[AMRadio] R 388


kk4tr kk4tr at hotmail.com
Thu Jul 12 07:17:59 EDT 2007


Ok John thanks for the advice. That was the the info that I needed.  I gues 
I will have to take out the PTO and make the adjustment.  Thanks John

Joe KK4TR


----- Original Message ----- 
From: "John Lawson" <jpl15 at panix.com>
To: "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Sent: Wednesday, July 11, 2007 9:45 PM
Subject: Re: [AMRadio] R 388


>
>
> On Wed, 11 Jul 2007, kk4tr wrote:
>
>> THe problem is the band spread seems to be too wide on all bands and it 
>> has been this way all the time.
>
>
>
>  By "change the slide rule dial" tdo you mean that you are adjusting the 
> 'ZERO" screw, or are you actually changing the location of the pointer 
> along the dial cord?
>
>
>   At any rate, I would suggest a bit of 'triage': Remove the bottom cover 
> of your rig, go to the place in your schematics where it shows the PTO 
> injection point ( I'm on business travel and can't recall the VT-number of 
> the tube). Using a known-accurate 5-digit frequency meter, connect to that 
> point, to observe the output frequency of the PTO. I stress that the freq 
> meter must have sufficient digits to read megahertz to 10 cycles, and of 
> known accuracy.
>
>  Find a strong WWV signal, 2.5, 5, or 10 Mhtz, and set the dials 
> mechanically so that they read properly - ie. if you're centered up on WWV 
> at 10 Mhtz, the slide rule should be on '10' and the KHtz dial on 0'.
>
>   Now roll down to the low end of the dial, go to '0' on the KHtz knob at 
> the exact end of the slide rule - note the frequency of the PTO.  Roll up 
> to the top end of the dial, be sure the Khtz knob is on '0', and measure 
> the PTO frequency at this point.
>
>
>   This will tell you immediately if the PTO frequency span is too narrow, 
> as I suspect it is.  If it is grossly 'narrow, it is likely that you will 
> need to R&R the PTO for further work... the crystal calibrator, BTW, is 
> it's own signal source and is independent of the PTO.  The PTO is the only 
> source for frequencies for tuning in the R-388.
>
>
>
>  But first collect the 'real' data so you can make that determination. 
> Also, it should be a matter of course that you check the power supply 
> voltages to be sure they're in tolerance.
>
>
>
>   And for sure let's keep this on the List - you never can tell when 
> someone else might be having the same problem and need the exact 
> info/experience that you're going to dig up.  A lot of my BA Radio Lore 
> came from exactly this kind of 'mail copying', if yahknowhuttamean...
>
>
>   I imagine others will add to this, suggest other ideas, etc.
>
>
>
>   Cheers
>
> John
>
> KB6SCO
>
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