UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

sobell1980 · 3rd Dec 2019, 7:32 am

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.

3rd Dec 2019, 7:32 am	#34
sobell1980 Octode Join Date: May 2011 Location: Bromyard, Herefordshire, UK. Posts: 1,241	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.