[TechAssist] Re: Radio designed for B and A batteries: want to convert to ac
- From: "Wayne Vanaman" <Wayne@xxxxxxxxxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Wed, 18 Dec 2002 14:41:31 -0600
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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