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ITT Radio Cassette alarm CCR 300

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ITT Radio Cassette alarm CCR 300

Post by crackle » Mon Apr 25, 2016 11:04 am

This has just arrived to be added to my ITT collection,
ITT CCR 300.jpg

it is a similar style to the stereo version SCR 200

The clock display has a few segments not working, I wonder where or if you can still get these.
clock display.jpg

Also I found one of the push button click contacts floating around in side the case. It has fallen out of its circuit board along with its other pair because the sellotape holding it in place has gone hard and fallen off.
So I need to find another click pad as well.
push button.jpg

Can anyone please help or suggest a source for the parts.

Thanks
Mike
Last edited by crackle on Mon Apr 25, 2016 11:13 am, edited 1 time in total.

 
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Re: ITT Radio Cassette alarm CCR 300

Post by PYE625 » Mon Apr 25, 2016 11:11 am

An interesting gadget to play with when it wakes you up :bba

A trawl on ebay or car boot sales could yield a suitable donor for the click pad.

 
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Re: ITT Radio Cassette alarm CCR 300

Post by Lloyd » Mon Apr 25, 2016 7:40 pm

Hi,

If you have the patience, you can replace the dead sections LED's with SMD LED's, very fiddly, but it does work! I have successfully repaired and LED volume level meter, and a CD player display this way.

Also, a while back I saw some green LED clock displays for sale, I'll see if I can find the listing if it's still active.

As for the click pads, some other cheapo clock radio's use them too! I have an old Alba one somewhere with the same selotaped on click pads.

Regards,
Lloyd.

 
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Re: ITT Radio Cassette alarm CCR 300

Post by crackle » Mon Apr 25, 2016 8:35 pm

The main problem with the led display was corrosion on quite a few tracks. Whilst mending these I think I damaged some very fine wires which were connecting one half of the led to the other pad. They were not protected and I didnt see them when I first started handling the board. My eye sight is quite poor now for this fine work.

I found this, not an exact match but would be better than the current one.
http://www.ebay.co.uk/itm/Quad-LED-Disp ... 3641.l6368
Mike

 
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Re: ITT Radio Cassette alarm CCR 300

Post by crackle » Tue Apr 26, 2016 7:03 am

I have ordered the new LED display mentioned in the last post. It is almost the same height but the width is less. But now I have looked at the drawings closer I have doubts as to whether I will be able to use it.
The new display appears to have 7 anode connections common for all the sections of the 4 digits. I dont see how it can display different numbers on each digit.
new clock display.png


Whereas the ITT one has separate anode connections for each segment LED.
ITT clock display.jpg

Can anyone please shed some light on this, and help explain to me how the new display would work and maybe even how it would wire up.

I am beginning to think the only option would be to solder in some SM LED's as suggested by Lloyd earlier.
But I am not sure where I can get some that are small enough. All the available ones seem to be "ultra" bright types. I need fairly low power ones and they need to be not much more than 1mm across.

Thanks
Mike

 
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Re: ITT Radio Cassette alarm CCR 300

Post by crackle » Wed Apr 27, 2016 12:12 pm

Today I bought an old Morphy Richards radio alarm clock with a very similar LED dial but unfortunately red.
I have relieved it of a push button contact so that problem is now fixed.
The display is not pin compatible with the ITT one, and again I am confused as to how it can work and light individual LED segments when they are paired together.
display compare.jpg


Mike

 
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Re: ITT Radio Cassette alarm CCR 300

Post by Cathovisor » Wed Apr 27, 2016 12:26 pm

I recall those click pads were used in the old Thorn TX10 remote controls...

 
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Re: ITT Radio Cassette alarm CCR 300

Post by Lloyd » Wed Apr 27, 2016 7:04 pm

I don't know if it applies to this type of clock radio, but I remember reading about how some displays are multiplexed to save on connections to each individual LED, so all of the segment cathodes are connected together, but the anodes left as individuals, or something like that anyway! I know that when I made my own LED clock it ended up with about 40 odd connections to the display! If you can find the number off the top of the clock chip, then googling it might bring up a datasheet which might explain how it goes about scanning the display.

As for replacing the individual LED's, I did manage to find some really tiny ones, and I might still be able to find the eBay listing for them. I couldn't find the listing for a whole LED display that I mentioned before, I guess they sold, or just stopped listing them.

