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 7th Feb 2018, 11:21 pm   #1
Oldelectronics
Heptode
 
Join Date: Jan 2016
Location: Nottinghamshire, UK.
Posts: 676
Default Hacker Herald RP30 quiet spots

The RP30 I have been working on is now working the on/off switch changed (not switching) also changed two AF117s, changed for 2N2084s along with what looks like an AF125? and a AA119 diode fitted to replace the one I broke! All Checked on my new tester Good bit of kit. The radio is now working on MW/LW and I can get one station very loud on both wavebands and the amp seems to be working fine along with the new on/off/volume switch Thank you Mark! for your article http://www.markhennessy.co.uk/articl...trols.htm#rp18? Problem is the rest of the stations are there but faint despite orientating the set this radio does seem to have been messed with. With these symptoms is it likely the cores have been twiddled?
Regards

Kev

Last edited by Oldelectronics; 7th Feb 2018 at 11:26 pm.
Oldelectronics is offline  
Old 8th Feb 2018, 3:47 pm   #2
crackle
Rest in Peace
 
Join Date: Mar 2011
Location: Basildon, Essex, UK.
Posts: 4,100
Default Re: Hacker Herald RP30 quiet spots

You could try zapping the AF117's, check to see if the shorts have gone, and put them back in the radio. You could then see if the problem is one which was introduced by the use of the 2N2084 transistors.
crackle is offline  
Old 8th Feb 2018, 4:41 pm   #3
Herald1360
Dekatron
 
Herald1360's Avatar
 
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,528
Default Re: Hacker Herald RP30 quiet spots

One strong station on each waveband sounds like a problem with the aerial tuning somewhere.
__________________
....__________
....|____||__|__\_____
.=.| _---\__|__|_---_|.
.........O..Chris....O
Herald1360 is offline  
Old 8th Feb 2018, 5:51 pm   #4
ukcol
Rest in Peace
 
ukcol's Avatar
 
Join Date: May 2003
Location: Harlaxton, Lincolnshire, UK.
Posts: 3,944
Default Re: Hacker Herald RP30 quiet spots

Hello Kev

I remember from an earlier thread

https://www.vintage-radio.net/forum/...d.php?t=143457

that you replaced the overload diode (circuit ref CR1). Just lift one end of the diode and see if the set becomes sensitive again, you may have a duff diode or even have fitted it the wrong way round. There are plenty of other possible causes of course, but it's worth checking.
ukcol is offline  
Old 8th Feb 2018, 9:00 pm   #5
Oldelectronics
Heptode
 
Join Date: Jan 2016
Location: Nottinghamshire, UK.
Posts: 676
Default Re: Hacker Herald RP30 quiet spots

Thanks Guys much appreciated.

Kind regards

Kev
Oldelectronics is offline  
Old 8th Feb 2018, 10:08 pm   #6
Oldelectronics
Heptode
 
Join Date: Jan 2016
Location: Nottinghamshire, UK.
Posts: 676
Default Re: Hacker Herald RP30 quiet spots

Hi Ucol. I did check the diode and it seemed ok on my tester? I assume the black band is the cathode band? and its orientated to R5 the 680 Ohm resistor

Kind regards
Kev
Attached Thumbnails
Click image for larger version

Name:	IMG_2157.jpg
Views:	160
Size:	80.3 KB
ID:	157057   Click image for larger version

Name:	IMG_2158.jpg
Views:	114
Size:	54.9 KB
ID:	157058   Click image for larger version

Name:	IMG_2160.jpg
Views:	110
Size:	64.8 KB
ID:	157059  
Oldelectronics is offline  
Old 9th Feb 2018, 8:47 pm   #7
boxdoctor
Rest in Peace
 
Join Date: Sep 2010
Location: Ripley, Derbyshire, UK.
Posts: 785
Default Re: Hacker Herald RP30 quiet spots

Just a thought - could the problem be conductive muck between the plates of the tuning gang? Tony
boxdoctor is offline  
Old 10th Feb 2018, 12:49 pm   #8
Oldelectronics
Heptode
 
Join Date: Jan 2016
Location: Nottinghamshire, UK.
Posts: 676
Default Re: Hacker Herald RP30 quiet spots

That's a thought Tony I will give it a blast with a dry contact cleaner later and let you know.

Thanks

Kev
Oldelectronics is offline  
Old 10th Feb 2018, 1:01 pm   #9
ukcol
Rest in Peace
 
ukcol's Avatar
 
Join Date: May 2003
Location: Harlaxton, Lincolnshire, UK.
Posts: 3,944
Default Re: Hacker Herald RP30 quiet spots

Quote:
Originally Posted by Oldelectronics View Post
Hi Ucol. I did check the diode and it seemed ok on my tester? I assume the black band is the cathode band? and its orientated to R5 the 680 Ohm resistor
Yes that is correctly fitted Kev. I just mentioned it as a problem there would give the symptoms you describe. Sadly not the case here.
ukcol is offline  
Old 10th Feb 2018, 1:42 pm   #10
Oldelectronics
Heptode
 
