Photo-Genic

Here’s part two of the ultrasonic repair. Replacement ultrasonic resonator fitted.

Still didn’t work, strange, measured the new unit, and it’s 3.8nF, measured the old unit and its 5.2nF even though it’s marked 3.7nF.

The circuit is looking for approximately 3.7nF, so the new unit is correct. Then I noticed there’s an extra capacitor fitted to the circuit that the larger ultrasonic cleaner doesn’t have.

I’m guessing this is because there are two ultrasonic resonators in parallel, so the capacitance would have to be doubled, so I thought what the hell let’s match the other cleaner and see what happens, took the capacitor out and the thing works fine.

I guess I’ll have to experiment to find the perfect resonant circuit, but for the meantime things are okay. I’m assuming the wound coil is not the correct mH to make the circuit run properly.

Just a side note, if you want to test an ultrasonic cleaner, the best way to visually see how it’s performing is to place a piece of aluminium foil in it, and switch it on, if all is working well, the aluminium foil will be dissolved in the places where the ultrasonic cavitations are the strongest.

Okey, a bit special this one, it’s just over fifty years old, so needs a little love and no new components if at all possible. The idea is to preserve this radio as it has it’s box and instructions in mint condition.

Got the manual ready for the setup.

Careful strip down and hooked up to the test equipment.

All good to go.

Playing some classical music.

Well, the ‘Franken-Roberts’ lives, found some NOS displays that I bought years ago, because they were cheap 😀 Anyway, fitted one (after finally finding a manufacturers pdf of both displays) and bingo, it’s alive.

Repaired the psu and I think I’ll relegate it to the workshop as a background noise machine. Another job, jobbed.

Sorting out a box of valves, to try and find something, To my surprise, underneath the box I found a Sony Diskman. Even though I worked for Sony, I never actually owned one.

Honestly don’t remember ever seeing it before. Must’ve been in with the valves, and got overlooked. It had 20-year-old alkaline batteries in it, which had leaked all over the place.

Miraculously the leakage had missed the circuitboard.

Lots of cleaning up with vinegar, the contacts were back to almost perfect.

Lots of polish, plastic polish and a service and all is well again.

I’m quite pleased I now own a minty one by accident. 🙂

After it’s close call with a whole lot of leaky capacitors, the ICF-SW7600 is alive and good for another 30 odd years, hopefully more. 🙂

And here are the offending little monsters.

On the bench today, the little red radio.

And now the mammoth task of replacing two capacitors. 🙂

Okey, pickled.

And finally after setting up…

Now to find some other colours. 🙂

This one’s a bit poorly, and is suffering from the usual dodgy capacitor problem. However, it’s in a lovely condition so be ashamed to let it die.

The little round silver things are the capacitors, and are directly soldered onto the circuit board, they are filled with fish oil, yes you heard it right, fish oil, and unfortunately this leaks all over the board when these go faulty.

So, its a case of removing each one individually with two soldering irons, and then replacing them with quality replacements. This is not a job for the fainthearted, as if you try to twist these capacitors off on this type of board, you’ll damage it because the traces just lift off straightaway. Be warned, these circuit boards are very delicate.

Pop back in a few days to see how it goes…

So, the cheap ultrasonic cleaner wasn’t great from the start, it would take about five minutes to start up and when it did it was like a mouse fart. It worked for a while and was useful in it’s own way.

In the mean time I bought a larger capacity one and took this home for small jobs.

So now comes the time i need it to clean up some parts and it fails completely. Poop.

After taking it apart, it seems they are quite well made for the money, everything is shielded in the right places and ground points are well attached etc.

The ultrasonic transducer was toast, probably not that great from the start, but there you go. Also the resistors between the Base and Collector of the driver transistors were charcoal.

Which left me in a bit of a dilemma. What were the values? There was nothing on the internet and the company hadn’t lasted long enough to complain, let alone get any information from.

Then a thought popped into my head, I wonder if the other ultrasonic cleaner had a similar drive board in it. A week goes by and a trip to workshop one was overdue. To my relief, the other ultrasonic cleaner had the same board, and being a much later version had some modified and upgraded parts too.

The original resistors measured around the 30k mark, but looked like they started life in the 10k – 11k range as there was still one undamaged band left on one of them. The new beefier resistors were now 47k (five band jobbies, so yellow, violet, black, red, brown) (470×100 Ω ± 1%).

Anyway, checked everything else was ok, which it was, fitted some new resistors, and ordered a new transducer. The ones fitted in this range are 40khz @ 60watts. Just for reference.

So that’s how far I have gotten with this so far. I will have to wait for the new transducer to turn up and see how things go. Watch this space…

..or moreover, the lack of therein. Roberts radio’s seem to have particular propensity to losing these things at an alarming pace. And I have a significant amount of radios that require them. So I decided to make some…

I had to make former to place them on to finish off the surface on the top, but I think they finished up looking rather nice.

Just a quick post to show the new camouflage Roberts dab radios now in stock.

These radios have been fully refurbished, repaired, and recovered in camouflage material. And are now available in the shop.