Late 1960's BFO

[HECTOR]

This was my very first detector. The "Golden Hunter". Hand made Japanese quality.
Would anyone be interested in helping me explore the circuit?
I was going to RE it to see if it has any valuable qualities. Maybe to use as an extra depth pinpointer or something. I can't throw this classic bit of engineering away
I've already labeled and listed the components that have ID's. A few more hrs to trace the circuit and I can make a schematic.
Anybody game?
Maybe this is a common circuit? Maybe has unique design? A bit more elaborate than the basic designs that I've seen. Look familiar? I can post more pics.

[Skippy]

I suspect one of the things that will make a full reverse-engineer job difficult is the 10mm transformer. Unless it is a 'standard' 455KHz/470KHz IF transformer (look for a part number on it, often like 'KACS12345') it will be a skilled job to RE. It could have up to three windings, and two capacitors in it.

[HECTOR]

I suspect one of the things that will make a full reverse-engineer job difficult is the 10mm transformer. Unless it is a 'standard' 455KHz/470KHz IF transformer (look for a part number on it, often like 'KACS12345') it will be a skilled job to RE. It could have up to three windings, and two capacitors in it.

None of the transistors even have a dot or line. How did they orient them?? The 10mm has no markings visible. I have a freq counter. Can we guess the value if we know the operating freq? Pretty sure the iron core transformer is a step up for audio.
Is this going to be too hard to do? Seems like it should be fairly easy.

[homefire]

The Toyko type transformer (RED) should have some Marking on the Top stamped in.

If not letters on the side.?

Easy enough to check the Transistors for Type PNP or NPN.

I bet any Audio types would work fine.

The other your right should just be a Maching Transformer for the AUdio.

[jap]

If the transformer is the sound is almost located in the old radio and is the last stage of the audio.
-For I found another problem, the second transformer(red),Frequency determines from the color!!!!!
best time.
j.

[HECTOR]

[QUOTE=homefire;155521]The Toyko type transformer (RED) should have some Marking on the Top stamped in.

Fukoku
Tsushin
No other markings.

[homefire]

Well that didn't work.

What pins are wired?

Does it have a cap in the bottom.

Red was for IF work but there are a ton of different windings it could be.

[homefire]

Looking down at the Transistors there is a flat spot. (Mounted On PCB)

Assuming the Pin out of the day Most was Emitter, Base, Collector Emitter to the Right of the Flat spot.

I played the Game Chasing those Transformers on the Sandbanks detector.

They are no longer made.

I did post a link that shown how to rewind one if your hands don't shake a much as mine.

Affraid your going to have to do some start of a Schematic before we could figure out what was going on.

[HECTOR]

Thanks for all the input!
Just ran it downstairs and put it on the freq counter. 75kHz Taken straight off the coil leads. About 1k for the audio. Tracing is about half way done. Should have a schematic ready by tomorrow sometime.
Should I desolder the ferrite core coil? Do we know enough by measuring the coil freq?
Oh, and the transistors are all identical, round, no notches, flat spots, no nothing but white paint on the bottom. Can't see clearly, might be marked on bottom. There are four of them, should be fairly easy to guess EBC or whatever.

[homefire]

Wait and see how the schematic starts to look.

[Skippy]

If you have a 'scope, it would be worth noting the signal levels at various points, particularly around that transformer, so hold off removing the 10mm tx until you have to.

[jap]

The sense of (RED)color determines frequency oscillator is available in the next to the variable condenser in the AM old radio .
-Such as picture.
***This is clear from the components he uses the AM old radio-frequency.
best time.
j.

[Skippy]

The colour of the adjuster has no meaning, it's just convenient for manufacture to have different colours, it avoids placement errors, etc.

[ivconic]

...

[Skippy]

I have a catalogue with loads of Toko transformer specifications/data. It may help in determining what type of core would be needed to reproduce this detectors inductor/transformer. This particular style of 10mm transformer is normally used at 400KHz up. I suspect the lower running frequency is achieved by use of large capacitors, maybe up to 10nF. For lower frequency use (10 to 200KHz) the transformers are physically different, having screw-threads in the can, and larger ferrite innards.