Advance E2 Signal Generator repair - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Tim · 5th Jan 2018, 6:20 pm

ISTR I changed the AF output socket on mine to a standard 1/4 inch jack, and found it very convenient. I think it fits in the hole as is, no drilling required.

thejazzageuk · 21st Jan 2018, 11:45 am

I've done some further testing after changing the 2 caps. Now when I switch on the internal modulation I can hear a high pitch tone even with nothing connected to the generator- is this to be expected?

Now the scope is showing a modulated wave- but is measuring it a 4kHz not 400Hz- can anyone suggest a reason for this?

Station X · 21st Jan 2018, 12:09 pm

A high pitched tone suggests something higher than 400 Hz. Where is it coming from though? Presumably a component is vibrating? T2 perhaps?

ms660 · 21st Jan 2018, 12:11 pm

Are the replacement capacitors the correct value?

Lawrence.

Station X · 21st Jan 2018, 12:14 pm

There's certainly a 47nF there which presumably is a replacement for a 0.05uF ie C12 or C13.

ms660 · 21st Jan 2018, 12:21 pm

Yes, they both look the same too, can't see the 'scope pic too well for the settings, I'm assuming it's been read correctly.

Strange that the frequency is 10X.

Lawrence.

ms660 · 21st Jan 2018, 4:24 pm

Ok, I've magnified the scope image (the modulated one) as best as I can, very fuzzy but frequency readout (bottom left) is 4.23725kHz?

Time per div is 2ms?

Going on that, the time period of the modulating frequency is 2.4ms which equates to a frequency of 416Hz (approx.)

Maybe the 'scopes frequency determining method is getting confused between the carrier frequency and the modulation frequency.

On the other hand I might be completely wrong...

Lawrence.

barrymagrec · 21st Jan 2018, 4:29 pm

Since the signal is an amplitude modulated carrier the scope probably can't detect the modulation?

Station X · 21st Jan 2018, 4:31 pm

The obvious thing to do would be to check the signal at the AF output socket.

ms660 · 21st Jan 2018, 4:35 pm

It would, I think the modulated waveform on the 'scope has confused his report.

Lawrence.

thejazzageuk · 26th Jan 2018, 1:36 pm

Thanks all. I've now re-checked the modulation frequency from the AF socket as suggested by Station X, and indeed the frequency is very close to the expected 400Hz (actually measured at 409 by the scope).

So- thanks to everyone who has assisted, and it now looks like the generator is working correctly, I guess we can close this thread and go back to the original one and try using the SG to get better LW reception on the Beau Decca radio.

5th Jan 2018, 6:20 pm	#21
Tim Dekatron Join Date: Jan 2003 Location: Bradford on Avon, Wiltshire, UK. Posts: 3,310	Re: Advance E2 Signal Generator repair ISTR I changed the AF output socket on mine to a standard 1/4 inch jack, and found it very convenient. I think it fits in the hole as is, no drilling required. __________________ "Nothing is as dangerous as being too modern;one is apt to grow old fashioned quite suddenly."

21st Jan 2018, 11:45 am	#22
thejazzageuk Pentode Join Date: Feb 2014 Location: Carmarthen, Wales, UK. Posts: 238	Re: Advance E2 Signal Generator repair I've done some further testing after changing the 2 caps. Now when I switch on the internal modulation I can hear a high pitch tone even with nothing connected to the generator- is this to be expected? Now the scope is showing a modulated wave- but is measuring it a 4kHz not 400Hz- can anyone suggest a reason for this? Attached Thumbnails

21st Jan 2018, 12:09 pm	#23
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Advance E2 Signal Generator repair A high pitched tone suggests something higher than 400 Hz. Where is it coming from though? Presumably a component is vibrating? T2 perhaps? __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

21st Jan 2018, 12:11 pm	#24
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Advance E2 Signal Generator repair Are the replacement capacitors the correct value? Lawrence.

21st Jan 2018, 12:14 pm	#25
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Advance E2 Signal Generator repair There's certainly a 47nF there which presumably is a replacement for a 0.05uF ie C12 or C13. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

21st Jan 2018, 12:21 pm	#26
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Advance E2 Signal Generator repair Yes, they both look the same too, can't see the 'scope pic too well for the settings, I'm assuming it's been read correctly. Strange that the frequency is 10X. Lawrence.

21st Jan 2018, 4:24 pm	#27
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Advance E2 Signal Generator repair Ok, I've magnified the scope image (the modulated one) as best as I can, very fuzzy but frequency readout (bottom left) is 4.23725kHz? Time per div is 2ms? Going on that, the time period of the modulating frequency is 2.4ms which equates to a frequency of 416Hz (approx.) Maybe the 'scopes frequency determining method is getting confused between the carrier frequency and the modulation frequency. On the other hand I might be completely wrong... Lawrence. Last edited by ms660; 21st Jan 2018 at 4:31 pm.

21st Jan 2018, 4:29 pm	#28
barrymagrec Octode Join Date: Dec 2017 Location: Morden, Surrey, UK. Posts: 1,561	Re: Advance E2 Signal Generator repair Since the signal is an amplitude modulated carrier the scope probably can't detect the modulation?

21st Jan 2018, 4:31 pm	#29
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Advance E2 Signal Generator repair The obvious thing to do would be to check the signal at the AF output socket. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

21st Jan 2018, 4:35 pm	#30
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Advance E2 Signal Generator repair It would, I think the modulated waveform on the 'scope has confused his report. Lawrence.

26th Jan 2018, 1:36 pm	#31
thejazzageuk Pentode Join Date: Feb 2014 Location: Carmarthen, Wales, UK. Posts: 238	Re: Advance E2 Signal Generator repair Thanks all. I've now re-checked the modulation frequency from the AF socket as suggested by Station X, and indeed the frequency is very close to the expected 400Hz (actually measured at 409 by the scope). So- thanks to everyone who has assisted, and it now looks like the generator is working correctly, I guess we can close this thread and go back to the original one and try using the SG to get better LW reception on the Beau Decca radio. Attached Thumbnails