Eddystone 870 no reception, help needed - UK Vintage Radio Repair and Restoration Discussion Forum

mfred68 · 18th Jul 2016, 3:58 pm

Hi guys
I have been given an Eddystone 870 radio to repair by one of my customers.
It was originally dead due to R18 becoming o/c.
I have replaced R18 with a suitable replacement, now the radio comes on but all the wave bands only pick up noise and various buzzes which changes as the tuning capacitor is turned from one end of the scale to the other, occasionally i can hear a very weak reception of a station on MW but so weak among the noise that you can't really understand whats being said.

I have tested all resistors which all read within their tolerances. various electrolitic capacitors have already been replaced from a previous repair by someone else.

I even tried using a 10m washing line type antenna but it still only picks up noise.

Could it be the valves ? Any advice would be most welcome.

thanks
Manfred

Station X · 18th Jul 2016, 4:29 pm

As this radio has been brought in by a customer, I assume you have a reasonable level of competence when it comes to repairing radios?

Some info here:-

http://eddystoneusergroup.org.uk/Tec...-%20S.870A.pdf

I would start by taking some voltage readings.

HamishBoxer · 19th Jul 2016, 8:08 am

Just a thought and we have all managed it at some time. This is worth going over again in case the lack of performance is a fault you have put on. Even a wrong value resistor for instance in place of correct value.

Radio Wrangler · 19th Jul 2016, 9:26 am

Do you know when it last worked? There may be time-saving clues in what has happened or been done to it since.

The very weak stations at least indicate that the LO is running.

In cases like this, you just need to get the isolating transformer and sig gen out and work your way from the audio end to the antenna socket, fixing things as you go.

David

Skywave · 19th Jul 2016, 9:56 am

Quote:

Originally Posted by Radio Wrangler

In cases like this, you just need to get the isolating transformer [and sig gen] out . . .

Manfred: are you "O.K." with the need to use an a.c. mains isolation transformer with this set? I do not wish to question your expertise and experience, etc., but simply enquiring: thinking of your safety.

Al.

Herald1360 · 19th Jul 2016, 5:39 pm

Also, don't forget that nowadays, the urban environment (possibly more so if you're located in a town centre) is absolutely filthy with interference from switched mode power supplies, Ethernet over the mains wiring, plasma tellies etc etc. The local noise level may simply be higher than any signals you might otherwise receive.

Skywave · 19th Jul 2016, 7:30 pm

Quote:

Originally Posted by Herald1360

. . . . nowadays, the urban environment (possibly more so if you're located in a town centre) is absolutely filthy with interference from {various sources} . . . .

And if you are in a rural or semi-rural area where the 415 v. 3-phase a.c mains is routed around the place on overhead wires strung between poles, there is likely to be a LOT of PLT interference.

And there seems little that we can do about that, also.

Al.

mfred68 · 20th Jul 2016, 3:55 pm

Hi again, Yes I'm an electronics engineer but valve equipment is quite before my time, though have successfully got many valve radios working. I'm self taught, and yes I always use an isolation transformer when working on live chassis.

Back to the Eddystone, On my circuit diagram there are no voltage readings given, but the anodes have about 100v on the anode of the LO valve.

I have a small transistor radio which I tune to a quiet area on AM and put it near the valve radio, I can hear it whistle as I turn the tuning cap, which indicates that the LO is working to a certain degree.

I don't have a valve tester, not worth me buying one, so now I'm wondering if anyone on here with a valve tester would be willing to test the valves for me if I send them by post?
PM me if you are.

Any further advice would be very welcome too, and thanks again.

Skywave · 21st Jul 2016, 10:50 am

Quote:

Originally Posted by mfred68

On my circuit diagram there are no voltage readings given, but the anodes have about 100v on the anode of the LO valve.
Any further advice would be very welcome too, and thanks again.

Then this should be useful: cct. diag. with table of voltages.

http://eddystoneusergroup.org.uk/Man...from%20Tor.pdf

Al.

Hermit6345 · 21st Jul 2016, 11:55 pm

As others have stated, it's essential to run this radio from an isolated supply whilst working on it, as it's an AC/DC receiver. With mine, a couple of the valveholders were dodgy and moving the valves in their holders caused the radio to burst into life. I can't remember if they were of McMurdo make but some of their B7G holders were prone to broken sockets. Fortunately, if you have a donor socket you can replace single pin holders. The IFT cores are easily broken so you might check that yours are intact. I found that running the set on 230 volts made it run very hot indeed so I found a little 230 to 110 volt transforner, set the voltage selector on the dropper to 110 volts and the set then ran quite cool. I guess that you will have checked the DC voltages and replaced all of the waxy decouplers as well. I had slight difficulty in sourcing the rectifier valve as low HT might be due to low emission.. The radio, when working correctly is quite sensitive, but does require some kind of aerial (Random wire) as it's well screened. The signal generator and output meter should tell you which part of the set is defective. R4 on 198 kHz can bea help as far as sensitivity is concerned.

Good luck!

G6Tanuki · 22nd Jul 2016, 9:06 am

Could it be the antenna connection ?

If you're using an end-fed wire you connect it to one of the "A" terminals and use the supplied link-plug to jumper between the other "A" terminal and the earth terminal.

If using a dipole antenna you connect the 2 ends of the feeder to A and A and don't use the earth terminal.

