Cossor 464 - UK Vintage Radio Repair and Restoration Discussion Forum

RobertF · 25th May 2019, 10:33 am

Hi,
I am a very amateur electronics enthusiast.
I am working on a Cossor 464 radio. I have replaced all the wax and electrolytic caps and a couple of resistors which were very high. I have now got some stations coming in on all three bands.

On MW I have got a good clear station coming in on the lower end of the scale but as I go up the scale, I get loud interference. Does this mean the set needs to be realigned?.
Looking at the schematics the I.F. alignment suggests adjusting the cores of L15, L14, L13, and L12 in that order. on the I.F cans I cannot see where to do those adjustments.
Can anyone with a bit more experience point me in the right direction, or is alignment the answer.

Station X · 25th May 2019, 10:45 am

Hello and welcome to the forums.

Attempting realignment is the very last thing to try. Try using an external aerial, if you're not already doing so, a few feet of wire will do. Clean the contacts of the wavechange switch with Servisol. Check voltages and compare them with the service sheet.

I can see what looks like an original electrolytic capacitor in your picture?

Sideband · 25th May 2019, 11:08 am

Not sure how much MW reception you will receive in Ireland, a lot of MW stations closed down. Also these radios are not the best of performers. You will need a good aerial, probably more than just a few feet. A lot of the interference on MW and LW is caused by modern electronics, computers, modems, plug-in power supplies, central heating controllers etc. If the interference persists, try the set in a different location. As stated, realignment is the last thing to try.

ms660 · 25th May 2019, 11:12 am

Quote:

Originally Posted by RobertF

Looking at the schematics the I.F. alignment suggests adjusting the cores of L15, L14, L13, and L12 in that order. on the I.F cans I cannot see where to do those adjustments.
Can anyone with a bit more experience point me in the right direction, or is alignment the answer.

This is for info, not advice to go tweeking...The slotted adjusters are on the top and the bottom of the IF transformers, they are also shown on the Trader sheet chassis pictures.

Lawrence.

HamishBoxer · 25th May 2019, 11:51 am

Very rarely does a set (untouched) need alignment.

Of course,Welcome to the forum.

Argus25 · 25th May 2019, 1:16 pm

Whether a radio is in perfect alignment, or not, you can never know until you set it up with a good test generator (correctly coupled-see below) and have a very good meter or scope monitoring the detected output.

Ideally, you take measurements and collect data first, then after the alignment process you collect data again and then you would know if it was out of alignment and if you have improved it in any part of the band it tunes.

Generally, it pays to heed the manufacturer's instructions on the particular radio for the process. They normally specify frequencies at the upper and lower end of the band to be peaked, and the correct IF frequency and there are the issues of ensuring correct dial pointer adjustment.

Generally when the test RF signal (from a known good and accurately calibrated RF generator) is coupled to the radios RF inputs it is best that it is as loosely coupled as possible. One big error is to load the tuned circuits that are being adjusted. The same applies to the IF stage adjustments.

Unless you are experienced in the process and collect initial baseline data on the radio's sensitivity at at least 3 or 4 points on the band, you may never know if you have genuinely improved the sensitivity or performance of the radio, after you have attempted alignment, or perhaps made it worse.

Many people are so keen to attempt an alignment, in the rush, they do not collect baseline data and therefore can never be 100% sure they have made things better, the only reference then being the manufacturer's sensitivity specs which sometimes are not that helpful.

Over the years I have come to align all of my MW & SW radios with a transmitting antenna on the other side of the workshop, to avoid any loading effects of coupling directly into the radios circuitry.

There is also the issue of the radios AGC. If you consider, under difficult conditions, you are trying to pull in a very weak station, the agc is inactive, so it is actually better to align under this condition. High signal levels and AGC action mask the exact tuning peaks and even shift them. So the generator level is very important too, that its not too high and just enough to overcome the noise.

RobertF · 25th May 2019, 2:26 pm

Thanks for the advise.
That original looking cap in the picture is only the shell, It has been replaced with a modern cap.
I have an external aerial about 30m long connected which gives me some channels on SW and better volume on the other 2 bands.
I don't know much about this model of radio and am just comparing the sound to another radio I have. Perhaps this is as good as the sound gets.

paulsherwin · 25th May 2019, 2:45 pm

To restate what others have said, radios do not normally go seriously out of alignment unless somebody has been twiddling.

