pin 4,5 ic112 to ground and You should have 0V on Pin6 but you have not.

Pin 37 expansion port BUSRQ to ground, pin 1,2 ic112 to ground and You should have 0V on Pin3 and you have.

Ok, thanks. I'll try that too.

These SN74LS32 are listed on eBay, 10 for just over a fiver. Photo seems to show the correct SN74LS32N but can you confirm these are correct for me to order.

https://www.ebay.co.uk/itm/166211136961

Thanks again to all!

[McArti0]

YES ok

[Tezz]

I've now removed IC112 from the board and installed a socket. The new SN74LS32N are on the way.

I wanted to test this logic IC in my TL866II but the latest version of xgpro seems to have removed all the 74 logic from the list. Is there something I'm missing with this latest version in order to test it?

[Rabs]

Select Tools then Logic Test and 7432 but this is with version 11.9

You cannot view this attachment.

[Tezz]

Select Tools then Logic Test and 7432 but this is with version 11.9

You cannot view this attachment.

Ah, thanks for the info, I did see 7432 listed but wasn't entirely sure it was actually 74LS32 as they were specifically listed in previous versions 

[Tezz]

Test seems to pass with the same result as your screenshot 

[McArti0]

Mayby not work on hi freq. Try now connect 4,5 pin to z80 pin 20,21.

[Tezz]

The 7432s arrived this morning but no change with the new one installed unfortunately. 

[McArti0]

Last test ic112 before desolder.
Pin 37 expansion port BUSRQ to ground, pin 4,5 ic112 to ground and You should have 0V on Pin6 but you have not.

Pin 37 expansion port BUSRQ to ground, pin 1,2 ic112 to ground and You should have 0V on Pin3 and you have.

You can instead search for busrq Just take out the Z80.

[Tezz]

Last test ic112 before desolder.
Pin 37 expansion port BUSRQ to ground, pin 4,5 ic112 to ground and You should have 0V on Pin6 but you have not.

Pin 37 expansion port BUSRQ to ground, pin 1,2 ic112 to ground and You should have 0V on Pin3 and you have.

You can instead search for busrq Just take out the Z80.

Ok, will check this out next, thanks.

[Tezz]

Last test ic112 before desolder.
Pin 37 expansion port BUSRQ to ground, pin 4,5 ic112 to ground and You should have 0V on Pin6 but you have not.

Pin 37 expansion port BUSRQ to ground, pin 1,2 ic112 to ground and You should have 0V on Pin3 and you have.

Ok made some time today to do this...

Pin 37 expansion to ground, pin 4&5 of IC112 to ground, pin 6 reads 0v

Pin 37 expansion to ground, pin 1&2 of IC112 to ground, pin 3 reads 3.6v

[McArti0]

Pin 37 expansion to ground, pin 1&2 of IC112 to ground, pin 3 reads 3.6v

this is proof that ic112 has a defect. but the computer shows that this track is working properly, so you probably shorted pins 1,2 to ground incorrectly.

[Tezz]

Pin 37 expansion to ground, pin 1&2 of IC112 to ground, pin 3 reads 3.6v

this is proof that ic112 has a defect. but the computer shows that this track is working properly, so you probably shorted pins 1,2 to ground incorrectly.

Hi, I double checked that pins 1&2 were shorted to ground. I used one wire across pins 1&2 to ground

[McArti0]

Ok. Now Insert ROM diag, and when CPC freeze You connect new Diode, catode to Pin 6 ic112, anode to Z80 WAIT line (or READY on exp port) this connect must be strong and const.
This halted Code on Read 8255 PB instruction. You can check input voltage on D0-D7 line. D0 should be 0 , D1-7 ~5V.

But have You diode?

[McArti0]

0+0=0 you cant have 3,6V on Pn3

[Tezz]

I have some 1N4148 diodes

[Tezz]

0+0=0 you cant have 3,6V on Pn3

I'll repeat the test again in the morning

[McArti0]

test input 8255

[Tezz]

test input 8255

Thanks, I will certainly do this.

I didn't get free time yesterday to progress with testing but I intend to look more into the PIO.