MDPC CTX3: A load of doubtful marketing bollocks lands on my crimp connectors page

I promise the day will come when I stop banging on about crimp tools, but, indulge me just one more time. Somebody just posted a link to the below crimp tool on my crimp connectors page:

MDPC CTX3 Crimp tool: £55. Like a well choreographed cooking channel, it’s pictured on wood. Hoping to invoke a woody reaction among prospective purchasers. Source:

Website link. It looks rather like a re-badged IWISS SN-28B to me, for double the money.

IWISS SN-28B. Made in China, £25 and common as blow-flies.

Thier website is loaded with incredible assertions (quoted):

“The MDPC “10th Anniversary Edition” crimping tool MD-CTX3 replaces the legendary CT1 model, which earned the reputation of being the reference for the last 7 years.”

I was not able to find any pictures or references (other than that statement) of the fabled “CT1”. Unexpected for a tool that’s been around 7 years? As for it being a reference – A reference crimping tool can only ever be the connector manufacturer original tool, which can cost hundreds to even over a thousand dollars, and for a good reason. I have detailed many of these (all of the relevant tools for PC modding) on this page.

“5-axis CNC shaping of the essential structures, made in Germany, to achieve the highest standards in crimp terminal shaping over all 3-axis (!) of the crimp terminal – based on the official MLX guidelines.”

Made in Germany? It seems rather improbable that two nearly identical looking tools would be made in both China and Germany. I have many German made crimp tools in my collection, the cheapest retails for over £300.

MLX guidelines? Let’s google that shall we…

A highly scientific looking diagram provided by the marketer. Must stick out? You’d bloody hope so. Even if it does, you haven’t scratched the surface of crimping considerations. Note to the knuckleheads who produced this graphic: The “Top” is called the Crimper and the “Bottom” is called the Anvil. The “Rear” is the wire die, and the “Front” is the insulation die. Source:

If you’d like to learn some actual science about crimping – take a look at this video:

A further note to PC modders

I recently looked at a new tool from IWISS – the SN-025 which actually does a better job at crimping the main two types of connector used in PCs (DuPont / Mini-Fit Jr), than the IWISS SN-28B (and by extension, the illustrious MDPC CTX3).

It is not suitable for crimping Commercial Mate-n-Lok terminals or look-a-likes. You will still need the SN-28B for those, but I wouldn’t imagine many are used anymore. Having not purchased the CTX3, you’ll be able afford both, with money left over for a couple of beers.

An easy to build MCS-48 programmer, and something to use it for

Recently I’ve been working on a new shield for my HVEPROM project to program internal ROM UV erasable versions of Intel’s first microcontroller, released in 1976. I built it because I was trying to repair something with one of these in it, and being able to disassemble and modify the code was a key part of that repair. My universal programmer (quite an expensive one) didn’t support these. Others do, but I wasn’t keen to go splashing out again.

Read more about it here.

Why stop there? Having gone to all that trouble, I thought it’d be interesting to build an entirely new project based on one of these, and see what they’re all about.

Pictured above is the result of that effort. An MCS-48 based dual temperature sensor. It uses one or more DS18B20 one-wire bus temperature sensors.

Read more about it here.

IWISS SN-025: Another head scratching “DuPont” crimp tool lands

Following on from my recent review of the Preciva PR-3254 crimp tool, I hit up eBay and Amazon to see if any other such tools may have surfaced lately. I found one:


We have a new tool (Amazon UK link), which is also apparently specifically designed for these terminals. At the time I wrote this article, the SN-025 is not (yet) listed on IWISS’s website?

Two terminals apparently crimped with the IWISS SN-025. A “DuPont” terminal, and, err, what’s that other one? One auction listing mentions TE “Superseal” terminals, which look quite different to the one on the white wire. Recognise it? please drop a comment.

