ZX Spectrum repair 128k +2 with BONUS Tape Deck Repair
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- เผยแพร่เมื่อ 30 มิ.ย. 2024
- Another ZX Spectrum 128k plus 2 on the workbench! This one booting into 48k mode and showing a memory fault on the Brian Alford diagnostics.
A juicy fault on the tape deck has me scratching my head for a while.
The other video with more detail about the factory video and audio fixes
• Factory Mistakes and D...
Paul Universal Retro Boss
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00:00 Introduction
00:35 Switch On
01:32 Diagnostics
03:08 Open it Up!
04:34 Desolder the Faulty Chip
05:48 Test the Faulty Chip
06:59 Retesting
07:38 Diagnostics Again
08:00 Clean the Sockets
09:30 Dirty Edge Connector
10:35 Fix Factory Errors
11:30 Video Mod
12:40 Repair the Tape Deck
12:28 Loading a Game From Tape
16:56 Goodbye!
#zxspectrum #zxspectrum40 #computerrepair - วิทยาศาสตร์และเทคโนโลยี
i love that these machines came out 35 odd years ago and we are still repairing factory defects that have gone unchecked all this time :)
Can you imagine the conversation at Amstrad hq when they realised all these machines were defective? Lucky for them not many used composite output, and if they did and found it was bad quality they probably just put up with it!
@@MoreFunMakingIt i remember my 14" tv constantly had the RF tuning door always open for constant fine adjustment..it was always a compromise between picture & audio with the +2 . fast forward to 2022 and a big flat screen (RGB) with audio being sent through multi channel amp
Got this model Speccy on my bench and the first thing I did was reversing T4, T5 and T7 and replacing electrolytics; then I moved LK7 to LK8 to enable audio on the DIN connector making it possible to use a fully fledged SCART cable and freeing up the audio output for amp/mixer/etc. LK4 and LK1 were originally in place and I'll keep them that way, this will let me use composite video on the connector if I need it for some screens. But still, a real RGB + blanking + comp sync + audio cable is how it will be used. The brightness resistor and diode network is already built in and that's why I don't need LK7 or any diodes in the SCART plug.
Then I pinned that bad tape deck hum down to the tape read amplifier, and fixed it by moving the opamp power to the leaf spring contact together with the motor, so that it works only during record/playback. I bolstered the filters too (removing R306, using a 100Ω filter resistor from leaf spring to amplifier power rail, and changing C315: 470µ instead of 100µ). Way better now. I'll do the C31 audio/modulation fix too.
As for transistors, I grab the case with medical forceps, add some solder for better thermal conductivity, heat all the pins at the same time, pull the pesky little bugger out by the forceps and then clean the holes hot with a syringe needle.
I have 3 more of these on the bench right now. One of them is going to get the works, all the fixes and "upgrades". I really like the idea of moving the opamp power to motor leaf switch. Thats inspired. Might have to borrow that one!
Nice to see another machine being brought back to reliable operation. I dread to thing how many people chucked theirs assuming it was dead, when all that was wrong was poor connections due to corrosion.
Just as many got thrown away because they were considered worthless junk taking up precious space. It's a sad thought.
As long as we keep doing our part now there's more to last for years to come
Glad I found your channel, and I'm enjoying your backlog. I bought this exact model Spectrum some months ago during a trip to the UK and brought it back with me to the US. It's been sitting in the repair backlog since. It was advertised with a bad keyboard, but seeing you mess with those ribbon cables in your other videos makes me think it might have just delaminated. Also good to know about those incorrectly placed components on the board lol. That's pretty funny. I ordered the same SCART cable you're using from eBay, took a while to arrive but its finally here. I've finally taken the plunge and bought an upscaler with a SCART input. I don't even care that much about the line doubling etc. I really just wanted a good way to connect SCART to my HDTV here in the US. All that's to say, I'm ready to tackle this thing soon, and I'm excited to experience it for the first time and tinker with it once I get it working. Seems like such an important part of British tech history. Great content and awesome videos!
Thank you so much for that lovely comment!
I have watched lots of your own excellent content and saw back when you brought home the machines from the UK. The 128K +2 you showed looks grey in the video, which threw me, but you catch a glimpse of the back of the machine and it looks like the PSU is a DIN type, which should make it a +2a at least? The grey +2 in this episode is earlier and used a standard barrel jack 9v like earlier machines. If your machine is a +2a it probably won't have the same problems with reversed transistors inside. But it has a range of other things that are fun to fix! 🤣
If you ever need any help please feel free to drop me a line. Either Discord, Twitter or good old email, and I will do what I can to fill in the gaps.
Bleh, just when I thought I had finally started to wrap my head around all the variations! Okay, good to know, I’ll be on the lookout to confirm which model I have before it goes under the knife. Thanks very much for the offer of help, I’ll have to wait and see how much trouble I get myself into once I start working on it :P Cheers my man.
@MoreFunMakingIt I just realized we have the same Multimeter. Keep up the good content.
It's a good value meter! I would like one with the ability to discharge high voltage caps though 😜
Not sure if you realize it (probably do) but I notice your video format has similarity with 1980's manufacturing documentaries. Intentional or not, I love it.
You know, I wasnt consciously aware of that! But now you mention it I must have been channeling that on some level 😂
I might lean into this...
@@MoreFunMakingIt Especially when you had the background music, that's what triggered the association. Now, like Adrian's digital basement intro, screw up the picture so it looks like 80's VHS and you're done LOL
But seriously, the docus of How it's made also have similar format. Concise voice-over combined with informative example video sequences and that typical background music that becomes prominent when the voice-over pauses.
