ZX Spectrum Power Supplies

[@cooldryplaceuk5873]

Loving this video - It reminds me of one of those old science videos from school.

[@andrewlane7517]

I was waiting for you to say, 'oh no, Tufty's been run over'.

[@eLJaybud]

Bought a grey +2A power supply at a knock down price to use on my 48k plus. Tested it and it is all within the correct parameters. Thanks for the info.

[@andygozzo72]

of course, it will power all 9v ish input spectrums, AND zx80 or zx81s with an adapter lead

[@MrWaalkman]

For those of you in the States and have purchased a Speccy from the UK, this is how I modified the +3 power supply to work here: I purchased a Meanwell MPT-45B and removed the Molex headers by melting the solder on each pin and removing that pin by pulling it up through the connector. These were discarded. I used the original UK power cord but replaced the UK plug with a US 110V male cord cap (okay, "plug") installed on it. I soldered the wires in the correct places, and if you make this mod, you should too. I then hot-melt glued it down. The power supply fits in the case very nicely and it's pretty hard to tell that something is different about it. Aside from the completely wrong cord cap. It was such a simple thing to do, I wouldn't have bothered with a video. But I was asked for a how-to, so I put it up here: kzbin.info/www/bejne/oILMc3uppbGqnMk

[@popeymongames]

Thanks very much to you, for this excellent video. It was a great help to me when I first started taking Spectrum equipment apart.

[@BertGrink]

Hi I just came across this video, and i find it very well researched, documented and presented. Good Job! Of particular interest to me is the part where you show how to repair a broken strain relief, as i have some PSUs that need that particular repair. Thanks. By the way, i have subscribed and upvoted.

[@ChrisWalshZX]

Great video. Very insightful. Thanks

[@stefanschomburg8456]

Again, a very useful video. Thanks for that.

[@ronsarcade1448]

This really helped when I was hunting around for a PSU to test some older Issue 2 boards with, so I know now I can use my Grey +2 PSU safely. However, one question... I also own a Spectrum power supply that has '1200' on it! This isn't mentioned in the video so can anyone shed light on this please?

[@marcinwolcendorf3821]

Do you know what kind of rectifier diodes are used in them? I would assume 2A ones are enough for the 1.4A power supply? My diodes do not have type markings, even the cathode markings are hardly visible.

[@JorgeCarvalho_web_dev]

excellent video, very educative. Can you please point the reference of the diode used? Thank you very much. Channel subscrived

[@JoulesperCoulomb]

+Jorge Carvalho I used a MR856RL. Almost any silicon diode rated to carry a continuous current of at least 2 A should work.

[@andygozzo72]

use RL201 to RL207 (2A) or 1N5401 to 1N5408(3A) or similar..

[@amigalads]

I have just seen a 111 degree one as one what would be better

[@eyribalt99]

Fantastic video, helped me a lot. Many thanks!

[@TheBezumax]

I have power supply which smoked (cleaned from flux and it stoped)and needs to be diagnosed and repaired, it is Investronica 9v 1.6 A marked and looks like UK700. Does anyone have it? it has tumbler on/off and red lite diode but don't has a termal fuse. 4700/16 Frako cap., Fagor B40 c2000/1500 diode brige. Should I recapp it?

[@TheBezumax]

I changed the diode brige it was faulty but it gives only 7V and 0.29 mA ...

[@TheBezumax]

Ok. Changed capasitor to a new and now it gives 12,4 V and 0.5A . I think it's ok but why it's not as marked 9v 1.6A ?

[@hannonm]

thanks for the video. i have my own transformer looking to re-design it.

[@JamesSasso]

Hey there, Nice video. I was wondering if you'd be able to help me out possible. I have a zx spectrum +2(A) and I believe the PSU is faulty. Pulled it out of it's box to have a play and after plugging in, the red led that normally illuminates remained blank. I pulled out my multimeter and checked the terminals, the +5v terminals are reading ~+1.5v, the +12v terminals are reading ~+3.6v and finally the -12v terminal is reading ~-13.9v. Can also hear a little rattling from within the PSU itself when gently shaken. Think this is salvageable from the info provided? would I have damaged the spectrum unit itself when I tried to plug it in? (I really hope not :( ) would I just be better off picking up another PSU from ebay or the like? would It be possible to wire a computers PSU to a 5 pin DIN simply using the 5/12v lines provided? any info you had would be greatly appreciated! Kindest Regards, James/DrSasso

[@Jenny_Digital]

+DrSasso I know it's been a long time buty are you still in need of repair to a +2A power supply. I did a very careful tear-down and analysis of my +2A power supply. I even went to the effort to create a schematic with EAGLE for it if you're still interested.

