Marconi Instruments TF2102M1 A.F.Oscillator - UK Vintage Radio Repair and Restoration Discussion Forum

Julesomega · 9th Mar 2019, 10:24 pm

I asked earlier for service info on this little Marconi signal source, and this week I thought to try the Marconi Instruments Yahoo Group. I had one reply and to my delight Nigel Adams was able to provide PDFs for the original and a later version of the model. I commented on the basic 'entry level' nature of the product which does not even have an on/off switch, and during the ensuing discussion I learned that the later "Luxury" version included a rotary mains switch and a power idicator. The only difference between the models, TF2012M1 and TF2012M, is that a switch and indicator were added, and that is also the only difference between the two manuals.

The 2102 is something of a "cheap and cheerful" unit, but it is also specified as having no amplitude bounce, making it useful for vibration testing setups. This is because a diode detector with an arbitrarily fast response is used for amplitude stabilisation rather than the usual thermistor or tungsten bulb. The output amplitude is unusually high, using a Class-B output to give 10V rms into 600ohms, or 20V emf.

Mine is working ok, so I thought to test and adjust the supply rails as a start. The rails are helpfully labelled +40V and -40V so I was worried when I measured about ±47V. A quick inspection shows that the 'regulator' circuits are just emitter-followers with no adjustments, set for about 95% of the rectifier output voltages, no doubt just to minimise hum. Mine had been assembled with incorrect value resistors making the rails more like 99%, so I have changed them to be as intended and the supplies are now about ±45V.

It has calibrated up nicely, with hair's width frequency accuracy and good amplitude calibration. There are more detailed pictures on Radio Museum

Ferguson 2000 · 13th Jun 2019, 5:58 pm

Dear Julian,

I also have a Marconi TF2102MI, mine has a toggle switch and LED at top right. I find the ability to sweep the communications audio band (300-3000 Hz) without having to change range very useful and it is one of the few units that allows this.

Would you be willing to share the service manual PDF as I would like to add a lower level output at the right level to go straight into my RF signal generator without any adjustments and at the same level every time.

rolosa1147 · 21st Jun 2019, 3:42 pm

Dear Julian:
I am new in the site. I need the manual of TF-2102M. If you have please, if is possible, send to me a copy in pdf?.
Thank you so much
Best regards
Roberto

Julesomega · 22nd Jun 2019, 11:26 am

Apologies to Geoffrey for not seeing your request earlier. I shall have a little scanning session later today and upload the schematic somewhere, which I hope will help Roberto also.

Julesomega · 22nd Jun 2019, 11:58 pm

I have put the TF2102M1 on http://rosestone.me.uk/temp for the time being, HTH

Ferguson 2000 · 9th Aug 2019, 11:43 pm

Dear Julian,

Many thanks for putting the manual up for me, I will print it out next week and try to find an easy way of getting a second output.

Best wishes, Geoffrey.

9th Mar 2019, 10:24 pm	#1
Julesomega Nonode Join Date: Dec 2012 Location: Stockport, Greater Manchester, UK. Posts: 2,105	Marconi Instruments TF2102M1 A.F.Oscillator I asked earlier for service info on this little Marconi signal source, and this week I thought to try the Marconi Instruments Yahoo Group. I had one reply and to my delight Nigel Adams was able to provide PDFs for the original and a later version of the model. I commented on the basic 'entry level' nature of the product which does not even have an on/off switch, and during the ensuing discussion I learned that the later "Luxury" version included a rotary mains switch and a power idicator. The only difference between the models, TF2012M1 and TF2012M, is that a switch and indicator were added, and that is also the only difference between the two manuals. The 2102 is something of a "cheap and cheerful" unit, but it is also specified as having no amplitude bounce, making it useful for vibration testing setups. This is because a diode detector with an arbitrarily fast response is used for amplitude stabilisation rather than the usual thermistor or tungsten bulb. The output amplitude is unusually high, using a Class-B output to give 10V rms into 600ohms, or 20V emf. Mine is working ok, so I thought to test and adjust the supply rails as a start. The rails are helpfully labelled +40V and -40V so I was worried when I measured about ±47V. A quick inspection shows that the 'regulator' circuits are just emitter-followers with no adjustments, set for about 95% of the rectifier output voltages, no doubt just to minimise hum. Mine had been assembled with incorrect value resistors making the rails more like 99%, so I have changed them to be as intended and the supplies are now about ±45V. It has calibrated up nicely, with hair's width frequency accuracy and good amplitude calibration. There are more detailed pictures on Radio Museum Attached Thumbnails __________________ - Julian It's good here

13th Jun 2019, 5:58 pm	#2
Ferguson 2000 Tetrode Join Date: Jun 2008 Location: Stratford upon Avon, Warwickshire, UK. Posts: 80	Re: Marconi Instruments TF2102M1 A.F.Oscillator Dear Julian, I also have a Marconi TF2102MI, mine has a toggle switch and LED at top right. I find the ability to sweep the communications audio band (300-3000 Hz) without having to change range very useful and it is one of the few units that allows this. Would you be willing to share the service manual PDF as I would like to add a lower level output at the right level to go straight into my RF signal generator without any adjustments and at the same level every time. __________________ Best wishes, Geoffrey. Last edited by Ferguson 2000; 13th Jun 2019 at 5:59 pm. Reason: Signed twice!

21st Jun 2019, 3:42 pm	#3
rolosa1147 Retired Dormant Member Join Date: Jun 2019 Location: Buenos Aires, Argentina. Posts: 1	Re: Marconi Instruments TF2102M1 A.F.Oscillator Dear Julian: I am new in the site. I need the manual of TF-2102M. If you have please, if is possible, send to me a copy in pdf?. Thank you so much Best regards Roberto

22nd Jun 2019, 11:26 am	#4
Julesomega Nonode Join Date: Dec 2012 Location: Stockport, Greater Manchester, UK. Posts: 2,105	Re: Marconi Instruments TF2102M1 A.F.Oscillator Apologies to Geoffrey for not seeing your request earlier. I shall have a little scanning session later today and upload the schematic somewhere, which I hope will help Roberto also. __________________ - Julian It's good here

22nd Jun 2019, 11:58 pm	#5
Julesomega Nonode Join Date: Dec 2012 Location: Stockport, Greater Manchester, UK. Posts: 2,105	Re: Marconi Instruments TF2102M1 A.F.Oscillator I have put the TF2102M1 on http://rosestone.me.uk/temp for the time being, HTH __________________ - Julian It's good here

9th Aug 2019, 11:43 pm	#6
Ferguson 2000 Tetrode Join Date: Jun 2008 Location: Stratford upon Avon, Warwickshire, UK. Posts: 80	Re: Marconi Instruments TF2102M1 A.F.Oscillator Dear Julian, Many thanks for putting the manual up for me, I will print it out next week and try to find an easy way of getting a second output. Best wishes, Geoffrey. __________________ Best wishes, Geoffrey.