[TechAssist] Re: Radio designed for B and A batteries: want to convert to ac
- From: walter wood <wwood_38478@xxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Wed, 18 Dec 2002 13:07:20 -0800 (PST)
What about a "wall wart" type power supply??
I've seen some of them that had selectable
voltages.
Seems like I've even seen one that was rated at
1.5vdc.
Went to a radio shack alarm clock/calculator.
HTH
Walter
--- Wayne Vanaman <Wayne@xxxxxxxxxxxxxxxxxxxxx>
wrote:
>
> Make a ladder resistor voltage divider off of one
> of your other supplies,
> you could run it through a coil stolen off of a
> kine board somewhere for a
> little extra filtration.
>
> Several years ago I played with a Zenith TV that
> had a bad input choke.
> 20,000uF of electrolytics was required on the
> main power input line to drop
> the noise down to what that input choke did.
>
> Wayne Vanaman
> Omega Electronics
> 6904 W Fairfield Dr
> Pensacola, FL 32506-3310
>
> 850-456-5995 voice
> 850-458-6369 fax
>
> Wayne@xxxxxxxxxxxxxxxxxxxxx
> www.PensacolaTVRepair.Com
>
> ----- Original Message -----
> From: <wjstv@xxxxxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Wednesday, December 18, 2002 2:27 PM
> Subject: [TechAssist] Radio designed for B and A
> batteries: want to convert
> to ac
>
>
> >
> > Anyone less than 50 years old should probably
> delete now.
> >
> > This is a Sears radio model 2541 using 4 tubes,
> 1A7, 1N5, 1A5, and 1H5 and
> > designed to operate off 2 "B" batteries @45v
> each (90v in series) to power
> > the B+ and an "A" battery @2v to operate the
> tube filaments. We have the
> > schematic.
> >
> > Very good friend wants us to convert it to ac.
> Using two bench dc power
> > supplies we found that the radio works and
> sounds good. We made a 90v dc
> > supply out of a bridge rectifier and the power
> transformer from a circa
> 1977
> > Zenith tv which had lots of taps to choose
> from. (first use we've found
> for
> > these transformers other than two bolted
> together to make a boat anchor).
> > Problem is the 2v filament voltage. If we use a
> bench power supply or a
> 1.5v
> > battery to power the filaments, radio plays
> fine. If we use an ac-dc
> adaptor
> > or a little transformer and bridge rectifier to
> power the filaments we
> have
> > loud ac hum (with volume turned down). Adding
> additional filter
> capacitance
> > helps but not enough.
> >
> > Any suggestions appreciated.
> >
> > Smith TV Service
> > 1930 Main St
> > Newberry, SC 29108
> > 803/276-4946
> >
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=====
Walter Wood
Future Tech Home Center
2786 Hwy. 43 N.
Lawrenceburg Tn. 38464
931-829-3337
Fax 931-829-4044
mailto:wwood_38478@xxxxxxxxx
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