Found the LED's I bought! http://www.ebay.co.uk/itm/SMD-SMT-LED-0603-0805-1206-White-Red-Blue-Green-Yellow-Orange-Pink-WarmWhite-U-V-/321604978839?var=&hash=item4ae1268897:m:mK-_HAhdV5hXYasieTRcXPg I bought the 0603 type in green. I still haven't used them yet, so can't say how bright they are. I have a whole display to do with them!

Regards,
Lloyd.

 
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Re: ITT Radio Cassette alarm CCR 300

Post by crackle » Wed Apr 27, 2016 9:38 pm

Hi Lloyd
Thanks for the link, I have ordered 50 each of the middle and larger size.
It will be a massive challenge for me to solder them in, I have not worked with surface mount components before. I plan to tin the pads leaving a reasonable layer of solder then hold the LED on in the correct position and heat the pad again.
Any more advice is welcomed.
Mike

 
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Re: ITT Radio Cassette alarm CCR 300

Post by rob t » Wed Apr 27, 2016 11:04 pm

I know there are probably a hundred reasons not to do this but i have to resort to a dab of super glue on the board and place the components with a pair of tweezers .
i also found it easiest to use an iron bit with a point.
years ago when i used to rebuild the psu in pace set top boxes i used to use a match stick to hold the component then with solder on the iron tack one end. properly solder the other end the make good the first end.
Rob T

 
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Re: ITT Radio Cassette alarm CCR 300

Post by jjl » Thu Apr 28, 2016 10:32 am

Mike

The Kingbright and Morphy Richards displays are indeed multiplexed as Lloyd stated. The idea is that each digit is lit in turn by presenting the 7 segment bits and then applying power to the common connection. This repeats many times per second to trick the eye into seeing a steady display. This simplifies the connection between the clock IC and any driver components and the display.
The disadvantage is that the LEDs are continually being switched with square wave signals which generate RF interference at harmonics of the switching frequency - not what you need in a low cost AM radio where filtering the display drive signals and / or screening the clock electronics and its display would add significant cost. As a result, some LED clock radios drove each display segment directly and didn't multiplex the digits.

John

 
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Re: ITT Radio Cassette alarm CCR 300

Post by crackle » Thu Apr 28, 2016 11:03 am

Hi John
Thanks for that explanation I understand now. So neither of the replacement ones I got are ever going to be compatible with the original ITT one, good job they are very cheap.
Just as well Lloyd found the link to the miniature LEDs, it looks like they will be my only hope of fixing this display.
Cheers
Mike

 
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Re: ITT Radio Cassette alarm CCR 300

Post by crackle » Fri Apr 29, 2016 4:11 pm

The little green LED's arrived and I have soldered in one of each size just as a comparison test. They are not bright enough at 2 volts, so I have just ordered some yellow ones which appear to work at a lower nominal voltage of 1.8 volts, as opposed to 3.1 volts for the green ones.
Mike

 
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Re: ITT Radio Cassette alarm CCR 300

Post by crackle » Tue May 03, 2016 8:12 pm

This has been the most difficult repair I have done to date. Not so much from the technical point of view but the physical difficulty of soldering the tiny little LEDs onto the circuit board.
It is all done now and working 100%, not exactly the original green but this rather nice soft yellow will have to do.
new led display.jpg
It is not the neatest of SM soldering, but they all work
new led display 2.jpg

If you remember the green LEDs that I originally bought needed a higher voltage than the clock could supply and they barely lit at all. The yellow ones seemed the only alternative and they are better than having 50% of the clock display segments not working.
ITT_CCR300_cassette2.jpg


Mike

 
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Re: ITT Radio Cassette alarm CCR 300

Post by Lloyd » Tue May 03, 2016 9:08 pm

Hi Mike,

Well done fixing the display! Those little SMD's are horribly fiddly, I've seen some in our stuff at work which look about the same size as a grain of sand, I don't fancy having to change any! I didn't see the original shade of green, but from your photo's the display looks good. At least it works now! Quite a nice machine :thumb

Regards,
Lloyd.

 
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Re: ITT Radio Cassette alarm CCR 300

Post by marc » Tue May 03, 2016 9:15 pm

That's certainly an impressive repair and even if the colour is not quite right it still looks very good on the completed display.
Great job ! :aad

Marc.

 
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Re: ITT Radio Cassette alarm CCR 300

Post by crackle » Tue May 03, 2016 9:33 pm

Thanks guys, it was rewarding to get it all working again.

