[Hallicrafters] R45/ARR-7 Receiver by Hallicrafters

[Richard Knoppow]

    Dot I mean is the upper left corner of six dot coding of the 
sort found on postage stamp mica caps. Silver or white for paper, 
black for mica.
    My AR-88 had several of both Micamold and Solar paper caps in 
the RF compartment. The parts list in the original handbook shows 
these to be RCA-made mica caps. Mine has one RCA mica cap in it. 
They are sort of lozenge shaped and the one in my receiver is an 
odd violet-pink. RCA had a patent on making stacked type mica 
caps. I think the reason for using the paper substitutes was that 
mica was in very short supply during WW-2. Mica continued to be 
used where nothing else would do but evidently these flat paper 
caps had low enough inductance to work. Both the Micamold and 
Solar caps are similar in construction with stacked layers of 
paper and foil with end connections. They were too far gone to 
try to measure their parasitic inductance. I replaced these with 
polypropylene plastic caps, as in fact, I did with all the paper 
caps in the receiver except the oil filled paper filter caps 
which tested OK.
     I remember being warned off Micamold along with BBs by my 
mentor when I was in my teens so they were evidently known as 
trouble makers.
     I have never seen any advertising for them although Micamold 
ads appear in some of the electronic trade journals aimed at 
manufacturers.  Solar did some advertising in amateur magazines, 
they are a complete mystery. I have a 1947 edition of the 
"Radio's Master" catalog which shows Solar in the index with the 
note "reserved". The pages don't exist, not removed, never 
printed. Earlier Solar ads in QST have the company name as Solar 
Manufacturing Co, I think in Bayone N.J. Later ones have the name 
Solar Sales Co. with a N.Y.C. address. Looks to me as though they 
were in trouble and the "sales" company was clearing out 
inventory. If anyone knows what happened to either Micamold or 
Solar I would be glad to have the information. My suspicion is 
that they got into financial trouble when war-time contracts were 
cancelled.

On 3/5/2018 11:54 AM, Alf Fisher wrote:
> Hi Richard,
> Thanks for the info.
> I will have to have a better closer look at the caps to see who 
> made them.
> Alf


-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL