Chasing the Sony CX20084 speed chip for D6C walkman

I forgot to mention I turned the speed pot as fast as possible but if you turn it higher it glitches out. The belt and rubber tire have been replaced, too.

 

Please create a new thread about this issue, as the solution likely won't be a one post one. If it proves to be related to the CX20084, we'll put a link to the separate thread.

 

@Silverera I'm afraid it's 100% fake. Take one out and use acetone, if the cotton swab looks like the picture below, don't even solder it. These are random repainted SO16 IC's. They heat up instantly and the only thing you can do is damage the device.

 

Hi. I have a d6c with big broken. No drive servo board. So i getting a drive motor from a walkman fx. And it working well. Wow&flute is ok. Look.

 

And what about this ic ba6301

 

- impressive work! Do you use the pulses from the tacho at all?

 

Well that's something at least. Way better to avoid wasting time and effort putting in a dud IC which could cause damage to other subsystems. As mentioned before in this discussion running your D6 on batteries and not cheap switch mode power supplies is also a good idea.
I might try the acetone swab test on mine out of interest.

 

Best thing is to get a donor wm-dd2 and desolder the original chip.

 

Slightly off topic but a wonderful showing of the first engine of the speaking clock.
The same problem we are discussing here must be solved: the governing of motor speed.
In the video a completely mechanical solution is shown. Quite remarkable.

 

$hitloads.
The chip suppliers culled a massive amount of products over the C-19 period and there will be loads of re-stamped and rebranded pieces of junk for sale and it will only get worse as relations with the western world and China continue to sour... I do have a plan to try and reverse engineer the CX but I will not be in a position to do this for at least 6 months....

 

Hi, would it be feasible to reverse-engineer the CX20084 chip with a very high definition picture of the exposed die?

 

it would depend on how complex the chip is.



this video by Robert Baruch shows schematics for a chip being obtained via opening it and photographing it through a microscope
it appears to be a pretty simple IC though.
the process would be time consuming and the equipment used appears to be somewhat specialised.



this video shows a much more complex chip being reverse engineered by Robert so I assume he would be capable of doing such a task if someone was able to contact him and send him a CX20084 IC to reverse engineer. If this were to be done then at least plans for the IC could be obtained.

manufacturing costs for custom IC's appear to be very high so maybe crowd-funding a batch would be a feasible way to raise the capital needed to order the parts, this would depend on demand for CX20084 chips though. if the capital was raised the 1st batch would be the most expensive as it would have to cover tooling for the chips this means that the 1st batch would probably exceed the value of current salvaged chips however, subsequent batches would be able to be made for a much lower price.

 

I was asking because I have the chemicals and some of the stuff needed for this kind of operations at my disposal.
The thing is, I don't really have the time needed to do the reverse engineering work, and I think I don't even realize how time-consuming it would be.
Regarding the issue of the custom IC manufacturing, I was hoping that the IC would be simple enough that it could fit on a circuit board instead, but I guess it was fit into a chip for a reason... Still, it's 80s tech, things have changed since then, maybe there's a chance.

 

the chip could probably be simulated on an Arduino but i do think it may be possible to just build it on a PCB. one of the reasons it was put in a chip was probably just to allow it to fit within the case of the Walkman as if it wasn't the extra circuitry would almost certainly not fit inside and would make it too bulky not to mention the extra power needed to drive the larger components which would lower the operating time of the Walkman

 

Yeah, that's what I thought. Plus, the chip is very tiny, a PCB of this size wouldn't leave much room for the components.
Digital processing through an Arduino would require some serious optimizations to emulate the original correctly.

 

I personally don't think manufacturing a new chip is very feasable, there's just not a big enough market for it to cover the R&D and manufacturing costs.
Of course that is assuming we have the people to do the reverse engineering and design the new circuit at the silicon level (which is not simple).
I tried to do a crowdfunding for a TC-D5(M) custom rubber ring (and we already have the person to do it) and only 5 people were interested to support such a funding, despite these rings do fail.

Reverse engineering the chip itself can be done, but doing the schematic is just one part. You need to find the right transistors with correct properties that work in certain circuits.
As for building it with discretes, it's certainly not possible in the original form, as the IC likely has a couple of dozen transistors in it (it's the reason they made a chip to begin with).
They did it in the form of IC for 2 main reasons: performance and cost. An IC produced in volume is a lot cheaper than discrete circuits.
Then you can make a more complex circuit inside an IC (hence better performance): on the same PCB area on which you make a 3 transistor discrete circuit you can make a 30 tranistor IC.
Size I don't think was a big concern as there is a lot of empty space in the case in that area, so they could have fitted a daugher board/hybrid module (but it would have increased the cost).

Building it with Arduino is seems like an easy idea at first glance (and has been presented before 2 or 3 times), but in my opinion it's a bit harder in practice.
The smaller Arduinos don't have clock frequencies high enough to obtain the very fast response you need in such a circuit and they also lack important peripherals such as a DAC and high speed ADC.
Going to more performant microcontrollers (with small footprint, high clock frequency and many peripherals) you will lack the pre-built libraries that you have in Arduino and will have to write everything from scrach.
Then it can be done analog with discrete components and op-amps (which can be available in very small footprints) on a daugher board that can be fitted on the component side of the board (there is space to put more than one).

 

reverse engineering would still be needed to obtain info about the circuit as I've not had any luck in finding the circuit schematics for the chip I've only seen logic diagrams. it might be worth trying reverse engineering and looking at PCB and emulation based solutions as a short term solution as neither are really a "good" solution as Valentin says an Arduino would struggle to meet the clock frequencies needed especially on their smaller board as well as the downsides involved in analogue-digital-analogue conversions.

I've tried finding alternative chips however most have different pinouts which would require the entire original PCB be remanufacturing to fit them and there would be uncertainty that the new chips would perform in the exact same way as the CX20084 causing compatibility concerns

 

Do we have any info on the latest version of the WM-D6C that was made around the early 2000s with a different chip? I couldn't find anything.

 

i haven't been able to find info about chip differences between D6C generations

https://data2.manualslib.com/pdf6/127/12694/1269374-sony/wmd6c.pdf?83570b1f03ea60441714c731ff51af52

this manual shows pretty nice illustrations starting at page 36 it does only show the use of the CX20084 chip, no other chip is mentioned as being able to fill its role. this is only a nicely illustrated version of the pages before it so I don't know if the later generations used different chips. surely it would increase the cost significantly due to R&D of the new chip and it wouldn't really be needed as the CX20084 would still be perfectly fine to use

 

@root32 The early 2000s D6Cs use the CX069, which was also used in the TC-D5(M). The circuit is quite different (FG amp is external for example) and would require a lot of mods (not really feasable without a new PCB).

There is no direct replacement of CX20084 indeed. The circuit itself and how it works is pretty unique compared to most other systems.
The fact that it uses FG feedback instead of just the motor current is one of the aspects. Then it can also accept an external PLL.