Ferguson 238A- only one station on MW!

[JoshWard]

Hi all,
I have recently pulled this set off the round tuit pile. After fitting a new output transformer, replacing the waxies and changing a couple of out of tolerance resistors it is now making some noises, but I have encountered a fault I have not come across before.

It works well on LW and SW picking up stations across the bands, but on MW I am only able to receive one station (Smooth Radio on around 250m). If I do the old trick of touching the end of the aerial wire I can receive a couple of other stations but it's still nowhere near as lively as it should be.

What appears odd to me is that Smooth comes in very well with plenty of volume. I have tried subbing valves but no difference.

Could it be that somebody has been twiddling in the past and peaked it up on one station?

Things get trickier in that I am currently without a signal generator (sadly I was forced to sell mine last year), so is there anything else I can try or should I put it aside until I can get another signal generator?


Thanks in advance,
Josh

[cathoderay57]

Hi Josh, is Smooth coming in at the right tuning point on the scale? If not then it is possible that the MW padder/tracker capacitor has drifted in value putting the scale off calibration. These are usually mica capacitors and the fault is rare but not unknown. Not sure if you have access to Trader Sheet #1001 but this capacitor is C9, 605pF connected between the bottom of L7 (MW oscillator coil grid side) and chassis. Also, with power off, check the MW oscillator coils L7 and L10 and MW aerial coils L2 and L4 for continuity. Finally, wavechange switch contacts usually benefit from a squirt of switch cleaner. If none of that helps, then even without a signal generator you should be able to get away with a careful tweak of C26 the MW aerial coil trimmer capacitor but do it at the HF end of the band and peak for max noise. Cheers, Jerry

[JoshWard]

Thanks Jerry.
Smooth is coming in where I would expect it. I have just checked the coils and all appear to be OK with the expected resistances.
I have already cleaned out the wavechange switch but sadly no difference.
When I tried adjusting C26 it made no difference to the noise level so could it be that C26 is somehow faulty?
Josh

[cathoderay57]

Hi Josh, the aerial coil trimmers aren't usually very "peaky" so you might get more tuneable results using a sig gen input. What are you using in terms of an external aerial? You could try peaking the LF end using the tuning slug adjustment on L2/L4. It looks like an iron dust core type and these are easily damaged and sometimes stick in the thread so go easy with it and use a plastic tool such as a knitting needle or cocktail stick with a screwdriver flat filed on the end. The reason I say that is mainly because a metal blade can easily crack the slug. Adjust the core at the LF end at say 433m and see if you can bring up R5 Live. Where you are you should also be able to receive R. Caroline on 463m. Once you have peaked the LF end, go back to the HF end and see if C26 will peak. Cheers, Jerry

[JoshWard]

Hi Jerry,
Thank you. L4 peaked up nicely on some background noise. I turned back to C26 and it isn't peaking as such. When tightened it gets quieter but when loosened it gets louder and louder. It isn't going 'quiet, loud, quiet' like I'd expect from a trimmer.

R5 Live is coming in very quietly. Caroline is inaudible but when I put my hand on the end of the aerial Caroline comes in with reasonable volume along with the rest of the stations I'd expect. This is my main reason for wanting to fix this fault. If I listened to Smooth I wouldn't mind, but I listen to Caroline!


My 'aerial' is just a couple of metres of wire. Whilst not exactly perfect I have never had a set struggle with it and both long and short waves are working well.


Josh

[cathoderay57]

The only other thing I can think of to improve things is to use a longer aerial. If the set isn't earthed then changing the mains cable for a 3-wire with earth connected to chassis might help. You are lucky getting good LW reception on only a couple of metres of wire! Maybe others can suggest alternative improvements. Cheers, jerry

[Sideband]

You can perform quite a satisfactory alignment without a generator....I was forced to do this several times when alignment details were not available and when I was asked to check a set away from home....(I was on holiday visiting a relative).

You can do a 'quick and dirty' check on IF alignment by choosing a weak station near the LF (500metre) end of MW and just carefully adjusting the IF cores for maximum output). Once you are happy with that, tune the set to the HF (200metre) end again find a weak station and adjust the aerial trimmer for maximum output. Tune again to the LF (500metre) end and adjust the aerial coil for maximum output.

Hopefully as the alignment becomes better, you'll find a few more stations available and can then asses if the oscillator trimmer needs tweaking. This should be done at the HF (200metre) end and in my area, I use Gold on 194 metres to assess if the oscillator is correct. At the other (LF end of MW you need to use the oscillator coil to adjust somewhere near 500metres. You will need to repeat these adjustments. With a bit of practice, you should be able to get quite acceptable results which of course you can improve on when you get another generator.

Of course you should ensure as far as you can first of all that there isn't another fault, causing the low sensitivity.

[JoshWard]

Thanks both.
Yes my 'aerial' is hardly an ideal set-up (I have been meaning to install a proper one for the workshop since I have lived here!) but I have always had very acceptable results whilst using it. Fortunately, being in the middle of nowhere means there is very little interference! I did try a much longer aerial on it this morning and whilst more stations came in they were very quiet, including Caroline.
I have noticed a nice Advance signal generator for sale online which is apparently working and fairly cheap so fingers crossed I can get that and do the job properly. If not I will try that method Richard and see where we get!

Maybe I should just listen to the same songs over and over again on Smooth!!

[HamishBoxer]

Is there an aerial coil on MW that could be faulty?

[Sideband]

Originally Posted by JoshWard

Maybe I should just listen to the same songs over and over again on Smooth!!

...oh you have that problem as well?? I lose interest after a while.....I don't know how many times they've played 'What A Wonderful World' by Louis Armstrong....!

[michamoo]

One reason that Smooth radio probably manages to get through on that set is that there is a Transmitter for it just up the road from you. It is at Great Barton just outside Bury st Edmunds. Was originally for Saxon radio back in the IBA local radio days.

[JoshWard]

In terms of coils I have checked L2/L4 and L7/L10 on the attached diagram. Are there any others which could cause a fault like this?


Yes, Smooth is very strong around here, although I hadn't realised the transmitter was only in Great Barton.

[dave_n_t]

Josh,

I know you've cleaned the wavechange switch, but are you sure that S2 and S5 (I think!) are both making good contact? Check that, when you turn the switch to MW, the appropriate contacts move apart slightly as the moving contact 'blade' goes between them.

daveMW is selected, the contacts move apart slightly