MaxDuino settings?

[mrtinb]

And Jesper, where do you live? Maybe we could meet to test with working hardware.

[jesperp]

And Jesper, where do you live? Maybe we could meet to test with working hardware.

That would be fine - to identify non working components.
If geographic distance is acceptable of course. I live near Roskilde.

[jesperp]

Maybe we should find out if the signal reaches the CPU.

How about 2 oscilloscope pins connected to D7 (tape in data) and /IORQ (I/O access).

Then we can see tape data when /IORQ is low. I don't know how many port reads/writes happens during tape read, but tape data read would be the most frequent.

Any suggestions elsewhere?

It is a step further into the details, but sounds like a good idea. Will try it out...

[mrtinb]

That would be fine - to identify non working components.
If geographic distance is acceptable of course. I live near Roskilde.

I live near Christiansfeld, so that is across the pond. So it would have been easier if you lived in Jutland.

[jesperp]

Maybe we should find out if the signal reaches the CPU.

How about 2 oscilloscope pins connected to D7 (tape in data) and /IORQ (I/O access).

Then we can see tape data when /IORQ is low. I don't know how many port reads/writes happens during tape read, but tape data read would be the most frequent.

Any suggestions elsewhere?

Hi Martin

Ref to the attached pdf:
Completed your suggested measurements - it seemes that LOAD"" and signal into the EAR input have an effect to the CPU IOREQ pin. But it is harder to figure out if CPU pin 13 (D7) have a acceptable signal and is relative to the EAR input.
By the way - where do you see that CPU D7 should be TAPE IN DATA?

PS Driving to the southern part of Jutland from Sealand would be economical suicide with present fuel prices.....;o)
PPS A fine little LM358 OpAmp mono music amplifier is ordered. (ref to: MOGGYS post in this tread from: Fri Sep 09, 2022 11:34 am )

Have a nice weekend!

[Moggy]

PS Driving to the southern part of Jutland from Sealand would be economical suicide with present fuel prices.....;o)
PPS A fine little LM358 OpAmp mono music amplifier is ordered. (ref to: MOGGYS post in this tread from: Fri Sep 09, 2022 11:34 am )

Have a nice weekend!

If I read your post correctly you have ordered the same low signal pre-amp you already have.

You need an LM386 POWER AMP as mentioned in my post to provide the drive needed on the EAR input of our type of computers not a line level pre-amp such as the LM358 which is only good for powering the INPUT of a power amp.
Also the LM358 is a dual op-amp (a noisy one too) and unless the second amp output is properly terminated, instability and excess noise can appear on the output of the section of the chip you are using,which as stated is incorrect for this purpose anyway.

[jesperp]

PS Driving to the southern part of Jutland from Sealand would be economical suicide with present fuel prices.....;o)
PPS A fine little LM358 OpAmp mono music amplifier is ordered. (ref to: MOGGYS post in this tread from: Fri Sep 09, 2022 11:34 am )

Have a nice weekend!

If I read your post correctly you have ordered the same low signal pre-amp you already have.

You need an LM386 POWER AMP as mentioned in my post to provide the drive needed on the EAR input of our type of computers not a line level pre-amp such as the LM358 which is only good for powering the INPUT of a power amp.
Also the LM358 is a dual op-amp (a noisy one too) and unless the second amp output is properly terminated, instability and excess noise can appear on the output of the section of the chip you are using,which as stated is incorrect for this purpose anyway.

Hi Moggy

Thx for your quick reply.
I replied wrongly (too quickly) regarding the ordered OpAmp - this is the one i ordered:
https://www.aliexpress.com/item/1005004 ... 1802AKkVAK

[Moggy]

That looks most excellent!

One thing for sure is that if this does not cure the problem then it can be eliminated and the fault lies elsewhere.

[mrtinb]

Ref to the attached pdf:
Completed your suggested measurements - it seemes that LOAD"" and signal into the EAR input have an effect to the CPU IOREQ pin. But it is harder to figure out if CPU pin 13 (D7) have a acceptable signal and is relative to the EAR input.
By the way - where do you see that CPU D7 should be TAPE IN DATA?

http://www.problemkaputt.de/zxdocs.htm#zx80zx81ioports

[1024MAK]

Keep in mind when using an oscilloscope to monitor D7 and /IORQ, we are ONLY interested in the state of D7 when /IORQ is LOW.

Ideally it would be better if you could put together a simple circuit using a 74LS32 quad 2-input OR gates. Then the Z80 /RD and address line A0 could be included.

The inputs would be A0, /RD, and /IORQ (you need to use two gates, with the output of the first feeding the input of the second). Then the output goes to the ‘scope. The output will then only be logic low when the Z80 reads from an I/O port where A0 is low, such as address 0xFE (ignoring the high byte).

Mark