Please don't ban me!

[joebog1]

I once made the mistake of making a "neat " wireless from a ( then Taiwanese ) radio.
Straightening all the ceramic disc capacitors completely detuned the radio.
Take a picture and DO NOT move bits what dont need moovin. !.

I worked for a company that imported hundreds of radios in the 1970's, that had "that contruction ".
Your test to work for the company was to get one working correctly.
It was a "many band " radio, that was essentially an IF strip with "many ", RF stages dangled off the input to the said IF.
FRom memory it was AM plus three short wave bands, plus aircraft band in two ranges. BUT it was AM, no FM as Aus didnt have FM back then.

It was affectionately called a "sh*tbox " radio.

Joe

[Mike Watterson]

   
Basic ways a ferrite rod aerial connects
1: FET or valve input.
2: bipolar transistor or old radio IC. Might use four wires.
3: AGC to valve or FET is usually decoupled at RF by a capacitor.
4: AGC to BJT or IC is usually decoupled at RF by a capacitor.

Not shown is the ZN414 IC. It's a variation of 3.

1: Could be a crystal set with crystal, ceramic or 4K Ohms headphones.
2: Could be a crystal set with 600 Ohms if you want more Q at expense of volume.


Just wire the LW coil from any transistor set as per the MW coil, via the bandswitch. If it needs to be version 4 rather 2 simply overwind 20 turns.

Peak at 198 kHz by moving coil in/out at end of rod. If it's not peaking on the rod then it's too few turns. If too much needs to extend past the end, then it's too many turns, but if it gets 252 kHz and 198 kHz then don't worry.

It may be be possible to connect it up without taking off scale cord etc.

Typically any external aerial uses about ten turns on main ferrite.

[boater sam]

Thanks again Mike.

I have some old Ferrite rod aerials somewhere, its just finding them that will tax my brain.

I'll get the LW back and then move on to the FM.

Sam.

[Mike Watterson]

What I meant on my last post is that most ferrite rod aerials for transistor sets are type 2 and you likely need type 4 if the IC outputs AGC to AM "RF in" via the coil.

[Mike Watterson]

Any progress Sam?

[boater sam]

Any progress Sam?

Got a bit waylaid of late.

Boat mechanicals needed a full service, the battery charger failed for the 3rd time in a year, credited u/g  so a new (different)  replacement one fitted, then the inverter failed so that has had to be replaced.

I will get back to it next week, I hope!

Thanks for asking.

[boater sam]

I searched for my stock of ferrite aerial assemblies. Found some too, but none would fit on the ferrite in this set.
So taking Mike's excellent advice I wound a new long wave coil, 240 and 24 turns, with some old single cotton covered wire I had lying around.  Just random wound like the original.
Fitted it in the set, and by a process of elimination and much trial and error got the connections correct, hurray, Long Wave Works!
I still could not work out where the connections go in relation to the chip, its wired nothing like the Thomson diagram I found.
I don't think its the same chip. Impossible to be certain as I still have not seen the printed circuit side of the board.

No FM though and that may be a real challenge. Just a background hiss, no trace of a program

[Mike Watterson]

Great!

Well, the FM only uses the chip for IF. Likely the VHF LO coil got moved/bashed a bit, maybe RF coils too. You can't connect direct, but the LO does leak out the aerial in, so you can use a 76 MHz to 120 MHz set to sniff LO. Likely 10.7 IF though 6.5MHz has been used. Possibly LO is 10.7 below RF so might be 76.8 to 97.3 for 87.5 to 108. If so tube the DUT to 100 MHz and a 2nd working set should get a signal at 89.3. A set with tuning meter, or put DVM on discrimator helps. Tune around on test radio to find LO from your faulty set.
Compressing LO coil lowers frequency.

Obviously a spectrum analyser makes it easy. The transistor nearer aerial will be buffer/preamp and 2nd transistor is LO, feeding an IFT feeding IC.

[boater sam]

Great!

Well, the FM only uses the chip for IF. Likely the VHF LO coil got moved/bashed a bit, maybe RF coils too. You can't connect direct, but the LO does leak out the aerial in, so you can use a 76 MHz to 120 MHz set to sniff LO. Likely 10.7 IF though 6.5MHz has been used. Possibly LO is 10.7 below RF so might be  76.8 to 97.3 for 87.5 to 108. If so tube the DUT to 100 MHz and a 2nd working set should get a signal at 89.3.  A set with tuning meter, or put DVM on discrimator helps. Tune around on test radio to find LO from your faulty set.
Compressing LO coil lowers frequency.

Obviously a spectrum analyser makes it easy.  The transistor nearer aerial will be buffer/preamp and 2nd transistor is LO, feeding an IFT feeding IC.

Got all that. It looks like 3 transistors in the FM front end.  Thomson diagram shows an oscillator module feeding into the chip, I think this one is different.
There is significant damage around the oscillator coil and the nearest transistor. I have straightened out the transistor legs, there was a short there. There was a coil spread out flat on the board, it had obviously been stood vertical originally as it was full of wax that sort of went back to shape as I stood the coil up.
This board is horrible, its a shame because the cabinet is very good and soundly made. Would be much better with a valve set in it!
Thanks for the help so far.

[Mike Watterson]

Look at coil in a working transistor set.
Since the tuning caps are nearly standard, the coils are too! Maybe poke to shape with a broken trimming tool, knitting needle or crochet hook wiggled up the inside. Melt off the wax first.