[Hallicrafters] Hallicrafters S-107 Mark 2. correction.

[Tom Lewis]

Richard,

I
 made a mistake when I calculated the leakage of the Tiny Chief 
Capacitors. When I measured the leakage I connected the positive side of
 the power supply to a capacitor. The other side of the capacitor went 
to the positive lead of a Fluke DVM set to volts. The negative lead of 
the meter went back to the negative side of the power supply.  For one 
capacitor the voltage on the meter read 1.1 volts. I divided 1.1 volts 
by 11 meg ohms  which is the impedance of the meter. This
 works out to 1 x 10 -7, which is 0.1 microamp not 0.1 milliamp.  So 
all the old Tiny Chief capacitors have 0.1 to 5 microamps of leakage.


I double checked this by connecting an old wax coated capacitor to the 
power supply and to a Simpson 260 analog meter set to milliamps. The 
meter showed 1.5 milliamps of leakage on the 10 milliamp scale. I changed the capacitor to the 
worst Tiny Chief capacitor and the meter barely moved at all on the 1 milliamp scale.

73 Tom


________________________________
 From: Richard Knoppow <1oldlens1 at ix.netcom.com>
To: Tom Lewis <n4tl2 at yahoo.com>; hallicrafters <hallicrafters at mailman.qth.net> 
Sent: Thursday, December 29, 2011 5:59 PM
Subject: Re: [Hallicrafters] Hallicrafters S-107 Mark 2.
 

----- Original Message ----- From: "Tom Lewis" <n4tl2 at yahoo.com>
To: "hallicrafters" <hallicrafters at mailman.qth.net>
Sent: Thursday, December 29, 2011 7:47 AM
Subject: [Hallicrafters] Hallicrafters S-107 Mark 2.


All the work on this radio is done and it's tuned up and back in the chassis.


I changed all the Tiny Chief capacitors with modern 630V Metalized Polypropylene Film capacitors. I also put new electrolytic capacitors under the chassis. I also changed the speaker. The original Speaker appears to have gotten wet. It sounded poor. I found a replacement speaker at Parts Express, (www.parts-express.com). The speaker is a BOSS BRS46 4" X 6" Dual cone replacement speaker, $6.39. Now the radio plays fine would a much better sound due to the new speaker. I did have to open up two of the speakers mounting holes a little with a round file. I used 3/16 inch spacers between the speaker and the radio.

I checked capacitance value of the old capacitors on a HP 4261A Capacitor meter. They all measure on the high side of the correct values. I also checked the leakage at 250 volts. The electrolytic and one Tiny Chief have 5 ma of leakage. The other Tiny Chief capacitors have 0.1 to 1 ma of leakage.


Thanks for all the comments about this radio.


73 Tom

    Is the leakage in _milliamps_ or _microamps_. Good paper caps should have less than about 5 microamps of leakage, good electrolytics less than about 15 microamps. Small amounts of leakage may make no difference in some circuits but be very critical for others. Check one of the new caps and see what sort of reading you get. My setup is somewhat
 makeshift but on new plastic film caps I don't get enough leakage to even indicate.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com