I would expect 400 ohms to be high voltage secondary winding. The secondary should be center tapped. Can you find a third wire which reads to this winding?
Filament winding are very low resistance.
AC input will be a little higher. It may only read 10 or 20 ohms on a meter. Look for a winding that low in resistance but more than a few ohms.
Norm
:Hi all I just got a transformer out of a old majestic 90b as a replacment for my radio which was missing the transformer, problem is the color on the wires is all faded so I am not sure how to tell which is the primary, doing a continuity check with my vom shows just about all the wires in the low 1 or 2 ohm range except 1 pair is about 400 ohms is this the primary? I hooked a 12.6 up to what I believe is the 2.5 secondary and what I think is the primary showed about 600 volts but how do I know this is not the secondary?
:any advise is apreciated
:
:
It appears that the power transformer for the 90B has 3 taps on the primary for 105, 115 and 125 volt operation. The primary will probably measure about 6 to 8 ohms. There is a 5 volt secondary for the 80 tube; it will read less than 1 ohm. There is a 2.5 volt secondary that has a center tap; this is for the two 45 tubes. There is another 2.5 volt secondary with no center tap; this is for the rest of the tubes filaments. Last, there is a center tapped high voltage secondary that goes to the the 80 plates.
Once you find the primary, which will have continuity on 4 wires, you can figure out what secondaries are 2.5, 5 the high voltage. Use the tap for 125 volt operation (highest resistance).
Johnnysan
The primary may be bad, or the transformer is from a different version of the 90B. Do you have a variac? If so, you can try bringing up the voltage slowly on the leads that measure 3 ohms; if they are not the primary then the current will quickly rise above about .2 amp. If it is the primary, and the 115/125 volt tap is open, then you are stuck with a transformer that is rated at 105 volts input; it may still be useful.
Johnnysan-
And, as a friend of mine learned a few years ago, any winding can be a primary. Thinking putting six Volts on the filament winding to check all the tube filaments, he powered up the whole radio and got the (insert expletive here) knocked out of himself. No, it wasn't me this time.
Lewis
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:
:
:
Do you have a filament transformer that can supply 5 or 6 volts? Connect this voltage and see what you get. A transformer will work in either direction. It can convert 120 volts AC to 6 volts or step up 6 volts to 120 volts.
Be careful the high voltage winding will be hot.
Norm
::::::Hi all I just got a transformer out of a old majestic 90b as a replacment for my radio which was missing the transformer, problem is the color on the wires is all faded so I am not sure how to tell which is the primary, doing a continuity check with my vom shows just about all the wires in the low 1 or 2 ohm range except 1 pair is about 400 ohms is this the primary? I hooked a 12.6 up to what I believe is the 2.5 secondary and what I think is the primary showed about 600 volts but how do I know this is not the secondary?
::::::any advise is apreciated
::::::
::::::
:::::
:::::It appears that the power transformer for the 90B has 3 taps on the primary for 105, 115 and 125 volt operation. The primary will probably measure about 6 to 8 ohms. There is a 5 volt secondary for the 80 tube; it will read less than 1 ohm. There is a 2.5 volt secondary that has a center tap; this is for the two 45 tubes. There is another 2.5 volt secondary with no center tap; this is for the rest of the tubes filaments. Last, there is a center tapped high voltage secondary that goes to the the 80 plates.
:::::Once you find the primary, which will have continuity on 4 wires, you can figure out what secondaries are 2.5, 5 the high voltage. Use the tap for 125 volt operation (highest resistance).
:::::Johnnysan
:::::
::::Thanks for your replies according to norm the 400 ohms should be the HV secondary and I did find a center tap so that is figured out also I have the filiments sorted , and I do have 4 wires left... but they all do not show continuity but each pair does ... 1 pair about 3 ohms, and the other about 1 to 2 ohms, if they are suppose to be taps I should get some kind of reading on all 4 of them correct? does that mean the primary is shot?
::::
:::
:::The primary may be bad, or the transformer is from a different version of the 90B. Do you have a variac? If so, you can try bringing up the voltage slowly on the leads that measure 3 ohms; if they are not the primary then the current will quickly rise above about .2 amp. If it is the primary, and the 115/125 volt tap is open, then you are stuck with a transformer that is rated at 105 volts input; it may still be useful.
