It happened..

A place to discuss the ZX80's and ZX81's younger brother - the Sinclair ZX Spectrum
mcarlson_sb
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It happened..

Post by mcarlson_sb »

It happened.
I've crossed the Rubicon and now own my very first Spectrum.
Before I went looking to relive my childhood by finding and fixing a Ts1000, then finding this board, I'd never even heard of the Spectrum.

Now here I am :D
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It came with another Ts1000 (my 4th) and a late 70's early 80's pong clone called a Glorytone (which I'd also never heard of).

I've got some fun learning ahead
mcarlson_sb
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Joined: Wed Apr 08, 2020 4:48 am
Location: San Francisco

Re: It happened..

Post by mcarlson_sb »

It turns out that the Spectrum+ is an issue 4s with a 6C001E-7 ULA

And I have no idea what that means :)
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Lardo Boffin
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Re: It happened..

Post by Lardo Boffin »

Issue 4S means it was made by Samsung I believe. It also means the keyboard membrane may even still be working!

Some further info here http://blog.tynemouthsoftware.co.uk/201 ... r.html?m=1

Has it been recapped? Its unusual to be able to see all of the polarity and rating markings on the caps when factory fitted.
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
Moggy
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Re: It happened..

Post by Moggy »

Same issue as mine and as Lardo says, made by Samsung. The keyboard membrane tails on this one(unless replaced) are of the superior plastic type as opposed to usual "paper" ones of earlier issues.
The ULA I believe is the last of the line series wise though will obviously stand correction if in error.
mcarlson_sb
Posts: 122
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Location: San Francisco

Re: It happened..

Post by mcarlson_sb »

Lardo Boffin wrote: Fri Sep 04, 2020 8:47 am Issue 4S means it was made by Samsung I believe. It also means the keyboard membrane may even still be working!

Some further info here http://blog.tynemouthsoftware.co.uk/201 ... r.html?m=1

Has it been recapped? Its unusual to be able to see all of the polarity and rating markings on the caps when factory fitted.
Thank you!
The keyboard membranes are in fact in great shape ;)

However, after doing a quick visual check and clean up with IPA I added power and got <drum roll> no signal

So, it looks like I have some fun ahead of me to fix my first Spectrum+

The linked article is a great start.
Thank you again
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1024MAK
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Re: It happened..

Post by 1024MAK »

Okay, please be clear on what you mean by “no signal”.

Some pointers:

If the Z80 is running (and the ROM, RAM and clock generator part of the ULA are working), then pressing a key (except one of the shift keys) should generate a keyboard ‘click’.

If the ULA has power and it’s crystal oscillator circuit is working, it will produce a video signal regardless of what the Z80 is doing (or not doing).

Loss of video can be due to the loss of the +12V supply (generated via an on board DC-DC converter from the +9V input. If this DC-DC converter is not running, there will also be no -5V bias supply for the 4116 (or equivalent) ‘lower’ DRAM chips. These really don’t like not having a -5V if the +5V and / or the +12V supplies are present.

So it’s always a good idea to test the +5V, -5V and the +12V supplies. Either on the 4116 (or equivalent) chips or on the edge connector.

The quickest way to kill a ZX Spectrum, is to apply a DC voltage to the power input with the incorrect polarity, or apply a AC voltage. The correct polarity for the 2.1mm/5.5mm mini power connector is: inside is negative and the outside is positive.

Fitting or removing expansions / interfaces while the computer is powered up can kill various chips. Or kill the transistors (TR4, TR5) that form the DC-DC converter.

One of the most common faults is failure of one or more of the 4116 (or equivalent) chips.

Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

:!: Standby alert :!:
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer later in the year.
mcarlson_sb
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Location: San Francisco

Re: It happened..

Post by mcarlson_sb »

1024MAK wrote: Fri Sep 04, 2020 7:09 pm The quickest way to kill a ZX Spectrum, is to apply a DC voltage to the power input with the incorrect polarity, or apply a AC voltage. The correct polarity for the 2.1mm/5.5mm mini power connector is: inside is negative and the outside is positive.
:shock: :shock: :shock:
Pretty sure I got that backwards last night.

I'm going to go *slowly* check traces and make sure I 100% know how power is getting to the 7805 before I plug it in again.
mcarlson_sb
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Location: San Francisco

Re: It happened..

Post by mcarlson_sb »

It looks like I got super lucky

4116 chips show +4.88v, - 5.17, 11.88

I'm getting a good 4mhz oscillation at the ULA

TR 1 - base shows a signal

TR 2 - base did not show a signal
TR 2 - collector shows a signal
TR 2 - emitter shows a signal

I live in NTSC land. My TFT display auto detected a PAL signal but still gave a blank "No Signal" screen.

There is no composite mod on this machine yet.
mcarlson_sb
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Location: San Francisco

Re: It happened..

Post by mcarlson_sb »

:D :D :D

This is the signal going into the RF modulator
NewFile2.jpg
Which (to my untrained eye) looks a bit like a video signal.
mcarlson_sb
Posts: 122
Joined: Wed Apr 08, 2020 4:48 am
Location: San Francisco

Re: It happened..

Post by mcarlson_sb »

I think I've got some memory issues - but I've got signal!
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