Spectrum Computing

You might be able to fit a composite connector to that monitor, it has markings for cvbs input, on a lot of those rebadged Philips (cm8833) monitors you can. Will not help if it lacks the PAL colour decoder circuitry... Does scart need voltage for it to switch? "Notice the +5 volts applied to ...

Although most TVs support composite video inputs on their SCART sockets, not all monitors do. So the first thing is to check any documentation for your monitor. The fact that you can get an monochrome red, green or blue image if you use one the red, green or blue RGB inputs without having to provide...

Thanks for reporting back

Have fun

Mark

Beware, the thinnest hair width solder splash can cause utter chaos...

Mark

Replacing IC14 is unlikely to make much, if any difference to the dot-crawl. The real problem is a design limitation. The 16K/48K/+ uses two different oscillators to produce the pixel clock and the colour sub-carrier/encoder. Hence they are not locked to each other. That's the problem (well, the mai...

Yeah, it's now okay

Will watch it later.

Mark

See also this topic.

Probably best to post any comments about this problem in the linked to topic rather than continue this topic.

Mark

The real problem here, is that many built in functions use the search even though the user or member may not be aware that said function is using the search system. For example, using the quick link 'active topics' (top left drop down menu) uses the search system. The second problem is that some oth...

No problem, I like helping people.

You may want to check the video settings, it's currently not working, instead we see a "this video is private" message...

Mark

The data lines and the keyboard input lines to the ULA are all pulled high by resistors, so yes, without anything to drive them, they should be around VCC (+5V). Which address lines on the ULA socket did you test? IC3 and IC4 will affect A0 to A6. A14 and A15 should be the same level as on the Z80 s...

Note, where I quote 5V, this is assuming your VCC / +5V rail is exactly 5V. So if this rail is 4.9V and you get 4.9V where I state 5V, that's fine. With TR3 removed, the ULA and Z80 not fitted: ULA pin 32 = 5V Z80 pin 6 = 5V TR3 base = 5V TR3 collector = 5V TR3 emitter = 0V Current test (between the...

So, from what I can tell, IC1, the ULA and IC14, the LM1889 are okay.

The problem appears to be TR1, R52 or the components or PCB tracks in this part of the circuit.

Mark

Hello Snipey and welcome :D Question, was this failure mode present before you started work on this board. Specificity, before you renewed TR1, TR2 and the axial electrolytic capacitors. - in the mean time, the Spectrum remains fully functional, even after the screen is black Can you please expand o...

That, but also because of how the ROM code detects how much RAM is present. The ROM is not testing to see how much working RAM there is, it's only testing to see how much RAM there is. This is an important distinction, as the test used assumes that all RAM that is present is fully working. The ROM c...

Adrian45 wrote: ↑Thu Feb 15, 2024 9:05 pm Just spent 20 min on Retroleum.co.uk , 16 items in my basket , went to pay and they only take paypal.

Have you tried contacting the site owner to ask about paying by credit card. He is normally very helpful.

Mark

Oh, and I feel that the small minority with an "80K" RAM upgrade are being left out :cry: Technically it is also possible to have a 32K Speccy (16K rubber key with 16K of expansion RAM). I don't know if anyone ever made expansion packs or fitted suitable DRAM chips internally for this thou...

Yeah but, no, but... Are we speaking about "straight" AY sound chip data, music notation, samples or what? 6K bytes of AY sound chip music data <> as data for samples. Then there is the mass storage system being used. Real tape LOADing on a real ZX Spectrum is rather slower than being LOAD...

Last one I had was okay...


Mark

No problem.

It's a lot easier when a DRAM chip fails and produces a binary 1 regardless. When they produce 'random' outputs or bianry zeros, it's a bit more tricky.

Mark

And artists are often capricious people ;) They may draw some stuff that won't fit you from a coding point of view, as the others said. If you tell them to redraw it, they will get offended and leave. That's it, I'm done with this, I quit, you can finish this topic on your own... :twisted: Mark PS ...

strangely the speaker makes no sound when i connect the meter - still reads 39 ohm , the diaphram looks good , moves nicely - does not appear to be held up from vibrating , but no noise - can i put 5 volts into it ? Err, not if you want it to work after. Wire a 220Ω or similar resistor in series to...

So… I was doing some AY music for an upcoming game by @gabriele amore. The actual game is under 48k, so I figured I'd have over 80k for the music, since it can only play on 128k machines. :shock: Oi! My AY card for the rubber key / + Speccy says otherwise... :dance As this is a hobby, I went for op...

I will be replacing every cap in the machine Just the electros I presume? Apart from C5 to C8 I mentioned above, the ceramics don't normally cause any problems. took the speaker out , getting 39 ohms across the terminals , from reading , thats good Yes. Does it click if you tap a meter lead as you ...

I feel your pain. Buying items from abroad is now a right pain. The U.K. leaving the E.U. has not helped. The real problem is IMHO called VAT. But let's not get into politics. Else we will get into trouble (in this forum, talking politics is almost taboo). The owner of Retroleum is very helpful. But...

Tell ya what, here a link to the seller I recommend

Mark