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-   -   Barlow Wadley alignment (https://www.vintage-radio.net/forum/showthread.php?t=161376)

neutronic 13th Nov 2019 10:37 pm

Barlow Wadley alignment
 
1 Attachment(s)
I recently acquired a Barlow Wadley radio XCR-30 ,old and butchered and with a remarkable lot of holes drilled in the housing.
It works, but probably needs some adjustments.By example;Radio Caroline is received at 1648 kHz instead of 648 kHz.
I have a service manual with I think the correct alignment procedure.
But that is somehow confusing,because it tells me to keep the front panel on,while the adjusting coil L3 can only be reached from behind this front panel.
Has anyone some experience with aligning this old portable?
Jard N.

Craig Sawyers 13th Nov 2019 11:23 pm

Re: Barlow Wadley alignment
 
I'm not sure of the configuration of this set and how the bandpass filters are arranged in detail. However the Racal RA17, which also uses a Wadley loop, is a sod to align and needs a wobbulator to set the filters up.

Craig

Argus25 14th Nov 2019 12:11 am

Re: Barlow Wadley alignment
 
Before attempting alignment or adjustment of any kind on the XCR-30 it is important to thoroughly understand the operation of the "Loop" (actually a mild misnomer, its a feed forward compensation system, not a typical loop of feedback).

I found the existing description of it totally sub-optimal and the method to set up the AGC defective. So I wrote my own article to explain the loop and how to set up the AGC.

Much of the other alignment instructions are "ok" but you require excellent lab gear generators & scope to do it properly. It is much more involved than a normal radio's alignment if you want perfect results from it. I have never yet found a single XCR-30 in perfect alignment. Many have been twiddled where the technician had no clue what they doing.

If you study this document it will help you:

http://worldphaco.com/uploads/THE_AM...LEY_XCR-30.pdf

Hugo.

neutronic 14th Nov 2019 11:35 am

Re: Barlow Wadley alignment
 
Thanks for your response Hugo,I already had your article printed out.
Test equipment nor experience should be the problem.
I ought to have both.

My concern is that the manual was written without feedback from practice.
By example;in the same script they tell you to set the fully opened capacitor to 0 MHz.
But then you do not get an equal of overtravel at both ends of the scale.
It is either way: or the thumbwheel is stopped by itīs mechanical endstops or by the maximum opening of the tuning capacitor.
Best wishes
Jard N.

Argus25 14th Nov 2019 11:42 am

Re: Barlow Wadley alignment
 
Quote:

Originally Posted by neutronic (Post 1191452)

My concern is that the manual was written without feedback from practice.

Jard N.

Often is the case , especially with alignment instructions where there are both electrical and mechanical alignment issues which interact that you have to contend with.

If you understand the design though, you can see what the designer intended, then its apparent what to do.

Radio Wrangler 14th Nov 2019 1:03 pm

Re: Barlow Wadley alignment
 
Quote:

Originally Posted by neutronic (Post 1191391)
It works, but probably needs some adjustments.By example;Radio Caroline is received at 1648 kHz instead of 648 kHz.
Jard N.

Experience of RA17, RA117, RA1217 and FRG7.

That could simply be mis-adjustment of the first LO, the high frequency one versus its scale. You need to see how far out it is at the top end of its scale as well as the bottom.

Don't touch the filters yet. You may not need to touch them.

David


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