Hello All,
I have this transformer (Triad-Utrad F-29U). It has 3 primaries, used to adjust the center tapped output voltage which is rated at 11 amps. If I used the 10 v setting and two diodes I will full-wave rectify and have 5v but converting to peak (DC) from RMS I will have about 7 volts.
The diodes I'll be using are 40 amp 1N249-RB diodes. I am considering either one filter capacitor. But I might use a resistor and another filter capacitor to reduce the noise. Is one filter capacitor enough or should I use the two?
I will be operating an antique car radio that has a solid state vibrator inside. This is the Mopar 808. Will I have enough current? The radio will draw between 6 and 8 amps at about 6 volts. I think in a 6 volt car it's 7.2 volts DC. I think this will work. What does everyone think?

Thanks,

Dave

:Hello All,
: I have this transformer (Triad-Utrad F-29U). It has 3 primaries, used to adjust the center tapped output voltage which is rated at 11 amps. If I used the 10 v setting and two diodes I will full-wave rectify and have 5v but converting to peak (DC) from RMS I will have about 7 volts.
: The diodes I'll be using are 40 amp 1N249-RB diodes. I am considering either one filter capacitor. But I might use a resistor and another filter capacitor to reduce the noise. Is one filter capacitor enough or should I use the two?
: I will be operating an antique car radio that has a solid state vibrator inside. This is the Mopar 808. Will I have enough current? The radio will draw between 6 and 8 amps at about 6 volts. I think in a 6 volt car it's 7.2 volts DC. I think this will work. What does everyone think?
:
:Thanks,
:
:Dave

Dave:
Car radios are designed to work through a pretty wide range of Voltages, from less than six to 7.2. you will, IMHO, do fine if the xfmr can handle the load. And, remember, there is lots of filtering in the radio itself, so one cap should do it OK. If it doesn't, add another cap.
Lewis

Lewis,
What value capacitor should I use? 1000 mf or higher? Is this too high? If the transformer is rated at 11 amps on the secondary, I think I'll have enough current. But I might not. As I was saying, the radio probably draws between 6 and 8 amps. The transformer will probably get quite warm.
I've restored many many of these car radios. But I usually use a 6 volt car battery to operate them. I've never used a power supply before because it cost much much more than a car battery and charger.

Thanks,

Dave
::Hello All,
:: I have this transformer (Triad-Utrad F-29U). It has 3 primaries, used to adjust the center tapped output voltage which is rated at 11 amps. If I used the 10 v setting and two diodes I will full-wave rectify and have 5v but converting to peak (DC) from RMS I will have about 7 volts.
:: The diodes I'll be using are 40 amp 1N249-RB diodes. I am considering either one filter capacitor. But I might use a resistor and another filter capacitor to reduce the noise. Is one filter capacitor enough or should I use the two?
:: I will be operating an antique car radio that has a solid state vibrator inside. This is the Mopar 808. Will I have enough current? The radio will draw between 6 and 8 amps at about 6 volts. I think in a 6 volt car it's 7.2 volts DC. I think this will work. What does everyone think?
::
::Thanks,
::
::Dave
:
:Dave:
:Car radios are designed to work through a pretty wide range of Voltages, from less than six to 7.2. you will, IMHO, do fine if the xfmr can handle the load. And, remember, there is lots of filtering in the radio itself, so one cap should do it OK. If it doesn't, add another cap.
:Lewis

Dave

Value of cap will be determined by how much current you plan to draw and allowable ripple. 1000mf may sound like a lot but at high current it will leave lots of ripple. I would use 10 times that.

Using 10 volt center tapped winding you wouldn't have enough voltage to operate the radio. Yes 5 volts X 1.414 minus diode drop will give about 6.5 volts but that's without load. Under load expect it to drop to around 5 volts. Exact voltage depends on loading and filter cap value.

Why not use a higher voltage and add a series regulator. This would give a quiet, stable voltage output.

Norm

:Lewis,
: What value capacitor should I use? 1000 mf or higher? Is this too high? If the transformer is rated at 11 amps on the secondary, I think I'll have enough current. But I might not. As I was saying, the radio probably draws between 6 and 8 amps. The transformer will probably get quite warm.
: I've restored many many of these car radios. But I usually use a 6 volt car battery to operate them. I've never used a power supply before because it cost much much more than a car battery and charger.
:
:Thanks,
:
:Dave
:::Hello All,
::: I have this transformer (Triad-Utrad F-29U). It has 3 primaries, used to adjust the center tapped output voltage which is rated at 11 amps. If I used the 10 v setting and two diodes I will full-wave rectify and have 5v but converting to peak (DC) from RMS I will have about 7 volts.
::: The diodes I'll be using are 40 amp 1N249-RB diodes. I am considering either one filter capacitor. But I might use a resistor and another filter capacitor to reduce the noise. Is one filter capacitor enough or should I use the two?
::: I will be operating an antique car radio that has a solid state vibrator inside. This is the Mopar 808. Will I have enough current? The radio will draw between 6 and 8 amps at about 6 volts. I think in a 6 volt car it's 7.2 volts DC. I think this will work. What does everyone think?
:::
:::Thanks,
:::
:::Dave
::
::Dave:
::Car radios are designed to work through a pretty wide range of Voltages, from less than six to 7.2. you will, IMHO, do fine if the xfmr can handle the load. And, remember, there is lots of filtering in the radio itself, so one cap should do it OK. If it doesn't, add another cap.
::Lewis

The F-29 has taps that will give you 12V center-tapped. That should give you about 8.5V DC, less about 1 V for rectifier drop. You could also use Schottky rectifiers and cut that drop down to under a half volt. As Norm says, use more filter capacitance. I usually estimate about 1000 uF per output ampere.

