UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Radio (domestic)

Notices

Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

Closed Thread
 
Thread Tools
Old 8th Feb 2019, 6:07 pm   #81
Findlay
Triode
 
Join Date: Jan 2019
Location: Chelmsford, Essex, UK.
Posts: 47
Default Re: Hacker Hunter FM volume R4

Thanks Paul and Mark. I really appreciate your help. It is so brilliant to be sitting hear listening to Classic FM on this great set again!
Findlay is offline  
Old 9th Feb 2019, 4:35 pm   #82
Findlay
Triode
 
Join Date: Jan 2019
Location: Chelmsford, Essex, UK.
Posts: 47
Default Re: Hacker Hunter FM volume R4

Just one other question - Classic FM comes up right at the end of the tuning scale on this set - I guess a lot of the Hackers have a limited tuning range - is there an easy tweak to extend the high frequency range a little to pull it more on scale? I'm not sure what to adjust and don't want to muck things up at this stage!

Last edited by Findlay; 9th Feb 2019 at 4:42 pm.
Findlay is offline  
Old 9th Feb 2019, 4:46 pm   #83
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,788
Default Re: Hacker Hunter FM volume R4

Yes, you need to adjust the oscillator trimmer slightly. This will obviously mean that the tuning scale frequency is incorrect, but that is easy enough to live with. I don't have one of these sets so can't tell you exactly where the trimmer is, but it should be easy enough to find (it is adjusted as part of the FM RF alignment process so should be described in the service info).

Obviously you shouldn't start twiddling things at random if you can't find it.

Mark may have additional comments regarding this.
paulsherwin is online now  
Old 9th Feb 2019, 5:09 pm   #84
mhennessy
Dekatron
 
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
Default Re: Hacker Hunter FM volume R4

Yes, have a read of the "RF alignment (FM)" section of the manual. That calls for the use of test gear that you probably don't have, but you can get by without. The RF will almost certainly be slightly off anyway (they always are!), so nothing much to loose.

Check the "pointer datum" first. With the tuning control wound fully anti-clockwise (88MHz end), the pointer should align with the right hand end of the opening in the scale window.

(For those who haven't seen one of these, that's not a typo. As you turn clockwise, the needle moves to the left!).

Next, disable the AFC by temporarily shorting out C21 on the IF PCB. Just a test lead with a croc clips on each end will do the job. Or short pin 8 of the FM front end to chassis - whatever is easiest. The manual doesn't mention this, but trust me, it makes it much easier with these sets.

Look to see where Radio 2 is. Hopefully you know the frequency for your area? If the pointer is in about the right place, skip to the next paragraph. If not, you'll need to tweak the oscillator coil (L6 on the FM tuner PCB) - put the pointer where you think it should be (e.g., it's 88.3MHz here), then (carefully) tweak L6 so that Radio 2 comes through loud and clear. Use a non-metallic trimming tool for this - and note that it's rather "touchy", so don't move it too far.

Now go up to the top of the band. Have a look at where Radio 1 falls. If that's wrong, you'll need to tweak the oscillator capacitor (TC2 on the front end). This can be adjusted with a regular screwdriver, but note that it is also very touchy.

Unfortunately, these two adjustments interact. So here begins the fun! Go back to Radio 2 and see how far that's moved. And tweak L6 again. Then do Radio 1 and TC2 again. Repeat for as long as it takes to get them right.

Having done that, look to see where Classic FM is. If it's still too high up to have decent control over it, then tweak TC2 to bring it back in. And then check Radio 2 and L6 again. And repeat...

Having arrived at settings that you're happy with - compromising scale accuracy for range if that's required - then you ought to think about the sensitivity tweaks. If you live in a decent reception area, this might be difficult to do, and might not be strictly necessary. But here's the idea:

Stow the FM aerial to reduce the sensitivity. Tune to Radio 2 Hopefully the signal will be noticeably weak - if not, perhaps try another version of Radio 2 from the next nearest transmitter? Then, adjust L2 for best signal.

