[1000mp] MPV Driving SB220

[Mike Schatzberg]

Hello Jim:

Heathkit part number 69-55, is a TPDT relay, with a 110 VDC coil.  It is
indeed driven by switched DC voltage from the simple half wave power supply
circuit off of one of the transformer windings.

Perhaps Heathkit produced more than one version of the switching, which
handles both antenna transfer duties and bias switching.

I have changed many of these amps to QSK using vacuum and reed relays, and
usually have several pulls in the junk box here.  They are all DC relays.

73 and Happy DXing,

Mike
W2AJI
----- Original Message ----- 
From: "Jan Erik Holm" <sm2ekm at telia.com>
To: "All about Yaesu 1000mp" <1000mp at mailman.qth.net>
Sent: Tuesday, October 24, 2006 11:06 AM
Subject: Re: [1000mp] MPV Driving SB220


> I see, then I do know what it is.
>
> Well now, the SB-220 has a AC operated relay, need
> I say more?
>
> 73 Jim SM2EKM
> ------------------------------------------------------------
> Bill Gode, Sr. wrote:
> > Snubbing Diode (From Wikipedia):
> >
> > When the current flowing is dc, another often seen form of a snubber is
> > a simple rectifier diode placed in a circuit in parallel with an
> > inductive load (such as a relay coil or electric motor). The diode is
> > installed in the direction that ordinarily does not allow it to conduct.
> > When current to the inductive load is rapidly interrupted, a large
> > voltage spike would be produced in the reverse direction (as the
> > inductor attempts to keep current flowing in the circuit). This spike is
> > known as an "inductive kick". Placing the snubber diode in inverse
> > parallel with the inductive load allows the current from the inductor to
> > flow through the diode rather than through the switching element,
> > dissipating the energy stored in the inductive load in the series
> > resistance of the inductor and the (usually much smaller) resistance of
> > the diode (over-voltage protection). One disadvantage of simple
> > rectifier diode used as a snubber is that because the diode allows
> > current to keep flowing, the relay may stay picked-up slightly longer;
> > some circuit designs must account for this delay in the dropping-out of
> > the relay.
> >
> > 73,
> >
> > Bill, W9NHQ
> >
> >
> > ----- Original Message ----- From: "Jan Erik Holm" <sm2ekm at telia.com>
> > To: "All about Yaesu 1000mp" <1000mp at mailman.qth.net>
> > Sent: Tuesday, October 24, 2006 8:34 AM
> > Subject: Re: [1000mp] MPV Driving SB220
> >
> >
> >> What is a snubbing diode? I have never heard that
> >> expression before.
> >>
> >> /Jim SM2EKM
> >> ---------------------------
> >> Pete Smith wrote:
> >>> You can also play safe by putting a 220-ohm resistor in series with
> >>> the switching lead to limit the current through the relay contacts;
> >>> that device was published in QST many years ago, when relays in
> >>> TS-930s like mine were being fried by the relay current - the stock
> >>> SB-220 relay has no snubbing diode, which may be part or all of the
> >>> problem.
> >>>
> >>> 73, Pete
> >
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>
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