S3200XL backlight replacement joy

Akai S3200XL original backlight for replacement

This is Lee’s old Akai S3200XL, the man who ran off to Canada to escape drum and bass. (Maybe not strictly true, but it’ll do.)

We used it in our daft hiphop band at the end of the 90s (along with the standard issue Atari ST), but it was always a bit of a mystery to me, never having much of a chance to play with it. I half-wonder now if we could got away with using my A1200 and Octamed, which I was using for my own dodgy big beat and drum and bass. Loading times would have been a drag off floppy discs, admittedly.

Unsurprisingly Lee didn’t take it with him, so it’s bounced around a bit before it ended up with me, still wrapped in the plastic it came in and looking generally pretty clean, but just with a dark screen. The photo above was taken in a super-bright room, which doesn’t help, but it was practically invisible in low-light as well.

Let’s have a look inside:

S3200XL overview of the inside

Nowhere near as stacked up inside as the packed-out S950. Nice how it’s separated by internal walls, presumably to shield each part (power supply and floppy/motherboard/digital to analogue audio out).

Here’s the power supply – says here it’s a Cosel PMC50E-1:

S3200XL power supply

…and it looks alright? It’s not been the most heavily used box, not like my S1000, so I’m hoping that there’s plenty of life left in those caps. I’m sure I could slot in a modern 50W PSU with +5V and +/-12V outputs in if I needed to.

Here’s a closer look at the analogue out section:

S3200XL audio out

Loads of PCM61 DACs, and a couple of unused spots on the board – one for another SM5840EP digital filter, and another for an 18CV8 (?): on searching around it seems like this would be a programmable electrically erasable logic chip, which has the pleasing acronym of PEEL.

Here’s the inverter for the screen! This might actually be the culprit as to why the screen is so dull.

S3200XL inverter

Alright, enough blurry photos of the innards, we’re here to replace the backlight. I’d seen this article on replacing the backlight on a S1100 with one from iPhone 6 Plus and wondered if I could do the same for this S3200XL.

This is what we’re faced with.

S3200 taps orffffff

Love that space next to the floppy, originally meant for a magneto-optical drive. Lee just used an external Zip drive, which actually still works, although he did always take care of his stuff. Maybe we could shove a bluescsi or SCSI2SD in there.

Once the power connections on the right have been desoldered, the backlight slides out from behind the display

S3200XL power connection

Here’s the backlight, which measures 13.6cm x 4.2cm.

S3200XL backlight

The power supply connects to this distribution board – I think this connector with the red and black wires was going to the floppy drive:

S3200XL power supply connectors

Somewhere in the blur there is the connector P410 – the lower two pins have ground and +5V on them, which is perfect for powering our replacement power supply for the backlight.

I didn’t have quite the right kind of connector but this one fits anyway:

S3200XL backlight power supply connector

And here’s the XL6009 DC-DC step-up board – 5V to about 17V. In retrospect this probably should have gone on the other side of the (grounded) wall, but anyway.

S3200XL XL6009 step-up voltage converter

When it came to wiring up the connector, I killed a fair few of the backlights.

Dead iPhone 6+ connector

The connector itself is really small, and it’s extremely easy to tear it off from the rest of backlight, and equally easy to tear the wires off and pull a part of the connector with it. The wires I was adding were heavy enough by themselves to twist the connector around. It’s worth testing the backlight as working, and putting some glue on the connector; also on this one I put some of the extra protective plastic from the backlight as a backing for the connector to make it a bit stronger. I didn’t take any photos of the resulting mess.

I decided to run the +17V through a resistor and a pot to set the brightness – and here it is in the same (very) bright room as earlier – way more readable, if not amazingly bright.

S3200XL new backlight installed

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bluescsi and an Akai S1000

I’ve got four or five old rack samplers which I’ve been poking at again recently, including this S1000 which I’ve had apart to replace the backlight.

akai s1000, having tea and biscuits in the front room

More on that calamity another time.

I thought I was alright with floppy discs, but I’ve been getting read errors. Possibly they’re just reaching the end of their lifetime, which makes me fret about all those Amiga disks I’ve not backed up yet.

Most of my samplers have built-in SCSI interfaces (apart from the S950, aieeee…) so I bought a SCSI2SD v5.0a off a vendor on ebay, and although it works fine with my S760 and my ESI2000, the thought of spending £109 for each of them for my various samplers wasn’t filling me with joy. (£109! I feel like I was done now – to be fair, the usual UK vendor of SCSI2SD boards seems to have been out-of-stock for a while)

Enter the bluescsi, which is intended to offer an open-source solid-state storage solution for vintage computers, mostly old Macs at this point in time. It’s based on the cheap “blue pill” STM32 board, hence the blue bit in the name.

There was some suggestion on their Discord server that it would work with Akai samplers, so I bought one from https://bluescsi.flamelily.co.uk for £32.

This is it plugged into an Amigakit DB25 to 50 pin IDC adaptor, and then into a DB25 to Centronics 50 pin cable so I can plug into the back of my poor, abused S1000.

Anyway, so I plugged it all in, turned the Akai on, and watch it boot up OK, although it didn’t seem to pick up the hard drive. I poked the hard drive settings for a bit. And then smelt a suspicious smell. And then watched in horror as smoke started to pour out of the back of the SCSI expansion board at the back of the S1000. I hurriedly yanked out the power cable.

The Amigakit adaptor just uses a right-angle header as the IDC connector, and it’s possible to offset the connector in the bluescsi socket by one pin, hence the smoke, which was caused by a burning track on the S1000 SCSI expansion. The track leads to a diode which presumably was blocking the voltage, so hopefully it didn’t cause any catastrophic damage.

If you buy one of the Amigakit adaptors, make sure you seat the connector correctly. I’m sure you’ll be more careful than me anyway.

