New Spectrum 48k

For experts to discuss very technical stuff and newbies to ask why the Spectrum they bought off ebay doesn't work.
payty
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New Spectrum 48k

Post by payty »

Hi,

I've started building a new Spectrum from a PCB bought online. I've bought just the pcb with very few components and started to gather the other parts. I have the memory chips, cpu, ULA and some resistors.

Regarding the power coil, can anyone help me with the specs for that? Number of turns for both sides and diameter of the core.

I am trying to build one as I think these are pretty expensive considering an ULA replacement can be found for 19GBP vs 12GBP for this coil.

Also, for the LM1889, I've found on ebay some very cheap ones 1.89USD each and some at 12GBP each. Should I trust the chinese sellers? Are those ok?
Anyone tried those?

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1024MAK
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Re: New Spectrum 48k

Post by 1024MAK »

Some sellers based in China are good, but others are just box shifters / resellers.

The good sellers (who are specialist electronics sellers) are likely to supply working chips. The same may, or may not be true of the other sellers.

A lot of the cheap chips are cleaned up ‘pulls’. Some are old new stock. Some are remarked lower specification parts that have been relabelled as higher spec parts. And some are faulty, partly faulty or fake.

That’s the fun of buying on trading sites :lol:

Mark
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peloritano
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Re: New Spectrum 48k

Post by peloritano »

I am also building the same one. but I recovered all the components from a damaged version.
I suggest you to weld the resistors and capacitors first and then the sockets for the integrated circuits.
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payty
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Re: New Spectrum 48k

Post by payty »

I have a few boards that are not working properly but the PCB is not damaged and can be fixed.

So I am trying to build this one with less recovered components.
I am very curious about the results. I know a guy that built one of these but has some noise on the video signal.
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payty
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Re: New Spectrum 48k

Post by payty »

So, anyone can help me with the coil specs?
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1024MAK
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Re: New Spectrum 48k

Post by 1024MAK »

payty wrote:
Fri Nov 15, 2019 3:41 pm
So, anyone can help me with the coil specs?
I would, if I knew what they were... Sinclair never, as far as I know, detailed the specifications. So to work it out, it means testing and disassembling an existing ‘coil’. Unless I missed something in the service manual.

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PABB
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Re: New Spectrum 48k

Post by PABB »

In fact it's a quite easy to recreate an original coil. Pear from speccy.pl made an excellent tutorial available here - https://www.speccy.pl/forum/index.php?topic=2236

I made a dozen of them - they all work without a problem.
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dfzx
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Re: New Spectrum 48k

Post by dfzx »

PABB wrote:
Sun Jun 21, 2020 10:32 am
In fact it's a quite easy to recreate an original coil. Pear from speccy.pl made an excellent tutorial available here - https://www.speccy.pl/forum/index.php?topic=2236

I made a dozen of them - they all work without a problem.
Does that site require a login? I get a form from your link. In polish. :)

Can you copy and paste here the coils specs? It sounds like information which needs wider circulation.
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PABB
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Re: New Spectrum 48k

Post by PABB »

It does - but registration it's quite simple (I can help).

I'll ask Pear if I can copy/paste his guide here...

Until then:
primary winding - 14uH
secondary winding - 78uH

coil core - RSZ-8X10-V-4P (available here - https://sklep.feryster.pl/)
winding wire - DNE-0,315-L-GR2 (as above)
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payty
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Re: New Spectrum 48k

Post by payty »

viewtopic.php?p=31658#p31658


you can find info in this post.
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