Sinclair Spectrum 128k Toastrack Fix Part 2: Building a Diagnostics Cart!

[@dant5464]

2:00 It's always nice when someone treats your small parts with a bit of respect.

[@digitalarchaeologist5102]

I was about say Blu Tak! Really does works so well. Even when it gets hot and sticks a little, dabbing it with another blob and it comes off. Thanks Mark, I love how you don't assume everyone knows which way to solder a cap, a transistor or a diode. I've learnt so much from vids like these.

[@retrogametherapy]

Loved this video thank you! I'm just about to start my own similar project wish me luck!!

[@MarkFixesStuff]

You got this!

[@clipshark1]

Please make part 3...I really enjoyed these videos thank you

[@MarkFixesStuff]

It is coming!!!

[@clipshark1]

@@MarkFixesStuff Thank you 😊

[@talideon]

Not a Spectrum owner, but it's like RESET isn't being pulled low at startup, which means the Z80 is starting in an uninitialised state. Looking at a schematic, it could be worth checking if there's an issue with the two caps involved in the reset circuit, or even a broken trace.

[@decidedly_retro]

Indeed. I'd vote for the reset circuit.

[@ewetoo]

Great insight, reset from the cart was fine, so it has to be the board reset circuit which is backed up by that initial behaviour.

[@decidedly_retro]

Looking at the schematic I'd check capacitor C27. That should be being used to keep the reset low for long enough for the CPU to reset and/or allow the rest of the system to get into a reasonable state after power up. Also check R31, as if this isn't connected there's nothing pulling the reset line high so the CPU will never start.

[@FlashPan73]

@26:34...thanks for the knowledge that you keep your slot clean and for others to keep theirs clean of grunge.....fnarr fnarr :)

[@frankowalker4662]

I got the Harlequin 128 kit from Ben, the packaging and instructions were done the same as this Diag Card. Such professionalism. I took my time and had it assembled and running within 2 days.

[@jerryfudd]

Love watching the videos, very soothing to watch some soldering work... no additional flux this time which I thought was unusual for your work :)

[@TheDarkHour684]

was going to say the same!

[@MarkFixesStuff]

I like to switch it up a bit sometimes, and on a pristine pcb with quality solder it’s not really essential for myself. It makes the job a bit more forgiving if you’re not someone who solders all the time.

[@Colin_Ames]

That looks like a nice kit. It will be interesting to see what is actually wrong when you make part 3.

[@andreaspitsch9004]

The point where you were "retrimming your parts" was the perfect spot for a Manscaped sponsor segment 😂

[@giulianomarco]

13:51 Legs akimbo! 😋👍

[@tommyovesen]

Nice video. Byte delight make great kits.

[@MarkFixesStuff]

Yes they do!!

[@tommyovesen]

I actually just ordered the same diag kit. I built the Harlequin ZX kit once before. It was great@@MarkFixesStuff

[@stephenpalmer9375]

100% agree.. my Harlequin 128 kit was the first significant kit I every tried, and whilst it took me a couple of days, it worked (second time lol)

[@DouglasTitchmarsh]

Nice job. Got to get those legs opened up to ensure your parts don't end up misaligned. Then in you go with your hot tool.

[@MarkFixesStuff]

Thanks for this future script!

[@DouglasTitchmarsh]

@@MarkFixesStuff I am strictly amateur compared to your innuendo game. I really don't know how you get them in. It must be hard at times.

[@Hellwyck]

@@DouglasTitchmarsh In YOUR end-o!

[@ukmk3supra]

Very nice diagnostic cart - the blinkenlights are very 80's :D

[@MarkFixesStuff]

Indeed it is! It feels so Sci-Fi!

[@StevesVariousStuff]

My suspicion is a slight voltage spike on start-up to one of the ROM pins meaning it's crashing as it starts up. It works when it pages in from the diagnostic cart because there start-up spike didn't happen.

[@stevesm2010]

Great vid @Mark I'm so happy you bounced back after the house fire. Looking forward to Pt. 3! I'm guessing there's an issue with the start up circuit. Perhaps not supplying enough power at cold boot but OK after start-up (hence the reset firing it up). A slow charging capacitor perhaps?

