Spectrum Computing

That’s a nice collection. You must pick up Stop the Express and Eric & the Floaters. Actual Spectrum games written by Hudson Soft - the latter being an early version of Bomberman.

Superb stuff, Mark! I'd never have found that in a million years. Glad I sent it to you. It's clearly gone to a better home

dfzx wrote: ↑Sun May 19, 2019 10:09 am

Liveinabin wrote: ↑Sat May 18, 2019 5:00 pm I’m glad it’ll belong to someone who can fix it or at least revive another Spectrum with it.

Having quietly followed the saga for 5 pages of comments, I'm now looking forward to Mark telling us all what's wrong with the flippin' thing!

Nothing before I started mucking about with it

That’s it exactly. I’m glad it’ll belong to someone who can fix it or at least revive another Spectrum with it. I already have two working Spectrums (and I’ll be getting a Next when they release that) so this whole enterprise was just about getting the thing to live for it’s own sake. The general id...

Blimey! That was quick

Yours.

Ah OK, further news :) Noticed that both of my Spectrums have the exact same revision of ULA so.... carefully popped both out and swapped them. ULA from my Samsung gave no picture at all on this spectrum. ULA from this spectrum gave garbled mess on the Samsung (random block characters and colours). ...

Hallo
11.58v on all of those pins.

Muttley Black wrote: ↑Thu May 16, 2019 7:58 pm You have already checked if 12 volts present on LM1889 (pin14), yes?

I’m getting 11.56v
That’s with ground probe on the plate near the voltage regulator and the positive probe on pin 14, if that’s correct.

Oooookay! Update time. Got a new LM1889. Fitted that. No difference (didn't think there would be but worth a pop, although desoldering that was a pain) New crystal in X2. Still mono. Reflowed and, in some cases resoldered and replaced some of the new capacitors around the video bit. Nope. Still grey...

In answer to your question about buying spares, yes, if you can afford it, it’s always a good idea. It’s not often that the LM1889 chip fails, they are normally reliable. I suspect one of the peripheral components or connections. If you are buying spares, buy a new crystal for X2 (4.43361875MHz). S...

So given that I'm currently bereft of any other test equipment; am I right in assuming the component we really needed to test was the LM1889 video encoder chip (as I'm figuring that it is responsible for the colour, mostly)? Reason I ask is, I'm about to order some bits anyway (keyboard membrane, vo...

So, some questions. First, have you used a magnifying glass to carefully visually examine the areas of the video section where you did any work. Both on the top side of the board and on the underside of the board. Do this under a good bright light, or better still, in good daylight. You are looking...

Thank you all. I’ll try and get some time tonight/poss tomorrow to go over the Spectrum carefully.

The mono image is perfectly fine (well, for a Spectrum).

TR1 looks faulty to me. Cause with neg at base, you should get "open", both on collector and emitter if i am not mistaken. If you are sure that you measure TR1 as TR1 and TR2 as TR2 then replace TR1. I say that because your TR1 measurements fit more to TR2 transistor. Anyway, to be 100% s...

Readings taken (I am learning a LOT about electronics here) Four readings for each: pos at base 1) neg at collector 2) neg at emitter neg at base 3) pos at collector 4) pos at emitter TR1 (BC549C) 0.63 0.70 1.73 1.68 TR2 (BC549C) 0.70 0.70 1.19 1.30 TR8 (BC184) 0.75 0.75 open open TR9 (BC184) 0.75 0...

Oh right, of course. I’ll post results tomorrow. Thanks for all of your help tonight. Sorry to take up so much of your Sunday evening

You change the TR1 & TR2 with BC549C just to give more brightness to your screen, am I right? If yes, that’s mean that you still got the 2x ZTX313 and they are in working order. Have you tried to put them back and see the results? Sorry, just spotted this. Um, no. I changed them a couple of wee...

Guesser wrote: ↑Sun May 05, 2019 10:58 pm PRINT COMIC$="GREAT"

FOR A=1 TO 10
PRINT "THANKYOU!!"
NEXT A

Look at the video below. JoulesperCoulomb shows the way you can test transistors. He do it on Tr4 Tr5 that is for dc converter. Do the same test on TR1,TR2,TR8,TR9 and post the results here. Superb video. Thanks. I'm getting around .7v on those transistors so, according to that guide, they check ou...

Okay. Reseated the ULA, checked the polarity of all the capacitors and reflowed/resoldered. Transistors are in the right way round (and I reflowed solder and checked some continuity) but I don't know how to test transistors in situ.
Still mono

Definitely BC549C

Well I wondered that. These are BC549C replacements (supposed to make the picture brighter) and the instructions were to install them the other way round from the original set.

Will do. I can see myself having fallen at either of ‘installed correctly’ and ‘soldered properly’.
I’ll try that out and get back to you.

Hi all. I’ve exhausted my wildly inadequate electronics knowledge and I’d appreciate some advice. Found a Spectrum issue 4A, mostly working. Just needed a RAM chip changing at IC15. Did that. Worked beautifully. So...for a lap of honour, thought I might use my nice new soldering iron to recap the wh...