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Old 22nd Aug 2017, 8:24 am   #1
bobskie
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Default Advance Signal Generator Model E2

Hi. I was recently given one of these from a forum member (thank you!) and I'm wondering how to actually test it out, I don't have access to an oscilloscope or test leads for it. Could I use a radio to pick up the RF? I need to replace the mains flex and have a check inside before switching it on, I assume using a dim bulb tester would be a good idea but what wattage of bulb? Thanks for the help,

Cameron
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Old 22nd Aug 2017, 10:13 am   #2
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Default Re: Advance Signal Generator Model E2

Hi Cameron,

Hopefully you will hear something as that's what this signal generator is for

There are several threads on the repair of these, treat it as you would when you perform initial checks on a valve radio. I always use a 60 watt bulb in my lamp limiter.

If it's not been changed, the Atten. RF (Radio Frequency) output should be by way of a Belling-Lee or 'TV' socket, Poundland sell a TV co-ax cable, just strip the end of one plug and use that or find some proper co-ax and plug and make your own lead up. Heed the warnings about putting a capacitor(s) in series with the output lead before you attach it directly to the radio via the Atten RF socket.

I assume this is your first signal generator so simply put; Set the E2's modulation to Int, select range 'E' and set your radio to MW. Put your output co-ax near the radio and tune the radio to around 800 kHz and tune the E2's dial to around 800 kHz and you should hear a whine. The strength of the 'whine' is controlled by the Voltage output control and the Multiplier control. Now turn the Internal Modulation to EXT/CW and the whine will disappear. The CW (Carrier Wave) is still there but because it is now unmodulated with an audio frequency you won't be able to hear it. Turn the modulation back on and check some other frequencies.

The AF (Audio Frequency) output is for testing the output stages of a radio, if you were to connect a small speaker to that socket you'd hear a tone.

Cheers - Andrew
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Old 22nd Aug 2017, 1:37 pm   #3
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Default Re: Advance Signal Generator Model E2

Thanks for your help, I have opened it up and it's fairly clean inside. I can only see one electrolytic capacitor and there are two on the schematic. Also someone has replaced a capacitor which goes across the small transformer (?) with two 0.01 uF caps.

Cameron
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Old 22nd Aug 2017, 2:07 pm   #4
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Default Re: Advance Signal Generator Model E2

Hi Cameron,

Yep, these are pretty airtight cases so you'd expect it to be relatively clean. I'm at work so can't check but that one electrolytic can you see has two 16uF inside from memory and there should be two 0.05uF capacitors on the oscillator output transformer. Yours are definitely 0.01uF? These could do with being 1kV rated components whatever they are.

Good luck in getting it going, these are very useful signal generators and as you've probably read, stay within their calibration very well.

Andrew
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Old 22nd Aug 2017, 2:16 pm   #5
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Default Re: Advance Signal Generator Model E2

Turns out they are 0.1uf(I wasn't in the workshop at the time of posting) There is a capacitor I find slightly confusing, it's rated at 0-25uf. Is it like that just to include tolerances?

EDIT - I have checked through my capacitors and I have 0.047uf ceramic caps rated at 2000v and polyester rated at 630V. Would the ceramic be ok to use here? They are not as stable so could they cause issues in this more sensitive instrument?

Cameron

Last edited by bobskie; 22nd Aug 2017 at 2:30 pm.
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Old 22nd Aug 2017, 6:17 pm   #6
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Default Re: Advance Signal Generator Model E2

Well I replaced them with the 0.047 uf ceramics and along with a new mains cable fired it up. The radio makes a high pitched noise which stops when switched to c.w ext and doesn't appear to be broadcasting any signal. When the power is switched off the tone rises rapidly then of course stops. Could this be caused my my capacitor replacements? I also tried a belling Lee connector but it doesn't fit, that was my first thought when I saw it but no luck. It does fit into the full RF and AF sockets but I don't think the centre pin reaches the connector inside.

Cameron
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Old 22nd Aug 2017, 7:02 pm   #7
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Default Re: Advance Signal Generator Model E2

With those capacitors fitted correctly the AF oscillator frequency should be approx. 400Hz.

With the Mod. (modulation) switch switched to Int. (internal) the carrier (the RF signal) is modulated by the AF oscillator (400Hz)

With all things working ok and the receiver tuned to a clear spot (no radio transmissions) and the signal generator adjusted to that same frequency you should hear the modulation tone (400Hz) Switching from Int. to CW/Ext. removes the 400Hz modulation from the carrier and the carrier is now just an unmodulated Continuous Wave (CW) and the frequency tuned to previously will just sound silent from the receiver's loudspeaker if the signal pickup is strong enough, if the signal pickup is weak then you will hear the usual atmospheric background noise coming through.