@@MoreFunMakingIt Just don't do a protect and survive, or dark and lonely water.. 😬
Amazing watch me bro! Never owned one of these bad boys. Nice repair buddy ☕🏴👍
Cheers Stewie! 😍
Thanks for sharing.
Add a bit of silicone tube on vaccum pump tip, it than has beter contact, plus it wont vack the board so hard
I had and wore an Ocean Pacific T-shirt in the late 80s to early 90s until I outgrew it and had to pass it down to my younger brother. It was hideous but comfortable.
I knew someone would recognise it!
Pacer mints! Ha. the football team for our school (Cronehills) had green and white striped tops, so we were called the Pacers.
Haha! You don't see people wearing bright green and white stripes these days. "You look like a pacer mint" was always the given reaction.
but that was 40 years ago
Proper job Lee!
Cheers Snorkers 😁
Another great ep Mr MFMI 👏
Thanks Jonathan 😁
Very nicely done!
Cheers Rudy!
14:14 one thing about these tape deck boards is there are two areas on the board where the two mounting screws are used to make a ground connection. This frequently causes issues, and it's a good idea to add a bit of wire to make the connection instead. The picture at this time stamp shows one screw missing - that would break the connection.
15:14 the buzzing is actually quite easy to deal with - a 1uF capacitor across R35 (a 180 ohm resistor) should solve it.
Any testing was done with the screws in place. I did check for good continuity.
i think i will try that on my next one as i normally reduce the tape output level by changing some resistors values
@@jaycee1980 please explain in detail or with video, the humming is so annoying.
@@djreminis8092 I might do that as I've got two tape decks knocking around which i've modified
Ledge, this was my exact issue, C232 Capacitor was causing the black screen upon plugging in the cassette plug. Put a new one in and boom, back to life, thanks man!
This makes me very happy! Glad it helped you :D
@@MoreFunMakingItI've searched high & low for an answer, you solved it, so pleased. Now if you have any ideas on how to tune it to get a better screen display that would be awesome 😂
@@djreminis8092 there are a number of fixes to improve the output. I have 3x +2's here that I intend to try these out with. Not sure how long it will take me to get round to doing that though
@@MoreFunMakingIt Dumb question, why can't I get sound, what cables required? I've forgotten, was my dad's pc 😭
@@djreminis8092 sound has a separate 3.5mm socket. Best thing you can do is get an RGB cable from Retro Computer Shack. They do 2 different ones depending which +2 you have, so make sure you get the right one.
I've always found the +2 heatsink rather curious. 🤔
I'm convinced it must be an off-cut left over from manufacturing something else that got recycled.
Like cooling fins from the head of a 125cc Honda motorcycle!
I changed to a chinese smd 5v regulator but left the heatsink in place as it's part of the vintage aesthetic. The RF is no longer usable due to interference introduced by the modern regulator but I hope to make a composite cable. No scart here.
I put in a cap the wrong way round once, and it popped its top right as I was leaning over it. I had a red dot on my forehead like a hindu for days. Got me right in the middle just above my eyes (lucky me).
Ouch! Good job it missed your eyes!
@@MoreFunMakingIt You ain't heard nothing yet, I've done some pretty stupid things in my younger years lol
But yeah, i was lucky there, since then I've become a lot more careful. I value my eyes more than anything, without them I'd just want to kill myself, no joke. Everything I love to do involves my eyes. Goes for most of us I guess, but you know what I mean.
Good work, Lee! Though I'm surprised that you're not a fan of working on cassette decks. 95% of the time they just need new belts... though I guess getting to those belts can be a pain on some decks (obviously not the deck on a Spectrum+2 tho).
The thing I really don't like is everything is connected with soldered wires. It's so easy to crack a solder joint when trying to work out what's wrong.
Im a bit late too the party but love this vid.... also can i ask you for some advice?
Sure! Although it's quite difficult in TH-cam comments. They don't always get through and after the first reply I don't get any notifications. If you really need help then either my discord or email. Discord link in the description and email in my about page
Did you run it with a +2 PSU ? it's strange that it almost fixed it's self.
No. Bench PSU. But I think it was mostly dirty sockets and edge connector
@@MoreFunMakingIt perhaps causing higher resistance so it needed more current.
Am I being dense? I couldn't find the link to the transistor and video fix you mentioned. Also would be good to know about the audio fix as I just picked up one of these the other day 😊
I put it as a card that appears on screen, but I'll go right now and drop a link into the description.
The links to the other fixes are in the description of the other video 😁
Thank you, I was watching it cast to my TV and didn't see the pop up 😂
I shall have to dig my machine out.
Where can I buy the Diagnostic card ready made? Had a quick google but couldn’t find much.
Lee Smith youtube.com/@leesmithsworkshop
Did a video recently on a diagnostic card that would be more suitable. The one I'm using is a bit more of an SD loader with ROMs built in. It's not easy to buy, you kinda have to make your own.
The dandanator mini 2 I use. I found it on eBay. it's got space on it for games but mine has Spanish games on it, except the diagnostic bit
Can I send you my ZX Spectrum to be repaired, just don't be surprised if it looks like a 2005 Mercedes C class w203 sports edition car.. It's just a XL Spectrum version
Don't be surprised if I replace all the capacitors and composite mod it!
@@MoreFunMakingIt just get it done by its next MO.. never mind