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Old 11th Aug 2018, 11:38 am   #1
kentplums
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Hi again
I had to share this. It's huge. 33cl beer bottle to show scale.
Just picked it up for 9€. As far as I can make out, from the serial number, it could be an LMT 67 although I can't find any info on such a model.
The tuning knob is very tight but the rest seem OK.
The visible wiring is pretty dodgy looking.
Out with the chassis! That's sorted my weekend..
Cheers
R
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Old 11th Aug 2018, 11:58 am   #2
HamishBoxer
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Default Re: LMT 67 radio.

Great find, goes there is nothing on radiomuseum.org?
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Old 11th Aug 2018, 12:01 pm   #3
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Default Re: LMT 67 radio.

I wonder if the 63 chassis is similar, the schematic for the 63 is available.

Lawrence.
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Old 11th Aug 2018, 12:42 pm   #4
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Default Re: LMT 67 radio.

The 63 certainly looks similar chasis wise. I'll get a valve line up etc and compare
Cheers
R
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Old 11th Aug 2018, 1:05 pm   #5
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Default Re: LMT 67 radio.

Sorry! should have put " guess nothing on radiomuseum.org".Another typo.
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Old 11th Aug 2018, 2:04 pm   #6
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Default Re: LMT 67 radio.

Yes good news - on the white dial is printed " LMT 63 2 EDITION " .

R
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Old 13th Aug 2018, 11:24 am   #7
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Default Re: LMT 67 radio.

Hi
Valve lineup seems to match the schema for the 63, although there seem to be some errors on the actual document. "vue superieure" on the first page shows valve 78 near rectifier wheras it is a 77, and the two 77's to the right of the view are 78's not 77's...A momentary lapse of concentration.

As far as replacing the electrolytics C26 C27 and C28 - they are listed as 8µf and 600v (no markings on the cans) except C28 listed at 6000v. Another lapse I think. Will 10µf at 450v do as I have some?
Finally C19 is listed as 12µf at 50v. Will 10µf do for that too?

Many thanks
R
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Old 13th Aug 2018, 12:11 pm   #8
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Default Re: LMT 67 radio.

The plan view looks ok to me, the 77 would not be used as an AGC controlled RF amp as it's a short cutoff valve, the 78 is vari mu.

Your proposed replacement electrolytics should be ok.

Lawrence.
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Old 13th Aug 2018, 12:26 pm   #9
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Default Re: LMT 67 radio.

Thanks Lawrence
I'm not sure what you mean though by the plan being OK, unless you mean the schematic which has the two 78's and one 77.
The 77 is described as "lampe de silence". That's a new one on me, furthermore it is adjustable with a knob on the back of the chassis. Curious.

RR
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Old 13th Aug 2018, 1:46 pm   #10
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Default Re: LMT 67 radio.

Quote:
Originally Posted by kentplums View Post
Valve lineup seems to match the schema for the 63, although there seem to be some errors on the actual document. "vue superieure" on the first page shows valve 78 near rectifier wheras it is a 77, and the two 77's to the right of the view are 78's not 77's...A momentary lapse of concentration.
I think the "view superieure" is correct and the schematic is correct.

Lamp de silence, so far as I can make out it limits/mutes the output from the detectors AF amplifier if the signal falls below a certain level such as when tuning between stations, the 77's control grid is connected to the AGC line, it's anode is connected to the AF amps load resistor at its HT de-coupling point, in effect a very weak or no signal shunts the detectors AF amplifiers anode to chassis due to the conduction of the 77, the amount of shunting ("silencing") depending on the setting of the 77's screen grid voltage by the pot P2...…

EDIT: Just to expand on that, when the signal gets weaker the -ve AGC voltage becomes less -ve which means the control grid of the 77 will become less -ve, thus increasing the 77's anode current.

Lawrence.

Last edited by ms660; 13th Aug 2018 at 1:54 pm.
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Old 13th Aug 2018, 2:11 pm   #11
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Default Re: LMT 67 radio.

Sounds like squelch to me.....
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Old 13th Aug 2018, 2:19 pm   #12
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Default Re: LMT 67 radio.

I just put squelch into Google Translate, not the valve I hope

Lawrence.
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Old 13th Aug 2018, 3:18 pm   #13
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Default Re: LMT 67 radio.

Thanks for your time and patience once again Lawrence.
Hi Herald1360

So , unless I've got the wrong end of the stick, which is probable, I assume the set has been slightly got at and the valves put in the wrong place.

Also I noticed that the bulb holder in one of the photos had had it's bulb removed and set aside. Could this bulb be bobine BF 3,5w (L6?). Whatever the case, it's strange that it should have been removed.
So, to proceed, would it be wise to place valves as per schema and have a go with a dim bulb tester (100w?) or would that be foolhardy?

The Cossor neon tube was in place and intact.

And is C18 the audio coupling cap?

cheers
R
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Old 13th Aug 2018, 3:25 pm   #14
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Default Re: LMT 67 radio.

There look to be two lamp holders one MES and the other (toward the front) a bayonet fitting

The bayonet fitting is probably for the Neon tuning indicator (3184).

Cheers

Mike T
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Old 13th Aug 2018, 3:34 pm   #15
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Default Re: LMT 67 radio.

@ Mike T Cobaltblue...yes correct - I'd just edited previous post to mention it
Thanks

R
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Old 13th Aug 2018, 3:57 pm   #16
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Default Re: LMT 67 radio.

The bulb holders are for the tuning scale bulbs (lampes de cadran) in the 63 they are individually switched into circuit, one when LW is selected and the other when MW is selected, they are not bobine's, a bobine is an inductor, the bobine you mentioned (L6) is part of the "loudness" network that's connected to the tap on the volume control.

I think the BF 3,5w you refer to is the audio output spec. in watts, although it's not entirely clear in the document, it could be 3.4 watts or 3 to 4 watts....3 watts at least...whatever.

Yes, C18 is the coupling capacitor to the output valves control grid.

EDIT: Post crossed.

Lawrence.
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Old 13th Aug 2018, 4:04 pm   #17
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Default Re: LMT 67 radio.

Ok, but - there are two bulbs (cadran) behind the black disc which project the station onto the white squares on the front of the unit. This bulb however sits beneath the little white round button on the façade and shines through a hole in the wood. On /off light or some sort of visual meter?
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Old 13th Aug 2018, 4:10 pm   #18
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Default Re: LMT 67 radio.

Yes, the tuning indicator, there should be 3 connections to the holder assembly:

http://www.r-type.org/pdfs/3180.pdf

Lawrence.
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Old 13th Aug 2018, 4:29 pm   #19
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Default Re: LMT 67 radio.

Yes, the tuning indicator is present and sits in the bayonet socket: the mystery
bulb sits in the mes socket also shown in the last photo...
This is the bulb....nothing spesh I don't think. Maybe this is the mod that made the 63 the 67!
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Old 13th Aug 2018, 4:52 pm   #20
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Default Re: LMT 67 radio.

Might be a power on or a switched PU indicator? Trace the wiring back.

Lawrence.

Last edited by ms660; 13th Aug 2018 at 5:04 pm. Reason: another addition
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