Spectrum Computing

Well I went to order mine from a UK seller on heebey but there was a back order in place, so guess it will take several weeks to arrive if they are being manufactured in china. Out of curiosity, how much did you pay for your board ? Oh dear, poor Mrs Clump takng 2nd place to the spectrum, I guess it...

I'd not put those 4116 DRAM chips in that board unless they were socketed and I had a large bag of them for backup.
There are the modern ram chips now and a smd ram addon board that populates the slots on Retroleums website.

Also when switching an inductor (coil, transformer), when the magnetic field collapses, high reverse voltages will be generated. You also want a transistor that has a high gain at a high current, and which has very fast switch on and importantly, a very fast switch off speed. If the transistor is t...

I nice cosy little setup with some freshment oktoberfest beer, German beer is the best there is, it's hard to find a good strong German beer here in the UK. You're gonna need a few beers if you are loading games from that tape machine

Interesting posts about the ULA, but that thing runs hotter than my Core2 2.6Ghz cpu so there's an awful alot of wasted power going on in there for something that runs at 4Mhz :shock: Back to my topic, I think I have found the problem with the constantly blowing TR4 transistor. I was using a ZTX450 ...

I was looking at one these boards a few months back as it looked like a fun project to build one from scratch with complete new components. Would look great inside transparent case with all new color matching resistors. You do know it is an exact copy of the original board, so placing used component...

Great! usually the force of the 2 sides is enough to keep the top plate flat over that part of the case, but I guess a little warping the plate can make it lift up and not stick well.

So do we get to see the result

Well, its a relief to know the ULA is out of the suspect list, I did pull the ULA and test on a known working board anyway. Just wasn't sure it was pulling any power from the +12V or -5V supply. I decided I'm going to pull the coil and replace with a known working one and take it from there. This is...

It’s rare for the LM1889 to fail. If you do suspect it, don’t immediately change it. Just lift one end of resistor R62 to isolate the +12V supply to it. Is the -5V supply voltage okay? Also are any of the 4116 chips running very hot? Mark I lifted the R62 and no change apart from no video output. T...

No problem, and yes adding 2 layers of tape will not flush with case and look terrible. If you have the paitence and nerves then replace the tape, otherwise stick with the glue (no pun intended)

OK, the top lip is very thin and has much smaller surface area for the tape to stick to. Just make sure that the tape is actually making full contact with the top lip. The tape should be very sticky, so much that it is hard to pull your finger from it, if it is just slightly tacky then it won't hold...

Is it a standard 16K/48K case or re-designed one ?

Can't say I've ever had issues with face plate not sticking. Can you post a photo of where the face plate is not holding down.

Thanks for reply Mark. I've checked the link you posted to upgrade the DC-DC circuit as that is something I have not looked at. The caps are all correctly positioned and yes the polarity is correct as I read up on the silk screen errors before the re-cap. I have good +12V and -5V power lines, althou...

Neat, thanks for the link. I see plenty of space on there for an Arduino

Hi there, I'm not sure if you are aware that the new rubber keypads have locating holes which are usually not fully exposed. Make sure the keypad is flush and firmly in place in the case. The sticky tape should be 3M labeled and is very very sticky, I have purchased a plate from ZX-Renew and they us...

Hello all, Just finished a repair (almost) of an issue 2 board 48K and having an issue now where TR4 transistor keeps overheating from excessive current. I am using a bench power supply and if I limit the current to less than 1A the little blighter starts up fine. The machine runs fine with a 1A cur...