Masterpiece BC Band Ant & 1st RF Alignment Issue

[Jack McMullen]

Evening all,

I've finally pulled out the Masterpiece after a long hibernation to finally get back into me patiently waiting Scotts. Went thru the girl 4-5 years back and did the cap/res overhaul. Putting her thru her paces yesterday found her a bit deaf compared to what I remember. So with freq gen & scope here we go......

IF came up fine as did BC OSC checks @ 1400, 600 & 950. However the RF Ant and Converter input coils peak perfectly at 1400, 950, 800, 700 with the trimmer, showing great sensitivity at 1.0uv dangling near by but drop off significantly tuning thru 650 to 600 (with cans in place, bottom cover off). At 600 there's a very noticeable delta in gain loss but using the brass side of the wand I can bring both coils back into peak about the same distance within the BC upper coils. Now Riders comments on removing a turn or two to solve this issue . I'm a bit hesitant on that drastic of an action and the coils are wound dense enough so there's no spreading possible.

Question to the experts, it is possible to short a turn on the upper 2 turns of the coils, scraping a bit of enamel off and bridging. Another less elegant possibility is to use a 1/4" ID brass tube (same as on my homebrew wand) and with coil on its side RTV into place inside at the peak. Since its covered who's to know.

What other options? I dont see Main Ganged Cap Cover removal as any possibility...I remember that ordeal! Other bands are to come after this obstacle is breached. 

Thanks Guys,

Jack

[Kent King]

Jack -

Pulling the main gang cover isn't that bad. I always solder extension wires onto the leads, makes it easier to pass them all through the feed holes and settle the cover back into place. The extensions then come off and the grid caps go back on.

However, I like your idea of inserting a bit of brass into the coil to make it peak correctly. It is a completely invisible and non-destructive fix for the set. I'd avoid doing anything with the winding wires, either removing them or trying the solder jump trick.

Good luck with it!

Kent

[Jack McMullen]

Morning Kent,

Yes the tuner cover really isn't that bad, and the extensions are the correct method, but at 2:30am here I just wasnt in the mood to face that alternative. 

I made the Scott Wand out of a 1/4" dia wood dowel about 8"-9"long. A typical dead PC switching power supply  will yield up a 1" ferrite stick ( usually +12 filter/-5vdc has a filter inductor  (~10 turns over ferrite). The brass is a 1/4" ID K&S tube (Ebay) 1" long. Both freeite stick & brass tube held on wood with shrink tubing.

I like the idea of inserting brass too and will give that a try today. I want to try multi-point tracking checks again with the wand inserted and see if the gain is maintained across the band. 

Will update

Thanks

Jack

[Jack McMullen]

Update, 

The brass inserted into the BC Ant and Converter coils correct the lack of alignment tracking. After retuning the trimmers at 1400khz and retesting at 950 & 600khz found both coils saw no improvement when either ferrite or brass ends of the wand were inserted. Tweaking the trimmers also did not improve gain. At that point I checked off the fixed box.

Pic #1 is Converter coil with 1" brass tube placed and "Goop'd". Pic #2 Ant coil with brass tube & freshly Goop'd. Wooden dowel still in place.  2 wraps of vinyl electrical tape over 1/4 dowel gives a bit of slide resistance making the 5/16" tube stay on the dowel for placement but the dowel removes easily when the Goop sets up in about 30 minutes. Pic #3 shows small clamp holding dowel in place when applying Goop to the brass tube and during 30 min. setup time.

Jack