The 15 is a 2 volt filament tube similar to the 6 volt 39/44. Might be your tester reading low? Be careful with 15 tubes. Not too many around and expensive. Even weak they should still operate ok.
You must have a battery radio? Be sure battery voltages are high enough.
Norm
:In one of my radios there are 2 type 15 tubes. They test 20% on both of my testers, the man I bought them from had written 80/100 on the pair. When in the radio, the radio turns on but does not recieve any stations. All other tubes are good and the chassis is restored. Where stations should be the radio makes strange noises and I think this is caused by these tubes. The 15's are thr R.F and I.F tubes. Is there a special scale for type 15 tubes? For example if certain tubes test 20% or 30% and they are considerd good for that type. Is this the case with type 15 tubes? Thanks Ian
Thanks Ian
6 volts @ 3 amps should be enough. What did you do with the vibrator? Most vibrators operate at 115 cycles. If you are using 60 cycles into the vibrator transformer it will be drawing too much current.
You could rewire filaments of the 15's so they have 6 volts and use 39 tubes. These tubes are less expensive and hold up better.
http://www.nostalgiaair.org/PagesByModel/251/M0025251.pdf
Norm
:yes this is a zenith 6v62, when touched the tubes make funny noises. I finished converting this to an ac radio, someone had started to convert it in the 50's. I tested both tubes on two different testers, and they both read 20%, everything else seems to be in order and these are mostlikely the problems. I installed a full wave rectifier and a 120-6 volt transformer, this transformer puts out 3 amps. This is not enough for the radio, and the transformer overheats. How many amps did 6 volt batteries have?
:Thanks Ian
You could try a larger transformer but expect the vibrator transformer would get hot. Not easy to double the AC input frequency. Best to use a power transformer with high voltage winding and eliminate the vibrator transformer.
Norm
:would a transformer with a higher amp output do the job without changeing cycle speed?
Maybe someone reading this has a unit already built?
Norm
:not easy to change input frequency? is it possible with simple parts?(capacitors, resistors, diodes, ect)
Sir Ian: I might also throw in this very simple possibilty, should you want to try it out first for its feasibility. Presently, you were having 60~ into your unit, while the vibrator powered unit was producing in the order of ~ 115 cycles for its operation. Therefore, you are wanting to get closer to operating at the design frequency of the smaller core mass of the original vibrator transformer. If you were to take two stud power diodes of the adequate current rating for the power level to be handled, and wire them into a fullwave rectifier,and just feed the raw output into the vib transformer, you would then be feeding it with 120~. However, the one fallacy of that waveform produced would be its asymmetrical variance from being a pure sinusoidal waveform. Now here is where a little experimentation aspect comes into play for its evaluation: If a paper/poly cap were to be shunted across the primary winding of that vibrator transformer, it would then form a parallel L-C resonant circuit in conjunction with the primary inductance and the flywheel effect of being in resonance should fill in, round up and enhance the negative nodes a bit Now, not having your vibrator transforner on hand to measure its inductive value and thereby being able to compute the required value of optimal resonating capacitance...I can only say that it will be in the several microfarads of value and one could initially start with a set value and then....if you are a scope person..monitor the amplitude and purity of the waveform as additional capacitance is shunted on...or merely monitor the developed output voltage from the power supply, as max will develop as the unit comes ever closer into 120~ resonance. |
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