[TechAssist] Re: Radio designed for B and A batteries: want to convert to ac
- From: "Peter oliver" <oliver_peter1@xxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Wed, 18 Dec 2002 23:41:55 +0000
The supply would have a fair amount of amperage since the tubes are
probbably in parell filiment config could always try an amp cap on the
powersupply ie 10000 uf or more. The tubes are probbably using the filiment
as the cathode if you still get ac hum on a filtered supply. I think that
when the country electrified some of these radios were retubed for indirect
cathode but that's 80 year old technology....
Peter Oliver
Tucson Radio TV
From: walter wood <wwood_38478@xxxxxxxxx>
Reply-To: techassist@xxxxxxxxxxxxx
To: techassist@xxxxxxxxxxxxx
Subject: [TechAssist] Re: Radio designed for B and A batteries: want to
convert to ac
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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