[Heath] HL-2200 amp problem

[Robert Groh]

Diode replacement for 1N191 - a silicon (e.g. 1N270) would probably do fine - you would lose a bit of output on the low end but it is only 'relative' power. A schottky such as the 1N5711 (readily available at Mouser for $0.50) would give the low forward voltage - reverse breakdown voltage is 70V but I don't think that is a problem. See next

The voltage problem is not a problem - there is a honking resistor divider(R24 and R26) from the RF output to the diode.  So crank a 68:1 (68K/1K) voltage reduction in there and your 70V breakdown is now 4,760 volts (i.e. 70 * 68) which is obviously not a problem. 

Also 1N34A will work with a Vbr of 35V (35*68 = 2,380V) and they seem to be readily available.

73 and happy DX
Bob Groh, WA2CKY



________________________________
 From: Alexander N. Gerli <ac1wye at gmail.com>
To: heathkit at mailman.qth.net; "heath at puck.nether.net" <heath at puck.nether.net> 
Sent: Tuesday, January 21, 2014 9:15 PM
Subject: [Heath] HL-2200 amp problem
 


Hi, everyone,


My HL-2200 is running fine except for one small thing: the Relative Power positions on the Meter switch don't read.


I've checked the parts in the chain, and I'll bet the 1N191 Germanium diode is shot. All the other parts in the resistive divider chain check out, both at the output SO-239 terminal strip and also on the terminal strip below the multimeter.

Gotta be that diode.


Problem is...1N191s aren't available any more, and they're Germanium which makes them a bit fragile for reverse voltage peaks. The '191 has a PRV of 90V which seems awfully low, even given the 68K ohm 2W sampling resistor ahead of it going to the SO-239.


What to do? Does anyone on the List have any suggestions for a good substitute which is readily available? I have some 1N270s, but they're Silicon and perhaps not as sensitive as those Germaniums. Seems to me that I should use a diode with a PRV of more than just 90V!
 

Thanks for your help, as always!

73,  Sandy AC1Y

Alexander N. Gerli, Sr.
548 Allred Mill Road
Mount Airy, NC 27030-2202

Scotsmen walk about 900 miles each year.
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