Microdrives not working and now neither oqtadrive

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bola_dor
ROM Dongle
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Microdrives not working and now neither oqtadrive

Post by bola_dor »

Hi, I recently Got my QL, I am used to ZX line but new to the QL. It's an ISSUE 7 board with its standard rom and now with new membrane.
I managed to connect it to a CGA compatible monitor as composite output just looks awful...
I have several mdv cartridges and a pair of ZX microdrive units (is there a word to diferente microdrive cartridges from the actual drive unit?). I refelted them and could format them with a ZX Spectrum and IF1 but couldn't read nor format any with the QL internal units nor even with the same external unit I can use with the Spectrum as mdv3_.
Motors and leds works but allwas get not found or format error. With mdv3_ it keeps spinning forever until I shutdown the machine.
As suggested by a member from the Fb group I've made an oqtadrve.. and after a pair of nights struggling with it (my 1st arduino project ever) it worked!!! (Thanks Xelalexv for the project!!!!) and could load something using the PC as a daemon..
Thing is that suddenly it stopped working.
I reviewed every connection, connector cable is 5cm short.. and tested it on the ZX IF1 and it's still working.
So I have to think something went wrong with the QL itself..
Both internal units are unplugged from the board so the oqtadrive is mapped from mdv1...
Where should I start? How can I verify that ZX8302 is working? And what components are critical for the drives to work.. I mean not just co motor or leds controls as now I'll be happy just with the external unit working and the I'll see whats happening withe internal drives...
I couldn't find an issue 7 schematics, is the issue 6 similar enough? And I think a components layout will help too.
I have a world of questions about this machine but now I will focus on getting the oqtadrive, or any drive to work..
Thanks


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Ernesto
ZX80 USA, ZX81UK, ZX Spectrum, ZX Spectrum+, ZX Spectrum 128+ UK, ZX Spectrum +2/A, Sinclair QL, CZ1000, CZ1500, CZ2000, CZ1000Plus, CZ1500Plus, CZ Spectrum, CZ Spectrum Plus, TK83, TK85, TK90X, TK95. TS2068. And more to come :D
Derek_Stewart
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Re: Microdrives not working and now neither oqtadrive

Post by Derek_Stewart »

Hi,

There does not seem to be any information anout the QL Issue 7 board.

I have some Otadrives to make, I have QL Issuse 5,6,7 so can do comparisons.


Regards,

Derek
bola_dor
ROM Dongle
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Re: Microdrives not working and now neither oqtadrive

Post by bola_dor »

2022-5-31 23-25-24.jpg
Derek_Stewart wrote:Hi,

There does not seem to be any information anout the QL Issue 7 board.

I have some Otadrives to make, I have QL Issuse 5,6,7 so can do comparisons.
Thanks, that may help, can tou compare issue 7 against issue 6? I will use issue 6 schematics as a guide.
And can you confirm if ZX8302 has pin 21 into the socket or bended away as I found in mine?
Thanks!!


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Ernesto
ZX80 USA, ZX81UK, ZX Spectrum, ZX Spectrum+, ZX Spectrum 128+ UK, ZX Spectrum +2/A, Sinclair QL, CZ1000, CZ1500, CZ2000, CZ1000Plus, CZ1500Plus, CZ Spectrum, CZ Spectrum Plus, TK83, TK85, TK90X, TK95. TS2068. And more to come :D
Derek_Stewart
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Re: Microdrives not working and now neither oqtadrive

Post by Derek_Stewart »

Hi,

In the picture is showing your 8302, there is a pin that is bent and possibly giving an intermittent connection.


The bent pin 21 is not standard on all QLs, only all example of someone not fitting the chip correctly.

You need to remove the 8302 and straighten the bent 21 pin, clean the pin legs and replace into the socket.
The 2 resistors are factory fitted to improve a microdrive reliability, will be required to be connected.this should solve you problem.

I saw your post on Facebook, but was surprised that no one suggested straightening the bent pin.


Regards,

Derek
martyn_hill
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Re: Microdrives not working and now neither oqtadrive

Post by martyn_hill »

Hi Ernesto!

I can confirm the advice below - Pins 19 & 21 of the ZX8320 are the RAW2 & RAW1 (respectively) data-lines connecting the 8302 to the MDV ULA(s) of the drive units themselves.

They must both connect cleanly with the socket.

The flying resistors soldered directly to these pins, and joined to the (relatively clean) -12V power-rail exposed at the RS232-level converter IC25, are there to provide the necessary 'pull-down' for the 2 data-lines of the MDV circuitry, which appear to be of the 'emitter-follower' type - i.e. the ULAs drive the lines High/active, but rely on external pull-downs to take the signal back to ground (or here, -12V, via the flying resistor modification.)

The soldering of that resistor mod on your unit may be interfering with the pin engaging with the socket, so the last time it was inserted, may well have bent the pin out rather than seating correctly...

Side note for anyone interested - On the ZX Interface-1, Sinclair used 2x 10k pull-down resistors to Gnd, rather than what we see on the QL. I have often specuiated as to why this mod was devised for the QL (which I typically re-arrange by re-soldering underneath the board, to allow ease of replacement of the 8302), rather than the simpler approach used on the Interface-1. Given what we now know about the relatively poor noise-floor of the QL power-supply Gnd line, I suspect that using a fairly clean power-line like the -12V rail instead - and using correspondingly higher value pull-down resistors - was a means to reduce the noise on the RAW1/2 lines. Removal of the pull-down resistors can still work (I have one QL without a -12V rail and just ditched the resistor mod altogether), but leaves you dependent on the inherent capacitance of the MDV bus to form an acceptably clean 'falling-edge' of the RAWx data-lines. Not recommended...


bola_dor
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Re: Microdrives not working and now neither oqtadrive

Post by bola_dor »

Hi Martyn and Derek,
First thing I've done was refitting the IC into the socket properly. And nothing changed. Microdrives still doesn't work and oqtadrive worked for a short period but now all I get is the "not found".
So I need to test the board part some how. Specifically the ZX8302 in case I have to buy a replacement..
Thebinfonabout pull downs will be useful as I know what to check there.
I have an original PSU and a newer I 've made with a 12v transformer and a switching DC PSU... I see no difference about drives .


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Ernesto
ZX80 USA, ZX81UK, ZX Spectrum, ZX Spectrum+, ZX Spectrum 128+ UK, ZX Spectrum +2/A, Sinclair QL, CZ1000, CZ1500, CZ2000, CZ1000Plus, CZ1500Plus, CZ Spectrum, CZ Spectrum Plus, TK83, TK85, TK90X, TK95. TS2068. And more to come :D
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Ruptor
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Re: Microdrives not working and now neither oqtadrive

Post by Ruptor »

bola_dor wrote:First thing I've done was refitting the IC into the socket properly. And nothing changed. Microdrives still doesn't work and oqtadrive worked for a short period but now all I get is the "not found".
Just a thought that if the pull down resistors were not in circuit because the pins were not in the socket & resistors R107 & R108 of 33K that are shown on the circuit are not fitted then the inputs of IC 29 & IC30 would be floating. Perhaps this could have blown up the inputs if they are open circuit and once blown would affect anything else connected to the RAW lines. If the Oqtadrive uses the lines then disconnecting the internal microdrives might allow it to work. I wrote this quick does it make sense? :?


martyn_hill
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Re: Microdrives not working and now neither oqtadrive

Post by martyn_hill »

Hi again Ernesto

A couple of points/questions...

1. The schematic for the Iss 6 is perfectly valid for the Iss 7 boards, in so far as the MDV circuitry is concerned - as far as I can tell, the Iss 7 has a slight rearrangement of the components plus some previously documented Iss 6 mods being applied at the factory. Whilst there may be some more subtle changes, I my experience, these won't impact what you are seeing here, so feel free to refer to the Iss 6 schematic.

2. You previously mentioned that, withe both internal drives fitted, the oqtadrive worked intermittently, but now does not. Likewise the external ZX MDV unit failed to allow format/reading when connected as MDV3_. My experience here pints to one or both of the internal units ULAs already on the verge of failure. If the ZX unit as MDV3 continues to spin , it can be because the ULA of one of the internal units is messing with the Comms Clk or Comms Select lines when they (should be left alone when the internal drives are de-delelected) that are fed out and into the next unit in the chain (more accurately, Comms Clk is common across all connected units, and Comms Select-Out on one unit feeds the Comms Select-In on the next drive in the chain.) Alternatively, if either or both of the ULAs of the internal units chooses to remain active when it shouldn't (because MDV3 is being selected), then the RAW data-lines may also being left active and interfering with the ZX or oqtadrive's ability to drive the data-lines, which can confuse QDOS which leaves MDV3 active rather than detecting the error and deselecting the drive as you would notmally expect .

3. Now that you have re-seated Pin 21 of the ZX8302, can you confirm whether the oqtadrive is now connected on its own as MDV unit 1 and, if so, does it still show intermittent behaviour?

4. My experience suggests that, whilst the MDV ULAs can and do fail, they are sufficiently 'robust' that the 'floating' RAW dataline shouldn't have permanently hurt them - more likely that one or both of the internal MDV unit ULAs are already kaput.

Good luck!


bola_dor
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Re: Microdrives not working and now neither oqtadrive

Post by bola_dor »

jut to clarify the history,
oqtadrivie at first worked OK with both internal MDV still attached,. as I couldnt map the oqtadrive as MDV1_ I opted to detach both the internal units. and all went OK, in fact I could load and run some MDV files I downloaded.
but when I wanted to load some other files it gave me a "not found" and never worked again.
As I told I rechequed the connections and the oqtadrive with the IF1. then Ive made sure it was mounting as a Ql when back to it..
I think internal units are completely out of the equation now.
how can I rule out the ZX8302 ? I have a cheap handheld oscilloscope that can help (up to 20Mhz)... ( I think I should borrow a better one if I have to check the crystal)


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Ernesto
ZX80 USA, ZX81UK, ZX Spectrum, ZX Spectrum+, ZX Spectrum 128+ UK, ZX Spectrum +2/A, Sinclair QL, CZ1000, CZ1500, CZ2000, CZ1000Plus, CZ1500Plus, CZ Spectrum, CZ Spectrum Plus, TK83, TK85, TK90X, TK95. TS2068. And more to come :D
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xelalex
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Re: Microdrives not working and now neither oqtadrive

Post by xelalex »

Hi Ernesto,

could you run the OqtaDrive daemon with debug log level and do a dir mdv1_ or a load and post the log here or send via PM? Maybe we can infer something from that.

And to clarify, you have OqtaDrive connected to the external connector, removed the internal drives, and bridged COMMS IN to COMMS OUT in both internal drive connectors?

If you haven't done already, also set DRIVE_OFFSET_QL to 0 in oqtadrive.ino, just to rule out that automatic offset detection is misbehaving.

Alex


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