All:

I attempted a power up of my farm radio this weekend. It takes 1.5 V filament voltage and 90 V B+. I attempted to use a "wall wart" that had 500 ma capacity, to power the filamets and a simple transformer-diode-filter cap arrangement to power the 90 V. I ended up drawing very heavy B+ current. Is it possible that I had a ground loop between the two supplies plugged into the wall?

Thanks
Lou

Are you using a well filtered supply for the fillaments??? Batery tubes are meant to be run on a very "clean" DC voltage. Not sure if this is your problem, but it might be. Try filtering your "A" supply to the fillaments.

A few things to consider: I don't know of many wall warts that put out 1.5 volts....are you sure you have the correct filament voltage. Unregulated wall wart voltage can some times be more than 50% over what it is rated at depending on the load.....monitor your filament volage. If you are drawing excess B+ current do you have the correct polarity. There may also be a defective component (usually a capacitor) in the radio. Sometimes in the farm radios a mouse moves in...look to see if the capacitors are chewed up. There are many more things to look at this is just a start. Please let us know your results.

Dim

:Are you using a well filtered supply for the fillaments??? Batery tubes are meant to be run on a very "clean" DC voltage. Not sure if this is your problem, but it might be. Try filtering your "A" supply to the fillaments.

Another suggestion: Try running the radio's filaments with a couple of D cells in parallel. Try running the B+ with some (10) 9 volt batteries in series. This will help you determin if your home brew power supplies are acting up or if the radio has a defect.
If you have applied over voltage (2X or more) to the filaments you may have fried them. In some cases the tubes light up but they won't conduct.

Dim

:A few things to consider: I don't know of many wall warts that put out 1.5 volts....are you sure you have the correct filament voltage. Unregulated wall wart voltage can some times be more than 50% over what it is rated at depending on the load.....monitor your filament volage. If you are drawing excess B+ current do you have the correct polarity. There may also be a defective component (usually a capacitor) in the radio. Sometimes in the farm radios a mouse moves in...look to see if the capacitors are chewed up. There are many more things to look at this is just a start. Please let us know your results.
:
:Dim
:
:
:
::Are you using a well filtered supply for the fillaments??? Batery tubes are meant to be run on a very "clean" DC voltage. Not sure if this is your problem, but it might be. Try filtering your "A" supply to the fillaments.

Thanks

I have a "wall wart" that advertises 1.5 Volts (selectable voltage). I thought that 500ma capacity would be more than enough.

I did not run over voltage. However, it did appear that the filament supply AND the plate supply were both being dragged down. I agree with running the set on pure DC to see what happens, and this is what I will do.

PS The set is very clean. It does not appear that I have had any "visitors" ( the chassis underside is fully enclosed anyway).

Thanks - Lou
:Another suggestion: Try running the radio's filaments with a couple of D cells in parallel. Try running the B+ with some (10) 9 volt batteries in series. This will help you determin if your home brew power supplies are acting up or if the radio has a defect.
:If you have applied over voltage (2X or more) to the filaments you may have fried them. In some cases the tubes light up but they won't conduct.
:
:Dim
:
:
:
:
:
:
:
:
::A few things to consider: I don't know of many wall warts that put out 1.5 volts....are you sure you have the correct filament voltage. Unregulated wall wart voltage can some times be more than 50% over what it is rated at depending on the load.....monitor your filament volage. If you are drawing excess B+ current do you have the correct polarity. There may also be a defective component (usually a capacitor) in the radio. Sometimes in the farm radios a mouse moves in...look to see if the capacitors are chewed up. There are many more things to look at this is just a start. Please let us know your results.
::
::Dim
::
::
::
:::Are you using a well filtered supply for the fillaments??? Batery tubes are meant to be run on a very "clean" DC voltage. Not sure if this is your problem, but it might be. Try filtering your "A" supply to the fillaments.

