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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

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Old 27th Jun 2021, 4:05 pm   #41
Radio Wrangler
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Default Re: Signal generators

Hmmm

I've seen those with the Acton company name on the front, but this one like yours is blank.

It too has the mystery pot.
I can't see meter connections on yours or this one (maybe obscured behind the pins?)
This one has a selenium rectifier, yours has had a silicon diode fitted.


One valve upwards one downwards! Is that the triode with two top caps? DET20 = CV6 or something like that. Commonly ripped out of 19 sets.

My guess for the other valve would be an SP61 used as an audio oscillator for modulation.

David
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Old 27th Jun 2021, 4:17 pm   #42
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Default Re: Signal generators

The meter should be an RF level meter, but it seems apparent now that they were fitted, but they were never connected!

So, the pics show there's a double valve in there and single valve, and the layout looks like it will be relatively easy to figure out the circuit.

The previous owner has obviously replaced the old selenium bridge rectifier and put in a (single) silicon diode, and replaced the big electrolytics.

B

overlapping posts with Wrangler

At the least the black Hunt's capacitor has been replaced, so that's good work on somebody's part!
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Last edited by Bazz4CQJ; 27th Jun 2021 at 4:25 pm.
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Old 27th Jun 2021, 4:50 pm   #43
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Default Re: Signal generators

So far as I can make out, the meter was to be connected to the output of the receiver that's being aligned:

http://www.vintageradio.me.uk/workshop/sg_ins.htm

Lawrence.
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Old 27th Jun 2021, 6:38 pm   #44
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Default Re: Signal generators

Yes - I had one on those horrible thing (could not afford an Advance as a schoolboy). The meter leads just came out of a hole and were to be attached across the speaker of the radio being aligned. The meter was just an old WD transmitter aerial current meter (thermocouple) with non linear scale so only for relative movement as you twiddled.
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Old 27th Jun 2021, 6:46 pm   #45
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Default Re: Signal generators

It is slightly horrible, but don't you have the feeling that this is Real Vintage Radio Repair and Restoration?

B
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Old 28th Jun 2021, 12:39 am   #46
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Default Re: Signal generators

Quote:
Originally Posted by buggies View Post
Yes - I had one on those horrible thing (could not afford an Advance as a schoolboy). The meter leads just came out of a hole and were to be attached across the speaker of the radio being aligned. The meter was just an old WD transmitter aerial current meter (thermocouple) with non linear scale so only for relative movement as you twiddled.
Yes you must be right! there is a random hole in the back! But does it not connect at all to the circuit? or does it just measure the speakers levels separately? Also, the metre has 5 band settings but on the dial it says 1+2 and 1+3 for more band settings.... what does that mean? I wish I had a manual!

I actually found a schematic that I am yet to work out if it is exactly the same. I did briefly look and some bits were confusing. Luckily, the person who drew this diagram up told me what voltages I should expect on the valves... but not all the cap and resistor ratings... which is a bit unfortunate. Ig does specify the tubes, which I can confirm are correct. I actually couldn't locate the 1uf cap (red one) that they used on the diagram, but I suppose this could be a revised model or old one. The image of the generator was identical to this.

https://i.ibb.co/d0D9DDb/Allwave.jpg
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Old 28th Jun 2021, 2:27 am   #47
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Default Re: Signal generators

It comes down to how you view the thing.

It is an historical artefact, an example of what people did in the immediate post war years. WWII had trained a lot of people up on radio and radar, then dumped them on civvy street. Many saw the radio and fast-growing TV fields as employment opportunities. People were poor and lots of war-surplus swords were beaten into ploughshares. This signal generator is one of them. It's crude and is only just up to the job in fairly skilled hands, but many people were skilled in the day.

Look at it instead as a tool to do a job, then it isn't a very good one. More expensive test equipment might make the job quicker, but the real go/nogo difference is in the demands on operator skill. An expensive synthesised signal generator will have a front panel keyboard. Type in your wanted frequency and amplitude, select the type and amount of modulation and let it get on with it. Very little operator skill needed. With a crude signal generator and an unbuffered output which can pull it around, plus a rather coarse frequency scale, as much effort will go into fighting test gear limitations as goes into fixing or aligning the radio set.

Is it a good instrument for a beginner? No, not really. But if there is a cost limitation then it may be the only choice there is.

One of the Advance RF generators would be easier to use, and also small and lightweight. One of the little Nombrex transistor ones would be little better than the Acton one. One of Marconi Instruments' boat-anchors would be a restoration job in its own right, but a lot easier to use when it's working.

There is no single right choice. The original poster has bought a little Acton unit, and will need help in how to fix it, use it, and overcome/dodge its limitations.

David
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Old 28th Jun 2021, 9:39 am   #48
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Default Re: Signal generators

Quote:
Originally Posted by Spencervs View Post
on the dial it says 1+2 and 1+3 for more band settings.... what does that mean?
It's as it says in the instructions (Post#43)

Scale 1x2 is the 2nd harmonic of range 1.

Scale 1x3 is the 3rd harmonic of range 1.

Eg: 15MHz on range 1 equates to 30MHz on the 1x2 scale (2x15MHz = 30MHz) and equates to 45MHz on the 1x3 scale (3x15MHz = 45MHz)

In other words 45Mhz output from the generator won't be a fundamental frequency (the 15MHz will be) but will be the 3rd harmonic of 15MHz.

Lawrence.

Last edited by ms660; 28th Jun 2021 at 9:51 am. Reason: extra info
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