Can IF transformers for transistor radios be used in tube radios? Is there much of a difference? Wouldn't something tuned for 455 kc in a transistor radio resonate well in a tube radio?

Thanks!

IF xfmrs in tube-type radios have high-voltage B+ on the primary. The winding insulation in transistor radio IF xfmrs isn't adequate.

:Can IF transformers for transistor radios be used in tube radios? Is there much of a difference? Wouldn't something tuned for 455 kc in a transistor radio resonate well in a tube radio?
:
:Thanks!

:IF xfmrs in tube-type radios have high-voltage B+ on the primary. The winding insulation in transistor radio IF xfmrs isn't adequate.
:
::Can IF transformers for transistor radios be used in tube radios? Is there much of a difference? Wouldn't something tuned for 455 kc in a transistor radio resonate well in a tube radio?
::
::Thanks!

Its worse, too. The characteristic impedance of transistor IFs is less for the lower voltages. At 455 KHZ the transistor IF will present lower impedance (resistance) for the plate of the IF or mixer tube than it should have. The result will be excessive current and rotten gain.
Then the whole thing will burn up for the reason Doug cited.

All the Best,

Bill Grimm

pitty. i need 10.7 mc transformers, and there are a ton on ebay. i don't see the voltage problem, since the primary and secondary are isolated from eachother. the only voltage at the capacitors would be the difference across each coil, which isn't much. the capacitors typically don't go from primary to secondary. however, the impedance issue sort of makes sense. with the low price, i'm tempted to buy them anyway, and give them a try. as you said, though, impedance may be different. transistors are high current devices, where-as tubes are high voltage. the lower current might not drive them as well.

Well duh!! Inherently, a vacuum tube is a high impedance device, whereas the transistor is a low impedance device, so driving and terminating circuitry of an IF transformer would be quite different for the two. Those parameters, external to the IF can will certainly affect the performance. Internal parameters, such as conductor spacing,
dielectric/insulation resistance could all fail under much higher operating voltages. A transformer winding
designed for much lower external circuit impedance(s)may not tune properly, and I suspect the -3db bandwidth will be altered.

marv

:pitty. i need 10.7 mc transformers, and there are a ton on ebay. i don't see the voltage problem, since the primary and secondary are isolated from eachother. the only voltage at the capacitors would be the difference across each coil, which isn't much. the capacitors typically don't go from primary to secondary. however, the impedance issue sort of makes sense. with the low price, i'm tempted to buy them anyway, and give them a try. as you said, though, impedance may be different. transistors are high current devices, where-as tubes are high voltage. the lower current might not drive them as well.
:

Well, go ahead and try it and let us know how it works. By the way, if it's FM xfmrs you're after, AES sells them (rated for transistors).

My concern about the voltage between primary and secondary is less than the voltage across the windings of the primary itself, which are wound on top of each other. Also, the voltage between the primary winding and the can. You've got perhaps 400V across a winding that was designed for just a few volts.

:pitty. i need 10.7 mc transformers, and there are a ton on ebay. i don't see the voltage problem, since the primary and secondary are isolated from eachother. the only voltage at the capacitors would be the difference across each coil, which isn't much. the capacitors typically don't go from primary to secondary. however, the impedance issue sort of makes sense. with the low price, i'm tempted to buy them anyway, and give them a try. as you said, though, impedance may be different. transistors are high current devices, where-as tubes are high voltage. the lower current might not drive them as well.
:

:Can IF transformers for transistor radios be used in tube radios? Is there much of a difference? Wouldn't something tuned for 455 kc in a transistor radio resonate well in a tube radio?
:
:Thanks!

I've done it in a tube portable radio. It works fine but has slightly less output. I must be honest, I did it as a temporary solution but was surprised how well it worked. It's been coupla years now. True, I don't use the radio everyday and would not recommend as a permanent solution but it works surprisingly well.

I have tons of new FM IF cans. Let me know what you need, I may be able to help ?

Z-

Do you have any 1 microhenry air-core chokes? Or where can I get the hollow core plastic stock to wind one? It's for an upcoming amp project to attenuate parasitics in the finals.