[Heathkit] meter basic movement in SB 220

[Tom Chesek]

According to my parts lists and 1984 master parts file the 
SB-200/201/220/221 do in fact use 200 uA 1400 ohm meter movements.  The 
HM-102/2102 use a 100 uA 1000 ohm meter so it sounds like Mark was right on 
the money.

Tom K3TVC


-----Original Message----- 
From: Mark K3MSB
Sent: Monday, June 09, 2014 19:36
To: John King
Cc: Heathkit List
Subject: Re: [Heathkit] meter basic movement in SB 220

John –



I have successfully used a meter from an HM-2102  to replace a blown out
SB-220 meter.



I believe BOTH the SB-200 and SB-220 amps use the same 200 uA meter.



I believe that SOME of the HM-102 or 2102 meters can be directly used, but
you have to check first.



I made measurements on an SB-220 meter and came up with the following:



280 mV for full scale deflection

1400 ohms measured resistance.



Full scale deflection current = 0.28 / 1400 = 200 uA



The meter from an HM-2102 was DIFFERENT:



105 mV full scale deflection

1040 ohms measured  resistance



Full scale deflection 0.105 / 1040 = 100 uA



My notes show that I put a 1760 ohm resistor in series with the HM-2102
meter, and shunted the pair with 2800 ohms.



I hope this helps.



73 Mark K3MSB


On Mon, Jun 9, 2014 at 2:54 PM, John King via Heathkit <
heathkit at mailman.qth.net> wrote:

> In the back of my feeble mind, I seem to remember that the movement in the
> HM102 watt meter is the same as the plate
> current meter in the SB 220 and the HM 102 meter can b used in the SB 220
> with a swap of meter faces from the the HW 102 to the meter in  the SB 220
> or Vice vesa. Please tell me what you know about the interchangeability of
> the Hm 102 movement with the plate current meter in the SB 220. Your input
> will be greatly appreciated. 73, John, K5PGW
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