No FM on my Fenman II - UK Vintage Radio Repair and Restoration Discussion Forum

brymac · 24th Apr 2007, 1:39 pm

Very pleased to have revived a very dead and grubby Fenman II (my second this year). Superb sound on MW and LW, but despite being "lively" (i.e. responding to a fluorescent tube being switched on!), I can't get a peep out of FM. I think I've tracked down the reason, but can't work out what is causing it!

All valves have been checked by susbstitution, so I set about the valve voltages - the FM RF amplifier EF80 (V1 on the Trader sheet) is showing 110 volts against an expected 135 volts, but there's a wopping 30 mA of current being passed as opposed to the expected 5.3mA!! I've replaced the 0.001 uF cap (C5) and checked that the resistor (R4) at the other end of the RF tuning coil (L4) is within tolerance - it is. I had previously replaced R18, which feeds the HT to the FM side of the circuit with a 5 watt resistor as the one fitted was out of tolerance and tired looking.

Help! What have I missed

Bryan

Steve_P · 24th Apr 2007, 4:46 pm

Does 10.7 Mhz come out OK?

Anyway - R2, C43, R25, C48.Just diconnect R2 and see if anything comes through. C2 ? Also, R3 and C3.

Cheers,

Steve P

Steve_P · 24th Apr 2007, 5:25 pm

Just had another look at this. The oscillator is V2, what's this like for Voltages and Currents. Check C6.

Cheers,

Steve P

Tim · 24th Apr 2007, 6:47 pm

Bryan.
Have you actually measured the current or calculated it(say from the drop across the anode resistor.)? 30 mA seems very high. What would be the drop across the anode resistors at that current. It probably adds up to nearly the HT. If your current(in both senses of the word) figure is based on maths (V/R) rather than actually connecting an ammeter in the circuit, there could be some RF about, affecting the meter reading. It might be possible to varify the figure by measuring the voltage across the EF 80's cathode rersistor, if it has one(if not try something like 100R and measure the voltage across that. I would also expect a VERY hot or even distessed looking valve and some funny smells. An oscilloscope would prove useful here.
See recent repairs(although it's not that recent now...) Murphy A272C..on Paul's main site. I had similar symptoms.

R18 could be the wrong value of course.
Good luck

brymac · 24th Apr 2007, 11:12 pm

Thanks for all of that - I'll work through it and let you know how I get on!! Bryan

brymac · 24th Apr 2007, 11:16 pm

Sorry - although I didn't say so, most of you will have guessed that the voltage and current referred to in the original post were on the anode of the EF80..... Bryan

brymac · 26th Apr 2007, 6:31 pm

OK - here's an update and a plea for some more ideas!!

Steve - R2,C43,R25,C48,R3, C3 and C6 either replaced (caps) or checked and within tolerance (resistors). Disconnecting R2 makes no difference.

V2a anode voltage 83 against Trader sheet 90; current 13mA against TS 9mA
V2b anode voltage 107 against TS 135; current 22mA against TS 2.7!!

Tim - R18 is OK - I'd actually replaced it with a 5 watt resistor as the orginal was looking hot and bothered.

Just to make sure that I'm not being thick about these current measurements - I'm setting my Avo to DC current and using the 0.1 amp range as it goes off the scale on the lower one. So - with FSD on the meter being 0.1 amp, and the negative connection to the chassis, I'm getting scale readings of 3 and 2.2 as referred to above, i.e. 0.03 Amps and 0.022 Amps which if my maths serves me well is 30 and 22 mA respectively??

A bit more about what I'm getting on FM (bear in mind this set works perfectly on MW and LW). There is a clear hiss and a clicking response to anything switched on and off near the set. At one point I could hear what sounded like a faint mobile phone ringing tone!

I have pulled the FM circuit valves and cleaned their pins and sprayed switch cleaner into their sockets. I've checked the FM aerial connections. I have not moved any of the coils cores or the behive trimmer by the FM coils.

I'm going to check out all the components around V2 (the ECF80 oscillator) tomorrow.

This will be a "kick myself" fault, but the bottom line is that the V1 and V2 anodes appear to both be drawing excessive current. Why??