The above graphic is provided by the Amazon seller, specifically pointing out that it wraps the insulation around the wire. It’s almost as-if they’ve been reading my crimp connectors page

While this is being sold as a “DuPont” crimp tool, it appears it is predominantly designed for another type. It has three dies:

  • AWG 28 for “DuPont” terminals?
  • AWG 20 for mystery larger terminal
  • AWG 18 for mystery larger terminal

The AWG 28 die

DuPont HT-95. The gold standard which I’ll be comparing against.

Let’s put some “DuPont” terminals in there and see what we end up with:

Of course SN-025 wasn’t going anywhere near the HT-95’s crown as ultimate “DuPont” crimp tool but it did do marginally better than the Preciva PR-3254 I reviewed previously.

The SN-025 not having an AWG 24 die, it over-crimped the insulation as we would expect, and the wire part isn’t crimped anywhere near as tight as it is supposed to be – typical for Chinese tools.

Verdict: Pass (for non critical applications).

If we were to cut open the wire parts of the DuPont vs IWISS crimps, we would find something like this. For the SN-025, likely a lot worse. Source: TE Connectivity

The other two dies?

I went through my crimp tool cupboard to see if I had any others like this. Of the, err, considerable number (I’ve lost count) of manufacturer original tools in my collection, just seven have an ‘O’ type insulation crimp. Only two of those were in this wire size range:

Top: TE Multimate crimp tool. Bottom: TE Economical Interconnect crimp tool

TE Multimate

An interesting type to compare against because Multimate terminals look quite similar to the one pictured in the image the tool is sold with. This tool may be designed for use with a similar type of connector of Chinese design/origin. Given how esoteric these are, no point in going any further into that.

Economical Interconnect

A common type stretching to AWG 20 wire size, which has an ‘O’ crimp. More about these here.

KK .396 (?)

Lost in translation? The range of terminals apparently crimped by this tool. Always good to have something to handle those Micro Timers.

In addition to the “DuPont” types, Molex KK .396 (.156″) is offered as a supported terminal type. Not something the average hobbyist is going to be reaching for. I’ve got the manufacturer original tool for these, it’s not quite an ‘O’ type crimp, but let’s give it a shot anyway:

Mini-Fit Jr (?)

The die in the manufacturer original tool is quite similar to the KK .396 tool, so we’ll look at these too.

Certainly not one for E.I. It was OK on the wire part but it didn’t touch the insulation crimp. Verdict: Fail.

For KK .396. Pretty good! the insulation part is a tad too loose on AWG18 wire (forget it for AWG 20). The results do not match the marketing image, I can only assume that was done by a different tool. Or, perhaps, the marketing image is depicting a smaller KK .254 terminal? Verdict: Pass.

Last but not least, it did a really good job on Molex Mini-Fit Jr. I’m so impressed with the results that I’ve decided to take a closer look:

AWG 18 wire crimped by 3 tools. On the left a typical result of a budget tool, with the insulation deeply pierced due to the very long tabs on these terminals.

For the SN-025 crimp on the right: It takes a bit of practice, and I’ve accidentally nicked the wire because I positioned the terminal too far forward, also the AWG 20 die must be used. The SN-025 has yielded a result very similar result to the Molex 63819-0900, correctly and cleanly wrapping the insulation support. The best I have ever seen from a budget tool.

Verdict: Pass.


Without a specification from the manufacturer, and subsequently knowing what it was actually designed for it’s difficult to give it a final judgement. Wire crimping force is quite respectable for larger terminals i.e. KK.396 / Mini-Fit Jr, but not so great for “DuPont” terminals.

As always my recommendation is that this tool (and any other tool in this price bracket) should only be used for applications in the “fun” category, specifically the kind of fun that doesn’t involve someone losing an eye when it goes wrong.

Manufacturers of tools around this price do not spend any time ensuring that the tools they produce crimp terminals to the specifications of a specific type, instead they are a broad brush design intended to crimp a range of terminals to a vaguely presentable standard. Yes we’ve got some nice crimps on Mini-Fit Jr, but that is purely luck, and only achievable with very specific terminal placement during crimping.

