128 2a problems

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new666uk
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128 2a problems

Post by new666uk » Mon Jun 24, 2019 11:24 am

Hi all

So I finally got my first Spectrum. It's only been 40 years since I first saw one but I don't like to rush into new technology. The bleeding edge is where you get cut.

Anyway. I picked up a boxed and clean 128 +2a (black case) which turned out to have a dead PSU. With my brothers help we've got a cisco router PSU wired up to work. I boot to the main screen and have tried loading a few tapes. Lots of noise of course but nothing loaded. One tape reached the end, another the screen stopped flashing.

I plugged a joystick in (it was the Sinclair one bundled originally) but in both ports is causes a buzzing sound until a direction or fire are pressed. Not done any work on that one yet.

The cursors don't work. I pulled the membrane out and cleaned with electrical contact cleaner and it worked briefly. Are these replaceable?

No doubt there will be more issues but sort of fixing them as I find them.

Any suggestions what/where to check for the above?

Once it's working I'll probably get a divmmc and not bother with the tapes.

Thanks
Paul

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1024MAK
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Re: 128 2a problems

Post by 1024MAK » Mon Jun 24, 2019 5:46 pm

Hi Paul

I’ve moved your thread into the Sinclair ZX Spectrum Hardware area.

A blown transistor is the most common cause of the +2A PSUs to fail. It’s a relatively simple repair (I also recommend the smaller control transistor is renewed at the same time).

I assume you were loading via the built-in cassette deck? May be a good idea to clean the head.

The joystick ports on the Amstrad produced machines, including the +2A that you have (which probably is actually a +2B board in a +2A case) have a non-standard pin-out. How many plugs and what colour are they on the joystick that you have? Of is it actually branded as Sinclair?

It’s not a good idea to clean the membrane with any kind of solvent or electrical contact cleaner. Just wipe each side with soapy water, then wipe again with clean water. Clean the other keyboard plastic parts in warm soapy water, and rinse with clean water. Then allow to dry completely before refitting. The membranes in these machines are fairly reliable, so new replacements are hard to find.

Where spare parts are available, they often are available to buy at Sell My Retro.

Mark

new666uk
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Re: 128 2a problems

Post by new666uk » Mon Jun 24, 2019 7:44 pm

Thanks Mark,

It was only when it booted I got the menu stating it was a 2a. The board is an issue 2.

The joystick I used was the Sinclair one that was included in the pack when new. It's the Action Pack with light gun.

Yes I was using the inbuilt tape drive. I thought the 3.5 socket was an output only, not an input or I'd use that. I didn't clean the heads so will get some IPA on that.

Thanks for the note on the membrane. I'll open up and clean with some mild soap then and try that.

I'll update as this develops but as always input appreciated.

Paul

new666uk
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Re: 128 2a problems

Post by new666uk » Mon Jun 24, 2019 7:47 pm

Oh and I forgot to ask, is there any sort of POST diagnostic in a +2a?

McKlaud
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Re: 128 2a problems

Post by McKlaud » Mon Jun 24, 2019 9:03 pm

Yes there is. See there https://www.dataserve-retro.co.uk/conte ... k/d66.html and scroll down to the bottom.
Claudius
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new666uk
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Re: 128 2a problems

Post by new666uk » Tue Jun 25, 2019 2:06 pm

Thanks I'll try that tonight as well as open up the joystick to see if there is a short / fault there making the buzz/hum when plugged in.

new666uk
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Re: 128 2a problems

Post by new666uk » Tue Jun 25, 2019 9:30 pm

Ok, tonight's update.

I cleaner the tape head last night and that now loads games. Fixed.

Cleaned the membrane and keyboard all seems to work although playing Knightmare the controls were all over the shop. Do things like the Graphic or Extend mode keys affect in game controls? Work in progress...

Opened the joystick and suspect the down pad on the PCB dead and possibly a short on one fire button registering as constantly pressed hence the sound I was hearing. My error, it wasn't a buzz but the sound of a key/button being held down.

More work to follow.

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1024MAK
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Re: 128 2a problems

Post by 1024MAK » Tue Jun 25, 2019 9:45 pm

new666uk wrote:
Tue Jun 25, 2019 9:30 pm
Do things like the Graphic or Extend mode keys affect in game controls?
Yes. Funny enough, I wrote a long post about the “extra” keys in a post over on Spectrum Computing that you may want to read.
new666uk wrote:
Tue Jun 25, 2019 9:30 pm
Opened the joystick and suspect the down pad on the PCB dead and possibly a short on one fire button registering as constantly pressed hence the sound I was hearing. My error, it wasn't a buzz but the sound of a key/button being held down.
Yeah, those ‘Sinclair’ branded joysticks were infamous for their poor quality, even back in the day...

It is possible to buy adaptor leads, then you can use ‘Atari’ standard wired joysticks.

Mark

new666uk
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Re: 128 2a problems

Post by new666uk » Tue Jun 25, 2019 10:14 pm

Will do. Thanks Mark.

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