The latest Addition to the ST Family

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JezC
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Re: The latest Addition to the ST Family

Post by JezC »

@rubber_jonnie If all else fails, I know someone who has been advertising IMP DMA chips for a reasonable price.
The NOS ones might have sold out now but there may be second hand ones still.

Hope it's not as bad to fix as that Mega of yours!
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rubber_jonnie
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Re: The latest Addition to the ST Family

Post by rubber_jonnie »

JezC wrote: Sat Sep 18, 2021 8:57 pm @rubber_jonnie If all else fails, I know someone who has been advertising IMP DMA chips for a reasonable price.
The NOS ones might have sold out now but there may be second hand ones still.

Hope it's not as bad to fix as that Mega of yours!
Cool, thanks. I'll have to go through my stock, see what I have.

If I come up dry I'll get back to you 👍
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: The latest Addition to the ST Family

Post by rubber_jonnie »

Thought this machine would be a good candidate for testing my full test harness:

IMG_20210919_115804.jpg
IMG_20210919_115804.jpg (300.55 KiB) Viewed 1684 times

This allows a full test of the hardware using the diagnostic cartridge.

As expected, DMA is a fail.....
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: The latest Addition to the ST Family

Post by rubber_jonnie »

Interesting, looking at the underside of the mainboard, the DMA socket appears to be factory fit, certainly the only time I've ever seen one like that in any of my machines.

Also interesting is that the FDD cable does have signs of rework, so I need to buzz that out and see what's what.

Having tried two alternative DMA chips now, it seems that there may be more than meets the eye here, as it is still not working and reporting a DMA issue.

Time for schematics and tracing! Maybe even a WD1772 swapout. Let the games commence!!
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: The latest Addition to the ST Family

Post by rubber_jonnie »

Great, I seem to have 3 dead DMAs to my name ATM :(
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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JezC
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Re: The latest Addition to the ST Family

Post by JezC »

In a couple of my stock STF/M models, I've also got the DMA in a factory fitted socket, so quite rare but not as rare as hens teeth...

Can't remember if you already checked the ACSI port functionality on the new addition...might help limit any troubleshooting to the Floppy if the hard drive works?

Other potential vulnerable part might be the sound chip maybe?

Edit: oh dear, just seen the latest update...bad news... hope that is the extent of the problem.
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rubber_jonnie
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Re: The latest Addition to the ST Family

Post by rubber_jonnie »

JezC wrote: Mon Sep 20, 2021 1:36 pm In a couple of my stock STF/M models, I've also got the DMA in a factory fitted socket, so quite rare but not as rare as hens teeth...

Can't remember if you already checked the ACSI port functionality on the new addition...might help limit any troubleshooting to the Floppy if the hard drive works?

Other potential vulnerable part might be the sound chip maybe?

Edit: oh dear, just seen the latest update...bad news... hope that is the extent of the problem.
I just did a bit more testing, and actually all of the DMAs work just fine, but the results are weird. On my H4 and my new machine, when I run the DMA port test, it fails. I have another machine on which the DMA port test works just fine, so tested all the 'faulty' DMAs there and they all pass, which suggests maybe a problem with the connectors, so I will have a closer look at that.

Also, all my machines fail with my Ultrasatan connected, in that they boot and then fail with 2 bombs before getting to the desktop. I think I need to whip out the bus resistors and replace, see what that changes. H4 shouldn't have that problem though, so that's a bit weird. Might just try booting from FDD with a blank SD card, see if that changes anything as the US works fine on my MSTE.
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: The latest Addition to the ST Family

Post by rubber_jonnie »

@JezC Quick update, using a blank SD card and booting from floppy seems to be OK. Bus resistors still need doing though, but will partition the SD card and see what's what.
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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stephen_usher
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Re: The latest Addition to the ST Family

Post by stephen_usher »

On the STFM I put the TF536 into changing the main bus resistors actually made things worse rather than better. I think it depends upon the chip. I know that the original chip got worse and worse with the US connected until it wouldn't read anything with the US fitted (but worked fine without it). I can't remember if I tried with a real ICD host adapter or not.
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
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rubber_jonnie
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Re: The latest Addition to the ST Family

Post by rubber_jonnie »

stephen_usher wrote: Mon Sep 20, 2021 2:28 pm On the STFM I put the TF536 into changing the main bus resistors actually made things worse rather than better. I think it depends upon the chip. I know that the original chip got worse and worse with the US connected until it wouldn't read anything with the US fitted (but worked fine without it). I can't remember if I tried with a real ICD host adapter or not.
As it goes, the blank SD card works fine, but when you try and boot using HDDRIVER is when the double bomb appears, so I tried with PPeras driver and can now boot from the US.
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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