:::Johnnysan-
::
::
::
::And, as a friend of mine learned a few years ago, any winding can be a primary. Thinking putting six Volts on the filament winding to check all the tube filaments, he powered up the whole radio and got the (insert expletive here) knocked out of himself. No, it wasn't me this time.
::Lewis
:::
:::
:::
:::
::
::
:unfortunately I do not have a variac , is there another way to test whether I do have the primary winding? the 4 wires left have me wondering if they are to the primary there are 2 long wires and 2 short wires ( Like some one cut them short) but any way 1 long and 1 short wire read about 3 ohms, the other long and the other short wire read about 1 to 2 ohms, the 2 short wires read about 1 ohm but the 2 long wires have no reading like they are open??? and if I mix the long and short wires they read open?? how can this be? unless they are not taps??? any ideas ?
:Thanks
:Elton
:
Thanks Norm , I did hook up a 12.6 filiment transformer to the primary with 3 ohms, and it appears to be correct 12.6 is about 10 % of full voltage and the filiments all seemed right the 5 volt was about .5, the 2.5 were about .2, but the secondary measured 150 volts, now seeing I am only inputing 10% of full voltage would the secondary be about 1050 volts at full power? does this sound right for this particular radio? does anyone know what the secondary voltage should be for this radio?
Thanks
Elton
:
:::::::Hi all I just got a transformer out of a old majestic 90b as a replacment for my radio which was missing the transformer, problem is the color on the wires is all faded so I am not sure how to tell which is the primary, doing a continuity check with my vom shows just about all the wires in the low 1 or 2 ohm range except 1 pair is about 400 ohms is this the primary? I hooked a 12.6 up to what I believe is the 2.5 secondary and what I think is the primary showed about 600 volts but how do I know this is not the secondary?
:::::::any advise is apreciated
:::::::
:::::::
::::::
::::::It appears that the power transformer for the 90B has 3 taps on the primary for 105, 115 and 125 volt operation. The primary will probably measure about 6 to 8 ohms. There is a 5 volt secondary for the 80 tube; it will read less than 1 ohm. There is a 2.5 volt secondary that has a center tap; this is for the two 45 tubes. There is another 2.5 volt secondary with no center tap; this is for the rest of the tubes filaments. Last, there is a center tapped high voltage secondary that goes to the the 80 plates.
::::::Once you find the primary, which will have continuity on 4 wires, you can figure out what secondaries are 2.5, 5 the high voltage. Use the tap for 125 volt operation (highest resistance).
::::::Johnnysan
::::::
:::::Thanks for your replies according to norm the 400 ohms should be the HV secondary and I did find a center tap so that is figured out also I have the filiments sorted , and I do have 4 wires left... but they all do not show continuity but each pair does ... 1 pair about 3 ohms, and the other about 1 to 2 ohms, if they are suppose to be taps I should get some kind of reading on all 4 of them correct? does that mean the primary is shot?
:::::
::::
::::The primary may be bad, or the transformer is from a different version of the 90B. Do you have a variac? If so, you can try bringing up the voltage slowly on the leads that measure 3 ohms; if they are not the primary then the current will quickly rise above about .2 amp. If it is the primary, and the 115/125 volt tap is open, then you are stuck with a transformer that is rated at 105 volts input; it may still be useful.
::::Johnnysan-
:::
:::
:::
:::And, as a friend of mine learned a few years ago, any winding can be a primary. Thinking putting six Volts on the filament winding to check all the tube filaments, he powered up the whole radio and got the (insert expletive here) knocked out of himself. No, it wasn't me this time.
:::Lewis
::::
::::
::::
::::
:::
:::
::unfortunately I do not have a variac , is there another way to test whether I do have the primary winding? the 4 wires left have me wondering if they are to the primary there are 2 long wires and 2 short wires ( Like some one cut them short) but any way 1 long and 1 short wire read about 3 ohms, the other long and the other short wire read about 1 to 2 ohms, the 2 short wires read about 1 ohm but the 2 long wires have no reading like they are open??? and if I mix the long and short wires they read open?? how can this be? unless they are not taps??? any ideas ?
