Wet 1969 ITT-KB junior battery radio

[audion_1908]

I knew this ITT-KB Junior had water damage, but was a little surprised when it arrived!

pics

[audion_1908]

What I found!

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Before


After some cleaning with an old toothbrush

[60 oldjohn]

I'm looking forwards to seeing the fully restored working set. have you set yourself a time limit ?

John.

[audion_1908]

I don't think the speakers salvageable!









A bit different from this

[ajgriff]

I'm full of admiration for the fact that you've got this far. Looks like it's been dredged up from the bottom of the ocean.

Alan

[Philips210]

Blimey! That's one of the worst I've seen. It looks as if it's been in the Thames for a good few years and has just been fished out . Only fit for the dustbin I'd say.

You're a brave man to attempt repairing that radio. The greatest problem is going to be with the IF transformers, Osc coil and aerial windings and the polyvaricon. The speaker coil is probably shot as well. I think it will need a large number of components replacing to get it working so not really viable unless you have a spare donor set to hand. Good luck all the same.

Regards,
Symon

[audion_1908]

Time limit? Lol I don't know, most of the transistors are silicon, so hopefully not to hard to find cheap subs is if the legs are rotted off and need replacement, the resistors at least visually look nearly perfect! But from long immersion in water they will either will all be good or be bad, Anyone have any idea how to get the tuning capacitor black wheel off? As I need to get to the back of the PCB for cleaning and repair, also the variable capacitor looks completely dead, so if I can unsolder and take it apart I might see if it's salvageable, I've managed to find full schematics for the radio and reviews apparently it has good performance!
does anybody have one of those cool sonic PCB cleaners?

[audion_1908]

Originally Posted by ajgriff

I'm full of admiration for the fact that you've got this far. Looks like it's been dredged up from the bottom of the ocean.

Alan

At least it doesn't have salt water damage though I think it might have been at the bottom of a pond or river for a while!
I was looking for the worst vintage radio on eBay, anyone know how far out of tolerance the resistors can be and the radio still work? As I don't really want to replace all the resistors!

It's a simple single sided PCB, and most of the tracks look ok, though some may need tinning with solder.
I forgot about the IF cans, is it best to leave them alone and just do a basic continuity test with a dvm, or unsoldier and open them? I know this is a silly project, I may have to unsolder nearly everything! Also if I do get it to work any one know where to get a cheap oval 8 ohm 0.4 watt or better speaker about 8.5 X 6cm

[Philips210]

Hi.

If it was my set then I'd remove the IFTs and Oscillator coil for inspection. Once out, the IFT screening cans are usually easily removed as in the TOKO and similar made units. I suspect a continuity test won't be enough to prove their serviceability. There's a good chance the corrosion may have resulted in shorted turns in the windings. Any damp muck and corrosion may adversely affect the Q of the transformers anyway. Many of these IFTs have an integral tuning cap in the base of the transformer. It's usually a miniature tubular ceramic type.

Regards,
Symon

[audion_1908]

The schematic shows 180 pf in each can, if ceramic tube I think the cap will be ok, the dvm test could show if they are definitely dead, I looked on eBay and transistor can coils like these can be bought for £2 each or £6 a set, I don't know how compatible they are? hopefully my ones are ok. the google pictures show the coils can be heavily varnished/waxed that could keep them serviceable.
the audio output transistors are so rusty I think they might be compromised, but the combined heat sink heat spreader is very cool, but the rust on them is scary, The rest of transistors are plastic moulded but damp may have snuck in.

These pics are after cleaning






Any one know how to get the tuning capacitor wheel off?

[Herald1360]

I'd be inclined to treat the polyvaricon as scrap and take a junior hacksaw to its shaft or you could try grinding off the rusty screwhead with a Dremel or similar.

[Lloyd 1985]

Good grief! I’ve worked on some right royal rust buckets before, but that one is by far worse than anything I’ve tried to revive!

As for removing the tuning wheel, is it not just held on in the centre by a screw? These sort normally are, but I guess the screw is unrecognisable now!

Regards
Lloyd

[audion_1908]

I found a resistor that is not in circuit due to the disintegrated band switch a 270k to a value likely to drift, and it's spot on! So the first good news! Obviously quality carbon resistors. R306

[audion_1908]

Originally Posted by Lloyd 1985

Good grief! I’ve worked on some right royal rust buckets before, but that one is by far worse than anything I’ve tried to revive!

As for removing the tuning wheel, is it not just held on in the centre by a screw? These sort normally are, but I guess the screw is unrecognisable now!

Regards
Lloyd

I can't see a screw? I have scraped at it, it's annoying I need to save the wheel but not the capacitor, I will scrape at it some more, I just want it to work I am not going to try and make it look stock

Stock new pcb


What I got


What I have after a long clean


Strangely battery anti-rattle foam is still good! I'm tempted to put it back, did a crude test on one 200uf cap, I set the dvm on 2mohm and watched it charge up, it only got part way then collapsed to nearly zero ohms, I was never going to use the original capacitors but was surprised there was any life left in the 51 year old TAICON caps! Where the caps originally quality or rubbish?

Nothing a bit of T-Cut wouldn't solve!!!

[Philips210]

Hi.

Just been up in the loft and found my ITT Junior. It has a blue case with a different speaker grille presentation but the PCB looks to be the same as yours. The IFTs are made by TOKO so these AM IF transformers may well be fairly standard. If you need to replace your IFTs and the type numbers are unreadable, then I'll try to get the type numbers off the cans in my set.

A couple of other points. Your radio seems to be missing its wavechange slide switch (well at least the metal body and plastic actuator). Also, the small trimmer caps on the board look very badly corroded.

I noticed on my radio there's a mix of carbon film and carbon composition resistors. The latter types could well prove to be out of tolerance.

Without putting the dampeners on it (pun not intended) , it's going to be a big challenge getting your set working properly and economically.

Regards,
Symon

[audion_1908]

Thanks for the offer to read the IFTs hopefully my ones are ok, the rusted trimmers didn't survive the cleaning, and all fell off! as I was scraping at the corrosion on the output transistors, T305 = BT-1 is revealed to have a hole in its head! It's the middle transistor in the three transistor sandwich and completely corroded also t306= cs1312 fell off! Most of the resistors appear to be brown Bakelite with sharp edges at the ends, a few look moulded like a modern resistor, the one I tested had Square edges and was spot on 270k.
If it's not too much trouble could I have a pic of your circuit board?

2 of the trimers are listed as 20 to 50pf but none of the other variable capacitors are listed! I have 2 different schematic diagrams for the radio, luckily the the schematic part numbers match so I can use them both together.

I have looked it up the square edged Bakelite looking resistors and they are carbon composition have a reputation of being the noisiest most unreliable most likely to drift, but my sample of 1 shows it seems to be ok, of course more testing needs to be done.

[Philips210]

Hi.

I'll bring it down from the loft tomorrow and take some pics and check the drive drum fixing on the polyvaricon.

Regards,
Symon

[audion_1908]

Thanks.