Next, go to something at the high end of the band - Radio 1, perhaps - and adjust TC1 for best signal.

As with the oscillator adjustments before, these two will interact, so repeat a few times.

Finally, remove the shorting link that disabled the AFC and enjoy

It's really not as difficult as it sounds, and providing you're careful, you won't damage anything. Do watch out for those cores in the inductors - they are brittle and can be broken if you're heavy-handed with them.

Good luck,

Mark
mhennessy is offline  
Old 9th Feb 2019, 5:21 pm   #85
Findlay
Triode
 
Join Date: Jan 2019
Location: Chelmsford, Essex, UK.
Posts: 47
Default Re: Hacker Hunter FM volume R4

Thanks again Paul and Mark for the fantastic detailed reply. I had better order a non-metallic trimming tool before I start anything so will do so straight away and get cracking as soon as it arrives!

Cheers,

Andrew
Findlay is offline  
Old 9th Feb 2019, 8:04 pm   #86
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,788
Default Re: Hacker Hunter FM volume R4

Although Mark's instructions are the right way to do it, you can get by by just adjusting the oscillator trimmer. Tune in R2 at the LF end of the dial, and adjust the trimmer. You will hear the signal detuning. Turning the trimmer in one direction will move the station up the scale, and the other direction will move it down it. Your objective is to place R2 at the extreme LF end of the tuning range, and hopefully the stations you do want to hear above Classic FM will now be there at the HF end. If the station you want is right at the end of the standard FM band then you may have to accept losing R2.

You can just use a screwdriver to adjust the trimmer.
paulsherwin is online now  
Old 9th Feb 2019, 8:09 pm   #87
Nuvistor
Dekatron
 
Nuvistor's Avatar
 
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,428
Default Re: Hacker Hunter FM volume R4

I had to do this with my 38A for Classic FM, it’s been said but you must have a suitable trimming tool. The wrong fit and you could break the core in the coil.
__________________
Frank
Nuvistor is offline  
Old 9th Feb 2019, 9:30 pm   #88
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,788
Default Re: Hacker Hunter FM volume R4

You need a trimming tool to adjust anything with a ferrite core, but not for the oscillator trimmer cap if that's all that you're touching.
paulsherwin is online now  
Old 10th Feb 2019, 12:48 pm   #89
Findlay
Triode
 
Join Date: Jan 2019
Location: Chelmsford, Essex, UK.
Posts: 47
Default Re: Hacker Hunter FM volume R4

Thanks guys,

I've made the quick adjustment to the trimmer capacitor to get Classic FM nicely on scale with R2 at the far end. I'll follow Mark's steps when I get the proper tool. Does this look suitable?

http://www.farnell.com/datasheets/308308.pdf
Findlay is offline  
Old 10th Feb 2019, 1:27 pm   #90
Nuvistor
Dekatron
 
Nuvistor's Avatar
 
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,428
Default Re: Hacker Hunter FM volume R4

That will adjust TC1 etc but not the inductors in the tuner.

Is the radio working ok with both R2 and Classic FM and the rest of the stations in between?If they are I would leave it alone, the old maxim, if it’s not broke don’t fix it.
__________________
Frank
Nuvistor is offline  
Old 10th Feb 2019, 1:59 pm   #91
Findlay
Triode
 
Join Date: Jan 2019
Location: Chelmsford, Essex, UK.
Posts: 47
Default Re: Hacker Hunter FM volume R4

Thanks Frank. I get all the stations in between OK so I might leave it for a while. I'll certainly wait until I can find the right tool.
Findlay is offline  
Old 10th Feb 2019, 2:05 pm   #92
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,788
Default Re: Hacker Hunter FM volume R4

I agree, leave it alone if it's working well. A full FM RF/IF realignment is a big job for a beginner and it's easy to mess things up. You really need a wobbulator and oscilloscope to do it properly.
paulsherwin is online now  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 3:21 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.