[Milsurplus] My Latest Project ART-13/B AM Transmitter

[Gary Pewitt]

You say you got it as a basket case last Monday?  And it looks like the 
picture today?  All I can say is "you sure do work fast"!  Magic  
maybe?  73  Gary  N9ZSV


On 5/26/2012 5:36 PM, Mack McCormick wrote:
> I'd like to thank those who responded to my ART-13 queries last week.
>
> Here are two photos of my latest restoration project. This is a Collins
> ART-13/B AM Transmitter. It came to me as a basket case last Monday
> (purchased at Dayton) missing much of its paint and many parts. This unit,
> the B model, features a rather rare crystal oscillator that allows up to 24
> crystal controlled channels (20 HF and four LF) to be selected. I'm using
> 1,200 VDC on the plates, low B+ is 400 VDC and the filaments and tuning
> motor uses 28 VDC at 10 amps.
>
> *It is producing plenty of carrier and tunes nicely. It does seem to need
> more audio modulation. I'm using an amplified D-104 which I've used
> successfully with another ART-13. I tried another mic. The sidetone volume
> is loud with this mic. The MCW tone is also way down on the carrier but not
> on the sidetone jack. I'm wondering if I have a bad T202 transformer
> between the speech amp and modulator tubes. Modulator tubes have 1,200 VDC
> when keyed and zero volts when keyed with the emission switch in the CW
> position (not a shorted relay). The plate current meter does swing on
> talking but just about 40 ma. Look at the modulated carrier on a spectrum
> analyzer does show modulation, just not a great deal (perhaps 20 %)
> Suggestions?*
>
> https://plus.google.com/photos/103063296550398702279/albums/5746961278027694465
>
> You can read more about the radio here:
> http://www.collinsclubs.com/carc/b-29/radio.html
>
> You can see the auto tune in action at my QTH or via this YouTube video
> produced by another ham.
> http://www.youtube.com/watch?v=j1S6-FDRmlA
>


-- 
Gary Pewitt   N9ZSV
1500 French Prairie Rd
Booneville, AR  72927