[@PaulinesPastimes]

Excellent video and what a great kit. So well thought out and clearly documented. It's a joy to see. Looking forward to see the solution to the problem. I'll bet it something stupidly simple enough to make it seem like something complicated. Cart to the rescue! I hope Terry and Dave don't work it out first. 😊

[@DaveDoc1984]

Was the board being held in Reset and using the Cart's Reset Button was an override to that?

[@chriscrossan8034]

Oooh, wire wool on your tip? Like that is it?

[@SophieFeet]

Must get one of those diag cards. My guess would be the cap on the CPU reset line (can't remember if you recapped already)

[@MarkFixesStuff]

Yes... fresh caps but you might still be on to something...

[@XTronical]

I was unlucky with that miss fitting switch. Had to splay legs a little as you did but when I powered up the board wouldn't work properly. Swapped out for one I had in stock that fitted perfectly and all was good. Contacted bytedelight and I think he said he would sort but obviously not yet. Well over a year since I reported problem. Apart from that a excellent kit. So if anyone has problems swap out the switch if you had to splay it.

[@Zanaz728]

Hi.. I'm relatively new to the retro world.. so the diag cart is essential for beginners, yes?

[@MarkFixesStuff]

Oh no. There are many other options like the Dandanator Mini. This is just for repairing things if you like blinkenlights!

[@Zanaz728]

@@MarkFixesStuff of course I do 😂

[@jt1968-io2ne]

this is a great video for me just got one delivered yesterday going to build it Monday hope it works as well as yours did

[@nyanpasu64]

I think that added flux will help clear solder bridges.

[@mikegage3326]

Check the reset circuit? A bad cap or timer ic?

[@RyanMercer]

I'm not wearing any pants, film at 11.

[@Vortagh]

The popcorn you are eating has been pissed in, film at 11.

[@RyanMercer]

@@Vortagh ♥

[@cjh0751]

Thanks for this video Mark.

[@BrainSlugs83]

Seems like a problem with the reset circuitry / reset timing at start-up. How does the reset button work on the cart, is it just shorting two pins together? If so, you can try that externally with a paperclip and see if it works without the cart... And if it does, then there is probably a broken trace somewhere, or a bad IC (as it's not generating they proper reset signals at start-up).

[@stephenpalmer9375]

Interesting! I would have put good money on it being the ROM. I guess the answer is to look at just what parts of the speccy this board is fundamentally replacing when switched on. And that strange need to press the reset on the diag cart before it would work could be a clue. Could be as simple as a z80 on it's way out?

[@ThermionicValve]

I assembled the same unit. I used it on my issue 4S Spectrum+ and detected a faulty upper RAM IC which I was unaware of as it appeared to work normally. I swap it with another IC on the same board to see if it is really faulty, It picked it out again. I replaced it with a new IC and now all ICs passed.

[@bobbus_74]

Intriguing stuff. I wasn't expecting that Speccy to pass all of the checks. How strange. 🤷🏻‍♂️

[@ClassicRetroByte]

I enjoyed this , On with P3

[@DavidBrant]

Always important to handle one’s parts in a clean and methodical manner 🌚 🎉

[@MrClump]

The Bytedelight carts are great, when they work in my experience. My Retroleum diag cart is completely bomb proof, whereas my Bytedelight has failed several times requiring the replacement of logic ICs. It's ended up in the doesn't work bin in my workshop.

[@SiaVids]

As a first guess it would seem that there is something amiss with the reset circuit.

[@retrorobbins]

Great video welll explain and I must admit I've done seven of these diagnostic cards and even though I don't need to do anymore they're kind of addictive to do😂 ,

[@frankowalker4662]

The problem with the Toastrack could lie with the RESET pin of the Z80 or ROM select of the ULA. (?)

[@markretro3612]

maybe reset is not being triggered at boot .. bad cap/resistor on the reset pin ?

[@skonkfactory]

I'm gonna go with "take a look at the reset circuit". On the Speccy that's just an RC delay circuit, so with the mess that was the previous recap, I bet there's something wrong there.

[@johnwells558]

Not a bad price as well.

[@peddersoldchap]

Where's part 3?

[@MarkFixesStuff]

Still coming but very soon now. You've actually reminded me to buy a membrane (which is what the hold up keeps being).

[@n3ffo]

Crisp 4k

[@neakmenter]

Can't help feeling that by the time they'd put all the components in those bags, and labelled them, they might as well have soldered them to the board! might've been quicker! lol

[@MarkFixesStuff]

It’s like buying “fun kit”. It’s a crazy level of organisation!! I loved it.