Bryan

PJL · 26th Apr 2007, 8:29 pm

I don't have access to a circuit diagram but how about a full set of pin voltages for the ECF80? Have you tried a replacement?

coil1234 · 26th Apr 2007, 8:52 pm

Not sure if I've interpreted you current measurement connections correctly, but unless you are measuring the current in the cathode circuit the Avo -ve should not go to chassis.

To measure the current correctly you will have to 'break into' the circuit which will require unsoldering one end of the relevant resistor.

Bear in mind any DMM / Avo presents a very low resistance at the terminals when set to measure current think of it as a short circuit.

Apologies if you know this already and I've not understood your method.

Best of luck
Mike A

brymac · 26th Apr 2007, 9:34 pm

No - that's my lack of knowledge about valves, I'm afraid! Looks like I'll have to start again with the anode current measurements, but I'm no nearer a solution to the lack of FM....

Bryan

Steve_P · 30th Apr 2007, 3:34 pm

You getting anywhere with this?

Cheers,

Steve P

brymac · 30th Apr 2007, 7:24 pm

Steve - thanks for asking! The answer is no!!

I'm now down to checking the wavechange switch, having replaced almost everyting that moves around V1 and V2. It is so frustrating to have this set perform so well on MW and LW but just hiss at me on FM!!!

I'm having a serious go at it tomorrow, so any ideas would be most welcome............

Bryan

maitiustandun · 30th Apr 2007, 7:42 pm

was it the wave change switch

?maitiu,

brymac · 30th Apr 2007, 7:46 pm

I don't know yet - but I'm beginning to suspect that it is.....what do you know about that problem??

Bryan

Steve_P · 30th Apr 2007, 11:09 pm

On the trader sheet I have, there is a list of which switches are Open on all Settings. Check em with an Avo.

Cheers,

Steve P

brymac · 30th Apr 2007, 11:30 pm

Steve - yes, that's tomorrow's job!! I have the Trader sheet..........

Bryan

Studio263 · 1st May 2007, 8:25 am

Noise but no stations sounds as if the oscillator has stopped (triode section of the ECF80). If it is running there should be a small negative voltage on the grid. If this is the case there should not be too many suspect components, as this set is inductively tuned the small value capacitors are the favourites.

I'm sure you have probably checked allready, but are the ferrite slugs that move up and down in the tuning coils still there?

Finally I can confirm that the wavechange switch is a troublesome component but it is not as daunting as you think because most of it is to do with the AM side of the set (aerial and oscillator coils etc) and so not relevant to the problems you are having. The main area of concern would be the contacts that switch HT to the front end but as the valves are passing current one would assume that these are sound.

brymac · 1st May 2007, 1:05 pm

I AM SO STUPID!!! After 3 days, I've just discovered that when I replaced C13, I soldered it to the wrong point on L7 (there were only two to choose from)!!! It's now working perfectly!!

Moral of story - check all the compenents you have replaced - over and over again!!!!

Phew - now I can get this one finshed and off the bench and start on the Beau Decca radiogram.

Many thanks to all of you for your patience - I'm glad I didn't have to take the w/c switch apart!!

Bryan

paulsherwin · 1st May 2007, 1:12 pm

Quote:

Originally Posted by brymac

I AM SO STUPID!!! After 3 days, I've just discovered that when I replaced C13, I soldered it to the wrong point on L7 (there were only two to choose from)!!! It's now working perfectly!!

Most of us have been there Bryan. Glad to hear it's working now.

Paul

Steve_P · 1st May 2007, 1:22 pm

Everyone does that! I'm glad it's sorted, as I was running out of ideas!

Cheers,

Steve P

24th Apr 2007, 1:39 pm	#1
brymac Hexode Join Date: Nov 2004 Location: East Sussex, UK. Posts: 389	No FM on my Fenman II Very pleased to have revived a very dead and grubby Fenman II (my second this year). Superb sound on MW and LW, but despite being "lively" (i.e. responding to a fluorescent tube being switched on!), I can't get a peep out of FM. I think I've tracked down the reason, but can't work out what is causing it! All valves have been checked by susbstitution, so I set about the valve voltages - the FM RF amplifier EF80 (V1 on the Trader sheet) is showing 110 volts against an expected 135 volts, but there's a wopping 30 mA of current being passed as opposed to the expected 5.3mA!! I've replaced the 0.001 uF cap (C5) and checked that the resistor (R4) at the other end of the RF tuning coil (L4) is within tolerance - it is. I had previously replaced R18, which feeds the HT to the FM side of the circuit with a 5 watt resistor as the one fitted was out of tolerance and tired looking. Help! What have I missed Bryan