Unfortunately there is a lot of electrical interference in the modern world, and this may be the root of your problem. Digiboxes, computers, mobile phones and CFL light bulbs are just some of the things that can wipe out AM broadcast reception. To complicate things further, the big RTE transmitters at Tullamore and Athlone no longer operate, so there may not be strong MW broadcast signals at your location.

crackle · 25th May 2019, 3:06 pm

Flat screen computer monitors give of tremendous interference that can swamp any radio on FM and AM if they are in close proximity to the radio.
Fluorescent lights, LED lights and ordinary light dimmers and all sorts of mains power supplies all contribute to the mush and static which can prevent a radio from receiving properly.
Mike

RobertF · 25th May 2019, 5:26 pm

I moved the set to a different location with much better results. there is a little bit of interference but nothing like what was in the work area.
Having a look around the work area, I have everything that members say could cause interference.

I can live with the set as it is. Thanks for the advice. I will put it back together and will shortly be working on another set.

MurphyNut · 25th May 2019, 6:34 pm

Quote:

Originally Posted by RobertF

I moved the set to a different location with much better results. there is a little bit of interference but nothing like what was in the work area.
Having a look around the work area, I have everything that members say could cause interference.

I can hardly get decent worthwhile sound from my vintage radios in the house due to all those modern appliances mentioned.
Not everyone has the luxury, but my radios sound great in my outbuildings down the end of my long garden...location is "almost" everything!

rontech · 25th May 2019, 7:20 pm

Back in the 1940's the family radios were fed from a long aerial wire stretched from a pole at the bottom of the garden to the eaves of the house. There was a porcelain insulator at each end and the downlead was a screened cable. There was also an earth lead from the radio earth socket to a 2 ft copper spike driven into the garden soil.

We seemed to pick up programmes from all over the world.

If practicable, maybe some of these features could solve some of the present day interference problems.

A thought occurred to me that if the screened cable made the connection to the aerial wire at a point 1/3 away from the house, the active part of the aerial wire would be well away from interference sources.

The remote end maybe to a pole at the bottom of the garden fixed to the shed roof.

egerton · 30th May 2019, 11:21 am

Off topic but worthy of note: I used to have an aerial as you describe back in the 70s when I bought old radios from jumble sales. A word of caution - if the aerial is well insulated as described it should be disconnected in thundery weather. I used to unplug the set and fit a small spark gap between the aerial and earth and have seen small sparks when a thunderstorm was in the vicinity. That illustrated the high induced voltages that thunderclouds can create which would probably have damaged the set.

25th May 2019, 10:33 am	#1
RobertF Triode Join Date: May 2019 Location: Cavan, Republic of Ireland. Posts: 42	Cossor 464 Hi, I am a very amateur electronics enthusiast. I am working on a Cossor 464 radio. I have replaced all the wax and electrolytic caps and a couple of resistors which were very high. I have now got some stations coming in on all three bands. On MW I have got a good clear station coming in on the lower end of the scale but as I go up the scale, I get loud interference. Does this mean the set needs to be realigned?. Looking at the schematics the I.F. alignment suggests adjusting the cores of L15, L14, L13, and L12 in that order. on the I.F cans I cannot see where to do those adjustments. Can anyone with a bit more experience point me in the right direction, or is alignment the answer. Attached Thumbnails

25th May 2019, 10:45 am	#2
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Cossor 464 Hello and welcome to the forums. Attempting realignment is the very last thing to try. Try using an external aerial, if you're not already doing so, a few feet of wire will do. Clean the contacts of the wavechange switch with Servisol. Check voltages and compare them with the service sheet. I can see what looks like an original electrolytic capacitor in your picture? __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

25th May 2019, 11:08 am	#3
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,571	Re: Cossor 464 Not sure how much MW reception you will receive in Ireland, a lot of MW stations closed down. Also these radios are not the best of performers. You will need a good aerial, probably more than just a few feet. A lot of the interference on MW and LW is caused by modern electronics, computers, modems, plug-in power supplies, central heating controllers etc. If the interference persists, try the set in a different location. As stated, realignment is the last thing to try. __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....

25th May 2019, 11:51 am	#5
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,932	Re: Cossor 464 Very rarely does a set (untouched) need alignment. Of course,Welcome to the forum. __________________ G8JET BVWS Archivist and Member V.M.A.R.S