[@MarcKloos]

Did the captain tape survive the fire and the sellotape not?

[@RealElaineee]

hhaha here comes ELAINEE!!

[@TheDarkHour684]

PCB is the way

[@RealElaineee]

@@TheDarkHour684 haha fully agreed🤗

[@richards7909]

I checked for grunge. Couldn’t see Nivana anywhere…

[@TheDarkHour684]

Have you tried smashing your pumpkin?

[@MonsterMovieTV]

OK, diagnositics report nothing wrong and boot into the machine's ROM no problem. So, it's something between power on and the loading of the ROM. Does the ZX have a bios problem? I am assuming that any computer short of a mechanical one has a system for "this is how you start working".

[@Jollyware11]

How's the investigations going?

[@MarkFixesStuff]

No spoilers. Actually I was waiting for Ben from ByteDelight to have some time to appear in the second part but he’s got really busy now!

[@williefleete]

Power on reset circuit non functional?

[@rtramon]

Reset timing at startup faulty, resulting in stuck cpu?

[@Daz5Daz]

Amateur question but why not have a dual edge connector that doesn't need soldering? Perhaps held in place mechanically (screws, glue, whatever) rather than this soldered solution?

[@firstsurname9893]

Such a part doesn't exist commercially. If you think about how a female card edge connector is constructed you'll realise how utterly impractical it is to make a female to female connector.

[@johnabbitt690]

Another great video especially as I'm an old speccy fan. You make soldering look so easy, can solder stick to the rest of the board because it only ever seems to follow on the pads. Also, I noticed the instructions had a link for firmware upgrades but I could see a way to do that, i.e. A usb port or something. Just being nosy, keep up the good retro work!

[@stephenpalmer9375]

I imagine it's an EPROM programmer job :)

[@firstsurname9893]

Solder can only make a joint between the tin plated parts of the printed circuit board and the legs of the components. The black finish on the rest of the PCB is a coating known as solder mask which prevents the solder sticking to any other part of the board. Upgrades are done via a flash utility that runs on the Spectrum itself.

[@techkev140]

Great. I won't mention you know what? Why does it say RAM bank 0 1 2 3 4 then 6 7 are okay? Where is number 5 and is it alive? Been a while but how you coping after the fire? Update vid or do you just want to get on?

[@MarkFixesStuff]

Sorry, missed this! I don't really want to dwell on the fire. Starts to feel a bit like pimping grief, and I don't want to be seen as doing that. I'm not sure on the RAM question. I'll have a look back at the video if you have a timestamp.

[@techkev140]

​@@MarkFixesStuff27:30 Is the first time it shows. It says testing banks and paging and shows "0 1 2 3 4 6 7" on both lines, 5 is missing. What is going on here?

[@plan7a]

Oh no! Are Dave and Terry all right? If so, they must have had a very near escape during part of this one. Are they claiming on their work-related accident insurance? (See 26.21 approx in). Whoops! They never should have stood there in the first place; perhaps they escaped with nothing more than a headache? Just wondering! (LOL).🧸🧸

[@DavidDatura]

Where’s part 3? 🤷‍♂️

[@MarkFixesStuff]

I’ve actually not finished filming it!!! I still need to get a new membrane to complete the fix.

[@DavidDatura]

@@MarkFixesStuff 👍

[@dr_jaymz]

Power on reset isn't working.

[@flynn8860]

Bad reset, or clock not stabilized at end of reset.

[@davidretrogamesplayedbadly3533]

Was enjoying the build but then something called temu insisted I had to go shop like a billionaire. I'm now bankrupt, you sir shall be hearing from my solicitors.

[@MarkFixesStuff]

I think that billionaires send someone else to shop for them??

[@raarmasu]

Stop with thah whining about ppl going somewhere else, seriosuly I wanted to do that every time You mentioned it. Every person who is going to watch full video will do it.

[@TheDarkHour684]

He's joking...chill

[@MarkFixesStuff]

Yes. It’s a joke about how attention spans are easily shortened. Not whining. I promise

[@martsmiscmix]

It's called "irony", and MFS is certainly qualified to be able to apply loads of it! 😂

[@TheDarkHour684]

Soldering Irony@@martsmiscmix