:Thanks
:
:I have a "wall wart" that advertises 1.5 Volts (selectable voltage). I thought that 500ma capacity would be more than enough.
:
:I did not run over voltage. However, it did appear that the filament supply AND the plate supply were both being dragged down. I agree with running the set on pure DC to see what happens, and this is what I will do.
:
:PS The set is very clean. It does not appear that I have had any "visitors" ( the chassis underside is fully enclosed anyway).
:
:Thanks - Lou
::Another suggestion: Try running the radio's filaments with a couple of D cells in parallel. Try running the B+ with some (10) 9 volt batteries in series. This will help you determin if your home brew power supplies are acting up or if the radio has a defect.
::If you have applied over voltage (2X or more) to the filaments you may have fried them. In some cases the tubes light up but they won't conduct.
::
::Dim
::
::
::
::
::
::
::
::
:::A few things to consider: I don't know of many wall warts that put out 1.5 volts....are you sure you have the correct filament voltage. Unregulated wall wart voltage can some times be more than 50% over what it is rated at depending on the load.....monitor your filament volage. If you are drawing excess B+ current do you have the correct polarity. There may also be a defective component (usually a capacitor) in the radio. Sometimes in the farm radios a mouse moves in...look to see if the capacitors are chewed up. There are many more things to look at this is just a start. Please let us know your results.
:::
:::Dim
:::
:::
:::
::::Are you using a well filtered supply for the fillaments??? Batery tubes are meant to be run on a very "clean" DC voltage. Not sure if this is your problem, but it might be. Try filtering your "A" supply to the fillaments.

Lou,

Have you recapped the radio? Viewing the schematic for the radio, I see two electrolytic caps, C23 & C13, which could be shorted or very leaky. This can cause excessive current draw on the +90 volt supply. Also another culprit would be C22 from the 1LB4 plate to ground and C14. There are caps in branch circuits off the +90 volt that can be shorted or leaky, such as C4, C8, C12 etc. All the caps will need to be checked with an ohmmeter for leakage.

Radiodoc

:Thanks - I have not tried to recap the radio. Do you have the schematic in electronic format? I am having trouble securing a copy.

Thanks in Advance
Lou

:Thanks
::
::I have a "wall wart" that advertises 1.5 Volts (selectable voltage). I thought that 500ma capacity would be more than enough.
::
::I did not run over voltage. However, it did appear that the filament supply AND the plate supply were both being dragged down. I agree with running the set on pure DC to see what happens, and this is what I will do.
::
::PS The set is very clean. It does not appear that I have had any "visitors" ( the chassis underside is fully enclosed anyway).
::
::Thanks - Lou
:::Another suggestion: Try running the radio's filaments with a couple of D cells in parallel. Try running the B+ with some (10) 9 volt batteries in series. This will help you determin if your home brew power supplies are acting up or if the radio has a defect.
:::If you have applied over voltage (2X or more) to the filaments you may have fried them. In some cases the tubes light up but they won't conduct.
:::
:::Dim
:::
:::
:::
:::
:::
:::
:::
:::
::::A few things to consider: I don't know of many wall warts that put out 1.5 volts....are you sure you have the correct filament voltage. Unregulated wall wart voltage can some times be more than 50% over what it is rated at depending on the load.....monitor your filament volage. If you are drawing excess B+ current do you have the correct polarity. There may also be a defective component (usually a capacitor) in the radio. Sometimes in the farm radios a mouse moves in...look to see if the capacitors are chewed up. There are many more things to look at this is just a start. Please let us know your results.
::::
::::Dim
::::
::::
::::
:::::Are you using a well filtered supply for the fillaments??? Batery tubes are meant to be run on a very "clean" DC voltage. Not sure if this is your problem, but it might be. Try filtering your "A" supply to the fillaments.
:
:Lou,
:
:Have you recapped the radio? Viewing the schematic for the radio, I see two electrolytic caps, C23 & C13, which could be shorted or very leaky. This can cause excessive current draw on the +90 volt supply. Also another culprit would be C22 from the 1LB4 plate to ground and C14. There are caps in branch circuits off the +90 volt that can be shorted or leaky, such as C4, C8, C12 etc. All the caps will need to be checked with an ohmmeter for leakage.
:
:Radiodoc
:

You really should re-cap the radio. At least test capacitors for leakage with your multi-meter. You must disconnect a capacitor in order to test it. If you don't, you are wasting your time. A capacitor that has any leakage at all, even in the 10s of millions of ohms, is unacceptable, and should be replaced. If your meter needle jumps up, it must fall back to exactly where it started. For values under .001 MFD, the needle most likely won't jump up under normal circumstances. If it does, make sure that it goes back to EXACTLY where it started. If not, the unit is leaky, and should be discarded. Leakage in the millions of ohms won't drag down your power supply, but it'll cause poor performance (trust me).

