UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio 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.

Reply
 
Thread Tools
Old 30th Oct 2019, 12:18 am   #21
Techman
Nonode
 
Techman's Avatar
 
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 2,601
Default Re: Ekco U49 restoration

It's not disconnected from the mains - it's just switched off at the on/off switch. It's probably got a pole down due to having been welded closed when the suppression caps went bang. Whoever replaced them should have checked for this as it's a very common thing to happen, and can leave a chassis live when the set is switched off.

Remember, those dial bulbs form part of the heater chain in conjunction with the resistor that they're across. It might be worth checking that this resistor, or the connections to it, aren't dodgy. Clip a meter across it and go round with an insulated screw driver handle and tap tap tap it while carefully watching the meter. Also tap other components, particularly the rectifier, but be ready to switch off quickly if there's a blue flash!
Techman is offline   Reply With Quote
Old 30th Oct 2019, 3:20 pm   #22
Techman
Nonode
 
Techman's Avatar
 
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 2,601
Default Re: Ekco U49 restoration

Trying not to over complicate explanations here, but I guess the OP realises that mains neutral isn't connected directly to chassis, but via the dial lamps and shunt resistor, so all the current drawn by the radio passes through them both. You won't get sensible readings without the lamps in place and working, but you can't fit replacement lamps until the fault has been found and rectified. With blown dial lamps the resistance in series with the set will be higher, and the voltage across the rest of the resistance left in circuit will be higher.

You need to check that both poles of the on/off switch are opening on switch off, but this isn't so important at this stage other than it possibly making the chassis live after switch off, so SAFETY - always pull the mains plug out of the wall socket when making adjustments or touching the chassis frame.
Techman is offline   Reply With Quote
Old 30th Oct 2019, 11:29 pm   #23
sobell1980
Octode
 
sobell1980's Avatar
 
Join Date: May 2011
Location: Bromyard, Herefordshire, UK.
Posts: 1,096
Default Re: Ekco U49 restoration

I've not had a lot of time this evening to work on the set. I managed to grab a few minutes before going out. I've checked out the mains switch, both poles on the switch are showing to be opening when switched off, closing both poles when switched on.
Dave.
sobell1980 is offline   Reply With Quote
Old 31st Oct 2019, 2:51 pm   #24
thermionic
Heptode
 
thermionic's Avatar
 
Join Date: Apr 2003
Location: Cornwall, UK.
Posts: 683
Default Re: Ekco U49 restoration

Maybe the dial lamp shunt resistor is dry jointed or going open circuit intermittently when passing current and warming up.

SimonT.
__________________
The honesty of imperfection..........
thermionic is online now   Reply With Quote
Old 31st Oct 2019, 4:20 pm   #25
Techman
Nonode
 
Techman's Avatar
 
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 2,601
Default Re: Ekco U49 restoration

That's what I'm thinking. A bit of quick and gentle tapping with an insulated tool while monitoring voltage should soon have the fault tracked down.
Techman is offline   Reply With Quote
Old 10th Nov 2019, 8:41 pm   #26
sobell1980
Octode
 
sobell1980's Avatar
 
Join Date: May 2011
Location: Bromyard, Herefordshire, UK.
Posts: 1,096
Default Re: Ekco U49 restoration

Good evening all. I've been on and off the set throughout the week evenings. I've resoldered the scale lamp shunt resistor. I've also supplied R36 a better path back to chassis ground.
I've fitted some 6 volt bulbs (all I had). I've switched the set on for a good 10 mins. The bulbs survived and there was no intermittent very bright pulses from the bulbs. Across the series bulb chain I had a steady approx 12volts ac. R36 had been replaced some weeks back for a 10watt type wire wound. I've also replaced all but two of the large waxies.
I think the voltage I was finding on neutral with the set off was my mistake. I was assuming it was direct to chassis but it is not. If I now measure from the chassis side or bulb side to chassis and neutral I measure 0.00 v ac.
I hope this makes sense. It still hasn't blown the 6 volt bulbs but I will be ordering the correct type this week. The thing is, Fitbit were a bad soldered joint on R 36, surely the bulbs would only draw what they needed? They wouldn't see full mains? The shunt is to complete the path back to chassis if the bulbs blow, right? I haven't found something definate amiss, but reworking my soldered connections in that area seems to have cured it.
Dave.
sobell1980 is offline   Reply With Quote
Old 18th Nov 2019, 8:55 pm   #27
sobell1980
Octode
 
sobell1980's Avatar
 
Join Date: May 2011
Location: Bromyard, Herefordshire, UK.
Posts: 1,096
Default Re: Ekco U49 restoration

Hello all, sorry for my sporadic replies on here lately. I do appreciate everyone's input. Work has been commencing on the set. I have now completed the recap, well all the big waxies . I have replaced some perished wiring too along the way. All the electrolytics have been replaced too. You will be pleased to hear the correct rates bulbs have now been fitted and the set was running an hour without blowing the bulbs or seeing them glow intensely every now and again like they did before. I soldered the shunt resistor for the bulbs again and possibly recapping the set may of helped if the bulbs were seeing an occasional high DC from a leaky cap.
I have also found the alignment way, way off. I found the tuning slugs for both IF transformers screwed all the way in. I've set it up on my sig gen by ear for now. I now receive radio 4 on LW, Talk Sport and Absolute radio on MW. Here is the thing, I only get very good reception with a crock clip and lead clipped to the control grid of V1 or the TC connection. This is the same on LW or MW. The set performs tremendously with this lead clipped on to the top connection of V1. On MW I traced back trying the lead in various points. I worked back through both sides of L8 with the lead clipped onto various terminals I was testing. All made the set burst into life. I then moved back to L6 . Clipping my lead onto the S13 side of L6 again made a whopping difference. When I tested the other side of L6 connected to R2, no difference, the set can just be heard as quiet as a mouse. Move back to s13 side of L6, bursts loudly into life. The same happens on LW but I've not gone across the LW coils with my test lead yet. When I was aligning the set by ear, I connected the test leads of the sig gen to sockets A and E and nothing could be heard. Also connecting a length of wire to the aerial socket makes no difference. Only probing from S13 side of L6 through to CG of valve 1 will burst the set into life. Could it be an AVC issue? I thought this because its across all wavebands. Could I disconnect R2 to see if it is AVC issue? Any thoughts or to make me think in the right direction would be very grateful.
Very best
Dave.

Last edited by sobell1980; 18th Nov 2019 at 9:00 pm.
sobell1980 is offline   Reply With Quote
Old 21st Nov 2019, 5:06 am   #28
sobell1980
Octode
 
sobell1980's Avatar
 
Join Date: May 2011
Location: Bromyard, Herefordshire, UK.
Posts: 1,096
Default Re: Ekco U49 restoration

Hello all,
If anyone could help guide and push me in the right direction with this I would be ever do grateful. Apologies for delayed replies to your previous posts. I don't have as much time as i used to, so I just grab the odd hour here and there as and when I can. Many thanks
Dave
sobell1980 is offline   Reply With Quote
Old 23rd Nov 2019, 9:52 am   #29
sobell1980
Octode
 
sobell1980's Avatar
 
Join Date: May 2011
Location: Bromyard, Herefordshire, UK.
Posts: 1,096
Default Re: Ekco U49 restoration

Hello
I have found R2 to have gone high. It should be 100 K ohms. On my set it measure 182 k ohms. It is the control grid decoupling resistor for V1. I think it also forms part of the AVC feedback. I ran the set briefly with R2 out of circuit. Not sure if this is condoned but the set would not receive so I've soldered it back for now. Can anyone confirm if this could be a likely cause for my faults in posts #27 and #28.
Dave
sobell1980 is offline   Reply With Quote
Old 23rd Nov 2019, 11:05 am   #30
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 8,422
Default Re: Ekco U49 restoration

Although it measured high resistance I doubt it.

I would check the RF circuits and if need be the RF alignment, also in cases like this it's always worth going over any work you have done just in case.