Join Date: Jan 2016
Location: Nottinghamshire, UK.
Posts: 676
Default Re: Hacker Herald RP30 quiet spots

Hi Colin It was worth a look though! Thanks for the input
Kind Regards

Kev
Oldelectronics is offline  
Old 10th Feb 2018, 9:27 pm   #11
Oldelectronics
Heptode
 
Join Date: Jan 2016
Location: Nottinghamshire, UK.
Posts: 676
Default Re: Hacker Herald RP30 quiet spots

Hi Folks.I have been having ago this evening Removing and checking some electrolytic capacitors and T2 Which seemed to make the volume go up (no dry joint)When tapped and moved )new components fitted While they were out seemed pointless not to) Lw seems much better but MW is very quiet I notice the slug in L3 is right at the top of its travel is this normal or do you think the phantom twiddler has been in there?

Regards

Kev
Attached Thumbnails
Click image for larger version

Name:	IMG_2161.jpg
Views:	103
Size:	61.3 KB
ID:	157150   Click image for larger version

Name:	IMG_2162.jpg
Views:	129
Size:	65.2 KB
ID:	157151  
Oldelectronics is offline  
Old 21st Feb 2018, 4:52 pm   #12
Oldelectronics
Heptode
 
Join Date: Jan 2016
Location: Nottinghamshire, UK.
Posts: 676
Default Aerial for a Hacker RP30

Hi Folks

I am still having fun with this Herald RP30 gradually sorting problems from a new volume control to replacing the AF117's and the electrolytics on the tuner board and it started to work albeit very quietly apart from the odd station. I use Gold 945 MW as my standard as it booms through on my other sets. Back to the manual where it says to check all the decoupling capacitors if low gain or instability the only sensible way to test them seemed to be to take them out as once out it made sense to fit new ones. All the decoupling capacitors done apart from C5 which I am waiting for from a vendor. Testing the set after each replacement and it got gradually much better LW now seems fine. The old Dallys that were replaced were mostly way out one nearly double what its supposed to be and one reading 0.00uF! The set though booms through on MW if I hold the MW coil. Does this mean there is an alignment problem, or am I missing something? The slug does seem far out on this can I was wondering if this may be a problem?

Kind regards

Kev
Attached Thumbnails
Click image for larger version

Name:	003.jpg
Views:	86
Size:	65.2 KB
ID:	157932  

Last edited by Oldelectronics; 21st Feb 2018 at 5:08 pm.
Oldelectronics is offline  
Old 21st Feb 2018, 10:31 pm   #13
simpsons
Octode
 
Join Date: Feb 2007
Location: Harrow, London, UK.
Posts: 1,483
Default Re: Hacker Herald RP30 quiet spots

Kev

Just which stations can you hear. Make a note of the station and look up the frequency.

Then you have to convert their transmitter frequency into its wavelength. This because the Hacker RP30 dial was designed in the UK days of metres not KHz.

T3 is the oscillator transformer. You say that the slug is too far out?

Well, that it may be but before you twiddle, check out if the stations you hear are close to the wavelength shown on the dial.

Gold 945KHz is almost 317 metres which is a shame as it isn't exactly shown on the dial.

BBC Radio 4 LW though is still 1500 metres. Okay, for the purists 198 KHz or 1548 metres, and this on your dial.

Should radio 4 long wave be at the right place on the dial, all is well with T3.

The fact that putting your hand around the ferrite rod aerial makes the radio "come alive" suggests that the problem lies in the RF circuit, not IF.

It could be as easy as poor wavechange switch contacts or not so easy a broken wire of an aerial coil or dry joint.

See that the stations appear on the dial reasonably ok then move on to the RF circuit. There is both a list of MW transmitter frequencies and, KHz to metres conversion chart on the web.

I have the schematic in a Newnes and will look out for how your'e getting on.

Chris

Last edited by simpsons; 21st Feb 2018 at 10:32 pm. Reason: grammar
simpsons is offline  
Old 21st Feb 2018, 11:09 pm   #14
Oldelectronics
Heptode
 
Join Date: Jan 2016
Location: Nottinghamshire, UK.
Posts: 676
Default Re: Hacker Herald RP30 quiet spots

Thanks for that Chris that should be very helpful Gold is in approximately in the same place (about 300) on the dial as my working Hackers with an even fainter version a bit further down the dial I will have a look tomorrow when I get out to the man shed and get the exact readings to do as you suggest.

Thanks Again Chris

Kev
Oldelectronics is offline  
Old 22nd Feb 2018, 5:00 am   #15
Argus25
No Longer a Member
 
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,679
Default Re: Hacker Herald RP30 quiet spots

For the radio to have good sensitivity (or as uniform as possible) across the band it requires that the tuned frequency, which is the local oscillator frequency minus the IF frequency matches the frequency of the tuned antenna coil on the ferrite rod as closely as possible, across the whole band.

In practice, it (the tracking) is never perfect but there are three points it is bang on, near each end of the dial (or tuning range) and in the middle with small opposite errors in between.