25th May 2019, 1:16 pm	#6
Argus25 No Longer a Member Join Date: Oct 2016 Location: Maroochydore, Queensland, Australia. Posts: 2,679	Re: Cossor 464 Whether a radio is in perfect alignment, or not, you can never know until you set it up with a good test generator (correctly coupled-see below) and have a very good meter or scope monitoring the detected output. Ideally, you take measurements and collect data first, then after the alignment process you collect data again and then you would know if it was out of alignment and if you have improved it in any part of the band it tunes. Generally, it pays to heed the manufacturer's instructions on the particular radio for the process. They normally specify frequencies at the upper and lower end of the band to be peaked, and the correct IF frequency and there are the issues of ensuring correct dial pointer adjustment. Generally when the test RF signal (from a known good and accurately calibrated RF generator) is coupled to the radios RF inputs it is best that it is as loosely coupled as possible. One big error is to load the tuned circuits that are being adjusted. The same applies to the IF stage adjustments. Unless you are experienced in the process and collect initial baseline data on the radio's sensitivity at at least 3 or 4 points on the band, you may never know if you have genuinely improved the sensitivity or performance of the radio, after you have attempted alignment, or perhaps made it worse. Many people are so keen to attempt an alignment, in the rush, they do not collect baseline data and therefore can never be 100% sure they have made things better, the only reference then being the manufacturer's sensitivity specs which sometimes are not that helpful. Over the years I have come to align all of my MW & SW radios with a transmitting antenna on the other side of the workshop, to avoid any loading effects of coupling directly into the radios circuitry. There is also the issue of the radios AGC. If you consider, under difficult conditions, you are trying to pull in a very weak station, the agc is inactive, so it is actually better to align under this condition. High signal levels and AGC action mask the exact tuning peaks and even shift them. So the generator level is very important too, that its not too high and just enough to overcome the noise. Last edited by Argus25; 25th May 2019 at 1:23 pm.

25th May 2019, 2:26 pm	#7
RobertF Triode Join Date: May 2019 Location: Cavan, Republic of Ireland. Posts: 42	Re: Cossor 464 Thanks for the advise. That original looking cap in the picture is only the shell, It has been replaced with a modern cap. I have an external aerial about 30m long connected which gives me some channels on SW and better volume on the other 2 bands. I don't know much about this model of radio and am just comparing the sound to another radio I have. Perhaps this is as good as the sound gets.

25th May 2019, 2:45 pm	#8
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,943	Re: Cossor 464 To restate what others have said, radios do not normally go seriously out of alignment unless somebody has been twiddling. Unfortunately there is a lot of electrical interference in the modern world, and this may be the root of your problem. Digiboxes, computers, mobile phones and CFL light bulbs are just some of the things that can wipe out AM broadcast reception. To complicate things further, the big RTE transmitters at Tullamore and Athlone no longer operate, so there may not be strong MW broadcast signals at your location.

25th May 2019, 3:06 pm	#9
crackle Rest in Peace Join Date: Mar 2011 Location: Basildon, Essex, UK. Posts: 4,100	Re: Cossor 464 Flat screen computer monitors give of tremendous interference that can swamp any radio on FM and AM if they are in close proximity to the radio. Fluorescent lights, LED lights and ordinary light dimmers and all sorts of mains power supplies all contribute to the mush and static which can prevent a radio from receiving properly. Mike

25th May 2019, 5:26 pm	#10
RobertF Triode Join Date: May 2019 Location: Cavan, Republic of Ireland. Posts: 42	Re: Cossor 464 I moved the set to a different location with much better results. there is a little bit of interference but nothing like what was in the work area. Having a look around the work area, I have everything that members say could cause interference. I can live with the set as it is. Thanks for the advice. I will put it back together and will shortly be working on another set.

25th May 2019, 7:20 pm	#12
rontech Heptode Join Date: Jun 2017 Location: Southport, Merseyside, UK. Posts: 646	Re: Cossor 464 Back in the 1940's the family radios were fed from a long aerial wire stretched from a pole at the bottom of the garden to the eaves of the house. There was a porcelain insulator at each end and the downlead was a screened cable. There was also an earth lead from the radio earth socket to a 2 ft copper spike driven into the garden soil. We seemed to pick up programmes from all over the world. If practicable, maybe some of these features could solve some of the present day interference problems. A thought occurred to me that if the screened cable made the connection to the aerial wire at a point 1/3 away from the house, the active part of the aerial wire would be well away from interference sources. The remote end maybe to a pole at the bottom of the garden fixed to the shed roof. __________________ Time flies like an arrow, fruit flies like a banana

30th May 2019, 11:21 am	#13
egerton Pentode Join Date: May 2018 Location: Beverley, East Riding Posts: 110	Re: Cossor 464 Off topic but worthy of note: I used to have an aerial as you describe back in the 70s when I bought old radios from jumble sales. A word of caution - if the aerial is well insulated as described it should be disconnected in thundery weather. I used to unplug the set and fit a small spark gap between the aerial and earth and have seen small sparks when a thunderstorm was in the vicinity. That illustrated the high induced voltages that thunderclouds can create which would probably have damaged the set.