If you’re building something critical and/or expensive, name brand terminals and the manufacturer tool should be used. I have detailed a lot of these on this page.

A new budget “DuPont” crimp tool is bought to my attention

Preciva PR-3254 crimp tool

Back in 2015 when I first wrote up my crimp connectors page. I pointed out that there was no cheaply available tool which could crimp “DuPont” terminals properly (cheap Chinese connectors which resemble DuPont’s Mini-PV connector).

Crimped Mini-PV Terminals
Crimped Mini-PV look-alike Terminals

At the time pretty much all tools in the $30 or less price bracket got you a result like on the left, because the insulation crimp die was a ‘B’ shape when it needed to be an ‘O’ shape.

Comparison of the DuPont Mini-PV crimp tool, and the die of a typical budget tool

Anyway… onto the tool in question. This was bought to my attention by a reader, and it’s actually sold in a kit (Amazon UK / US). It’s very affordable and it’s got a die specifically designed for “DuPont” terminals. My first reaction: Wow. The bounty for such a tool has been out for 5 years now. Could this be the one?

First impressions unfortunately weren’t particularly good.

PR-3254 “DuPont” die compared to DuPont HT-208 (AWG 24) die

When the die is fully closed, it ends up with an uncomfortable “oval” shape, rather than the circular shape all DuPont original tools have. You cannot partially close it either because the wire part wouldn’t be crimped at all.

Top: AWG 24 wire crimped with PR-3254. Bottom: AWG 28 wire crimped with PR-3254

Results aren’t too bad. It’s doing the right thing, wrapping the insulation crimp instead of making a mess of it. For AWG 24 wire, there’s far too much force on the insulation, crushing and damaging it, but the wire part is reasonable.

For AWG 28 wire, force is about right on the insulation, but there’s not enough force on the wire part. In the long term, moisture may get into that and cause troubles. You could double it over to mitigate this to an extent.


It’s very encouraging to see a budget tool specifically designed for these terminals.

It does so-so job of AWG 28 on “DuPont” terminals. Its other dies are fairly standard and ones like it are found in other tools, for example the IWISS SN-2549. Don’t go rushing to buy it. I’m looking at another tool at present which may be a little better than this one.

This tool is probably OK for people who are building temporary/non critical things, however ultimately this particular effort appears to have stopped for a cigarette just short of the finish line.

So… are those Amazon sourced £20 drill batteries any good then?

In the case of the one I purchased: No.

Warning: this post contains a lot of technical details the average person isn’t going to care much for. Feel free to skip to the end.

I wouldn’t normally contemplate buying an “off brand” battery for anything, but this year genuine batteries for my 14.4V Bosch power tools (which I have a few of) were discontinued.

I could re-pack my batteries with quality cells, but for now, I’ve decided to give a common off-brand battery a go.

There are three main things we care about in a battery:

  • Safety
  • Longevity
  • Capacity

I’m not going to be doing any safety checks here, and as for longevity, come back here in 5 years, I might give an update. For now all we can look at is capacity.

My cheapo battery, purchased from (which is a front for a Chinese operation which buys crap off Amazon on your behalf and has it shipped directly to you) is advertised with a capacity of 3.0Ah (3000mAh) – the same as the highest capacity genuine battery, a battery which cost three times the money. I’m already suspicious.

While it is possible to get a licked-finger-in-the-air measure of the capacity of a battery with two multimeters, a resistor, stopwatch and an exceptional attention span; testing the true capacity of a battery is rather difficult. This type of test is typically performed with a DC Electronic Load which has the necessary circuitry and software to perform this type of measurement.

For my test I’ll be using a Keithley 2380 DC Electronic Load – one of the best available at the time of writing.

There are two parameters we need to enter into it to perform this test:

  • The discharge rate
  • Voltage we consider the battery to be “flat”.