Mike

 
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Re: ITT Radio Cassette alarm CCR 300

Post by Michael Watterson » Wed May 04, 2016 5:43 pm

Amazing!

 
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Re: ITT Radio Cassette alarm CCR 300

Post by crackle » Wed May 04, 2016 8:59 pm

Here is a photo I took of the radio before I took it apart and made matters worse.
before.jpg

The original fault was about 5 segments not working, caused by corrosion of the copper tracks. During the repair to the tracks I managed to change this to about 6 segments not working due to accidental damage to the ultra thin whiskers connecting the anode of the LED to the + pad. It was so thin that I did not notice it, let alone that it was not protected with a cover of epoxy.
original LED.png
the arrow points to the thin whisker of the anode connection
original LED.png (86.71 KiB) Viewed 1743 times


The LED's I finally used were the middle size in this table. 2.0mm x 1.25mm
LED Spec.png


Trying to handling the LEDs with tweezers to place on the pads was probably the most frustrating part. It seemed every time I touched one to pick it up, it acted like a tiddly wink counter and jumped like a demented flea, always landing upside down and the wrong way round so I had to turn it to the right orientation again to pick it up in the tweezers..
new LED.png
new LED.png (84.46 KiB) Viewed 1743 times

Once the LED was positioned I held it in place with the smallest jewellers screwdriver pressing on it whilst I attempted to heat the each pad with a fine pointed iron tip to melt the pre-tinned solder.

Mike

 
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Re: ITT Radio Cassette alarm CCR 300

Post by Michael Watterson » Wed May 04, 2016 10:47 pm

I have a vacuum tweezer and about 10 kinds of regular ones to suit different SMD. I use a regular 2mm to 3mm chisel bit used for regular soldering so as to reflow faster.

It certainly needs a magnifying lamp.
My professional friend that assembles 2GHz to 400GHz circuits uses a low power wide field binocular microscope designed for SMT work.

I'm impressed.

PCBmill03122008.jpg

Milling a PCB for RF SMD, in my job back in 2008. It's 0.8mm PCB and the big squares are capacitors. There are "inductors" too. The other side is milled too.

Some SMD (400MHz to 2GHz) VCOs I did on Veroboard compared to an 800MHz Minicircuits VCO module
vco_modules.jpg

On the bottom left, the coil is a thin vero track as a stripline inductor. The reverse of all the veroboards is copper foil soldered to all the 0V pins and cut away at other pins. It's a 6GHz transistor with SMD varicaps, capacitors and resistors, apart from the one obvious ordinary one.

I got a load of SMD LEDs; red, amber, orange, yellow, green (two shades), cyan, blue etc to make "magic" eye type devices. Never got round to it

 
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Re: ITT Radio Cassette alarm CCR 300

Post by davegsm82 » Fri May 06, 2016 5:28 pm

I just fished a couple of alarm clock LED panels out of some junk I was binning and have checked them but they are;

A) Red
B) The same pinout as the one in the bottom picture of your pin-to-pin diagram near the top of the thread.

Congratulations on the repair though.

If I may add to JJL's description of how these things work;

The multiplexing is actually done at 50HZ for good reason, the 2x commoned cathodes (alternatively they can be anodes in some designs) are connected to both ends of a Centre tapped mains transformer, one of the ends also goes to a special pin on the clock chip.

When the mains goes negative cycle (in this example) the clock chip detects this and outputs the appropriate segments for that half of the mains cycle and the LED's connected to the negative going side of the transformer all illuminate, meanwhile the LED's on the positive going side are thusly prevented from illuminating. On the next half of the cycle the exact opposite happens and the whole thing continues for ever and ever.

As well as using the mains to sync the display, it's also used as the clock source, as per older mains clocks with synchronous motors :aad And as such, the clock chips usually have a pin dedicated to 50/60Hz switching for UK/USA markets.

Take a look at the following interesting link where the author tears down and builds another clock (in a later posting).

http://blog.tynemouthsoftware.co.uk/2012/12/led-clock-part-2-teardown.html

Dave.

 
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Re: ITT Radio Cassette alarm CCR 300

Post by crackle » Sat May 07, 2016 7:48 am

Hi Dave
This must be an early version of an LED clock and display as each LED is driven separately, although this is not shown clearly in the circuit diagram. But as you say it looks like the clock does get its time source from the AC mains rather than an independent crystal..
clock circuit.png

Mike


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