Lawrence.
ms660 is online now   Reply With Quote
Old 24th Nov 2019, 12:52 pm   #31
sobell1980
Octode
 
sobell1980's Avatar
 
Join Date: May 2011
Location: Bromyard, Herefordshire, UK.
Posts: 1,096
Default Re: Ekco U49 restoration

Good morning, Lawrence
Thanks for the reply. I did think about the RF alignment as if I clip a lead on one side of the tuning coils the set doubles in volume. If I go the other side of the coil no difference is made and the set remains audible but very quiet. But before i went through the alignment i thought i would go through the RF components, resistors and caps etc.
I should have just gone with my hunch on checking the alignment. Afterall, if you read my previous posts I found the IF transformers cores screwed all the way in on all 4 cores! The sealing paint, locking compound seal blatantly being broken. On this set the IF transformers cores are very easily adjusted simply with the back cover removed from the set, so the phantom twiddler could have easily been at work here, which they have. However the RF tuning cores and osc tuning are only accessible with the chassis removed. I was hoping this was not the case but upon closer inspection these too have all been messed with. L5,L6, L7, aerial tuning coils and L12, L13 and L14 have all been tampered with. The tuning screws are all completely loose and seals broken. Some are screwed way out and wobble. There is only one screw that remains tight and sealed in its coil. This why I when I put my sig gen on sockets a and e I couldn't here a tone/signal getting through. I will replace R2 as a matter of course as its gone high. I will run through a full and thorough alignment. This may not be today but hopefully throughout the week. This brings us up to where we are at.
Dave.
sobell1980 is offline   Reply With Quote
Old 1st Dec 2019, 6:32 pm   #32
sobell1980
Octode
 
sobell1980's Avatar
 
Join Date: May 2011
Location: Bromyard, Herefordshire, UK.
Posts: 1,096
Default Re: Ekco U49 restoration

Hello all
Not got onto the alignment yet on the RF side. I'd forgotten I'd snipped out R2. I was just making sure everything was connected to the right sides of R2 and I noticed something strange. One end of R2 should be connected to L5,L6 and L7. The other end of L2 should be connected to the non chassis side of c24, the non valve side of r23 and the non L8 side of R3. It was here I noticed one side of R3 is connected to L8, the other is connected to the same coils side as R2 ! So between L5 and L6 and is connected to the wave change switch. It should be to the same common connection as R2, c24 and R23 . Now I haven't touched R3 at all, is this a known mod or a previous incorrect repair or I've blatantly misread something. So essentially R3 is in series with R2. Many thanks
Dave
sobell1980 is offline   Reply With Quote
Old 2nd Dec 2019, 1:43 pm   #33
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 8,422
Default Re: Ekco U49 restoration

In the manufactures schematic I'm looking at the 4.7meg resistor is connected between the input side of the TV sound tuned circuit and the junction of the AGC line decoupling components (the 100k and the 0.05uF) and the SW, MW & LW tuning coils (bottom ends).

Lawrence.

Last edited by ms660; 2nd Dec 2019 at 1:53 pm. Reason: addition
ms660 is online now   Reply With Quote
Old 3rd Dec 2019, 7:32 am   #34
sobell1980
Octode
 
sobell1980's Avatar
 
Join Date: May 2011
Location: Bromyard, Herefordshire, UK.
Posts: 1,096
Default Re: Ekco U49 restoration

A frustrating few repair sessions on the set. I have replaced R2 100k ohm that had gone high and replaced R3 also as also that was reading 7 meg rather than the quoted 4.7meg ohm. I also connected the end of R3 to the correct side of R2. C9 was replaced as I'd snipped it out of circuit as well as c2 has now also been replaced.
I found the reason for not being able to hear the sig gen when connected to sockets a and e. C3 had become detached from terminal e . It looked like it was soldered in but had broken away from the joint. Finding this and rectifying it meant I could continue with checking the full alignment.
Please bear in mind the reason for checking the alignment was because I could only receive stations with a length of wire connected to the TC connection of valve one, this was even with c3 reconnected to terminal e.
I was receiving quite a few channels on MW including, Sunshine radio! Again with an aerial connected to TC of valve 1. I pressed on with the alignment, thinking the RF alignment was out. I followed it all to the letter. I've aligned successfully several sets before. I completed the procedure and went for a switch on and try. Well, I was met with silence across all wavebands. I could just catch something warbling on MW. I focused on this and tuned the two IF transformers by ear till the station reappeared loud and clear. After doing this tuning by ear, radio 4 returned on LW.
Using my sig gen put the set further out of alignment. I've returned everything to where it roughly was but it's still not right.
I put my sig gen on my scope to test the frequency.
460khz on the sig gen measured on the scope as 500khz for IF.
600khz on the sig gen came out on the scope as 666khz for mw setting.
166khz on the sig gen came out spot on if my maths is correct for LW.
The mhz range became harder and harder to read the trace so I checked it at 1mhz. The scope read at 1.11 mhz.
In the experts opinions I'm assuming that this is enough to misalign a set? I also found I could not peak up SW at 50 metres on the tuning scale. I could tune into the sig gen on SW and chase the tone up the scale and it would disappear, I also ran out of adjustment on the tuning coil. Could I also have a valve, mixing problem? Any thoughts most welcome,
Dave.
sobell1980 is offline   Reply With Quote
Old 4th Dec 2019, 6:59 am   #35
sobell1980
Octode
 
sobell1980's Avatar
 
Join Date: May 2011
Location: Bromyard, Herefordshire, UK.
Posts: 1,096
Default Re: Ekco U49 restoration

I suppose the next thing is to put the scope on the set, see if v1 is stalling on SW and what I'm getting on MW and LW at given frequency?
sobell1980 is offline   Reply With Quote
Old 4th Dec 2019, 3:59 pm   #36
sobell1980
Octode
 
sobell1980's Avatar
 
Join Date: May 2011
Location: Bromyard, Herefordshire, UK.
Posts: 1,096
Default Re: Ekco U49 restoration

If any of the experts on here could confirm I am or I'm not heading in the right direction with this set. I feel this set might beat me or I've just got a mental block.
Dave
sobell1980 is offline   Reply With Quote
Old 4th Dec 2019, 7:33 pm   #37
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 8,422
Default Re: Ekco U49 restoration

If your observations are correct your sig gen looks to far out so far as I would be concerned, others may take a different view, if the sig gen was mine I would check it with a frequency counter or against some known transmissions.

That aside, before attempting any Osc/RF alignment or alignment checks it's important that the IF transformers are tuned to something approaching the manufactures specified IF, my own preference would be to be within +- 5 kHz, next after that is cursor alignment with respect to the tuning gangs rotor position at fully meshed or fully unmeshed in the absence of any manufactures datum reference.

All adjustable RF circuits should peak if the signal is coming through provided that the coupling from the sig gen to the tuned circuit isn't overdone, eg light coupling.

It sounds like the osc is working, so far as the mixer voltages go it's the usual that's expected to be seen at the anode and the screen grid, the voltage on the control grid using a 10meg digital meter should be -ve by a volt or two at least, how much -ve depends on the strength of the signal that's present at the AGC detector.

Lawrence.
ms660 is online now   Reply With Quote
Old Yesterday, 10:03 pm   #38
sobell1980
Octode
 
sobell1980's Avatar
 
Join Date: May 2011
Location: Bromyard, Herefordshire, UK.
Posts: 1,096
Default Re: Ekco U49 restoration

I've had the set on the scope to confirm my suspicions.
I tuned the set to 1500metres LW. That works out to exactly 200khz. 200khz plus 460khz should give a scope and frequency reading of 660khz.

The actual reading I got. I had a time period of 0.7 graticules measured at 2 micro seconds.
0.7 2uS =1.4
11.4= 714khz
714-200 = an IF of 514khz actual intermidiate frequency.
So I guess I'm getting my sig gen repaired!
Dave
Attached Thumbnails
Click image for larger version

Name:	20191204_170828.jpg
Views:	7
Size:	50.3 KB
ID:	195105   Click image for larger version

Name:	20191204_170837.jpg
Views:	7
Size:	87.4 KB
ID:	195106   Click image for larger version

Name:	Screenshot_20191204-192425_Gallery.jpg
Views:	5
Size:	33.6 KB
ID:	195107  
sobell1980 is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 2:27 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 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2019, Paul Stenning.