Having recently identified a mystery radio on this forum, it appears that the speaker that came with it is a substitution. It's a Rola with a 1Kohm field coil. If what I have as far as set identification is correct - the schematic shows a 2.5Kohm field coil. The radio - all nicely recapped now - plays great. Should I be concerned about the difference in field coil ratings or should I leave it as is? Thanks...

:Having recently identified a mystery radio on this forum, it appears that the speaker that came with it is a substitution. It's a Rola with a 1Kohm field coil. If what I have as far as set identification is correct - the schematic shows a 2.5Kohm field coil. The radio - all nicely recapped now - plays great. Should I be concerned about the difference in field coil ratings or should I leave it as is? Thanks...

Hi Bill,
I would look for two things. First check your voltages and see if they are high, especially around the power output tube. Second, check the heat coming from the field.
My concern is that the field could be overloaded and eventually fail. Excessive heat coming from it would be the indication that this can happen.
If the field is too hot or the voltages too high, try putting a 1.5K 1 watt resistor in series. The voltages should come in and the field cool down.
If the field is cool and the voltages not too much higher, just sit back and enjoy a job well done.

Best Regards,

Bill Grimm

::Having recently identified a mystery radio on this forum, it appears that the speaker that came with it is a substitution. It's a Rola with a 1Kohm field coil. If what I have as far as set identification is correct - the schematic shows a 2.5Kohm field coil. The radio - all nicely recapped now - plays great. Should I be concerned about the difference in field coil ratings or should I leave it as is? Thanks...
:
:Hi Bill,
: I would look for two things. First check your voltages and see if they are high, especially around the power output tube. Second, check the heat coming from the field.
: My concern is that the field could be overloaded and eventually fail. Excessive heat coming from it would be the indication that this can happen.
: If the field is too hot or the voltages too high, try putting a 1.5K 1 watt resistor in series. The voltages should come in and the field cool down.
: If the field is cool and the voltages not too much higher, just sit back and enjoy a job well done.
:
:Best Regards,
:
:Bill Grimm

Bill G,
I've only run this radio an hour or so at the time since I've recapped it - but I did make note to feel the txfmr and the field coil previously - neither of which got hot. The voltages are, however, another story. On the 47 I was getting around 350V on the plate and screen. I added a 5 watt 1.5Kohm and the voltages dropped to 260 - 270V range. The resistor gets quite hot to touch. I think - for safety's sake - I'll put the resistor in.

Agree, best to add the resistor. A #47 tube wasn't designed to operate with 350 volts on the plate. Typical voltage is 250. You will be ok with 260-270.

If you drop 90 volts across the 1.5K resistor it is dissipating 5.4 watts. Best to have 10 watt or greater rating.

Norm

:::Having recently identified a mystery radio on this forum, it appears that the speaker that came with it is a substitution. It's a Rola with a 1Kohm field coil. If what I have as far as set identification is correct - the schematic shows a 2.5Kohm field coil. The radio - all nicely recapped now - plays great. Should I be concerned about the difference in field coil ratings or should I leave it as is? Thanks...
::
::Hi Bill,
:: I would look for two things. First check your voltages and see if they are high, especially around the power output tube. Second, check the heat coming from the field.
:: My concern is that the field could be overloaded and eventually fail. Excessive heat coming from it would be the indication that this can happen.
:: If the field is too hot or the voltages too high, try putting a 1.5K 1 watt resistor in series. The voltages should come in and the field cool down.
:: If the field is cool and the voltages not too much higher, just sit back and enjoy a job well done.
::
::Best Regards,
::
::Bill Grimm
:
:Bill G,
:I've only run this radio an hour or so at the time since I've recapped it - but I did make note to feel the txfmr and the field coil previously - neither of which got hot. The voltages are, however, another story. On the 47 I was getting around 350V on the plate and screen. I added a 5 watt 1.5Kohm and the voltages dropped to 260 - 270V range. The resistor gets quite hot to touch. I think - for safety's sake - I'll put the resistor in.