You could also run the 10V configuration as a bridge rectifier (4 diodes) with a regulator... might be good for about 5 amps output.

Rich

:Dave
:
: Value of cap will be determined by how much current you plan to draw and allowable ripple. 1000mf may sound like a lot but at high current it will leave lots of ripple. I would use 10 times that.
:
: Using 10 volt center tapped winding you wouldn't have enough voltage to operate the radio. Yes 5 volts X 1.414 minus diode drop will give about 6.5 volts but that's without load. Under load expect it to drop to around 5 volts. Exact voltage depends on loading and filter cap value.
:
: Why not use a higher voltage and add a series regulator. This would give a quiet, stable voltage output.
:
:Norm
:
:
:
:
:
::Lewis,
:: What value capacitor should I use? 1000 mf or higher? Is this too high? If the transformer is rated at 11 amps on the secondary, I think I'll have enough current. But I might not. As I was saying, the radio probably draws between 6 and 8 amps. The transformer will probably get quite warm.
:: I've restored many many of these car radios. But I usually use a 6 volt car battery to operate them. I've never used a power supply before because it cost much much more than a car battery and charger.
::
::Thanks,
::
::Dave
::::Hello All,
:::: I have this transformer (Triad-Utrad F-29U). It has 3 primaries, used to adjust the center tapped output voltage which is rated at 11 amps. If I used the 10 v setting and two diodes I will full-wave rectify and have 5v but converting to peak (DC) from RMS I will have about 7 volts.
:::: The diodes I'll be using are 40 amp 1N249-RB diodes. I am considering either one filter capacitor. But I might use a resistor and another filter capacitor to reduce the noise. Is one filter capacitor enough or should I use the two?
:::: I will be operating an antique car radio that has a solid state vibrator inside. This is the Mopar 808. Will I have enough current? The radio will draw between 6 and 8 amps at about 6 volts. I think in a 6 volt car it's 7.2 volts DC. I think this will work. What does everyone think?
::::
::::Thanks,
::::
::::Dave
:::
:::Dave:
:::Car radios are designed to work through a pretty wide range of Voltages, from less than six to 7.2. you will, IMHO, do fine if the xfmr can handle the load. And, remember, there is lots of filtering in the radio itself, so one cap should do it OK. If it doesn't, add another cap.
:::Lewis

Dave,
See my post 02-02-09, under "Electrolytic Age"

marv

:Hello All,
: I have this transformer (Triad-Utrad F-29U). It has 3 primaries, used to adjust the center tapped output voltage which is rated at 11 amps. If I used the 10 v setting and two diodes I will full-wave rectify and have 5v but converting to peak (DC) from RMS I will have about 7 volts.
: The diodes I'll be using are 40 amp 1N249-RB diodes. I am considering either one filter capacitor. But I might use a resistor and another filter capacitor to reduce the noise. Is one filter capacitor enough or should I use the two?
: I will be operating an antique car radio that has a solid state vibrator inside. This is the Mopar 808. Will I have enough current? The radio will draw between 6 and 8 amps at about 6 volts. I think in a 6 volt car it's 7.2 volts DC. I think this will work. What does everyone think?
:
:Thanks,
:
:Dave

Dave,
Here's a whole thing on easy conversion of an old used ATX computer supply to a powerful lab supply:
http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply

Remember, however, that computer power supplies are switch-mode. Several implications:

- they are designed to work with a minimum load and could be unstable with load disconnected.

- being switch-mode, you can get all sorts of radiated and conducted RFI if you don't have good shielding and filtering.

Personally, I would stick with conventional linear designs for a lab supply.

Rich

:Dave,
:Here's a whole thing on easy conversion of an old used ATX computer supply to a powerful lab supply:
:http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply

Rich,
Agree There's enough noise and interference coming thru the air, without introducing more into the radio via a power supply. I was repairing a 12V Delco truck radio, and my batt supply was getting discharged, so hooked up a 12V switcher sitting on my bench, and the volume dropped significantly. Not so much noise, but think some ultrasonic noise was affecting the AVC. The suggestion in my earlier post was a simple linear regulator, using scrapped PC supply parts.

marv

:Remember, however, that computer power supplies are switch-mode. Several implications:
:
:- they are designed to work with a minimum load and could be unstable with load disconnected.
:
:- being switch-mode, you can get all sorts of radiated and conducted RFI if you don't have good shielding and filtering.
:
:Personally, I would stick with conventional linear designs for a lab supply.
:
:Rich
:
:
::Dave,
::Here's a whole thing on easy conversion of an old used ATX computer supply to a powerful lab supply:
::http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply