Ekco A724 (yes, A724) repaired

[dave_n_t]

I picked up this set at the Royal Wootton Bassett auction in February 2017; I was attracted not by the looks, nor the condition, but because it was (I was fairly sure) an export set, with 2 SW bands and MW.

The bakelite cabinet was reasonably OK - no cracks but a couple of small chips and a few deep scratches. The 'compressed fibre' rear cover was pretty tatty - coming apart in numerous places, and already with a few pieces missing. The tuning scale was OK; the paintwork at the front a little tatty, the speaker cloth a little distorted. Overall, I decided this was to be a 'repair' rather than a 'restore'.

Opening it up (and carefully preserving what I could of the fibre board back to repair later) I noticed a few things:

- a sticker with the valve line-up (ECH81, EF89, EBC81, EL84, EM84, EZ80)
- and the frequency coverage (MW 525-1640 kc/s, MSW 2.3-7.1 Mc/s, SW 6.8-22.5 Mc/s)
- the coupling capacitor to the EL84 grid had been replaced with a shiny new orange polyester one.

The last of these gave me faith to power up the set (as is my wont). I was rewarded with faint, distorted MW coverage, masses of hum, and extremely noisy controls. This was encouraging! All the major components were working, at least after a fashion. One scale bulb worked, the other didn't. The magic eye lit up and the stripe wobbled a bit.

I couldn't find a service sheet on the CDs nor DVD, nor on-line (but I didn't try that hard - with that line-up there was unlikely to be too many surprises). So I opened her up, to take out the chassis to work on.

The knobs (two inners and two outers) were all push-on. I immediately applied some vaseline to them so as not to forget. There were only 2 retaining screws in the card back, rather than the 4 - something to replace later. The ferrite rod 'rotation' knob assembly unhooked from a screw fitted into the wooden front of the set. The speaker unscrewed from the front panel (only 3 of the black-painted woodscrews were present). There were two set screws holding the metal chassis sub-frame to the floor of the bakelite case - easily removed. Two metal brackets should each have had two, 4BA nuts holding them on to the wooden front panel - all 4 were missing, but the holes in the brackets were enagged with the bolts, so they were doing some good.

With the chassis out, I could see a few more things: the main electrolytic (reservoir + smoother) had spilled its juices all over the smoothing resistor and the chassis. There had been a couple of other capacitors replaced (most noticeably a 0.1uF blue and yellow beastie).

I ended up replacing

- 50uF+50uF 350V working electrolytic
- 1500 ohm smoothing resistor (with 1600 ohm 7W)
- 2.2uF screen-grid decoupler for the EL84 (with 4.7uF 450V)
- 0.1uF screen-grid decoupler for the ECH81 and EF89
- a couple of 0.04uF decouplers around the AGC line
- EF89 (low gain)
- EZ80 (low emission - HT was down at 140V before replacement)
- 3 ohm Rola loudspeaker (the cone was torn multiply; patches of tissue paper soaked in watered-down PVA glue didn't stop all the rattles: I think the shape was really too far gone)
- the mains cable (it was a tad too short)

and cleaning

- the volume control and tone control (concentric 820K log track pots): dismantled, a small dab of vaseline on the tracks, re-assembled and moving parts lubricated
- the chassis and cabinet where electrolyte had spilled
- the cabinet (with Polishing Paste N0. 5)

I touched up the trimmers for best reception near the high frequency ends of all 3 ranges; and checked with a scrap of ferrite rod (extra inductance) and a shorting loop (reduction in inductance) that the ferrite aerial was in the best place - it was.

I did wonder about touching up the IF alignment - it seemed to be set at 470kHz, and didn't improve much with adjustment of the 4 cores. Indeed, there didn't seem to be much adjustment at all. I wonder if the adjustment on IFTs with parallel, but displaced coils is less than the ones I'm used to (two coils on the same former, with a dust core slug for each).


Finally, the disintegrating back. Previous attempts had been made to shore it up, using squares of veneer, stuck with (probably) a contact adhesive. Out came the trusty hot glue gun, to bolster not only the veneer squares, but also every joint that had been made. It's now fairly strong, if not pretty....


The radio now performs very nicely on all 3 wavebands, even in daytime with just a shortish 'throw out' aerial on my workshop. The eye almost closes on strong MW stations (5, TalkSport), but doesn't move quite so much on the SW bands. And it sounds pretty good (as one would hope with EL84 output). Another one saved!

To do:
If I decide to put some more effort into this set, there's already a list of things to do:

- extricate and polish the brass strip around the station marking scale
- replace the mounting rubbers on the tuning cap (they're just about OK at present)
- re-string the tuning cord (I think a previous owner has wound it the wrong way round the tuning knob's axle, resulting in a 'reverse' action)
- replace the EBC81 (I think it's a bit low in gain, but I don't have a spare. I might make up a pluggable replacement from an EBC41, of which I do have a few)
- find a suitable donor compressed-fibre back and graft on some more patches
- respray the painted bit of the front of the cabinet
- fit some new, undistorted, speaker cloth.


dave

[paulsherwin]

It appears to be based on the U319, at least cosmetically. The back from a scrap one of those would probably fit.

https://www.radiomuseum.org/r/ekco_u319u_31.html

[Synchrodyne]

There is evidence that Ekco used the 700-series numbers for its export models.

The A725 was mentioned in this thread: https://www.vintage-radio.net/forum/...d.php?t=101548.

And the A733 was noted in this Wireless World 1959 September item:



The 700-series was also used for National Ekco production in India, as recorded in this thread, in which were mentioned the A730, A731 and U717: https://www.vintage-radio.net/forum/...d.php?t=107413.


Cheers,

[dave_n_t]

Originally Posted by paulsherwin

It appears to be based on the U319, at least cosmetically. The back from a scrap one of those would probably fit.

https://www.radiomuseum.org/r/ekco_u319u_31.html

Paul,
Thanks for that. As you say, the similarity is very striking. I'll keep my eyes peeled!
dave