As can be seen from the above graph the battery is completely discharged at 1.0 V per cell, and as we tend to use power tools until the battery is totally dead (and often beyond) we’ll use that number for this test.

To conduct this test I’ll be using my trusty false charger – which allows me to safely connect the tool batteries to other stuff.

Bosch AL1404 with its insides removed, and puny contacts replaced with the beefier variety of contact found in the tools, those wired to an AWG12 cable with a 50A Mini-Fit Sr connector on the end.

First I’ll run this test on a genuine battery. In this particular case a 3.0Ah battery part# 2 607 335 693. It is 4 years old, and I estimate it has been cycled about 250-300 times. It still performs well so am expecting it to be close to the advertised rating.

For the discharge rate I’ll go for 0.5C (discharge over 2 hours). Discharging too fast will give me a false low reading, and discharging too slow will take forever. I’m not a patient man.

The original battery tested at 2.12Ah. A little disappointing but given its age and regular use, about what we would expect.

Now for our crappy knock off:

From the feel and appearance of it I already have a bad feeling about this one.

And there we have it. The capacity of this battery from brand new, fully charged, measures at just 1.176Ah. Even at a puny discharge rate of 0.5C / 1.5A (a tiny fraction of what the drill would discharge it at) it only lasted 2823 seconds (47 minutes).

An astonishingly poor result and practically only a third of its advertised capacity of 3.0Ah. You get what you pay for. It’s a damn shame the option to pay more no longer exists.

Attaching a 5¼” floppy drive to a laptop, that wasn’t designed to have one attached to it

For years now I’ve had a honking big Tandon TM100 360K 5¼” floppy drive which has been screaming out to be used, and there is something I’ve wanted to use it for – on a “go between” PC so I can shunt files to and from my XT era PCs which I tinker around with.

The easiest way to do this is to have, say, a Pentium II era desktop PC on a network, etc – but that’d be a big lump of junk I don’t want taking up space in my cave.

I could also splash out on a Kyroflux, which would let me attach it by USB to a modern machine but Kyroflux being a specialty tool for data recovery, isn’t convenient in my use-case whatsoever because it only works on entire disk images, doesn’t do drag and drop – it isn’t really what I want. If only I could attach it to my Thinkpad 760 – which I can easily network, and has an external floppy connector.

I’ve been pondering this for a long time now, but knew it wasn’t going to be straight forward.

Difficulty #1 – What is the sodding pinout for that connector?

I had previously spent hours searching around for a schematic, spec, any kind of information on this connector but came up with bupkis. I could buy an external floppy for it, bust it open and have it in minutes but in the UK where I live, most 700 series Thinkpads were sold with internal floppy drives, so these are pretty much unobtainable. I’d have to ship one from the US at massive expense.

Given the ridiculous amount of spare time lockdown has created – I decide to do this the hard way.

Day 1: I completely dismantle the laptop. Inside I discover that it has a half a dozen PCBs connected together with ribbons and board-to-board connectors. It’s a nightmare. I found the floppy controller, but it’s not accessible when it’s all assembled, so I can’t just beep it out. I started to beep out the rear connector to some of the intermediate connectors but it’s a sucky, time consuming exercise.

I eventually discover that only two pins (RDATA, WDATA) are directly connected to the floppy controller, the rest are buffered separately from the internal drive, and the buffers are under the I/O PCB, between it and the CPU PCB which is really difficult to get at. I give up. While I’m at it, I can also get the +5V and GND pins easy enough. I re-assemble the laptop and ponder my next move.

Day 1 ends, I know more than I did at the outset, but unfortunately there’s still a lot of pins to work out.

Day 2: I discover that signals from the floppy controller to the internal floppy are observable on the rear connector, but signals going the other way, aren’t, because of the internal buffering. Doing some accesses to the internal floppy with a scope attached I can get a few more pins – STEP, WGATE, SIDE, DIR.

Day 2 ends, and there’s still more to go.

Day 3: I’ve now written a small DOS program which allows me to read and write the registers in the floppy controller. With this I am able to get TRACK0, WP, DSKCHG and DRVSEL/MOTEN.

A quickly lashed up tool to assist with the identification of pins on the floppy connector

Day 3 ends, I’ve got one signal left: INDEX. All of the inputs have 20K pull-ups on them, so I have to assume that the remaining unidentified pin with a 20K pull-up is INDEX.

Day 4: I’ve got all of the floppy signals now, I’ve got still got quite a few unknown and it bugs me that I wasn’t able to confirm the INDEX signal. It seems to work with it disconnected, so do I really have the INDEX signal? FFS. Pull it open again…

The laptop is dismantled for the second time – to beep out that blasted last INDEX signal. This time the I/O board is removed so I can get at those buffers on the underside

While I was at it, I got another two signals, DRATE0/DRATE1. Not sure what those are for. I haven’t used them.

The Thinkpad external floppy pinout

(On models which use a 26-pin mini-D ribbon connector) – I can proudly announce:

Note: Newer models (i.e. 770) use a slightly smaller D-type connector. This may not be the pinout for those.

Difficulty #2 – Cable

The pigtail coming from the DC shell carries the +5V line, which in future will be used to switch external drive power

There’s nothing special about the connector – it’s a Mini-D Ribbon connector (MDR). I found some cheap ones on eBay labelled “1Pcs SCSI 26 Pin MDR Male CN Solder Plug” which were exactly what I wanted – solder termination, also including a decent shell.

After much pondering as to what would go on the other end – I’ve settled on a standard DC-37 (yes, DC. Not DB) external floppy connector as used on IBM machines in the 1980s.

As one can imagine this cable is quite a bit of work to assemble.

Difficulty #3 – The BIOS doesn’t support 5¼” drives

This is hardly surprising as Laptop BIOSes typically don’t have features not corresponding to official accessories, and realistically, who on earth would have wanted to do that at the time.

I was fearful that there’s be a serial EEPROM in the floppy drive containing product identification data, that I’d be stuffed without the contents of, but that doesn’t turn out to be the case. I attached a generic 3½ floppy drive to my newly made cable – it works. An additional bonus, I can also boot from an external 3½ drive of my choice, should I ever feel the need to.

Back to the matter at hand. My Thinkpad 760 runs Windows NT 4.0, which has its own floppy disk driver, not using the BIOS at all, except, it does interrogate it to find out what kind of drive is attached, which is where we have a problem.

The type of drive is retrieved by NT very early on via an INT 13h call to the BIOS, that data gets stashed in a holding area, finally retrieved by floppy.sys a bit later on when it starts up.

Hacking the response to the INT 13h call would be pretty difficult, so instead I’ve gone down the path of hacking floppy.sys, whose source code is in the NT4 DDK.

After days of screwing around with my floppy NT driver hack not quite working I change approach – and go hack NTDETECT.COM – an obscure 16 bit executable which is used during the NT boot process to probe the BIOS for hardware information, including attached floppy drives. Using the NT leaked sources, this turned out to be absurdly easy, however re-compiling it most certainly was not.

Very little modification is required to force B: to 5.25 360K

Eager hackers have gone to the trouble of re-creating Microsoft’s build environment from the early 1990s. Even with all of the know-how in the public domain this is still an awful lot of work, so I put together a custom build environment for it instead. My new NTDETECT is quite a bit bigger (35K) than the original (26K) for some reason, but it works.

There is something rather satisfying about having a B: drive – especially when it’s a 5¼”

Read data troubles

I noticed fairly quickly that I was having quite a lot of read errors, so I got out the scope to have a look at RDATA

It seems that the 20K pull-ups inside the laptop aren’t sufficient for my cable rig. I had to add 1K pull-ups on the RDATA and INDEX signals to get things looking a bit cleaner.

Would you believe it…

The day after I complete this, after nearly two years of watching eBay – a first generation Thinkpad external floppy appears on eBay UK. I nab it for £6.50.

Let’s crack it open and see what’s inside.

It turns out the external floppy is just a caddy which can have the internal floppy drive inserted into it. Busting it open actually tells us nothing about the pinout of the rear connector, because we don’t know the pinout of that large 100 pin connector inside it.

To get the pinout I had to detach the Mylar FPC which runs between that connector and the physical drive, which has a 26 pin connector on it, which we do know the pinout for, because it’s a TEAC FD-05HF-8830 for which the datasheet is available. Finally, I can beep this thing out properly.

What did I learn from it?

The only new information I got is that the HDSEL signal is actually present on the external floppy interface. It’s a bit of an odd one. It’s an output from the drive which is LOW when a 720K disk is inserted, and HIGH when a 1.44MB disk is inserted.

What’s the point of it? Not sure. Generally floppy drivers do this detection in software, first trying the highest format for that type of drive, if that fails, step it down, try again, and again and so-on.

Because it’s not connected to the FDC (it’s connected to an undocumented IBM ASIC) nothing much would be able to make use of it anyway. It’s probably used by the BIOS to make format detection a bit quicker, but the BIOS is also able to do format detection in software, so, really not needed.

Other than that, a few mystery pins were found to go to NC pins on the drive. I think it’s for some kind of drive identification mechanism, which isn’t used on the drive I have.

A general note about using 5¼” drives on modern computers

You may be sitting here thinking: “I don’t have one of those ports on my laptop. Why couldn’t he have shown how to do this with an interface I have on my computer”. I hear you.

I would also dearly love to to just plug this drive into my Windows 10 laptop, have that 5¼” icon show up in My Computer and use the drive like a modern USB floppy, heck, even running one from a parallel port would be amazing.

Unfortunately, when the writers of the USB Floppy Specification decided only to include 720K and 1.4MB formats on 3½” drives in the standard, they made this extremely difficult. Because of this, a whole new software stack would have to be written, for which ever OS you want to use (it’d be easier on Linux – being open source you could modify what’s there). For Windows this would take even an experienced driver developer several months. Ditto for any other interface.

Maybe, just maybe, the source code for a newer Microsoft operating system (with the USB floppy driver) will one day find its way into the public domain. We can then modify it to support 5¼” drives – 90% easier than re-writing it from scratch. Until this day comes, hacks like the one this article describes are about as good as it’s going to get.

Failing that, there are other possible solutions. It is theoretically possible to attach a Super I/O (with floppy controller) to the LPC bus (assuming your mainboard has a header for it – many do). A bit of new hardware would have to built, as well as a bit of software hackery, but this would still be fairly easy compared to building a whole new soltion.

I have some EPROMs, from Russia

What is our fixation with chips produced by the Soviet union by the help of industrial espionage? Or is it just me that likes to collect these?

Today, I’ve received another consignment of them:

This is a set of 4 U552C’s – the Soviet version of the Intel 1702A which I recently built a programmer for.

Before I get started, there is a familiar problem which is that the pin spacing of these chips is a metric 2.5mm, not the usual imperial 0.1″. Engineers from the USSR apparently felt the need to correct the oddities of the imperial past. Sockets with this pin spacing are more difficult to come by than the chips that plug into them, but today I’ve got some, so I’ve built a little adapter:

Just for a laugh – I though I’d try program them using the x86 build of that programmer on another Soviet chip: the K1810VM86 – a clone of Intel’s 5MHz 8086 processor.

The test setup – an un-holy mix of components from either side of the iron curtain.

On the first run I nearly burnt out an EPROM because I’d forgotten that the x86 HvEprom build is hard coded for a 10MHz CPU, whereas the K1810VM86 only ran at 5MHz, so I had to go back and re-do all of the timings.

They all programmed and verified no problem.

The last test is to pop them in my 1702A reader, and we can see that the ASCII letter ‘K’ is in the first position as expected.