[@JamesSasso]

+Duncan Gunn hey! Yeah I did manage in the end thanks :) opened it up very carefully and the fuse had fallen out of place as he metal tabs that hold it were a bit flimsy so bent them a bit so it h

[@JamesSasso]

+DrSasso so it holds it fine now :) (damn thing sent too early haha)

[@Jenny_Digital]

+DrSasso Glad to hear of your speedy resolution. I did unearth a design issue with the +2A and +3 PSU's in that they put the output fuse on the 0v line. A short between any rail and -12v will burn the -12v rail out every time. It's worth adding an extra fuse into that line just for peace of mind.

[@blackterminal]

every Sinclair supply I have measured has been pumping out 12v. None should be used without a inline regular to drop the voltage or just use a modern power supply.

[@JoulesperCoulomb]

It is usually a good idea to use some means to slightly reduce the voltage being fed from an original Sinclair supply to help control the temperature of the ZX Spectrum. I sometimes use an 8.5 V regulator circuit and on/off switch that I have assembled in a small metal box that can be connected in-line with the power supply output. However, in the vast majority of cases, no immediate harm will result from connecting a properly working Sinclair supply directly to a ZX Spectrum. After all, millions were used in this way for many years and they didn't melt or burst into flames.

[@andygozzo72]

were you measuring 'off load' 12v? if so, thats roughly correct, you need to check on load, as for reducing the output, 1 or 2 1N5401s in series with the output are useful, or double up on the 4 rectifiers, use 8, 4 pairs of series connected ones..

[@psyzanzan]

Hello , i have a lose ZX Spectrum +3 without any cables or power supply , is it possible to turn it on by providing +12v and +5v at the correct power supply connector pins and just ignor the required -12v ?

[@JoulesperCoulomb]

I think the -12 V supply is used only by the serial/aux interface and so it should work perfectly, apart from those features, if you connect +12 V and 5 V.

[@psyzanzan]

JoulesperCoulomb I have tried it and it works ! Thank you.

[@BertGrink]

This is correct.

[@CortinasAndClassics]

I have found a power supply for the 48k and the +3 but neither have plugs on them. I can't remember what fuses go in them. Any advice please

[@JoulesperCoulomb]

I assume you mean the fuses for the mains plugs. In both cases, a 1 A fuse would be sensible. 2 A or 3 A wouldn't be bad choices either. Don't fit a higher rating of fuse.

[@CortinasAndClassics]

JoulesperCoulomb Yes it is for the mains plugs, many thanks for the help. The video is very interesting and informative I must say. :-)

[@andygozzo72]

uk700 for a spectrum.? ! are you sure? my issue 1 psu is uk1400 but rated at 1.2 amp! zx81s had uk700s and uk1200 (1.2 amp)

[@andygozzo72]

as for not trusting the label.. i have a uk1200 with the smaller transformer of a uk700, and has burnt up quite severely..

[@amigalads]

Could you help for the fuse I can only seem too find a 3a 240v 131 degree is that any good or could you tell me were I might get one from

[@JoulesperCoulomb]

Thermal fuses are not the most common of devices, but most larger suppliers of electronic components stock a small range. The exact rating isn't especially critical, so long as it'll disconnect the power before the power supply goes up in flames. I'd think the one designed to fail above 111 C would be suitable, so long as its physical dimensions are appropriate. Remember it's designed to fail when it gets hot, so complete the soldering quickly and perhaps clip on a heat shunt or a couple of crocodile clips between the fuse body and where you'll solder the lead. Also, make sure the mains plug has a suitable fuse fitted (I'd suggest 3 A maximum, 1 A if you can find one) as that'll offer extra protection in overload conditions.

[@magnus87]

Can I use a Sega Genesis/Megadrive power suply for a ZX Spectrum + ?

[@JoulesperCoulomb]

I don't know, but, information I've been able to look up says the MK-1602 supply for the Sega Genesis 1 produces 9 - 10 V DC and can supply up to 1.2 A. That should be fine for a ZX Spectrum+. HOWEVER, it apparently has an output connector with a positive centre pin. This is the incorrect polarity for a ZX Spectrum and would cause damage. The connector would either need to be replaced with a new one wired correctly or an adaptor used. Take great care never to connect a supply with incorrect polarity to a ZX Spectrum.

[@billcameron2223]

I have owned a great many power supplies for the Sega Mega Drive. Although the yellow tip power supplies for the Mega Drive 2 are centre positive, the barrels are far too narrow to fit either the original Mega Drive or the Spectrum+. However, the power supplies for the original Mega Drive 1 consoles have black tips, are centre negative, and should work with the Spectrum+. See the following link for more information: www.gametrog.com/GAMETROG/How_which_do_i_need_SEGA_AC_Power_Supply_Information_Specs_Model_mk-3025_mk-1602_mk-2103_mk-1479_mk-4122_aa-s95j.html