EDIT: 400Hz sine wave:

https://www.youtube.com/watch?v=33qV3d3U0q4

Hope that helps.

Lawrence.

Last edited by ms660; 22nd Aug 2017 at 7:08 pm.
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Old 22nd Aug 2017, 7:19 pm   #8
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Default Re: Advance Signal Generator Model E2

I wrote the radio makes a noise but I meant the signal generator, unfortunately I can't edit for some reason. I don't get any sound on the radio itself. Very odd.

Cameron
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Old 23rd Aug 2017, 10:58 am   #9
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Default Re: Advance Signal Generator Model E2

You should be able to find a manual and circuit diagram on line. I converted the connectors to BNC on mine (to keep the test lead rail under control ) and use a frequency counter connected to the 'full RF' output. It's reasonably stable when warmed up for an hour or so. A higher ratio on the slow-mo drive would be useful .... maybe a future mod.
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Old 23rd Aug 2017, 11:31 am   #10
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Default Re: Advance Signal Generator Model E2

Quote:
Originally Posted by bobskie View Post
I wrote the radio makes a noise but I meant the signal generator, unfortunately I can't edit for some reason. I don't get any sound on the radio itself. Very odd.

Cameron
Where exactly is the noise (audio) coming from within the SG?
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Old 23rd Aug 2017, 3:02 pm   #11
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Default Re: Advance Signal Generator Model E2

I just tried it again and tried to hear where the noise is coming from but I honestly can't tell, it's fairly loud and in such a small area I can't pinpoint it. I will get a video later perhaps the microphone will make it more obvious, and you will also be able to listen.

Cameron
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Old 23rd Aug 2017, 3:11 pm   #12
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Default Re: Advance Signal Generator Model E2

Have you tried connecting a speaker to the audio output socket to prove the modulation oscillator is working?
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Old 23rd Aug 2017, 3:18 pm   #13
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Default Re: Advance Signal Generator Model E2

The noise might be the modulation oscillator coil itself- it's not unusual for a high-level wound component like this to "sing" somewhat in use, though the sound can seem mysterious, hard to place and all-pervading.
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Old 23rd Aug 2017, 4:48 pm   #14
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Default Re: Advance Signal Generator Model E2

I will try and get a signal on the radio again but no luck last time. I'll get a video too.

Cameron
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Old 23rd Aug 2017, 5:32 pm   #15
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Default Re: Advance Signal Generator Model E2

Well the noise is seemingly normal as suggested and upon trying again I'm hearing the tone through the radio. It's bang on calibration too (at least to my radio). I'll get it put back together for now and look at fitting new sockets as mine do not fit a standard Belling Lee connector even though they look like they should, no idea what that connection would be called. I'll maybe change to BNC as suggested.

Thank you all for your help in getting this working.

Cameron
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Old 27th Aug 2017, 11:41 pm   #16
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Default Re: Advance Signal Generator Model E2

Those two capacitors MUST be 1000V working. Due (presumably) to the effects of the wound components in the oscillator circuit there is nearly 600 volts across them. A short/leaky one of those will certainly stop the AF modulator from working. As I remember the AF output is available from a jack (I had fitted a 1/4 inch jack, but may have a co ax/aerial plug fitted) on the front. It should give enough AF output to drive a small speaker.
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Old 28th Aug 2017, 11:47 am   #17
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Default Re: Advance Signal Generator Model E2

Well I have some 2kv rated ceramics but they are for power supplies and can vary quite a bit in capacitance, would they be ok on this situation do you reckon?

Cameron
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Old 28th Aug 2017, 12:09 pm   #18
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Default Re: Advance Signal Generator Model E2

Your 0.25uf is a .22uF capacitor in modern terms.
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Old 30th Aug 2017, 5:22 pm   #19
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Default Re: Advance Signal Generator Model E2

My E2 also hums to itself when the internal modulation is on.
I believe the technical term is 'magnetostriction' and its caused by the modulation current in the modulation transformer.
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Old 30th Aug 2017, 6:41 pm   #20
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Default Re: Advance Signal Generator Model E2

Yes it's strange it seems most people's don't. I'm glad I'm not the only one and I have now learned a fancy new word
I still haven't got round to putting in those higher voltage caps but I came across another problem, when turning the tuning knob it slips and you need to pull it out to get it working, is it a rubber wheel or something? I will also need to fit BNC connectors and make up a dummy antenna for it.

Cameron
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