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Old 17th Jul 2020, 9:37 am   #1
newlite4
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Default Retro Signal Tracer

I had been wanting to make my own signal tracer for some time to go alongside my Heathkit IT-12 and Taylor model 22. The opportunity arose when I picked up a non functioning Tesco Retro DAB radio for a few pounds at the car boot three weeks ago. This would form the basis for an early sixties style instrument which would complement my existing signal tracers.
The chassis is angled within the shallow case to allow more top surface area and to assist cooling. The internals of the plastic case were carved away accurately to allow easy installation of the chassis.
The circuit is fairly straightforward using an ECC83 as signal pre-ampifier and EM84 magic eye driver and an EL84 as a simple audio amplifier. AF and RF inputs are via separate sockets to avoid using a changeover switch. One of the two speakers was retained for use, the other was removed to allow the fitting of the mains transformer.
In use the EM84 gives a bright easy to view display and the audio output from the 4 ohm/5 watt speaker is more than adequate.
By its nature the instrument is quite compact and is easy to store on a shelf where it looks rather like another early sixties valve radio.
Neil
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Old 17th Jul 2020, 9:53 am   #2
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Default Re: Retro Signal Tracer

Now that's one upcycling project that was well worth the effort, lovely stuff Neil.
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Old 17th Jul 2020, 10:07 am   #3
newlite4
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Default Re: Retro Signal Tracer

Thanks John, yes I feel it was a project well worth doing. There are many retro inspired consumer goods at the car boots these days many of which no longer work so the raw materials are readily available to make original looking valve based test gear and radios.
Neil
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Old 17th Jul 2020, 2:03 pm   #4
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Default Re: Retro Signal Tracer

Very nice job Neil, I like it. Compact, useful & bench sized. I can't think of a better way to up cycle a DAB radio. That'll learn it!
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Old 17th Jul 2020, 2:47 pm   #5
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Default Re: Retro Signal Tracer

Smashing project with an excellent result. I love it.
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Old 17th Jul 2020, 3:15 pm   #6
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Default Re: Retro Signal Tracer

Excellent Job,
As has been said, a great upcycling Job, and a better use than the original one.


I couldn't help notice the Bambinetta Radio in the Photo.

I inherrited the exact same Radio (In Red, but now Pink).

I remember my Mother listening to the Archers every week on it.

Must get round to seeing if it still works.



Ian
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Old 17th Jul 2020, 5:47 pm   #7
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Default Re: Retro Signal Tracer

Yes, unusually it looks as though the Tesco DAB was modelled on the Bambinetta. Bambinettas are quite nice little radios but the outer shell case tends to split after some years and they are a bit squeeky having a very simple circuit design.
Yes, get that DAB nonsense out of that nice case and build something sensible into it , I couldn't agree more.
Neil
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Old 22nd Jul 2020, 5:45 pm   #8
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Default Re: Retro Signal Tracer

Great job! I am equally impressed that you found a car boot to go to. It's pretty quiet on that front up in the NW, as far as I know.
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Old 24th Jul 2020, 6:42 pm   #9
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Default Re: Retro Signal Tracer

Hi Neil,

an interesting little project which I would like to copy. Can you confirm that the value of the resistors on the anodes of the ECC83, pins 6 and 1 are 15k and 10k respectively? The drawing is a little unclear.

Many thanks
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Last edited by eddie_ce; 24th Jul 2020 at 6:42 pm. Reason: Typo
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Old 26th Jul 2020, 4:14 pm   #10
newlite4
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Default Re: Retro Signal Tracer

Sorry for the late reply, just dipped back in to this post. ECC83 pin 6 is 150K and pin 1 is 10K. The car boots around here started last month, but bad weather has left them a little patchy.
Neil
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Old 26th Jul 2020, 4:25 pm   #11
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Default Re: Retro Signal Tracer

Thank you Neil
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