Normally, if the radio has a 2 gang V/C where both gangs are the same max capacitance, a padder capacitor is placed in series with the oscillator section of the V/C to get the tracking right, or instead the oscillator section of the V/C is simply made with a smaller capacitance as it was in many transistor radio dual gang V/C's which don't use a padder and the oscillators low tuning range is set by the slug.

In any case it requires that the trimmer capacitor across the V/C gang that tunes the oscillator and the oscillator's coil inductance (and/or the padder value) and the IF is correctly set on its frequency, to ensure that the received signal range matches the radio's dial markings near both ends of the band so it pays to check that first and that the IF center frequency is correct and the oscillator is therefore tuning the correct frequency range. If the received frequencies appear to match the dial markings, most likely that part is all ok.

However, it then also requires that at the top end of the band, the trimmer capacitor across the V/C section that tunes the antenna coil is peaked, typically on a received signal around 1200 to 1400kHz (Alignment instructions state where). And at the low end of the band the antenna coil slid on the rod to peak it there and then re-do the top end trimmer.

Many transistor radios though are set up with wax/glue so the coil can't be moved along the rod easily and low end tracking errors just get accepted.

So it could be that it is simply the result of bad alignment, but I think it is suspicious that the antenna coil on the ferrite rod is not resonating with the V/C at the correct frequency or at all, due to a break in the wiring or switching problem.

Normally when a ferrite rod antenna system is working it is very insensitive to the electric component of the electromagnetic wave, only the magnetic component. So the fact the signal comes up a with your hand near it suggest the input stage (mixer or mixer osc) is not properly connected to the rod's coils of there is a break in the wiring.

It is easy to tell if the ferrite rod coil is resonating correctly (even with the radio powered off), but it requires an RF generator to apply a signal to a wire loop added around the rod via a series resistor and a scope to observe when the voltage on the loop comes up at resonance.
Argus25 is offline  
Old 22nd Feb 2018, 11:24 am   #16
Oldelectronics
Heptode
 
Join Date: Jan 2016
Location: Nottinghamshire, UK.
Posts: 676
Default Re: Hacker Herald RP30 quiet spots

Thank you for that Information Argus22 Your point about the coil being sensitive does seem to make sense as it does not apply to the LW coil it has no affect when touched and LW seems to be fine I just need to check 1500m later this morning when I get chance as Chris suggested I will gently go through the coil wiring as well.
thanks again
Kind Regards

Kev
Oldelectronics is offline  
Old 22nd Feb 2018, 1:13 pm   #17
Argus25
No Longer a Member
 
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,679
Default Re: Hacker Herald RP30 quiet spots

Kev,

Regarding this remark in my post:

"the trimmer capacitor across the V/C section that tunes the antenna coil is peaked, typically on a received signal around 1200 to 1400kHz"

That also means that if everything is normal (all the connections are normal and the ferrite rod antenna coil is resonating correctly with the V/C) then adjusting that trimmer will result in an easy to detect peak in the signal amplitude if you tweak it on a received signal around the 1200 to 1400 kHz mark.

If there is no obvious peak detected when you adjust that trimmer, then there is something wrong in the resonant circuit formed by the V/C and the ferrite rod's antenna coil, possibly broken connection-bad switching etc.

I like your remark about "gently going through the coil wiring". A soft and gentle approach to the repairs is always very helpful for vintage transistor radios as some of the wiring in the ferrite rod area can be quite delicate.

Hugo.
Argus25 is offline  
Old 22nd Feb 2018, 2:00 pm   #18
Oldelectronics
Heptode
 
Join Date: Jan 2016
Location: Nottinghamshire, UK.
Posts: 676
Default Re: Hacker Herald RP30 quiet spots

Thanks for that Hugo Much appreciated
Kev
Oldelectronics is offline  
Old 22nd Feb 2018, 3:00 pm   #19
Oldelectronics
Heptode
 
Join Date: Jan 2016
Location: Nottinghamshire, UK.
Posts: 676
Default Re: Hacker Herald RP30 quiet spots

I have now checked and the stations seem to be where they are supposed and Radio 4 at its best at 1500m I can't see any obvious wiring faults and the set works perfectly on MW and LW with an external aerial plugged into the ext aerial socket but not on MW with its ferrite aerial so back to the shed and the AVO to recheck those wires! and eliminate those first!
Kev
Oldelectronics is offline  
Old 28th Mar 2018, 10:19 pm   #20
Oldelectronics
Heptode
 
Join Date: Jan 2016
Location: Nottinghamshire, UK.
Posts: 676
Default Re: Hacker Herald RP30 quiet spots

Hi Folks just to bring the Saga up to date I treated my self to a Vishay trimming tool off of e bay and on the assumption that I have a radio that has been previously messed with apparently prior to any component changes? I adjusted the cores Primarily L3 Counting the turns and it now seems ok? And holding the cores in place after adjusting with wax. The Radio is now nice and loud I appreciate its hardly recommended practice and would not have done it if it wasn't obvious that the phantom twiddler had been in there. And at least it hasn't been relegated to the bottom of the round tuit pile!

Cheers

Kev
Oldelectronics is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 10:15 am.


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.