[Boatanchors] Lettine 240 Transmitter Plug In Coils

[LEE BAHR]

 Carl:

What kind of building did they use to construct the Lettine 240?  Or , did 
they build them in a cave?  If I didn't know better, I would have suspected 
Mad Man Muntz built this thing.  RF chokes?  Who needs RF chokes!

Lee, w0vt
>
>
>
>> Ah, the infamous Latrine 240. I spent many afternoon and weekend hours as
>> a HS student helping to assemble those TVI generators for a most nasty 
>> and
>> ungrateful pair of owners. At least they were in my home town and I could
>> ride the bike there in about 15 minutes. I quit after about 3 months and
>> positively burnt the bridges behind me!
>>
>> Carl
>> KM1H
>>
>>
>>
>>
>> ----- Original Message ----- 
>> From: "LEE BAHR" <pulsarxp at embarqmail.com>
>> To: <boatanchors at mailman.qth.net>
>> Sent: Tuesday, December 14, 2010 2:15 PM
>> Subject: Re: [Boatanchors] Lettine 240 Transmitter Plug In Coils
>>
>>
>>> As I mentioned earlier, the Lettine is a rats nest under the chassis.
>>> Everything needs to be replaced including the AC line cord.  The
>>> transmitter
>>> was modified to include a changeover relay which is also in a rats nest
>>> fashion plus much of the cloth wiring looks like it could stand
>>> replacing.
>>> Combine this with the fact many of the tie points have no lugs but are
>>> just
>>> "free in the clear floating connections", I decided I will "strip the
>>> chassis down and start over.
>>>
>>> I ordered all new caps and resistors plus a 3 prong power cord yesterday
>>> from Mouser for the re-construction.  Lettine placed some of the parts 
>>> in
>>> some really strange places.  Because of this,  I am not sure I want to
>>> remove everything at once and then start over or just replace everything
>>> section by section.  I am inclined to do it the later way as the wierd
>>> parts
>>> placement at times plus the lack of tie lugs, which I plan to add, lead
>>> me
>>> to believe I can keep parts placement closer to original specs if I do 
>>> it
>>> section by section.  I'll probably start with the power supply and then
>>> move
>>> on to the oscillator and then to the final.  Once the RF is working,
>>> I'll
>>> move on the to audio input and modulator stages.  The only problem doing
>>> the
>>> restoration this way is it is going to be harder replacing point to 
>>> point
>>> wiring.  (I think I need to take a few pictures of it as it now stands 
>>> in
>>> case I run into trouble.  I am a little nervous of using the BAMA manual
>>> as
>>> it was "re-drawn".  (I already found three small mistakes in the BAMA
>>> re-drawn schematic).
>>>
>>> When ordering the new parts,  I ordered much larger wattage resistors
>>> then
>>> the originals to make the new parts closer in size to the originals as
>>> many
>>> new parts of the same wattage are much smaller today.  Instead of 8 mfd
>>> filtering I will have 16 mfd of power supply filtering.
>>>
>>> The plate choke and parasitic supressor as original are a real joke.  I
>>> am
>>> seriously thinking of putting in a real multi-pi RF choke feeding the 
>>> 807
>>> plate and also put in a more standard parasitic supressor on the plate
>>> lead.
>>>
>>> As it stands, this is a real complicated restoration when you consider
>>> this
>>> is a simple transmitter with not too many parts.  The unorthodox layout,
>>> bad
>>> wiring job, lack of tie points and rotted wires all make the restoration
>>> difficult more difficult.  Once restored, the bottom chassis will look
>>> very
>>> unencumbered and look like it was a piece of cake to restore.
>>>
>>> Then, comes the restoration of a plug in coil set for this transmitter.
>>> This is a "cool" kind of rare transmitter.  If it were not for it's 
>>> great
>>> outside appearance, the time spent restoring this transmitter could not
>>> be
>>> justified.  When finished it will be a jewel, but you could never get
>>> your
>>> time and money out of it if you ever would want to part with it.  I know
>>> this going into the restoration.  As I mentioned earlier,  a WRL Globe
>>> Scout
>>> 40A looks like a Collins internally compared to this rigs guts.  The
>>> Lettine
>>> cabinet, front panel and transformers were all first class.  From that
>>> point
>>> on it was all downhill.
>>>
>>> Lee, w0vt
>>>
>>>
>>>
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>>
>
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