One spectrum better at loading than another?

[Wall_Axe]

I bought two rubber keyed spectrums.
One loads games 80% of the time with old games bought off Facebook marketplace.
The other about 10% of the time.

I'm just wondering why this might be?

I'm using quite a modern tape recorder with no tone settings, just volume.

The volume has to be quite low to load on the good spectrum, so the tape recorder must be quite loud.

[1024MAK]

Different ULAs do affect loading.

The state of the Ear socket contacts also has an effect (how clean they are and if they have enough springiness to make good contact).

If the electrolyic capacitors are in a poor condition, the increased noise on the internal DC supplies will also have an effect.

Mark

[Wall_Axe]

Different ULAs do affect loading.

The state of the Ear socket contacts also has an effect (how clean they are and if they have enough springiness to make good contact).

If the electrolyic capacitors are in a poor condition, the increased noise on the internal DC supplies will also have an effect.

Mark

That sounds likely thanks.

The good one has had comp mod fitted. So I assume it was refurbished.
The bad one was just bought off eBay without any mods. Could be needing new caps or something

[1024MAK]

I presume the 10% one is actually working as a 48K machine?

Mark

[Wall_Axe]

Yes it works, and has 48k

[zx64]

Are they both same issue?

[Wall_Axe]

Are they both same issue?

How do I check?

[PROSM]

You can open up the Spectrum and check the writing near the bottom of the PCB (on the component side), which will tell you the issue. Of course, there is the danger when taking the computer apart that you could damage the keyboard ribbons, as these have become brittle with age.

You might be able to determine the issue without dismantling the computer by shining a torch down the edge connector and comparing what you see against photographs of the PCB of each issue: https://k1.spdns.de/Vintage/Sinclair/82 ... ogonal%29/ Granted, the differences you'll be able to see from that limited perspective will be quite subtle with certain issues.

[Wall_Axe]

I don't fancy opening them but the bad one has pink rainbow capacitors and the good one has black capacitors. Maybe the black ones are modern? I don't know.

Other than that they look identical when looking into that expansion hole. I think both circuit boards are green on the back and yellow on the other side.

[1024MAK]

The colour and type/make/brand of the capacitors is not reliable indicators.

Various were used during manufacturing and they are not matched to the board issue.

The board colour (solder resist layer) is also not always helpful.

Things to look for are: can you see a heatsink above the edge-connector?

Are the tracks curved (laid out by hand) or straight/angled (CAD)?

How many 40 pin chips can you see? Issue one to 4S only have two (processor and ULA). Issue 5 and 6a have three (one replaces the smaller 74LS series logic chips, most of which can be seen through the slot). Note that the ULA is hard to see. Please refer to the board layout diagrams (e.g. here). More board photos here as well (click the buttons next to "board issue").

Is there a transistor on top of one of the 40 pin chips (on the processor)?

Mark