You can also build a fairly good power supply with a couple of 1.5 ampere 12 volt transformers from Radio Shack. Also purchase a variable voltage regulator transistor and the required resistors (one is variable). Filter well the voltage going into and out of this regulator. Use 2000+ MFD condensers. Adjust output voltage for 1.5 volts. The other transformer has its secondary connected to the secondary of the filament powering transformer. It will raise the voltage back up to 120, which can then be rectified and filtered as necessary by the usual means. Use appropriate resistors to reduce the voltage. A resistor around 2700 ohms will probably drop the voltage to 90. This is fairly standard in 3-way portables. Adjust resistance appropriately for your radio.

If you can get by with wall warts, then by all means. This is the simplest method. If not, though, the above power supply will do a fine job. If necessary, place .1 MFD condensers across all of the rectifier diodes (A and B supply). This will reduce hum caused by the quick switching of the diodes. If you wish, you may use a 117Z6 tube as the B rectifier. This will look nice, and also has enough internal resistance that it won't cause hum problems caused by solid state diodes. Radio Shack sells nice small aluminum chassis. The tube and one of the transformers can be mounted attractively on top. The other transformer and all the rest of the goodies may be mounted underneath.

Thomas

Lou,

The schematic can be found at:

http://techpreservation.dyndns.org/schematics/

The files are in DJVU format so you will need either the djvu browser dropin or the djvu standalone program to view. Both are at the site.

Radiodoc

::Thanks - I have not tried to recap the radio. Do you have the schematic in electronic format? I am having trouble securing a copy.
:
:Thanks in Advance
:Lou
:
::Thanks
:::
:::I have a "wall wart" that advertises 1.5 Volts (selectable voltage). I thought that 500ma capacity would be more than enough.
:::
:::I did not run over voltage. However, it did appear that the filament supply AND the plate supply were both being dragged down. I agree with running the set on pure DC to see what happens, and this is what I will do.
:::
:::PS The set is very clean. It does not appear that I have had any "visitors" ( the chassis underside is fully enclosed anyway).
:::
:::Thanks - Lou
::::Another suggestion: Try running the radio's filaments with a couple of D cells in parallel. Try running the B+ with some (10) 9 volt batteries in series. This will help you determin if your home brew power supplies are acting up or if the radio has a defect.
::::If you have applied over voltage (2X or more) to the filaments you may have fried them. In some cases the tubes light up but they won't conduct.
::::
::::Dim
::::
::::
::::
::::
::::
::::
::::
::::
:::::A few things to consider: I don't know of many wall warts that put out 1.5 volts....are you sure you have the correct filament voltage. Unregulated wall wart voltage can some times be more than 50% over what it is rated at depending on the load.....monitor your filament volage. If you are drawing excess B+ current do you have the correct polarity. There may also be a defective component (usually a capacitor) in the radio. Sometimes in the farm radios a mouse moves in...look to see if the capacitors are chewed up. There are many more things to look at this is just a start. Please let us know your results.
:::::
:::::Dim
:::::
:::::
:::::
::::::Are you using a well filtered supply for the fillaments??? Batery tubes are meant to be run on a very "clean" DC voltage. Not sure if this is your problem, but it might be. Try filtering your "A" supply to the fillaments.
::
::Lou,
::
::Have you recapped the radio? Viewing the schematic for the radio, I see two electrolytic caps, C23 & C13, which could be shorted or very leaky. This can cause excessive current draw on the +90 volt supply. Also another culprit would be C22 from the 1LB4 plate to ground and C14. There are caps in branch circuits off the +90 volt that can be shorted or leaky, such as C4, C8, C12 etc. All the caps will need to be checked with an ohmmeter for leakage.
::
::Radiodoc
::