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 LEKMEK 540 1938 Restoration
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 Return to top of page · Post #: 1 · Written at 7:30:24 PM on 27 July 2017.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 508

A few photo's of the project so far, I bought this in a sad state, it had been plastered in white paint, so had to be stripped with nasty old paint stripper, then sanded and sanded. Then stained and a coat of varnish. I had trouble with the corners, just couldn't get the traces of white paint out without gouging the veneer, so instead after the first varnish coat, used a tiny brush with brown acrylic craft paint to dab into the corners. All to do now is a couple more coats with a light sand in between. how many I'm not sure, will appraise as I go. I used Cabot's Cabothane for this, it seems to be giving me a really good finish. The chassis suffered from a burnt out candohm, open between each section. A donor to who I am very grateful to, sent me another which I have fitted, until I find a 425 ohm 5 watt resistor I have 3 one watter's patched in parallel giving me 400 ohms, so in the ball park and now the radio is working and I have the correct voltages at the candohm taps, but my HT is still 40 odd volts too high . 265 volts which should be about 225? Something to figure out, but the HT comes straight from the 80 rectifier via the speaker field coil, strangely there are 3 wires coming out of the speaker going nowhere and only when two of these are joined will the speaker voice coil have continuity so maybe there was something wired in series with the voice coil? If anybody has or knows of anybody with a Lekmek 540, I'd like to talk with you! In any case the radio is working fine and I can't see the extra 40 volts causing any greif, I'm just going to have to power it up and watch for an hour or two before assembling it. One resistor reading 5,900 ohm should be 5,000, so that might have a bearing on the high voltage, that's my next job, then finding a new dial glass if I can, there is a bloke I believe who makes these. Coming along nicely!!!

Lekmek 540 Console Radio
Lekmek 540 Console Radio
Lekmek 540 Console Radio
Lekmek 540 Console Radio
Lekmek 540 Console Radio
Lekmek 540 Console Radio


 
 Return to top of page · Post #: 2 · Written at 9:57:22 PM on 27 July 2017.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6347

Photos uploaded.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 3 · Written at 9:58:26 PM on 27 July 2017.
Vintage Pete's avatar
 Location: Albury, NSW
 Member since 1 May 2016
 Member #: 1919
 Postcount: 1993

Hi Jamie,
Its a pain in the butt when people paint these things!
Particularly if they used water base paint as its a dog of a thing to get out of the grain, and best way out of it is to colour the grain as you did !.
White water base can be hard to get out with out too much rubbing
Those veneers look a bit like Blackheart in the photos.nice veneers .im on a tablet so I can only see a small photo
Pete


 
 Return to top of page · Post #: 4 · Written at 11:01:43 PM on 27 July 2017.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 1574

One thing I would like to ask is how do Candohm resisters work? I mean to say that it looks like its a continuous winding with metal clamps at certain gaps, are the windings actually connected to the clamps via solder or are they just clamped and thats it . I have never pulled one apart to see . I do understand how the resistance is divided .


 
 Return to top of page · Post #: 5 · Written at 11:41:59 PM on 27 July 2017.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6347

They were very commonplace in Australian 1930s receivers. No solder was used on the clamps, aside from terminations. They are just like hose clamps and touch the winding in just the right spot. Some were made of bare resistance wire on a fibre former and others had a coating on them to help prevent corrosion.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 6 · Written at 12:36:59 AM on 28 July 2017.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4337

Those were actually used as a voltage divider. Some were a continuous 15K others 25K. One end B- the other B+.

If a set wanted 100V for screens the clamp would be put into that position which did that. The middle would be half applied voltage, but that would change with loading. Some were used in negative to provide valve grids fixed bias. Others were tapped such that one end was back bias.

Useful, but not always reliable.


 
 Return to top of page · Post #: 7 · Written at 9:00:36 AM on 28 July 2017.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6010

Great work on the cabinet there, Jamie. A lot of effort indeed, but looks like it's paying off.


 
 Return to top of page · Post #: 8 · Written at 5:51:55 PM on 28 July 2017.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 508

Yeah that's my first coat, I'm up to five now, with a light 400 grit sand in between! Each time it dry's I notice a couple of runs or a bristle stuck in it, but I'm aiming for seven coats, but it'll get whatever it needs really. Yes I used Oak stain on the sides and the centre around the speaker area on what you'd call the head, foot, transoms and mullions, (using window terminology) also the flat bits between the very top and sides, however the top and front facings have no stain, just the wood which appears to be real English oak ply. It is actually a very attractive cabinet, why some nutter would plaster it with white paint is beyond me, but there was a "white paint" period in the mid to later 20th century where lunatics desecrated anything they could with the stuff?!?!

The candohm now fitted is coated yet there is a slot visible along the top with an uncoated strip. Yes there is a screw on the clamp which clinches it in position. The original candohm was slightly shorter and fatter and I had to modify an original clamp as the new candohm only came with one. I simply bent it back against itself twice in one spot to make a protrusion which fits into the slot in the candohm and this also brought the circumference of the clamp perfect for its application. You can slacken the clamps and move them to get any desired voltage at the taps (with the power off when adjusting) using a multimeter DC volts. My HT is still 40 volts too high, but it has been suggested a weak 42 output valve may be causing this, plus one high resistor showing 5,900 ohms which is supposed to be 5,000, so once that's swapped out and another valve tried in place we'll see the result and I'll report back to you!
Cheers! Jamie.


 
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