If you use an end-fed wire into one "A" terminal but don't have the link in place, sensitivity will be pathetic.

Skywave · 22nd Jul 2016, 11:13 am

Quote:

Originally Posted by Hermit6345

With mine, a couple of the valve-holders were dodgy and moving the valves in their holders caused the radio to burst into life. I can't remember if they were of McMurdo make but some of their B7G holders were prone to broken sockets.

A lot of Eddystone radios used valve sockets of the 'split pin' type. I've had no end of trouble with this type of valve socket in Eddystones. Their replacement with sockets having 'wrap around' pins is my usual fix.

Al.

18th Jul 2016, 3:58 pm	#1
mfred68 Diode Join Date: Jul 2016 Location: Swansea, Wales, UK. Posts: 5	Eddystone 870 no reception, help needed Hi guys I have been given an Eddystone 870 radio to repair by one of my customers. It was originally dead due to R18 becoming o/c. I have replaced R18 with a suitable replacement, now the radio comes on but all the wave bands only pick up noise and various buzzes which changes as the tuning capacitor is turned from one end of the scale to the other, occasionally i can hear a very weak reception of a station on MW but so weak among the noise that you can't really understand whats being said. I have tested all resistors which all read within their tolerances. various electrolitic capacitors have already been replaced from a previous repair by someone else. I even tried using a 10m washing line type antenna but it still only picks up noise. Could it be the valves ? Any advice would be most welcome. thanks Manfred

18th Jul 2016, 4:29 pm	#2
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,286	Re: Eddystone 870 no reception, help needed As this radio has been brought in by a customer, I assume you have a reasonable level of competence when it comes to repairing radios? Some info here:- http://eddystoneusergroup.org.uk/Tec...-%20S.870A.pdf I would start by taking some voltage readings. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

19th Jul 2016, 8:08 am	#3
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,931	Re: Eddystone 870 no reception, help needed Just a thought and we have all managed it at some time. This is worth going over again in case the lack of performance is a fault you have put on. Even a wrong value resistor for instance in place of correct value. __________________ G8JET BVWS Archivist and Member V.M.A.R.S

19th Jul 2016, 9:26 am	#4
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,858	Re: Eddystone 870 no reception, help needed Do you know when it last worked? There may be time-saving clues in what has happened or been done to it since. The very weak stations at least indicate that the LO is running. In cases like this, you just need to get the isolating transformer and sig gen out and work your way from the audio end to the antenna socket, fixing things as you go. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

19th Jul 2016, 5:39 pm	#6
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Eddystone 870 no reception, help needed Also, don't forget that nowadays, the urban environment (possibly more so if you're located in a town centre) is absolutely filthy with interference from switched mode power supplies, Ethernet over the mains wiring, plasma tellies etc etc. The local noise level may simply be higher than any signals you might otherwise receive. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

20th Jul 2016, 3:55 pm	#8
mfred68 Diode Join Date: Jul 2016 Location: Swansea, Wales, UK. Posts: 5	Re: Eddystone 870 no reception, help needed Hi again, Yes I'm an electronics engineer but valve equipment is quite before my time, though have successfully got many valve radios working. I'm self taught, and yes I always use an isolation transformer when working on live chassis. Back to the Eddystone, On my circuit diagram there are no voltage readings given, but the anodes have about 100v on the anode of the LO valve. I have a small transistor radio which I tune to a quiet area on AM and put it near the valve radio, I can hear it whistle as I turn the tuning cap, which indicates that the LO is working to a certain degree. I don't have a valve tester, not worth me buying one, so now I'm wondering if anyone on here with a valve tester would be willing to test the valves for me if I send them by post? PM me if you are. Any further advice would be very welcome too, and thanks again.

21st Jul 2016, 11:55 pm	#10
Hermit6345 Rest in Peace Join Date: Oct 2006 Location: North Wiltshire, UK. Posts: 638	Re: Eddystone 870 no reception, help needed As others have stated, it's essential to run this radio from an isolated supply whilst working on it, as it's an AC/DC receiver. With mine, a couple of the valveholders were dodgy and moving the valves in their holders caused the radio to burst into life. I can't remember if they were of McMurdo make but some of their B7G holders were prone to broken sockets. Fortunately, if you have a donor socket you can replace single pin holders. The IFT cores are easily broken so you might check that yours are intact. I found that running the set on 230 volts made it run very hot indeed so I found a little 230 to 110 volt transforner, set the voltage selector on the dropper to 110 volts and the set then ran quite cool. I guess that you will have checked the DC voltages and replaced all of the waxy decouplers as well. I had slight difficulty in sourcing the rectifier valve as low HT might be due to low emission.. The radio, when working correctly is quite sensitive, but does require some kind of aerial (Random wire) as it's well screened. The signal generator and output meter should tell you which part of the set is defective. R4 on 198 kHz can bea help as far as sensitivity is concerned. Good luck!

22nd Jul 2016, 9:06 am	#11
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,996	Re: Eddystone 870 no reception, help needed Could it be the antenna connection ? If you're using an end-fed wire you connect it to one of the "A" terminals and use the supplied link-plug to jumper between the other "A" terminal and the earth terminal. If using a dipole antenna you connect the 2 ends of the feeder to A and A and don't use the earth terminal. If you use an end-fed wire into one "A" terminal but don't have the link in place, sensitivity will be pathetic.