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Old 10th Mar 2019, 8:29 pm   #1
ekjdm14
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Default Ekco A320-A FM very weak/misaligned.

As per the title, following on from the recent thread in which Techman brought his Ferranti U1003 back from the brink, the parts to make my similar-chassis Ekco A320-A arrived and I've fitted these over the weekend. (7 caps in total replaced, including the 2uF item related to the ratio detector).


The set is working reasonably well on MW/LW although will need aligning properly when I manage to get a sig gen (peaked by ear on a station midways on the dial currently)

The issue I have is FM is very deaf, only pulling in 2 stations very weakly and way off where they ought to be (one station is Radio 2 (88.9, which appears with the cursor around 95MHz).

What is likely to be the cause of these issues, perhaps related?

One thing I should mention is the second IF for the FM side appears to have a problem, with no defined peak just a wide range of a few turns(!)

Thanks, Dan.
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Old 10th Mar 2019, 8:40 pm   #2
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Default Re: Ekco A320-A FM very weak/misaligned.

Do you mean the 2nd IF transformer or the transformer that's in the anode circuit of the 2nd IF amp? The ratio detector coil can be tweaked either way just a little bit to see if it's slightly out, that's assuming the ratio detector components are ok, the rest of the IF transformers for FM should only be adjusted using a signal generator.

Lawrence.

Last edited by ms660; 10th Mar 2019 at 8:51 pm. Reason: addition
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Old 10th Mar 2019, 8:46 pm   #3
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Default Re: Ekco A320-A FM very weak/misaligned.

Sorry, I mean the second IF transformer, the two leftmost slugs in the first transformer (well, I'm calling it first, left when viewed from the rear of the set!) have a very defined peak & brought the FM to a point where I could hear static and then tune to a strong station (prior to fiddling with alignment FM was utterly stone deaf), but the two leftmost slugs in the 2nd/right hand IF transformer can, they seem to do very little except for make it worse, but there's a broad range of a few turns where it's pretty much the same/as good as it gets.
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Old 10th Mar 2019, 8:59 pm   #4
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Default Re: Ekco A320-A FM very weak/misaligned.

I would check your IF alignment with a signal generator as per the alignment instructions.

Lawrence.
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Old 10th Mar 2019, 9:13 pm   #5
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Default Re: Ekco A320-A FM very weak/misaligned.

Presume you have checked voltages,wiring errors and tried a new ECC85 before touching the alignment . Unless some one has got at it they rarely require adjustment apart from perhaps a slight one in the ratio detector.
I have done 3 of these or similar and did't have to touch the IF alignment, slight adjustments to MW and LW RF circuits.
The VHF tuner as a separate drive cord to MW/LW, confirm that has not slipped before touching any alignment in the VHF tuner.
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Old 10th Mar 2019, 9:15 pm   #6
ekjdm14
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Default Re: Ekco A320-A FM very weak/misaligned.

Yes that was my thoughts, I've got AM acceptably good for the moment at least & there's a couple of reasonable stations on MW.

Hopefully have a sig gen on it's way soon to do the job right, I would have expected to get better by "ear" though.

Cheers, Dan.

Edit, unfortunately a replacement valve is something I don't possess at the moment. Apart from what's in the set the only other valves I have around the place are a UL84 and UY85 the set didn't appear "got at" until I got at it! I suppose it's possible somebody has tried running it before they sold it & damaged the valves, although it did come sans-plug with the cord tucked inside. I've checked/double checked my work, although no harm in triple checking I suppose. I don't believe the FM cord has slipped a turn but will check closely to see if it may have done.

Last edited by ekjdm14; 10th Mar 2019 at 9:19 pm. Reason: add reply to Nuvistor
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Old 12th Mar 2019, 10:48 pm   #7
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Default Re: Ekco A320-A FM very weak/misaligned.

On further research the signal generator I have is not likely to be over helpful with radio work as it's a TV set up tool and IIRC the lower of the frequencies it goes to is around 70MHz! Still will be an interesting and useful piece to have though.

For the moment, a further bit of "by ear" diddling tonight has things a lot more sensitive than they were although still a ways off. I'm actually pulling in frequencies over 107MHz, and they're in the middle of the dial. Cord is certainly in the right place so it's got to be something simple... could a weak ECC85 cause strange things like this?

Proper sig gen likely called for before it can all be fully diagnosed but the fact of 107MHz being around the middle of the scale has me wondering.
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Old 12th Mar 2019, 10:55 pm   #8
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Default Re: Ekco A320-A FM very weak/misaligned.

I would expect a faulty ECC85 making the radio deaf or no signals but never say never.
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Old 12th Mar 2019, 11:01 pm   #9
ekjdm14
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Default Re: Ekco A320-A FM very weak/misaligned.

That's what I hoped to hear! it was stone deaf on VHF when originally recomissioned and first "shot" managed to get 2 stations and not much white noise in between, this time round we have a good 5 or 6 "listenable" VHF stations and a lot more interference off-tune, just not where they ought to be.

Now it's at least functional to a degree where it can see some use as a bedside radio, I'll leave well enough alone until I have the proper equipment to verify how far off my "by ear" technique is. Thanks, Dan.
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