Sony TCD-D3 DAT replacement of battery BP-03

Hi,

A long story in short:
Has anyone ever tried to replace a 6V battery with two Li-Ion cells of 3.6V in series?

Here's the long story:
In my small collection I have a nice workin Sony DAT TCD-D3. I love this device, because of the fast load/unload of the tape and because the device has features for editing the Start-ID's (set, erase, renumber). The last function was not directly available in successor models TCD-D7 and TCD-D8 and was only reintroduced with the TCD-D100.

Fortunately, my device does still not suffer from the sticky rubber-surface and all labels are fine.




The device is either powered with a 9V adapter or a 6V battery (model BP-03). The battery is fixed with a kind of "bayonet fitting"

Of course the battery is dead since a long time. A few years ago there was a service in Germany, where the original cells were replaced by 5 small 1.2V NiMH 1100 mAh cells. This is a fine solution although you have to be very careful with charging time when the original power adapter is used and the playback time is very limited (less than 1 hour in reality).


Now I had the idea to use two Li-ion 18650 cells. The initial idea was, to glue the plate with the bayonet fitting direct to the battery holder and feed the unit that way. The Li-ion cells can the be removed and charged with a charger suitable for Li-Ion.
I hope, the pictures below may help to illustrate the idea (the green NiMH cells would be removed of course).

At this point I have some doubts.
The TCD-D3 has a 9V DC in and a 6V battery in.
2 Li-Ion cells in serial might have up to 8.4 V (fully charged). This might be too low for the 9V DC input but maybe far too high for the battery input.
A secure way to proceed would be to run a test by using the 9V DC input.
On the other hand, using the 6V battery input would be more "cool" because the battery and the unit would be in "one package".

Having a look at the service manual, It seems that both, DC In and battery In are using the same tracks on the PCB and that input voltage regulation/limitation is done elsewhere. From this point, even 9V at the battery Input should work?
C558, is a 10MF tantal chip (which is very sensitive to overvoltage) seems not to be a problem, because at the + side of C558 the voltage is limited to 6.3 V


Thank you for reading this and helping me out if I misses something.

I this forum there was a discussion to replace a 4V battery by Li-Ion for Sony Discmans. It would be great, if a replacement of a 6V battery with two Li-Ions would be possible.

Thanks,
Konrad /Analogtape (ok, this time is's a digital tape but still: It's a Sony )

 

Looking at the schematic, the battery and the DC in jack are in parallel so I have to assume the DC-DC converter (CP501) operates on a wide voltage range from probably below 6V (as it will have to work with those NiMH until they discharge) to 9V.
So it is very likely that this convertor is a buck-boost type, working with voltages both below its output (with 6V input the +/-7V are above its output working as a boost) and above its output (with 9V input the +/-7V are below its output working as buck).

I also see a comparator on the schematic (IC509) and one of the inputs is the DC in. This can be for the display to switch from battery to AC supply. I don't have a TCD-D3, but on the D7 and D8 the battery symbol disappears when plugged into AC supply.
So if you have a 9V battery, you will likely loose this functionality.

The capacitor C558 is not a concern as it operates on a different voltage rail and only its negative side is connected to the ground of the circuit.

By the way, what is the capacity difference between the 2 x 18650 and the green NiMH ones ? I'm reffering to the total capacity.
The 18650s have 12.6Wh/cell, so they would give a total of 25.2Wh.

I suggest to power the device from an adjustable lab supply and see where it cuts off on the lower side, but I assume it will probably work with 5.5V or even less.
On the high side, I won't go higher than 9V as it's unnecessary as even the fully charged 18650 will not have 9V.

Also as a sidenote, these TCD-D3, D7 and D8 suffer from old grease in the mechanism and it is highly recommended to clean and re-lubricate the entire mechanism in order to avoid problems.
Even if the unit appears to be working perfectly, higher friction can cause increased backtension and wear the drum quicker even if there are no symptoms.
"blank" message on display when FF (when tape is not blank) is another very common problem on this which indicates a service is needed.

 

Thank you Valentin for your reply.

Very useful and very much appreciated.
As I am still an absolute beginner in electronics, the circuit diagram is very hard to understand for me. No I feel much more safe.

The 5 green NiMH batteries are GP-110AFH type, with 1100mAh (1.32 Wh/cell) or 6.6 Wh in total. The D3 service manual specifies a power consumption of 3.6W. In reality it never reached more than 1 hour running time per charge cycle. Therefor I'm curious how long it will run with the 18650s.

When I bought this D3, the best result I achieved was a CAUTION on the display when trying to load a DAT cassette...
So you're right: There was a lot of know-how, work, material and some money to invest until the device worked perfect again. The first 3 things were provided by Paul Carrington who did an incredible job!

Thanks again!

 

At 6.6Wh in total for the NiMH, the 18650 cells have 3.8times more capacity so you should get close to 4 hours of use.
The NiMH ones seem to be rather low capacity, more modern ones being much better.
And then the power draw is pretty high at 3.6W, the TCD-D8 has a consumption of only 1.2W. I have the TCD-D8 and I'm happy with 2500mAh NiMH AA batteries in it.
In practice my TCD-D8 lasts 5 hours or more, but it is to be mentioned it never depletes the cells completely, as it's designed to work with 1.5V alkaline cells.

As for Paul Carrington, I totally recommend him for servicing these devices, which is an absolute must on all of them.
He's an expert on these DAT walkmans and will restore them to factory specs at a very reasonable cost. https://www.paulcarrington.co.uk/repairs

 

I'm curious to see how long the D3 will run in fact.
As the GP-110AFH has a dimension of only 17 x 28.5mm (d x l) i suppose that even more moderns will not have much more capacity.
Hope to be able to assemble the battery pack with the 18650 soon and also upload a picture.

I totally agree that Paul is the address for DAT. Another good address is alsoMr. Mickeleit from Germany ( http://www.datrecorder.de)
Beside of the D3, Paul also repaired also two TCD-D100 for me. I love this devices. They are beautiful and had almost all the functions of the desktop devices. In addition, they were designed for the use with NiMH batteries (they have another small battery to save time/date settings, that can be quite simple replaced).

Unfortunately this model suffers under the same problem like the cracked center gear of the WM-DDxx walkman series.
Mr. Mickeleit has posted an article on FB describing the problem.
Therefore it is only a question of time until ans TCD-D100 will stop working for good. I still hope, that one day there will be a fix like fantastic Marian did for the CG.

 

You mention that the TCD-D100 suffers from a potential broken gear of similar design to the WM-DD series (plastic molded on metal).
Do you have more info about this issue ? Wasn't aware of it, but if this is the case units with this issue are certainly worth a lot less.
Can you provide a link to Mr. Mickeleit facebook page describing the issue ?

As for a new gear, I would say we shouldn't hope too much for one as the product is too niche.
I hope the gear can be repaired and would be curious to find out more about it.

 

Et voilà.


As you mentioned, the battery indicator works not. The unit is still running after 3 hours (120 min tape LP mode).

The plastic of the original battery case has become very fragile over the years. I don't know how long it will last until the plate will break up. Also the use of the original leather carrying case is difficult.
Nevertheless, it was an interesting project.

I have not asked Mr. Mickeleit's permission to publish the link. So please google for "mickeleit dat" and klick on the fb "MCS Mickeleit-Computer-Shop + DAT Service" result. Then scroll down to an entry from 12 September 2018. The list is quite long and you may find other interesting items. Mr. Mickeleit taxes the TCD-D100 as "not repairable". Prices are rather high taking into account that this is another "clack-clack it'a Sony" device.