24th Apr 2007, 4:46 pm	#2
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: No FM on my Fenman II Does 10.7 Mhz come out OK? Anyway - R2, C43, R25, C48.Just diconnect R2 and see if anything comes through. C2 ? Also, R3 and C3. Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

24th Apr 2007, 5:25 pm	#3
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: No FM on my Fenman II Just had another look at this. The oscillator is V2, what's this like for Voltages and Currents. Check C6. Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

24th Apr 2007, 6:47 pm	#4
Tim Dekatron Join Date: Jan 2003 Location: Bradford on Avon, Wiltshire, UK. Posts: 3,310	Re: No FM on my Fenman II Bryan. Have you actually measured the current or calculated it(say from the drop across the anode resistor.)? 30 mA seems very high. What would be the drop across the anode resistors at that current. It probably adds up to nearly the HT. If your current(in both senses of the word) figure is based on maths (V/R) rather than actually connecting an ammeter in the circuit, there could be some RF about, affecting the meter reading. It might be possible to varify the figure by measuring the voltage across the EF 80's cathode rersistor, if it has one(if not try something like 100R and measure the voltage across that. I would also expect a VERY hot or even distessed looking valve and some funny smells. An oscilloscope would prove useful here. See recent repairs(although it's not that recent now...) Murphy A272C..on Paul's main site. I had similar symptoms. R18 could be the wrong value of course. Good luck __________________ "Nothing is as dangerous as being too modern;one is apt to grow old fashioned quite suddenly."

24th Apr 2007, 11:12 pm	#5
brymac Hexode Join Date: Nov 2004 Location: East Sussex, UK. Posts: 389	Re: No FM on my Fenman II Thanks for all of that - I'll work through it and let you know how I get on!! Bryan

24th Apr 2007, 11:16 pm	#6
brymac Hexode Join Date: Nov 2004 Location: East Sussex, UK. Posts: 389	Re: No FM on my Fenman II Sorry - although I didn't say so, most of you will have guessed that the voltage and current referred to in the original post were on the anode of the EF80..... Bryan

26th Apr 2007, 6:31 pm	#7
brymac Hexode Join Date: Nov 2004 Location: East Sussex, UK. Posts: 389	Re: No FM on my Fenman II OK - here's an update and a plea for some more ideas!! Steve - R2,C43,R25,C48,R3, C3 and C6 either replaced (caps) or checked and within tolerance (resistors). Disconnecting R2 makes no difference. V2a anode voltage 83 against Trader sheet 90; current 13mA against TS 9mA V2b anode voltage 107 against TS 135; current 22mA against TS 2.7!! Tim - R18 is OK - I'd actually replaced it with a 5 watt resistor as the orginal was looking hot and bothered. Just to make sure that I'm not being thick about these current measurements - I'm setting my Avo to DC current and using the 0.1 amp range as it goes off the scale on the lower one. So - with FSD on the meter being 0.1 amp, and the negative connection to the chassis, I'm getting scale readings of 3 and 2.2 as referred to above, i.e. 0.03 Amps and 0.022 Amps which if my maths serves me well is 30 and 22 mA respectively?? A bit more about what I'm getting on FM (bear in mind this set works perfectly on MW and LW). There is a clear hiss and a clicking response to anything switched on and off near the set. At one point I could hear what sounded like a faint mobile phone ringing tone! I have pulled the FM circuit valves and cleaned their pins and sprayed switch cleaner into their sockets. I've checked the FM aerial connections. I have not moved any of the coils cores or the behive trimmer by the FM coils. I'm going to check out all the components around V2 (the ECF80 oscillator) tomorrow. This will be a "kick myself" fault, but the bottom line is that the V1 and V2 anodes appear to both be drawing excessive current. Why?? Bryan

26th Apr 2007, 8:29 pm	#8
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: No FM on my Fenman II I don't have access to a circuit diagram but how about a full set of pin voltages for the ECF80? Have you tried a replacement?

