alignment

[pagu]

I have a hacker sovereign radio,caps and transistors have been changed,but this radio is in desperate need of an alignment,not having any tools apart from a soldering iron and a small multi meter, I am incapable of doing this myself.

Would anyone in the forum be willing to undertake this job?

I am willing to bring or send radio to anyone interested,with of course payment.

A little personal history,I am a pensioner (71) ,and I started this project for a side interest, I am not radio electrical trained,but have an interest in this kind of project having seen an article on youtube.

many thanks to all.

pagu

[Terry]

You're never to old to learn!

Is this an AM radio or AM/FM?

I assume from your post that the radio is now working but not very well. Is that correct?

If so, it will often be possible to re-align it without any equipment at all, other than the correct trimming tools* and your own ears! This will be especially easy if it is AM only or if only the AM section needs attention.

* Never, ever, touch a dust iron/ferrite core with metal bladed screwdriver - particularly if it has a hexagonal hole or slit running all the way through it. You will crack the core and it will be jammed and very difficult to remove without damaging the coil former.

If you provide the model number, I'm sure someone will be able to identify exactly which tools you need and probably where/how to to obtain them.

The idea is essentially to use broadcast stations as your signal generator. Turn the volume up high and tune to a weakish station, then adjust the IF transformers for maximum volume, turning the radio so that the ferrite rod aerial progressively receives a weaker signal as the alignment improves the sensitivity (or change to a weaker station).

The reason for using the weakest possible signal is to prevent the set's AGC from obscuring the point of maximum sensitivity.

Once the IF has been adjusted, use known stations as close as possible to each end of the MW band to correctly align the local oscillator and aerial circuits.

FM alignment isn't quite as simple but shouldn't prove impossible and you will end up with the satisfaction of having successfully  learned a new skill.

You certainly aren't the only pensioner on here - I'm 2 years older than you! - but I have to admit to this being a life long interest. However, 60 years ago I could only dream of one day having access to an accurate signal generator - unlike you, I didn't even have a multi-meter! - so the method I've outlined above was the only option I had - and it worked very well!

[Mark Hennessy]

All Hacker Sovereigns are AM/FM. The first 3 versions have separate AM/FM tuners; the Sovereign IV had a conventional combined IF strip.

In general, the RF alignment on these sets - on both AM and FM - will drift. IF alignment is rather more stable, and there is usually less to be gained from going through that, unless the set has been messed around with.

RF alignment can pretty much be done by ear, providing you know the frequencies of the stations you're receiving. Especially if you restrict the adjustments to just the local oscillators - if you still have sufficient sensitivity after doing this, then the RF tuning adjustments can be left alone.

Before doing anything, however, do make sure the "pointer datum" is correct. Unless already corrected in recent times, this is guaranteed to be out. At the far right end of the scale, the pointer should line up with the opening in the scale. On most of the Sovereign sets, you move the pulley in its slot to correct, and if that's not enough, slide the pointer along the string. Often, just doing this gets the scale alignment close enough...

[pagu]

thank you for replies,the set is an am-fm radio,I have some ceramic trimmers,but adjusting a little at a time I cannot seem to get a "sweet" spot,I believe a sweep generator is needed for best peaking,this is of course out of my reach.

Once again many thanks for your attention.

pagu.(this is the first two letters of my fist name and the first two letters of my second name)

a little bit of useless information.

[Terry]

You are correct in saying that a sweep generator is best but this only refers to FM IF alignment.

If by 'sweet spot' you mean a sharp peak when doing AM alignment, it means that the input level is too high and the AGC is obscuring the peak by controlling the gain to give a constant output.

That is why I stressed that you should set the volume control high and use the weakest available signal. The peaks will then be very sharp.

[pagu]

when I bought the set I knew there would be a few problems,namely transistors,these have been replaced with AF 125 ,when switching on I noticed the FM side was very much out of tune,using a small ceramic driver,I tried to tune the if trimmers using very small movements,but I had very little success,could get one station reasonably well but the others were way off .

This is why I asked if anyone would do an alignment.

thanks to all.

still in the abyss
pagu

[Refugee]

It sounds like there is an open circuit decoupling capacitor on the power rail supplying the IF stages.
The electrolytic capacitors all need to be good before anything do do with alignment gets done.

