Kempston Disk Interface issue

[Vyper68]

Hi,
The QL I picked up recently had a Kempston disk Interface fitted and although it works when I plug in either a 3.5” Drive or a Gotek the picture on the TV starts skipping. I am using a RGB SCART lead from Retrocomputershack.
If I unplug the floppy cable the skipping/jumping stops. I have replaced the Electrolytic capacitors and the 7805 regulator on the Kempston board and it made no difference. It does seem like it is causing some interference and wondered if anyone could offer some ideas to possibly mitigate it.

[Martin_Head]

Hi,
The QL I picked up recently had a Kempston disk Interface fitted and although it works when I plug in either a 3.5” Drive or a Gotek the picture on the TV starts skipping. I am using a RGB SCART lead from Retrocomputershack.
If I unplug the floppy cable the skipping/jumping stops. I have replaced the Electrolytic capacitors and the 7805 regulator on the Kempston board and it made no difference. It does seem like it is causing some interference and wondered if anyone could offer some ideas to possibly mitigate it.

What's the power supply for the disk drives like? If it's ripply, maybe it's introducing hum on the QL. The electrolytic capacitors may need changing.
The same may go for the QL power supply. If it's running on it's edge.
You may also have some kind of 'earth loop' happening. Try removing the RGB/SCART lead, and use the RF output instead.

[Vyper68]

Well it turns out it may have been my set up.
I had a SCART extension lead in between my RGB lead and the Telly. As I needed the extra length. It now seems that the CSync signal from the QL is not able to travel the distance and adding a disk Interface just adds to the problem.
Take the extension away and plug in direct and the picture stops skipping with a drive connected or not, although the picture is shifted to the left more than with the extension fitted.
I plan to fit Tetroids power board and do away with the 7805 and start recapping the Main PCB but at least I seem to have learned a valuable lesson here.
There is a learning curve with any new computer and I’m just starting out so it’s all valuable experience. I need to get an upscaler I think.

[bwinkel67]

I have a Kempston disk interface. Worked well for me back when I had a 3 1/2 inch floppy. I may eventually grab a Gotek. I wish they had thrown a little extra RAM on that board back in the day...an extra 128K sure would have been nice in the 90's.

[Vyper68]

I found a thread on here with a internal 512KB RAM expansion and it has the .jed files for the GAL and a .brd and .sch file to get the PCB made. So I plan to get 5 of these PCB’s when I have time which should take the RAM to 640KB. I have the PCB saved in my basket waiting to order it, just have a lot on right now.

[bwinkel67]

I found a thread on here with a internal 512KB RAM expansion and it has the .jed files for the GAL and a .brd and .sch file to get the PCB made. So I plan to get 5 of these PCB’s when I have time which should take the RAM to 640KB. I have the PCB saved in my basket waiting to order it, just have a lot on right now.

Oh yes, I followed tcat's design on that thread. I was planning this summer, when school is out, to build my own 512K plug-in internal board by tcat (even etching my own PCB). There was someone else then that took that design (I think) and made it fully internal, plugging it in where the CPU sits. I don't recall if a jumper wire was needed in addition to the board. Is that the one you are making or tcat's?

[Vyper68]

I found a thread on here with a internal 512KB RAM expansion and it has the .jed files for the GAL and a .brd and .sch file to get the PCB made. So I plan to get 5 of these PCB’s when I have time which should take the RAM to 640KB. I have the PCB saved in my basket waiting to order it, just have a lot on right now.

Oh yes, I followed tcat's design on that thread. I was planning this summer, when school is out, to build my own 512K plug-in internal board by tcat (even etching my own PCB). There was someone else then that took that design (I think) and made it fully internal, plugging it in where the CPU sits. I don't recall if a jumper wire was needed in addition to the board. Is that the one you are making or tcat's?

The one I am going to build is indeed the internal one which sits in the CPU socket and with a flying lead to pick up a signal. When the I get the PCBs made ( I’m only ordering 5 ) do you want one?

[Derek_Stewart]

Hi,

Can I have a PCB please?

[RalfR]

Can I have a PCB please?

Me too, please!

[bwinkel67]

I found a thread on here with a internal 512KB RAM expansion and it has the .jed files for the GAL and a .brd and .sch file to get the PCB made. So I plan to get 5 of these PCB’s when I have time which should take the RAM to 640KB. I have the PCB saved in my basket waiting to order it, just have a lot on right now.

Oh yes, I followed tcat's design on that thread. I was planning this summer, when school is out, to build my own 512K plug-in internal board by tcat (even etching my own PCB). There was someone else then that took that design (I think) and made it fully internal, plugging it in where the CPU sits. I don't recall if a jumper wire was needed in addition to the board. Is that the one you are making or tcat's?

The one I am going to build is indeed the internal one which sits in the CPU socket and with a flying lead to pick up a signal. When the I get the PCBs made ( I’m only ordering 5 ) do you want one?

Yes, I'd love one...