[Amps] SB-220 mod

[Carl]

Thats the one and I wasnt sure of the exact failure issue. Thanks for 
posting it.

Carl
KM1H


----- Original Message ----- 
From: "kingwood" <k5jv at kingwoodcable.com>
To: "Amp Reflector" <amps at contesting.com>
Sent: Sunday, August 23, 2009 1:21 PM
Subject: [Amps] SB-220 mod


> Greetings to all,
>
>        I found this HeathKit Service Bulletin.  If this is the bulletin
> Carl mentioned, it does apply to the filament transformer, but has
> absolutely nothing to do with what we were discussing with this thread.
>
>
> ------------------------------------------------------------------------------------------------------------------
>                        April 26, 1985
> SB-221                                          Bulletin No:
> 2 KW Linear Amplifier                           SB-221-14
>
>                T2 Overheats And Fails When Operating On 220 Volt Line
>
> When the linear amplifier is wired for 220 volt AC line operation, and
> the contacts on SW2 [PN 61-45] or a high voltage transformer winding
> opens, excessive current will flow through the primary of low voltage
> transformer T2 [PN 54-238],
> causing it to fail.  To prevent this failure, the black-green lead and
> the black-yellow lead of T2 are lifted and connected together with a wire
> nut.
>
> To do this, refer to the drawing at the right and remove the black-green
> lead at lug 3 of terminal strip AE [the lead from T2 at grommet AK] and
> the black-yellow lead at lug 2 of SW2.  Connect these wires together with
> a wire nut [PN 432-199].
>
> Make this wiring change on units you receive for service which are wired
> for 220 volt AC operation.  Let the customer know that this wiring change
> has been made.  If he wants to operate on 120 volts AC, he'll have to
> reconnect these wires as shown in the assembly manual.
> -------------------------------------------------------------------------------------------------------------------73
> de Lon, K5JV
>
> 1110 Golden Bear Ln.
> Kingwood, TX 77339
>
> 281-358-4207
> 281-358-4234 FAX
> 281-795-1335 CELL
>
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