Unable to format microdrives

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Bytesguy
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Re: Unable to format microdrives

Postby Bytesguy » Thu Mar 05, 2020 2:20 pm

martyn_hill wrote:Hi Bytesguy

Yes, those look about right and match the standard mods on my Iss5 board.

Whilst you're in touch with Rich, I'd very much recommend purchasing a spare 8302 - they are not expensive and it could well address the issue in one swell-foop :-)

And if not, having the spare IC will come in handy eventually...

Aside from the 8302, the services offered by the motherboard itself to the MDVs are:
a) Power cct for the motor
b) Current for the LED
c) Current for the Erase head
- All the above are switched by COMMS OUT from the respective MDV ULA. And...
d) Switching for the Erase current (TR3) through diode D28 and resistor R25. Capacitor C46 filters the switching action a little.

Given that power is flowing and that multiple drive units exhibit the same format failure, item d above should be your next line of enquiry...

D28 simply jacks-up the voltage by c 1V at the emitter of TR3 as far as I can tell, reducing the overall voltage seen across the Erase head when TR3 is saturated ON - i.e. when the drive is active (COMMS OUT active), the WP switch activated _and_ the ERASE signal from the 8302 active. By 'WP switch activated', I mean to say that the WP tab or replacement sticky-tape is fully engaging the WP switch - actually DEactivating WP :-)

TR3 could therefore be your culprit here - both Format and any Write activity will need TR3 to switch correctly.

It's the ubiquitous BC184 NPN type - easy and cheap enough to replace. There is only one Erase transistor for the entire MDV 'chain', so you might expect it to impact any and all units attached - as we are seeing here.

BTW - when using the ZX units with a QL, be mindful that the state of the WP tab/presence of sticky-tape will make NO difference to the QL's abiility to write to the cartridge! The QL will write and erase-away, blissfully unaware that it shouldn't :-)


Hi Martyn, I think you might be spot on with the TR3 idea know that you have given that explanation of how it works! I'll see if I can probe it this evening to check it's actually working, but regardless I have ordered some BC184 which should be here by the weekend, so I will probably replace it as a matter of course. It does sound highly likely this is the case as reading is fine but writing/formatting seems to be the issue. Will update the thread with more info once I get a bit further along. Thank you! :)


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Chr$
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Re: Unable to format microdrives

Postby Chr$ » Thu Mar 05, 2020 5:45 pm

martyn_hill wrote:Hi Bytesguy

BTW - when using the ZX units with a QL, be mindful that the state of the WP tab/presence of sticky-tape will make NO difference to the QL's abiility to write to the cartridge! The QL will write and erase-away, blissfully unaware that it shouldn't :-)


I didn't know that! That tip is going to save me a fortune in sticky tape.


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Ask me about near NOS re-felted good quality Microdrive Carts - many available.
Bytesguy
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Re: Unable to format microdrives

Postby Bytesguy » Fri Mar 06, 2020 4:14 pm

Received the microdrive cartridges from Rich today :) Unfortunately I think something else has gone wrong now as doing a dir mdv1_ for example will just never complete. The tape keeps spinning forever. Formatting still fails as well. I think now I will need to replace the 8302 and TR3 as a matter of course and hope for the best!!

Another issue I have noticed (only just started happening) when the microdrive plays up is that keys seem to be repeating a lot (if I type in dir I will end up getting ddddiiiiirrrr for example)


martyn_hill
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Re: Unable to format microdrives

Postby martyn_hill » Fri Mar 06, 2020 5:43 pm

Hi Buytesguy

That latest observation regarding the key-repeats might be unrelated, BUT, as the 8302 is also responsible for interfacing with the i8049 co-processor which in turn deals with the keyboard, we might well be seeing some degenerating issues with the 8302...

Did you order one from Rich? (I promise I'm not on commission! I just think having the spare ICs is essential in the armoury of anyone maintaining their QLs...)

We wait with baited-breath for your news!


Bytesguy
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Re: Unable to format microdrives

Postby Bytesguy » Fri Mar 06, 2020 5:57 pm

martyn_hill wrote:Hi Buytesguy

That latest observation regarding the key-repeats might be unrelated, BUT, as the 8302 is also responsible for interfacing with the i8049 co-processor which in turn deals with the keyboard, we might well be seeing some degenerating issues with the 8302...

Did you order one from Rich? (I promise I'm not on commission! I just think having the spare ICs is essential in the armoury of anyone maintaining their QLs...)

We wait with baited-breath for your news!


Hey Martyn :) Yeah I just ordered 3x 8302 from Rich so should get those next week. I ordered 3 because I have a habit of letting the magic smoke out of things!! I'm just glad I got this QL cheap as it needed more work than I originally thought :D I hope the 8049 isn't on the way out as those are a bit more pricey, but we will see!

I'll replace the 8302 first before doing anything else (if that doesn't help then the TR3) - should I replicate the resistors and flying wire mod after replacing the 8302?


martyn_hill
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Re: Unable to format microdrives

Postby martyn_hill » Fri Mar 06, 2020 7:19 pm

Hiya

Bytesguy wrote:should I replicate the resistors and flying wire mod after replacing the 8302?


What I do on my QLs is to take the opportunity to re-solder the resistors _under_ the board, taking care to insulate the flying leads from any pokey-bits, so as to ease switching-out the 8302 whenever I need to. YMMV...


Bytesguy
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Re: Unable to format microdrives

Postby Bytesguy » Fri Mar 06, 2020 8:44 pm

martyn_hill wrote:Hiya

Bytesguy wrote:should I replicate the resistors and flying wire mod after replacing the 8302?


What I do on my QLs is to take the opportunity to re-solder the resistors _under_ the board, taking care to insulate the flying leads from any pokey-bits, so as to ease switching-out the 8302 whenever I need to. YMMV...


Nice tip :) Never thought of that!


Bytesguy
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Re: Unable to format microdrives

Postby Bytesguy » Tue Mar 10, 2020 4:48 pm

Ok so received the 8302 chips today! Here is what I have done:

TR3 replaced
The main voltage reg replaced with a TSR 2450 to reduce the heat output
8302 replaced

The first replaced 8302, with soldered resistors, failed to boot and I was given a white/grey screen and no activity.

I replaced with another one (glad I bought multiple!) and that one did boot, but formatting is still failing :( I haven't yet soldered the resistors on to this one so maybe that is something to do with it, but I am starting to run out of options!!

I also swapped microdrives around, same issue (I soldered some turned pin sockets onto them too to ensure a good connection).

Could this be a faulty ROM or something? Maybe expecting something it shouldn't be to confirm the format?

In better news the microdrives seem to be performing a little better with the newly installed parts, they seem to be spinning more positively which is good (I can still load the Quill cartridge, haven't tried any other yet).

I do have a vdrive ql now so I can load some software from external sources. Maybe there is something that can help me test the microdrives and debug the issue more

Edit: Interesting observation - I was able to load a program from a tape Rich sent me and can dir it fine too, so reading seems to be no problem. Here is the interesting thing, if I tape over the write protect notch I can write a file to the tape *but* the microdrive never stops spinning until I reboot the machine, even though the cursor on the screen starts flashing again waiting for a new command. After rebooting I was able to run the file I wrote no problem. Could this be related to the formatting issue?


Derek_Stewart
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Re: Unable to format microdrives

Postby Derek_Stewart » Tue Mar 10, 2020 10:22 pm

Hi,

I see you put a Traco TSR 2450, in place of the voltage regulator.

The TSR-1-2450 is only 1A, this okay for an unexpanded QL with no memory expansions.

The L7805CV voltage regulator normally installed in the QL, can supply 1.5A

I did this change a while go and no expansions would run on thd QL. Probably needs the TSR-2-2450 supplying 2A.

Maybe this is the source of your problems.


Regards,

Derek
Bytesguy
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Re: Unable to format microdrives

Postby Bytesguy » Tue Mar 10, 2020 10:59 pm

Derek_Stewart wrote:Hi,

I see you put a Traco TSR 2450, in place of the voltage regulator.

The TSR-1-2450 is only 1A, this okay for an unexpanded QL with no memory expansions.

The L7805CV voltage regulator normally installed in the QL, can supply 1.5A

I did this change a while go and no expansions would run on thd QL. Probably needs the TSR-2-2450 supplying 2A.

Maybe this is the source of your problems.


Hi Derek, thanks for the info, I didn't realise that! Right now I am not using any expansions but it still won't format :(

Interestingly, I was playing around with my vdrive tonight and I can format an image on there perfectly fine, but any real microdrives and it won't work



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