Well I plugged her into a variac this AM and got no filament light.
Without even yet testing I think it may be the input line ballast resistor ( tall cage on the chassis ). What do I replace this with - got no technical data on it? Only a Stewart Warner number for the ballast. Number 61816.
Lou
Thanks
Lou
First, ohm out the ballast and transformer individually to make sure that you have indicted the correct part (there's a remote chance that the line switch could be open instead). If you confirm that the ballast is open, jumper across it and proceed as follows:
(1) Ensure that all tubes are installed.
(2) Put an AC voltmeter across the filament pins of one of the #45 output tubes.
(3) Starting at zero volts, turn on the Variac and bring its output voltage setting up slowly JUST UNTIL you read 2.25 VAC on the ACVM across the #45 tube. This voltage comes from the "expected voltages" table in the Rider service info for this set and represents the filament voltage "seen" by that type of tube.
(4) At that point, measure what AC voltage the Variac is outputting (don't trust the dial scale). Also break one of the AC in lines from the Variac and take a current reading.
(5) The difference between your local line voltage (120 VAC nominal) and your Variac setting measurement will be the voltage that the ballast resistor needs to drop. Using the current measurement will enable you to compute (using Ohm's Law, V=IR) the notional value of the ballast resistor and its minimum power rating (P=(I)(I)R). Derate your calculated power by 70% for reliability.
The above assumes that your Variac has enough VA capacity to source the necessary voltage and current.
It probably does but some of these early AC sets were real power hogs.
It may be possible to operate the set safely without the ballast resistor, but the above procedure will tell you that without running the risk of overheating the transformer or (perhaps even worse) burning out the expensive #45 tube filaments.
I bypassed the bad ballast and put the unit on a variac. I turned up the voltage briefly and noticed all filaments lighting - good start.
However, I also noticed a little "essence of allen bradly" coming from somewhere in the chassis so I immediately turned down the input AC line.
Next step is to monitor B+ and see what is happening and maybe unload the output side of the power transformer to make sure the trouble is not there.
PERHAPS the ballast unit failed due to a short in the chassis - it is a resistor but it also acts as a fuse!!
Lou
PS: I did do a little research on this unit. I have the metal cased chassis - looks like a table radio. BUT this unit REALLY comes in a wooden cabinet. So it means that my "table" radio actually drops into a console style cabinet.
Fun Facts!!
Lou
:It's no sweat to figure this out since you have a Variac.
:
:First, ohm out the ballast and transformer individually to make sure that you have indicted the correct part (there's a remote chance that the line switch could be open instead). If you confirm that the ballast is open, jumper across it and proceed as follows:
:
:(1) Ensure that all tubes are installed.
:
:(2) Put an AC voltmeter across the filament pins of one of the #45 output tubes.
:
:(3) Starting at zero volts, turn on the Variac and bring its output voltage setting up slowly JUST UNTIL you read 2.25 VAC on the ACVM across the #45 tube. This voltage comes from the "expected voltages" table in the Rider service info for this set and represents the filament voltage "seen" by that type of tube.
:
:(4) At that point, measure what AC voltage the Variac is outputting (don't trust the dial scale). Also break one of the AC in lines from the Variac and take a current reading.
:
:(5) The difference between your local line voltage (120 VAC nominal) and your Variac setting measurement will be the voltage that the ballast resistor needs to drop. Using the current measurement will enable you to compute (using Ohm's Law, V=IR) the notional value of the ballast resistor and its minimum power rating (P=(I)(I)R). Derate your calculated power by 70% for reliability.
:
:The above assumes that your Variac has enough VA capacity to source the necessary voltage and current.
:It probably does but some of these early AC sets were real power hogs.
:
:It may be possible to operate the set safely without the ballast resistor, but the above procedure will tell you that without running the risk of overheating the transformer or (perhaps even worse) burning out the expensive #45 tube filaments.
:
:
I do get adequate B+ ( measured at the type 45 socket pins) but the transformer overheats very badly.
The next test I will do is to remove the type 280 ( older type 80) rectifier and all the rest of the tubes to remove loading from the transformer and see if we still get the overheating.
If so then MAYBE this set is a goner!!
Lou
:Well getting there.
:
:I bypassed the bad ballast and put the unit on a variac. I turned up the voltage briefly and noticed all filaments lighting - good start.
:
:However, I also noticed a little "essence of allen bradly" coming from somewhere in the chassis so I immediately turned down the input AC line.
:
:Next step is to monitor B+ and see what is happening and maybe unload the output side of the power transformer to make sure the trouble is not there.
:
:PERHAPS the ballast unit failed due to a short in the chassis - it is a resistor but it also acts as a fuse!!
:
:Lou
:
:PS: I did do a little research on this unit. I have the metal cased chassis - looks like a table radio. BUT this unit REALLY comes in a wooden cabinet. So it means that my "table" radio actually drops into a console style cabinet.
:
:Fun Facts!!
:
:Lou
:
::It's no sweat to figure this out since you have a Variac.
::
::First, ohm out the ballast and transformer individually to make sure that you have indicted the correct part (there's a remote chance that the line switch could be open instead). If you confirm that the ballast is open, jumper across it and proceed as follows:
::
::(1) Ensure that all tubes are installed.
::
::(2) Put an AC voltmeter across the filament pins of one of the #45 output tubes.
::
::(3) Starting at zero volts, turn on the Variac and bring its output voltage setting up slowly JUST UNTIL you read 2.25 VAC on the ACVM across the #45 tube. This voltage comes from the "expected voltages" table in the Rider service info for this set and represents the filament voltage "seen" by that type of tube.
::
::(4) At that point, measure what AC voltage the Variac is outputting (don't trust the dial scale). Also break one of the AC in lines from the Variac and take a current reading.
::
::(5) The difference between your local line voltage (120 VAC nominal) and your Variac setting measurement will be the voltage that the ballast resistor needs to drop. Using the current measurement will enable you to compute (using Ohm's Law, V=IR) the notional value of the ballast resistor and its minimum power rating (P=(I)(I)R). Derate your calculated power by 70% for reliability.
::
::The above assumes that your Variac has enough VA capacity to source the necessary voltage and current.
::It probably does but some of these early AC sets were real power hogs.
::
::It may be possible to operate the set safely without the ballast resistor, but the above procedure will tell you that without running the risk of overheating the transformer or (perhaps even worse) burning out the expensive #45 tube filaments.
::
::
:
:
Lou
:What output voltage is the Variac set to?
:
:
:
So - I believe I have a shorted transformer - this is with all tubes removed.
If I leave it on too long - I start to get lovely smoke!!
Lou
:I will measure it and get beck to you. I do know the dial setting was somewhere around the 50% output point of the variac.
:
:Lou
:
::What output voltage is the Variac set to?
::
::
::
:
: