Help needed urgently!

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BrettRogersUK
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Re: Help needed urgently!

Post by BrettRogersUK » Wed Nov 24, 2021 1:57 pm

Just ordered a power supply recap kit for my DSP-508A. I have noticed a slightly bulging cap on the output side.

That's ordered so I'll not do anything else with it until the power supply has been redone.

Thanks to everyone for their help with this.

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rubber_jonnie
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Re: Help needed urgently!

Post by rubber_jonnie » Wed Nov 24, 2021 2:04 pm

BrettRogersUK wrote:
Wed Nov 24, 2021 12:06 pm
I've gone on the VIA at the bottom of the board where the trace goes to the underside. Tacked the wire onto that and now I have continuity all along the line and to the two pins where I didn't before.

However, I've put it all back in the case and I turned it on and just got the white screen again. Turned it off and flicked the switch on the TOS board and then I heard a crackle and pop from over where the power supply is.

No physical signs of anything popped or burnt but there was a faint smell of something towards the rear of the power supply where the plugs plug into it.
Make sure the mains lead is plugged in properly, if loose they can crackle. If its fizzing/crackling/popping at all when switched on, you need to check for shorts in the repairs you've made, specifically 5v to GND.

Your PSU sounds off too, so I'd suggest a recap or Meanwell RD-50a to bring it back inline.

I just checked on my own STE and the same pin on the ROM sockets of mine goes to that pin of the resistor pack, so that's OK, so aside from checking for shorts you need to check continuity of ALL of the pins on both ROM socket locations to be sure they go where they are meant to go.

Given you damaged a trace removing the ROMs, it is possible you've got hidden damage like a cracked via. Unless you continuity check everything (It's a slow process that drags, I know) then you will never know if you have another bad line or not.

Verify every single connection to the ROM sockets, and don't rush it. Also check to be 100% sure your ROM is correctly oriented in the Switcher.

Can you please provide a photo of both the top and bottom of the switcher.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...

BrettRogersUK
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Joined: Wed Sep 15, 2021 12:48 am

Re: Help needed urgently!

Post by BrettRogersUK » Wed Nov 24, 2021 2:33 pm

Hi,

Getting a pic of the bottom of the switcher might be a bit difficult as it is soldered into the board. Without desoldering it and possibly more damage being made I'm not able to take a pic.

I can take a pic of the top of it though.

On the power supply I'm getting 5.20v o the 5v output and 11.77v on the 12v output. That's with it sitting on the bench and plugged in so I can measure voltage on connector that goes into the motherboard.

16377642740802477911585399320103.jpg
16377642740802477911585399320103.jpg (414.51 KiB) Viewed 91 times

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rubber_jonnie
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Re: Help needed urgently!

Post by rubber_jonnie » Wed Nov 24, 2021 3:22 pm

So the ROM looks fine and you have a later version that allows for the pins to be either open or closed depending on the ROM you want to select, whereas my older one has 3 pins and one set must always be jumpered.

I have to come back to the continuity/shorts question.

Have you checked every last pin for continuity to their next hop? If you haven't then I'd really suggest you do than and check for any shorts.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...

BrettRogersUK
Posts: 32
Joined: Wed Sep 15, 2021 12:48 am

Re: Help needed urgently!

Post by BrettRogersUK » Wed Nov 24, 2021 3:39 pm

rubber_jonnie wrote:
Wed Nov 24, 2021 3:22 pm
So the ROM looks fine and you have a later version that allows for the pins to be either open or closed depending on the ROM you want to select, whereas my older one has 3 pins and one set must always be jumpered.

I have to come back to the continuity/shorts question.

Have you checked every last pin for continuity to their next hop? If you haven't then I'd really suggest you do than and check for any shorts.
Hi

That's what I'll be doing in a few minutes. Now I've got the schematic it'll make it easier.

Can I just ask, when I was unsoldering the 28 pin chips I was taking the solder out from each hole. So now I have 32 holes on each one (LO and HI) the first 2 (pins 1 & 2) and last 2 of each each chip (pins 31 & 32) of the 32 pin chip location don't have any solder in them. Could they cause any issues by not being soldered? I wouldn't have thought so but I'm not sure.

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rubber_jonnie
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Re: Help needed urgently!

Post by rubber_jonnie » Wed Nov 24, 2021 3:55 pm

BrettRogersUK wrote:
Wed Nov 24, 2021 3:39 pm
Can I just ask, when I was unsoldering the 28 pin chips I was taking the solder out from each hole. So now I have 32 holes on each one (LO and HI) the first 2 (pins 1 & 2) and last 2 of each each chip (pins 31 & 32) of the 32 pin chip location don't have any solder in them. Could they cause any issues by not being soldered? I wouldn't have thought so but I'm not sure.
They should be fine unsoldered, but you can always check for continuity top to bottom just in case.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...

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rubber_jonnie
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Re: Help needed urgently!

Post by rubber_jonnie » Wed Nov 24, 2021 4:52 pm

Annoyingly, my STE has decided to come out in support!!

It no longer boots and gives me a white screen, and nothing from the diag cart either.

Bit of my own diagnosis going on, but luckily my other is fine.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...

BrettRogersUK
Posts: 32
Joined: Wed Sep 15, 2021 12:48 am

Re: Help needed urgently!

Post by BrettRogersUK » Wed Nov 24, 2021 5:34 pm

Hi,

Oh dear doesn't sound too good! Hope you get it sorted out.

As for mine, I've checked the continuity. Question: should all top pins of the LO chip be connected to the top pins of the HI chip?

As for Voltages I'm getting 5.07v on the little square 68000FN8, the switcher board is receiving 5.07v. The power light on the keyboard is coming on, no disk activity though.

I'm not getting any noise from the keyboard either when pressing any keys. Nothing is shorting out as far as I can tell. I'm getting 5.07v on the floppy drive cable too and 11.77v on the blue wire I've got on mine.

Could it be that the 68000 square chip has somehow failed?

I've checked the vias that sit above the 68000 and they trace back to pins on the TOS switcher and the VIAs just to the below right hand side of the switcher where the mouse and joystick ports sit.

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rubber_jonnie
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Re: Help needed urgently!

Post by rubber_jonnie » Wed Nov 24, 2021 6:00 pm

BrettRogersUK wrote:
Wed Nov 24, 2021 5:34 pm
Hi,

Oh dear doesn't sound too good! Hope you get it sorted out.

As for mine, I've checked the continuity. Question: should all top pins of the LO chip be connected to the top pins of the HI chip?

As for Voltages I'm getting 5.07v on the little square 68000FN8, the switcher board is receiving 5.07v. The power light on the keyboard is coming on, no disk activity though.

I'm not getting any noise from the keyboard either when pressing any keys. Nothing is shorting out as far as I can tell. I'm getting 5.07v on the floppy drive cable too and 11.77v on the blue wire I've got on mine.

Could it be that the 68000 square chip has somehow failed?

I've checked the vias that sit above the 68000 and they trace back to pins on the TOS switcher and the VIAs just to the below right hand side of the switcher where the mouse and joystick ports sit.
If you had a bad CPU, the 68000, you likely wouldn't see very much, and wouldn't get a white screen I don't think.

As for the rest, you'd need to check the pinouts and schematics to see what should be connected where. Power, GND address and data lines should all map through.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...

BrettRogersUK
Posts: 32
Joined: Wed Sep 15, 2021 12:48 am

Re: Help needed urgently!

Post by BrettRogersUK » Wed Nov 24, 2021 7:03 pm

Hiya,

Have traced everything to where it goes even through the VIAs on the board and everything checks out.

Everything is connected how it should be. Both Hi and Lo are connected to where they should be. The 68000 chip is getting very warm though, should it be getting warm?

Thanks,

Brett

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