Help needed urgently!

Problems with your machine in general.
BrettRogersUK
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Re: Help needed urgently!

Post by BrettRogersUK » Wed Nov 24, 2021 10:05 pm

Hi All,

Just been reading on here about some tweaks and fixes that are recommended.

Should I look at changing the bus resistor arrays as they are still original. Would that have any effect on my issues?
viewtopic.php?f=17&t=2235&p=27504&hilit ... ray#p27504

Just clutching at straws at the moment.

Thanks,

Brett

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exxos
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Re: Help needed urgently!

Post by exxos » Wed Nov 24, 2021 10:09 pm

You should get the ROM problem sorted before changing other stuff, otherwise you are adding even more potential issues into the mix.

Problem you have, is you don't (I assume) currently know of any other possible broken via's or tracks on the board. Did you check the ROM's you took out to see if any via's are still on the ROM legs ?

Most of the ROM signals should be traceable back to the CPU, address and databus.
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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BrettRogersUK
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Re: Help needed urgently!

Post by BrettRogersUK » Wed Nov 24, 2021 10:14 pm

Yeah, I've checked them all. Everything checks out. I can trace tracks from the tos switcher to CPU, YM2149, DMA etc. Everything buzzes out with continuity on my meter. Unfortunately I don't have a scope or logic probe to go further.

I've checked that there is 5v getting to the tos switcher and there is 5.07v getting to it. There's also 5.07v on the CPU too. Ive checked the floppy drive as well. I've even checked the blue wire on the floppy drive cable and that gets 12.7v. Slightly over the 12v. I've ordered a psu recap kit as I've noticed that one of the capacitors is slightly domed on the output side.

There is one thing I haven't checked yet and that is the halt status on the CPU. I think I need to check pin 19 of the CPU for this. It might be a simple case of the PSU being faulty but my recap could change that.

The machine was in perfect working order before I took those rom chips out. The only thing that's happened is I've taken the rom chips out and the track has come up with it. I've repaired this and now nothing happens just a white screen.

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Re: Help needed urgently!

Post by exxos » Wed Nov 24, 2021 10:35 pm

You would need a scope to check the ROM CS signal on the ROM board to see if anything is even trying to access ROM. But you're getting onto some pretty long drawn out diagnostics which is very difficult to do remotely.

I think it's either find someone to try and diagnose it for you, or find a new motherboard.

Edit: also pressing the reset button can make things spring into life, as the caps in the reset circuit go bad .
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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BrettRogersUK
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Re: Help needed urgently!

Post by BrettRogersUK » Wed Nov 24, 2021 10:42 pm

Hi,

Funnily enough I've tried pressing reset but to no avail unfortunately.

I've been looking for a new board but unable to find an STE motherboard. They all seem to be stf or stfm boards.

Been trying to find a diagnostic cartridge but again none available anywhere. I don't think that would though in my case not sure.

I'm just at a dead end, it's annoying more than anything. 🤣🤣🤣

I would like to say though that I am grateful for all the help everyone has given.

Regards,

Brett

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Re: Help needed urgently!

Post by Icky » Wed Nov 24, 2021 10:54 pm

@BrettRogersUK you could speak to @Steve as he does repairs on these old machines. He may be able to get it back up and running.

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Steve
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Re: Help needed urgently!

Post by Steve » Wed Nov 24, 2021 11:33 pm

@BrettRogersUK looking at your photo on page 1 after zooming in I'm sure I can see at least 4 bent & broken vias. Man, when you're desoldering a chip if it doesn't come out easily it isn't fully desoldered yet. I could take a look but not right now because I've already got two people's machines I'm working on and I've got no more space.

If it were sent to me I would take the risk of desoldering it all over again and then checking every trace. I think it'd be easy to miss a broken trace when you can't see the top of the board. Then patch it all up. It's definitely a TOS issue you've got, definitely the traces, no point looking elsewhere IMO.

If you're patient I'll message you when my bench is empty, looking at a couple of weeks at least though.

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Re: Help needed urgently!

Post by BrettRogersUK » Wed Nov 24, 2021 11:58 pm

Steve wrote:
Wed Nov 24, 2021 11:33 pm
@BrettRogersUK looking at your photo on page 1 after zooming in I'm sure I can see at least 4 bent & broken vias. Man, when you're desoldering a chip if it doesn't come out easily it isn't fully desoldered yet. I could take a look but not right now because I've already got two people's machines I'm working on and I've got no more space.

If it were sent to me I would take the risk of desoldering it all over again and then checking every trace. I think it'd be easy to miss a broken trace when you can't see the top of the board. Then patch it all up. It's definitely a TOS issue you've got, definitely the traces, no point looking elsewhere IMO.

If you're patient I'll message you when my bench is empty, looking at a couple of weeks at least though.
Hi,

I was being careful as I could possibly be. I was desoldering, if it wasn't coming off I was desoldering again and unfortunately a bit of that track came up with that one chip. I have removed chips from boards before, some even older than this one but unfortunately this happens sometimes.

I looked at the board through a magnifier after desoldering and I could only see that one break which was obvious.

I've continuity tested all pins of the tos switcher and they all go out to their respective positions on the board. The HI and LO tos lines all bleep out and all pins that go to vias all bleep out to where they go to the relevant places DMA, YM2149, CPU etc. All Voltages are correct too, I've ordered a PSU recap kit as I've noticed a domed cap on the output side.

There is definitely something else that's a problem. How much would I be looking at roughly?

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Re: Help needed urgently!

Post by rubber_jonnie » Thu Nov 25, 2021 9:26 am

@BrettRogersUK I'd agree with the guys, we are now in 'very difficult to diagnose remotely' territory, and having somebody fix it will be the better option.

We can make suggestions as to what we'd do, but then we all have tools like 'scopes and logic probes/analysers that allow us to dig deeper into what's going on. We also have experience that will help us make diagnosis decisions.

All that's going to happen is everyone will get more and more frustrated, and you may do further damage to your machine.

Hopefully you can wait for @Steve to assist.

It's far from ideal for you, as you want your machine to work, but in the long run it may be for the best.
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Re: Help needed urgently!

Post by sporniket » Thu Nov 25, 2021 12:27 pm

BrettRogersUK wrote:
Wed Nov 24, 2021 11:58 pm
I looked at the board through a magnifier after desoldering and I could only see that one break which was obvious.
I would advise to buy one of those entry level "USB microscope" that can do 40x~1000x, like this one https://www.amazon.fr/Microscope-num%C3 ... 07BF86SRP/ if you can afford it (around 30€ normally)

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