[Hallicrafters] HT-37B Tube mystery

[David C. Hallam]

Simply replacing the vacuum tube rectifiers with SS devices does nothing to
solve the problem of transformer failure.  The problem is an insulation
failure between the HV windings and the 5R4 rectifier filament winding.
Replace the 5R4 rectifier with a SS device AND disconnect the 5V filament
leads at the 5R4 socket.  This takes the HV off the 5R4 filament windings.
Don't' worry about the increase in voltage of the HV circuit.  The 6146's
can easily take it.  This does not apply to replacing the 5V4 LV rectifier
with a SS device.  If you do this, you need to compensate  so that the LV
does not change.

David
KC2JD/4

> -----Original Message-----
> From: hallicrafters-bounces at mailman.qth.net
> [mailto:hallicrafters-bounces at mailman.qth.net]On Behalf Of Jack Schrader
> Sent: Sunday, April 13, 2008 7:43 PM
> To: Darryl Jones; hallicrafters at mailman.qth.net
> Subject: Re: [Hallicrafters] HT-37B Tube mystery
>
>
> According to my 32b the three tubes across the back of the chassis are :
> oa2, 5v4 and 5r4 next to the power transformer.
>
> >From my experience and others, replace the two rectifying tubes(5v4 &
> 5r4) with solid state devices before you burn out the transformer like I
> did. The tranny does not like the combination of a higher line voltage
> and the increase temp developed in the transformer. This same advice
> goes for the ht37.
>
> ----- Original Message -----
> From: "Darryl Jones" <1986944 at comcast.net>
> To: <hallicrafters at mailman.qth.net>
> Sent: Sunday, April 13, 2008 7:30 PM
> Subject: [Hallicrafters] HT-37B Tube mystery
>
>
> Hello All,
>
> I recently picked up an HT-32B and am having problems identifying a
> missing tube. I pulled all the other tubes, and replaced any that my
> Hickock didn't like, but have yet to figure out what the missing tube is
> that wasn't on the chasis. It's located directly behind the tuning
> capacitor on that board, and doesn't have a chasis marking for it.
>
> Anyone have an ID for me?
>
> Thanks for your help,
> Darryl
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