::Thanks
::Elton
::
:
:
Seems high for the secondary. Would expect most power transformers to be in 600 to 700 volt range. Half of this to center tap. Voltages will be lower under load.
Do you know which power supply used your replacement transformer? Some had line ballasts which reduced input voltage to 80 volts.
This Rider page shows Majestic power supplies:
http://www.nostalgiaair.org/PagesByModel/015/M0040015.pdf
Even though high I would go with what you have. The transformer is good and you know it was from a similar radio. You may need to drop input voltage?
Norm
::Hi Elton
::
:: Do you have a filament transformer that can supply 5 or 6 volts? Connect this voltage and see what you get. A transformer will work in either direction. It can convert 120 volts AC to 6 volts or step up 6 volts to 120 volts.
::
:: Be careful the high voltage winding will be hot.
::
::Norm
:
:Thanks Norm , I did hook up a 12.6 filiment transformer to the primary with 3 ohms, and it appears to be correct 12.6 is about 10 % of full voltage and the filiments all seemed right the 5 volt was about .5, the 2.5 were about .2, but the secondary measured 150 volts, now seeing I am only inputing 10% of full voltage would the secondary be about 1050 volts at full power? does this sound right for this particular radio? does anyone know what the secondary voltage should be for this radio?
:Thanks
:Elton
::
::::::::Hi all I just got a transformer out of a old majestic 90b as a replacment for my radio which was missing the transformer, problem is the color on the wires is all faded so I am not sure how to tell which is the primary, doing a continuity check with my vom shows just about all the wires in the low 1 or 2 ohm range except 1 pair is about 400 ohms is this the primary? I hooked a 12.6 up to what I believe is the 2.5 secondary and what I think is the primary showed about 600 volts but how do I know this is not the secondary?
::::::::any advise is apreciated
::::::::
::::::::
:::::::
:::::::It appears that the power transformer for the 90B has 3 taps on the primary for 105, 115 and 125 volt operation. The primary will probably measure about 6 to 8 ohms. There is a 5 volt secondary for the 80 tube; it will read less than 1 ohm. There is a 2.5 volt secondary that has a center tap; this is for the two 45 tubes. There is another 2.5 volt secondary with no center tap; this is for the rest of the tubes filaments. Last, there is a center tapped high voltage secondary that goes to the the 80 plates.
:::::::Once you find the primary, which will have continuity on 4 wires, you can figure out what secondaries are 2.5, 5 the high voltage. Use the tap for 125 volt operation (highest resistance).
:::::::Johnnysan
:::::::
::::::Thanks for your replies according to norm the 400 ohms should be the HV secondary and I did find a center tap so that is figured out also I have the filiments sorted , and I do have 4 wires left... but they all do not show continuity but each pair does ... 1 pair about 3 ohms, and the other about 1 to 2 ohms, if they are suppose to be taps I should get some kind of reading on all 4 of them correct? does that mean the primary is shot?
::::::
:::::
:::::The primary may be bad, or the transformer is from a different version of the 90B. Do you have a variac? If so, you can try bringing up the voltage slowly on the leads that measure 3 ohms; if they are not the primary then the current will quickly rise above about .2 amp. If it is the primary, and the 115/125 volt tap is open, then you are stuck with a transformer that is rated at 105 volts input; it may still be useful.
:::::Johnnysan-
::::
::::
::::
::::And, as a friend of mine learned a few years ago, any winding can be a primary. Thinking putting six Volts on the filament winding to check all the tube filaments, he powered up the whole radio and got the (insert expletive here) knocked out of himself. No, it wasn't me this time.
::::Lewis
:::::
:::::
:::::
:::::
::::
::::
:::unfortunately I do not have a variac , is there another way to test whether I do have the primary winding? the 4 wires left have me wondering if they are to the primary there are 2 long wires and 2 short wires ( Like some one cut them short) but any way 1 long and 1 short wire read about 3 ohms, the other long and the other short wire read about 1 to 2 ohms, the 2 short wires read about 1 ohm but the 2 long wires have no reading like they are open??? and if I mix the long and short wires they read open?? how can this be? unless they are not taps??? any ideas ?
:::Thanks
:::Elton
:::
::
::
:
: