Please don't ban me!

[Mark Hennessy]

Here is an internal image: https://www.radiomuseum.org/images/radio...761072.jpg

That's from Radiomuseum.org, the one publicly available to all from this page: https://www.radiomuseum.org/r/unknown_sp...d_rep.html - logged in users can access a slightly larger version of the image, but it doesn't really add a huge amount.

Sam, please feel free to upload a better image of the internals if you can - I'd be interested to see a bit more detail.

DSP based? My first thought went along the lines of "not enough pins" as the DSP chipsets I've seen are much bigger than 16 pins. But that prompted me to have a look around, and I stumbled across this one: https://www.skyworksinc.com/-/media/Skyw...25-A10.pdf - not saying this is what's being used here, especially as it's quite a bit newer than the radio, but it does demonstrate that 16 pin DSP solutions are available. Whether they were available - and cost-effective - when this radio was designed in an interesting question...

Our best hope is that someone recognises the PCB - it must have been used in other sets...

[Mike Watterson]

I bought a Dealz brand (Irl, Spain, PL, UK=Poundland) radio for €10 that's about 16 pin DSP. Ferrite rod for MW and no other tuned parts. Works better than I thought it would on 5.9 MHz to 18 MHz SW and on MW. Also BT speaker mode and USD/SD card playing.

Some years ago I bought a Tesco World Band radio very cheap and it proved to be 10.7MHz & 455 kHz IFs superhet. I bought another a few months later to give to someone and it had dire whistles on LW & MW. I opened it too and the "tuner" was a polymer pot. No tuned circuits and the part number visible on the DSP chip. Something like 16 pin SMD. Same happened with the Tesco "Kitchen" Radio, a nice size mains battery cheap superhet. I took the next one back as it was same whistlely on MW & LW DSP chip.
No difference on rear model numbers.

So I was amazed at the Dealz model that the MW & SW works well. No LW, unless there is a pin to switch. The Dealz model also has some other features and is rechargeable.

[Mike Watterson]

That's from Radiomuseum.org, the one publicly available to all from this page: https://www.radiomuseum.org/r/unknown_sp...d_rep.html - logged in users can access a slightly larger version of the image, but it doesn't really add a huge amount.

That's certainly a very old superhet, IFTs rather than ceramic filters, so maybe 1980s or earlier design. Likely ANY LW coil of similar era will work. With 3 or 4 wires. If only two wires then add 10 to 20 turns to feed the IC/Transistor. Possibly very generic Asian PCB. Even looks like volume control can be on the  PCB.

I'd add pics of DSP cheap radios but Attachments aren't uploading.
Edit: Oh it did!
Dealz 2021 model bought in March 2022

[boater sam]

I have been digging in the net. Sometimes the information you need is buried deep.

The site     https://www.spartonradios.com/566.html    shows the retro reproductions of the original 1936 Sparton Bluebird.

One is noted as  "Thomson"

Now, the Radiomuseum shows the back of a Thomson Bluebird set. 

  https://www.radiomuseum.org/r/unknown_sp...d_rep.html

The back panel is missing from my set, but apart from it not having a tape player it is the same set. I will be able to recreate a back panel if I can sort the electronics.

Detection continued and I have found an applications sheet for SGS Thomson using the TDA1220 B chip.

https://pdf1.alldatasheet.com/datasheet-...A1220.html

I am assuming it is the same Thomson. Am I correct?

I have not compared that circuit to the set yet but there are many similarities. The sheet does not show a long wave aerial coil. But there is a double pole double touch slide switch for the 3 wavebands so it should be straightforward to graft in a new coil. Or one salvaged from an old ferrite aerial of which I have lots.

The IF transformers and the 2 transistors are at first glance the same. The AF amp chip is a known item.

So hopefully this is the circuit diagram, yippee!

Given a bit of time I may be able to make some progress.

[Mike Watterson]

Yes, on AM/FM superhet ICs there is just a simple switch added to pad tuning cap and add the coil. To an extent you can change the extra cap larger if the coil is lower inductance and vice-versa.

I've actually got or had a radio with that IC. I had the datasheet already.
For MW Pg 11
1 & 2 is 106 turns
3 & 4 is 7 turns

So for LW about 210 turns = x4 inductance which would be only reduction to 400 kHz ) and also padding capacitor to lower frequency more and reduce tuning ratio. So possibly 250 to 300 turns. secondary would be about 14 to 20 turns.

IC Pin 2 is AM in (from smaller winding via switch. IC pin 4 is AGC so MW & LW secondary coils can be common
One side of tuning cap is to common/OV, the other side should go to coil primary of LW or MW via switch. One end of each primary coil goes to common/OV>
See page 9.

You can put a three way switch and do SW band too. A trimmer in series with tuning capacitor rather than to 0V. Maybe 20 turns to 5 turns on a small ferrite and capacitor to FM aerial. A suitable small capacitor between FM aerial and L1 would block SW and not affect VHF. Would work to 30MHz with suitable cap and pair of coils.

[boater sam]

        Had the 16 Dip chip under the microscope today. Engraved on it is I think X1A604P   7K. I have not found this in any reference list.

There are 3 transistors, two NPN   9018 which I think are in the FM front end and a 9014, maybe, its not clear, close to the audio amp chip.

The picture of the remains of the long wave aerial coil shows why I cannot reconstruct it.

I will have to compare the pcb with the Thomson data sheet.

[joebog1]

Well, Sam, I think you are expecting a little much from your little electric wireless.
After all it was built in a cave, with lighting provided by candles.
You can see where the wax has dripped onto the assembly.
Perhaps it was soldered with a piece of wire held in the candle flame to "heat it up ".

I would suggest that coil for long wave was wound on a treadle sewing machines bobbin winder!!.

:-)

Joe

[radioman]

Regarding the identity of the 16-pin AM/FM radio IC - one I've seen before is the TA7640 and it's clone the KIA7640.
It might be a variation of this...

Andy

[boater sam]

Regarding the identity of the 16-pin AM/FM radio IC - one I've seen before is the TA7640 and it's clone the KIA7640.
It might be a variation of this...

Andy

Thanks for that info. Its another possible circuit I can plot around and compare with the pcb.
Sam.

[boater sam]

Well, Sam, I think you are expecting a little much from your little electric wireless.
After all it was built in a cave, with lighting provided by candles.
You can see where the wax has dripped onto the assembly.
Perhaps it was soldered with a piece of wire held in the candle flame to "heat it up ".

I would suggest that coil for long wave was wound on a treadle sewing machines bobbin winder!!.

:-)

Joe

It is a disgustingly badly made item I'll grant you.

Wax everywhere, cock-eyed components, even some of the IFTs.
As for the coil winding I think you could be correct!

A redeeming feature, its not lead free solder! 

A further niggle, to get at the print side of the board to work out the circuit or actually fix the thing, I will have to remove the pointer, tuning scale and the cord drive which is quite complicated and all plastic bits. I had enough trouble just getting the control knobs off, they were glued on.