26th Apr 2007, 8:52 pm	#9
coil1234 Pentode Join Date: Jan 2006 Location: Almeria, Spain Posts: 221	Re: No FM on my Fenman II Not sure if I've interpreted you current measurement connections correctly, but unless you are measuring the current in the cathode circuit the Avo -ve should not go to chassis. To measure the current correctly you will have to 'break into' the circuit which will require unsoldering one end of the relevant resistor. Bear in mind any DMM / Avo presents a very low resistance at the terminals when set to measure current think of it as a short circuit. Apologies if you know this already and I've not understood your method. Best of luck Mike A

26th Apr 2007, 9:34 pm	#10
brymac Hexode Join Date: Nov 2004 Location: East Sussex, UK. Posts: 389	Re: No FM on my Fenman II No - that's my lack of knowledge about valves, I'm afraid! Looks like I'll have to start again with the anode current measurements, but I'm no nearer a solution to the lack of FM.... Bryan

30th Apr 2007, 3:34 pm	#11
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: No FM on my Fenman II You getting anywhere with this? Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

30th Apr 2007, 7:24 pm	#12
brymac Hexode Join Date: Nov 2004 Location: East Sussex, UK. Posts: 389	Re: No FM on my Fenman II Steve - thanks for asking! The answer is no!! I'm now down to checking the wavechange switch, having replaced almost everyting that moves around V1 and V2. It is so frustrating to have this set perform so well on MW and LW but just hiss at me on FM!!! I'm having a serious go at it tomorrow, so any ideas would be most welcome............ Bryan

30th Apr 2007, 7:42 pm	#13
maitiustandun Pentode Join Date: Aug 2005 Location: Dublin, Ireland. Posts: 157	Re: No FM on my Fenman II was it the wave change switch?maitiu,

30th Apr 2007, 7:46 pm	#14
brymac Hexode Join Date: Nov 2004 Location: East Sussex, UK. Posts: 389	Re: No FM on my Fenman II I don't know yet - but I'm beginning to suspect that it is.....what do you know about that problem?? Bryan

30th Apr 2007, 11:09 pm	#15
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: No FM on my Fenman II On the trader sheet I have, there is a list of which switches are Open on all Settings. Check em with an Avo. Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

30th Apr 2007, 11:30 pm	#16
brymac Hexode Join Date: Nov 2004 Location: East Sussex, UK. Posts: 389	Re: No FM on my Fenman II Steve - yes, that's tomorrow's job!! I have the Trader sheet.......... Bryan

1st May 2007, 8:25 am	#17
Studio263 Octode Join Date: Apr 2007 Location: Hampshire, UK. Posts: 1,578	Re: No FM on my Fenman II Noise but no stations sounds as if the oscillator has stopped (triode section of the ECF80). If it is running there should be a small negative voltage on the grid. If this is the case there should not be too many suspect components, as this set is inductively tuned the small value capacitors are the favourites. I'm sure you have probably checked allready, but are the ferrite slugs that move up and down in the tuning coils still there? Finally I can confirm that the wavechange switch is a troublesome component but it is not as daunting as you think because most of it is to do with the AM side of the set (aerial and oscillator coils etc) and so not relevant to the problems you are having. The main area of concern would be the contacts that switch HT to the front end but as the valves are passing current one would assume that these are sound.

1st May 2007, 1:05 pm	#18
brymac Hexode Join Date: Nov 2004 Location: East Sussex, UK. Posts: 389	Re: No FM on my Fenman II I AM SO STUPID!!! After 3 days, I've just discovered that when I replaced C13, I soldered it to the wrong point on L7 (there were only two to choose from)!!! It's now working perfectly!! Moral of story - check all the compenents you have replaced - over and over again!!!! Phew - now I can get this one finshed and off the bench and start on the Beau Decca radiogram. Many thanks to all of you for your patience - I'm glad I didn't have to take the w/c switch apart!! Bryan

1st May 2007, 1:22 pm	#20
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: No FM on my Fenman II Everyone does that! I'm glad it's sorted, as I was running out of ideas! Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?