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Old 29th Dec 2020, 6:00 pm   #1
_Cosmic_
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Default Phillips Engineer Morse Trainer with Speaker Capacitor Problem

Hope this counts as telephony and comms..
I know lots of you have Phillips Engineer Kits.

I just received an EE8 and an A20 addon as a fantastic Christmas present(to myself ha) as I had one when I was a kid (I didn't have the add on though!).
I just built the Morse trainer B2 circuit. I got it kind of working in that when you close the circuit with the Morse key it doesn't produce a tone (just joking, bear with me..) In fact nothing. YET when I remove the 10 microfarad electrolytic capacitor that's in series with the transistor emitter and the positive rail (I think I got that right) leading to the positive terminal on the pot switch the set produces a tone when you use the key. It works fine for a about 15 seconds then starts to crackle, so of course I have to quickly turn it off in case the transistors get damaged. I'm not an electronics engineer so all I can realistically do is to go through it again to see if I have made a mistake somewhere.

I just wondered if any of the tech's still have their kits and have had the same problem or can spot a mistake on the board.
It's the first one I built since opening the box so I'm half pleased it almost works!
Does anyone else have memories of getting one of these for Christmas in the 60's like I did. Just buying it and now building the kit was very nostalgic especially as both my folks have now departed...
The image shows the capacitor disconnected to the left of the key.
Cosmic
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Old 29th Dec 2020, 6:15 pm   #2
Sideband
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Default Re: Phillips Engineer Morse Trainer with Speaker Capacitor Problem

Not wanting to burst your bubble but these kits are now over 50 years old. In that time, electrolytic capacitors will deteriorate....yes even without use.....It is also possible that the transistors (I think they are of the AC126, AC128 variety) can develop a 'tin whisker' problem which will cause shorts within the transistor.

It's unlikely there is a fault on the board. I think Philips also provided the circuit diagram in the instruction book? If so a picture of that would help. I also had the EE8 and everything worked.

You might need some replacement components.
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Old 29th Dec 2020, 6:57 pm   #3
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Default Re: Phillips Engineer Morse Trainer with Speaker Capacitor Problem

I don't know the kit - so just guessing that the A-A and B-B at the bottom refer to the position of the slide switch.
Does it work with the switch in either position?

I can't work out what that (disconnected) capacitor is supposed to do. The circuit just seems to be a phase shift oscillator keyed in the ground line and feeding the output transistor via a pot.
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Old 29th Dec 2020, 7:05 pm   #4
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Default Re: Phillips Engineer Morse Trainer with Speaker Capacitor Problem

The A-A and B-B are just where the common (+ve) return goes under the board and back on top to form a loop to hold the "bottom contact" of the key in place.

The Capacitor is just across the key to stop the course disconnect when the key is raised.

When I last made up one of my kits it worked surprisingly well but I had to clean all the wires to remove oxidation.

As Sideband has pointed out there is a better than evens chance that the Tin whiskers have got to the transistors.

Cheers

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Old 29th Dec 2020, 7:20 pm   #5
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Default Re: Phillips Engineer Morse Trainer with Speaker Capacitor Problem

A bit of emery paper to the metal strip and a bit of inspection somehow brought on a miracle. It's now decided to work like a dream. A lovely solid clear tone when you operate the key. Now all I have to do is to learn Morse code...and have a crack at the three transistor am radio.
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Old 29th Dec 2020, 7:30 pm   #6
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Default Re: Phillips Engineer Morse Trainer with Speaker Capacitor Problem

That's great news.

It was the three transistor Radio I last built and I was frankly amazed how well it worked.

I don't recall being so impressed in 1965! (which was when I got the A20).

I used one of those green sponge scourers to clean the wires it cleared the muck without removing the tinning.

Cheers

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Old 29th Dec 2020, 7:41 pm   #7
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Default Re: Phillips Engineer Morse Trainer with Speaker Capacitor Problem

Thanks guys. I just knew that loads of you would have had one of these. Yes there is a bare wire that threads underneath the key. A screw on the key contacts the bare wire when it's pushed down. I did think that the transistors might have been abused but it looks like I'm lucky with these AC126's.
The EE8 kit also has a Mullard AF116, hope that's ok too...
I didn't know about tin whiskering of transistors..I will read up about that.

Here's a couple of photos for nostalgia's sake.

I think I will have a crack at the three transistor radio next!

I remember when I first got one of these that I didn't think that the Rain and Moisture indicator was very thrilling. You were supposed to put the sensor in a plant pot and wait until it dried out I think..I ask you, who's gonna do that!

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Old 29th Dec 2020, 7:46 pm   #8
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Default Re: Phillips Engineer Morse Trainer with Speaker Capacitor Problem

Here's the theory, in the image from the booklet.
-----------------
On my new kit, registration ticket to be uploaded, the springs and bottom clips are well oxidised with a grey coating, pity they are no longer shiny..I have seen replacements on the well known auction site being sold for far too much...My set has nice shiny wire and some nice new paper clips in too!!..The am radio coil had a dry joint on one of the tabs but I soon re-soldered that.
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Old 29th Dec 2020, 8:04 pm   #9
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Default Re: Phillips Engineer Morse Trainer with Speaker Capacitor Problem

I don't remember exactly which kit I had back in my youth (also back in the 1960s) but that all looks very familiar, so may well be the same one. Alas, I parted company with mine a long time ago. I have acquired a few (later) kits since, but not one of that ilk.
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Old 29th Dec 2020, 8:13 pm   #10
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Default Re: Phillips Engineer Morse Trainer with Speaker Capacitor Problem

And here's the registration ticket. 1964.
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Old 29th Dec 2020, 8:24 pm   #11
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Default Re: Phillips Engineer Morse Trainer with Speaker Capacitor Problem

Dave you can still buy them on eBay. Its surprising really, I didnt realise how popular they are. Probably people like us remembering the good old days. I bought mine to try and help me learn electronics again in a practical way. The text books I am wading through get a bit heavy going when you are teaching yourself, they lean a lot on the arithmetical aspect of everything, which is to be expected really. In my small collection of books I have "The radio Communication Handbook" Forth Edition. Its fantastically interesting but very hard to wade through. I think is really for reference. I'd love to do an electronics course but Covid's put an end to all that for the moment. The EE kit does go into a bit of the theory which is excellent. I don't remember finding it difficult when I was around 14. ha!

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Old 29th Dec 2020, 10:24 pm   #12
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Default Re: Phillips Engineer Morse Trainer with Speaker Capacitor Problem

The two and three transistor radio's work really well. Actually I only had the EE8 kit without the add-on but a pal had the add-on so I built the two transistor set in my kit and then copied the output stage from his and added it to mine using a few scrap components and an AC128 and a speaker that I pinched out of a radio. It worked well....Christmas 1965 and I was 13 years old. The first tune I heard was 'The Toys, Lovers Concerto' on what was then the Light Program (now Radio 2 for those that are too young to remember these things)!
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