[Mark Hennessy]

The capacitors are usually the normally-reliable Philips type. Occasionally you find something else on the AM IF panel, and these can cause problems on AM, but not alignment problems. When faulty, the set simply doesn't work properly on AM full stop.

EDIT: I should add that this applies to the Sovereign II. We don't actually know which set we're dealing with. However, the mention of AF-series transistors suggests a Sovereign RP18 or an early Sovereign II RP25.


Pagu, there seems to be a lot of confusion here.

Did you see my original post? Post #3. You haven't responded to that yet.

It is rare to need to adjust the IF on these sets. It is normal to need to adjust the RF calibration. Are you clear about the difference between the two? And please could you clarify exactly what you meant by "desperate need of an alignment" in your opening post? What are the symptoms, and how sure are you that alignment is the issue? There could be other faults.

I'm worried that if you mess about with the FM IF panel, you'll just make things worse.

To recap, RF alignment - so that the pointer ends up in the correct place - is normal, and relatively easy without specialist equipment. Sort the pointer datum first. However, IF is more difficult, but shouldn't be necessary.

It's no exaggeration to say that I've repaired hundreds of Hacker sets in recent times, and I know them quite well. I hope that doesn't seem immodest.

If you are ever in the Evesham area, I'll be able to help - given enough prior notice.

[pagu]

The set concerned is a hacker sovereign RP18, transistors have all been replaced with af 125,the electrolytic caps have been replaced with modern caps,
the set was not working when bought,this was expected,usual AF117 -114 issues,

Mr Hennessy ,your email ended up in the spam folder,I do not know how to reply direct on this site,having replaced transistors and caps,switching on the set I realised that the set had possibly been "played with".The pointer is pointing in the approximately correct area,sound on FM is distorted , definitely out of alignment ,knowing that to indiscriminately twirling the IF cores can only lead to hopelessly throwing the alignment out,is why I asked if anyone in the Widnes, Warrington, Wigan,area could help, bringing the set or posting via Hermes etc.

again,many thanks to all.

pagu

[Mark Hennessy]

Well, as I haven't sent an email, I assume you mean that the notification email from the forum software is what ended up in your spam folder. Certainly, everything I've said is contained here in this thread.

Thanks for finally confirming what the set actually is. That helps.

I've done a lot of RP18s, and based on my experience, I can't help thinking there is a fault. I'm not sure what though, as I've never had to do more than "zap" the AF11x transistors and replace electrolytics that aren't made by Philips. I've never encountered one that needed an IF alignment - but as I keep saying, the RF alignment is normally a bit off. Likewise for AM. I might try and tune the IF section up a bit if I know the customer lives in a difficult reception area but there's never any real point as the gains are marginal at best.

If you are absolutely sure that someone else has upset the FM IF alignment, then peak all the FM IFTs. Normally this is not recommended, but as it is already wrong (and will eventually be properly lined up), you've nothing to lose.

The final coil - the ratio discriminator - has most influence on the distortion. By ear, you should be able to get this reasonably OK*

If doing that doesn't help, then yes, you have a fault.

But because you might have a fault, I'd be inclined to leave the IFTs alone and investigate. Try looking at the diodes in the ratio detector. And check the bias adjustment - details are in the manual. An off-tune IF strip will give really, really weak reception rather than bad distortion - and the fact you haven't mentioned the former is what I keep coming back to...

The offer of help stands, but you'd have to bring it here in person (I appreciate that's easier said than done). If you post it, it'll sit in the queue for months and months. I'm always far too busy. But looking at it on a "while you wait" basis works well, providing things don't escalate out of control. It's also a good way to control costs.

Cheers,

Mark


* It is entirely possible to line up an FM IF section using an RF generator and an audio distortion meter. It's easier than the wobulator method, and just as effective - I don't know why no-one else does it (every time I mention it on a forum, no-one believes me - but then, I'm an audio person, and understand that the point of getting that nice straight line is to make the whole thing as linear as possible, therefore least harmonic distortion). Frankly, doing it just by ear gets things surprisingly good with practice.