No load bars

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petercushion
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Joined: Sat Jun 29, 2019 3:24 pm

No load bars

Post by petercushion »

Hi all,

first time posting newbie here :roll:

I've got two Speccys, one works fine. I bought a second one to do up and I've done a composite mod and replaced the keyboard membrane (and given it a good clean) but when I plug the mono gable in to the ear jack, it doesn't 'listen'. I read that I should start with IC1 5C112/6C001 ULA but quite honestly, I don't know what that is. Can anyone point me in the direction of some help? Everything I've done so far, I've learnt from YouTube videos and websites so if anyone can suggest a guide, that would be really appreciated!

Thank you :)
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1024MAK
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Re: No load bars

Post by 1024MAK »

Hello Peter, welcome to our forum :D

Which issue board is it (printed text near the front edge of the board)?

The audio level required for loading is not the same across all the different versions of the board or the different ZX Spectrum models. So do try other volume levels.

By the way, are you using a cassette deck, a PC / laptop or other modern device as the audio source?
Modern devices limit their audio outputs, so loading can be marginal even at maximum volume.

Can you also please post up a good quality photo of your board.
petercushion wrote: Sun Jul 28, 2019 12:46 pm IC1 5C112/6C001 ULA
This is a large 40 pin DIL (Dual In Line) integrated circuit (or IC) often referred to as a ‘chip’.
On the layout diagram (note, different for each issue board) and on the silk screen (printing on the top of the board) it will be labelled next to the chip as ‘IC1’. On the top of the chip, it will be labelled with the part number, 5C112 and 6C001 are each part of the range of part numbers, as there were various versions. Alas, the supply of original spares dried up long ago. There are replacement modules though.

But if the Spectrum is otherwise working fine, it is less likely that IC1, the ULA, is faulty.
So the next step would be to check the Ear socket to make sure that the contacts are clean, that they make good contact when a 3.5mm jack plug is inserted and also check on the underside of the board for any broken or cracked PCB tracks. Also check the solder joints that hold the Ear socket. They should be a bright shiny silver colour, with no signs of cracks or rings and no lumpy distortions. If you are not sure, post up a photo.

To add photos, use the Attachments tab below the edit box.

Mark
petercushion
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Joined: Sat Jun 29, 2019 3:24 pm

Re: No load bars

Post by petercushion »

Hi Mark,

thanks for the warm welcome! :)

the board issue is 3.

I'm using an android phone and an 'app' called PlayZX. It worked fine with the other Speccy, so I assumed it would work just as well with the new one but nothing after I type the command to load the game.

So do you think the issue could be with the app and the phone? Could the volume be too high?

Please excuse the capacitor poking out of the RF module! :oops:

Thanks again!
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petercushion
Posts: 5
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Re: No load bars

Post by petercushion »

1024MAK wrote: Sun Jul 28, 2019 2:00 pm Hello Peter, welcome to our forum :D

Which issue board is it (printed text near the front edge of the board)?

The audio level required for loading is not the same across all the different versions of the board or the different ZX Spectrum models. So do try other volume levels.

By the way, are you using a cassette deck, a PC / laptop or other modern device as the audio source?
Modern devices limit their audio outputs, so loading can be marginal even at maximum volume.

Can you also please post up a good quality photo of your board.
petercushion wrote: Sun Jul 28, 2019 12:46 pm IC1 5C112/6C001 ULA
This is a large 40 pin DIL (Dual In Line) integrated circuit (or IC) often referred to as a ‘chip’.
On the layout diagram (note, different for each issue board) and on the silk screen (printing on the top of the board) it will be labelled next to the chip as ‘IC1’. On the top of the chip, it will be labelled with the part number, 5C112 and 6C001 are each part of the range of part numbers, as there were various versions. Alas, the supply of original spares dried up long ago. There are replacement modules though.

But if the Spectrum is otherwise working fine, it is less likely that IC1, the ULA, is faulty.
So the next step would be to check the Ear socket to make sure that the contacts are clean, that they make good contact when a 3.5mm jack plug is inserted and also check on the underside of the board for any broken or cracked PCB tracks. Also check the solder joints that hold the Ear socket. They should be a bright shiny silver colour, with no signs of cracks or rings and no lumpy distortions. If you are not sure, post up a photo.

To add photos, use the Attachments tab below the edit box.

Mark
Hi Mark,

it's been a while since I've given the Speccy any attention but here I am again! :D

So, I've checked the soldering and the PCB tracks as well as the jack but I can't see anything that would suggest there is a problem. Photo's are here: https://s1344.photobucket.com/user/Kier ... sort=3&o=0, https://s1344.photobucket.com/user/Kier ... sort=3&o=1, https://s1344.photobucket.com/user/Kier ... sort=3&o=2

If it helps, I plugged in my other Speccy, which works fine and I noticed that after I type the command to load, it waits several seconds before "listening", with the screen being blank and grey and then I get a blue border around the screen that changes to red, before I hit play and then we get the stripes and eventually, the game loads. If I do the same things with my faulty Speccy, it switches to the grey blank screen after I hit enter after typing the load command but it doesn't start to display the blue border etc.

Any help would be really appreciated!

Thanks!

Kieran.
petercushion
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Re: No load bars

Post by petercushion »

Can anyone help?
Lardo Boffin
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Re: No load bars

Post by Lardo Boffin »

petercushion wrote: Tue Jan 14, 2020 7:36 pm Can anyone help?
If the ZX81 is anything to go by when something doesn’t work it is often the ULA. You can a brand new replacement from here:

https://www.retroleum.co.uk/zx-spectrum-chips

Yours looks socketed so should be easy enough to try. At time of posting there are two in stock.

You can also get a new voltage regulator and ditch the heat sink. You may need to in order to fit the new ULA.
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1024MAK
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Re: No load bars

Post by 1024MAK »

The ‘load bars’ are purely generated by the CPU executing the ROM code, which then tells the ULA to change the border colour. If the ROM code does not detect any ‘sound’, it will just site there waiting with a white border. When it thinks it has heard something, then it starts slowly flashing the border between two colours. When the code detects an audio signal that appears to be cassette tape data, you then get the stripped border.

The only way that the ROM code knows about the audio signal, is to constantly monitor the ear input I/O bit contained within the ULA. Sinclair improved the ULA circuitry with the ZX Spectrum ULA, and further changed it for the later ULA versions. This was done to reduce the effects of noise causing loading errors.

I still think the problem is a lack of volume. ZX Spectrum (along with ZX80 and ZX81) computers were designed to be connected to the mono cassette tape decks of the time. Modern consumer devices just do not produce a high enough volume (meaning insufficient voltage) to pass the threshold that triggers the ULA to detect a voltage change from low to high.

As I said earlier, NOT all ULAs are the same. Some are more or less sensitive compared to others, so the fact that one works with an Android mobile telephone does not mean that another ZX Spectrum will also work.

A lot of ZX Spectrum owners find that when using mobile telephones, MP3 players or laptop computers, they need a simple audio power amp to boost the signal so that their ZX Spectrum can reliably hear the audio.

Mark
petercushion
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Re: No load bars

Post by petercushion »

Thanks, guys.

Lardo, thanks for your help and typically, they've now sold out! :roll:

Mark:

on the subject of the audio power amp, is there anything that you know of that works well with boosting the audio? A particular type of amp? I haven't got one so I'll need to buy one.

Thanks again, guys. :)
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1024MAK
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Re: No load bars

Post by 1024MAK »

See this post for ideas.

Mark
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