Issue Tx boards discussions

[tetroid]

As you already see on Issue 6 updates thread , I made Issue T1 board.
This is version with minimal changes ( basically - remove hard to find components ).

The basic changes :

1. SER and CTL connector - D-SUB 9-pin male connectors.
2. Power system, now we need one channel power supply - 9V DC 3-4 A switching power supply with standard 2.1mm connector ( central pin - positive ). 7805 changed to the switching power module 5V 2A ( TSR2-2450 and others, really supply current of QL board - 0.6A, I think the 5V 1A module can be compatible ). 78L12 and 79L12 changed to 2-channel switching power module ( Am3G-0512DH30Z ).
3. You can use M1 RF module or Composite video out.
4. R107 and R108 ( 33 KOhm microdrives DATA1 and DATA2 lines ) on board now.
5. Buffer between CSYNC and J7 video connector ( to improve the Super Gold card compatibility with SCART video cable ).
6. Added protective diodes to RGB and SYNC lines
7. Other type of the NET socket connectors.
8. Added the trimmer capacitor to X3 crystal oscillator.

[tetroid]

I had some small problems with Issue T1 and now I need to change it to Issue T2. To improve the T2 board I am need the opinion of Ql guru / users for several problems :


1. SER and CTL M/F types and pinouts,
German and american QLs have D-SUB 9-pin connectors - CTL - male type, SER - female type. I made all male type, but I am not sure now.

CTL1 and CTL2 - Kempston/ATARI style joysticks. Possible somebody doesn't consider it convenient to use?



SER1 and SER2 - PC style serial connectors.

2 - RxD
3 - TxD
4 - DTR
5 - GND
8 - CTS
9 - +12V via resistor.

But I see different between SER1 ( J6 ) and SER2 ( J5 ) on Issue 6 board: RxD and CTS - input for SER2 but output for SER1, TxD and DTR - output for SER2 but input for SER1 ). I'm a little confused what the correct and useful pinouts for new board?
Possible I need to change to female type to prevent the wrong connection ( CTL devide to SER or SEr device to CTL ) ?


2. The quality of composite video out is not good, we need to adjust the trimmer capacitor periodically.
I plan to make the s-video connection to improve video connection. S-video - composite adaptor can be used too.





3.Discussions about more significant changes for the next versions ( not for T2 ).

Possible we need to remove the internal microdrives?
In any case we can use external microdrives and v-Drive QL.

Possible we need to remove the NET connectors or change it to sound connector ? I see the attempts to use the AY3-89x chip on QL.

[Peter]

As you already see on Issue 6 updates thread , I made Issue T1 board.

Superb. Personally, I'd prefer that one over the Issue 6 board.

2. Power system, now we need one channel power supply - 9V DC 3-4 A switching power supply with standard 2.1mm connector ( central pin - positive ).

Unfortunately this is the exact same connector as for the Q68, where it carries 5V DC. Risk of confusion!
Is there any chance to also use 5V input and create the higher voltages by step-up conversion? Since the higher voltages require less current than 5V, this might even be the "nicer" solution.

6. Added protective diodes to RGB and SYNC lines

Excellent.

Possible we need to remove the NET connectors or change it to sound connector ?

I strongly recommend to keep the NET connectors. Recent developments on the Q68 have pushed usage of QLNET, and there are ongoing efforts to even create USB to QLNET adaptors for PC emulators. QLNET is still the fastest connectivity for original QLs.

[vanpeebles]

More excellent work from the Ob QL Design Bureau

[Derek_Stewart]

Hi,

I do not loke to use Microdrives, I use QL-SD and vDriveQL.

Could the vDriveQL be fitted into the QL case?

I did consider fitting it into an issue 5 board, but it needed too much component change to loe profile or SMD.

[vanpeebles]

I thought there was an internal version of vdrive?

[dex]

SER1 and SER2 - PC style serial connectors.

2 - RxD
3 - TxD
4 - DTR
5 - GND
8 - CTS
9 - +12V via resistor.

But I see different between SER1 ( J6 ) and SER2 ( J5 ) on Issue 6 board: RxD and CTS - input for SER2 but output for SER1, TxD and DTR - output for SER2 but input for SER1 ). I'm a little confused what the correct and useful pinouts for new board?

Because Samsung DE-9 connectors are not "PC style", but "ZX Interface 1 style".
One is connected as DTE, the other as DCE.
I.e., in the PC world - one should be male and the other one female.

[Pr0f]

you have 2 choices here really - either wire them both as DTE and keep them maie connectors, or wire one as DTE and one as DCE as per the original intention of the QL design, and use Male / Female connectors. DTE - male, and DCE - Female.

Since ther is an abundance of both straight through and crossed over cables for the PC market, you could get away with both. Ideally a standard off the shelf cable should be able to connect to a USB RS232 adaptor on a PC and a slow speed serial connection made between the QL and the PC

[Cristian]

At least one microdrive should be kept. What about an audio connector next to the RGB connector?

...oh, by the way... what a surprising piece of work Tetroid!!!

[Chr$]

That's incredible!

So let me get this straight... this is basically intended as a replacement motherboard product? It will technically be about the same spec-wise as the original (but with proper D-SUB added, better video out and more convenient power requirements) but you'll still need to use your original custom chips like the ZX8301 and ZX8302 (because those aren't available new)?