The bluescsi is intended to work with hard disk images as files on a microSD card, with the card itself formatted as exFAT. I tried creating a blank disk image, but couldn’t get this to be detected by the Akai.

In the end I downloaded an Akai format ISO file from vintagemusicsamples, renamed the ISO to HD00_512.hda, where the first zero after the “HD” bit is the intended SCSI ID, and copied that onto the SD card.

Once I’d twiddled the settings in the Akai to use 0 as the hard disk ID (and moved the Atari disk ID out of the way to 7), it picked up the SD card as a disk, and I was able to load samples from the ISO. I wasn’t really that interested in the sample disc, although it’s nice to know it works, so then I used Arrange in the disk settings to initialise the directories. This had practical effect of binning all the existing samples, or at least marking the space as overwritable, so I was left with hard disks from A to I, with two partitions on the first drive.

The S1000 wouldn’t let me format the disk, which is a bit weird. Possibly there’s some bit set in the file for Akai format CDs which stops it from being able to format. I tested saving some files from an Akai S950 floppy, and that worked, and they loaded from the SD card after a reboot.

For a while I was mystified as to why I couldn’t rename the volumes, but it turned out that you actually need to have a file stored on the volume to rename it – this is common to actual S1000 hard drives as well.

The bluescsi supports multiple drives as files – I’ve had the other sample discs I downloaded as files HD10_512.hda, HD20_512.hda, and HD30_512.hda, accessible via the SCSI IDs 1, 2, and 3 respectively.

The bluescsi itself seems fairly quick, massively so compared to floppies, and infinitely quieter than the noisy hard drive I’ve got in there currently, which is also on its last legs. I wouldn’t be surprised if the limiting factor in terms of speed would be the S1000 given it originally came out in 1988.

The bluescsi has an advantage over the SCSI2SD v5.0a in that it supports more disks, but the v6 supports up to seven, and also allows files to copied to it over USB. But then the SCSI2SD v6 is usually three times the price.

Here’s me booting the S1000 (off floppy! I’ve still not plugged in the v4.4 ROMS yet), and loading a bunch of homemade drum loops I’d previously recorded on my S950 and saved to the bluescsi drive.

From the timings on the video, and given that this S1000 is fitted with 26MB of memory, and the loops take up 20% of the memory, it seems like it took about 17 seconds to load about 5.2MB of samples.

The (newly backlighted!) screen looks a bit rubbish in the video at this angle, but it’s much better from slightly above, and more legible in real life. I think it’s had a hard life – possibly I should’ve just stumped up for the LED screen.

It’s worth keeping an eye on the RaSCSI project as well, which is based on the Raspberry Pi – I just couldn’t find a UK source for the board at the time I looked, although it might be easy enough to buy some boards off DirtyPCBs or something. Check the Open Retro SCSI Discord for further discussion.

My “format an ISO” tactic to get the bluescsi up and running doesn’t seem particularly ideal, but it seems to work – let me know if you find a better way. Now I’ve got to put my S1000 back together, and to work out if I want to install the bluescsi in place of the floppy, or do something else.

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inevitable SEM clone testing

SEM testing box

Everyone’s done a SEM-clone, haven’t they? Or a SEM-type of thing. There’s a good reason for that, they do sound really nice.

I’ve been plotting this for about five years or so. I was stymied for a while by the designator-less PCB layout in the service manual, but finally got some boards made just before Christmas. I went through the pain of putting it all together in a PCB box just to test, seems like it works quite nicely.

SEM clone board

Maybe too nicely, I need to work up the motivation to make a panel PCB.

I went for multi-turn potentiometers for the presets, 0.1″ headers for the connectors rather than whatever freaky Molex connectors were on the original because I’m cheap, and kept the component spacing and track layout otherwise as far as possible.

I’m using 2N3906 and 2N3904 for the BJTs, and J112s for the FETs just because they seem to be available. The surface-mount adaptors for the LM301s seem to work alright (as long as you actually solder the legs…), and I kept with 741s. I’ve heard that the reissue uses TL062s, for whatever that’s worth.

I’ve bunged the usual CA3046 sub in for the CA3086. I was intending on using a surface-mount version in a DIP adaptor, but then found that the usual adaptor is too wide to fit in the standard socket. In retrospect I should’ve just actually used a surface-mount footprint on the board.

I stuck with the 723 regulator which was probably daft because they’re obsolete, but then I’m probably only going to make a couple of these. I found some probably-way-too-big silver mica caps for the filter capacitors, and some weird massive looking yellow film capacitors on the filter input, mostly chosen because they might be terrible. Maybe in a good way.

Mistakes that I made and discovered so far include swapping the designators for R73 and R75, a couple of transistors (Q7 and Q16) are flipped around the wrong way, and for some reason it seems like I just gave up when it came to the F connector in the middle of the board.

Let’s look at some wires, the horror behind my quick test setup. My wife thinks I eat them or something.

SEM temporary box wiring horror

I’ve deviated from my usual tactic of employing an Oakley PSU run off a Yamaha PA-20 (which works really well), and instead trying out a switching power supply from China off eBay, fronted up by an LM317/LM337 in a vague attempt to filter out any spiky noise. I haven’t put my oscilloscope on the rails, or made any great effort to try and reduce any noise, but the SEM seems to be behaving itself so far.

I made some recordings of the SEM-in-a-box, hopefully it sounds a bit like it should. It’s the usual MC-4-driven frenzied sequencer nonsense.


High pass!

Band pass!

Also I did a little recording with it along with the 606/Machinedrum for drums and System 100 for bass, and then thought it was boring so I started overdubbing a few more passes by hand. Like I say, this is just a temporary box for testing, it’s not going to have the Oberheim logo on it or anything when it’s done.

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