Kirk's Philco 40-145 - Printable Version
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Kirk's Philco 40-145 - morzh - 04-16-2016
Today thought after almost having finished the RCA I would rest, plus I am out of solder
But I looked in the box, sa Philco 56, some other monster with a speaker that weighs like my dumbells and 40-145.
I decided to stay on the latter.
Has been recapped, so I looked at the voltages and they were OK.
No sound though.
So after short investigation about 5 minutes, I found the speaker misses one of the wires between the VC and a lug. Had a bad speaker that was a cone paper donor, used its wire.
The sound appeared, no reception though.
Then after pressing a preset button I briefly had a reception but it went away.
Well, there is still much to do.
I will leave string routing to Kirk.
RE: Kirk's Philco 40-145 - morzh - 04-16-2016
I simply never had a pushbutton radio, so....
The rightmost button is "dial" (I do not have the front panel to guide me either), with it pressed BC band receives fine.
Th next band up received one or two stations, the next one clearly sees the antenna input but does not receive anything...then again, it is a short 1ft wireand SW is not that good without antenna.
A wire to the vol pot was cracked (yep the gutta-percha) and rubbing against chassis which explained the volume variations.
Cleaned the pot, changed the wires.
The speaker has a buzz to it which goes away if I touch the cone, only at large volume. Well it is a salvaged speaker, might need replacement or recentering of the cone if anyone is good at that, I'm not.
Kirk!
The Ycaps (those from AC wires to chassis) are supposed to be Y-type, not regular ecen if 630V rated.
Geez.
Will try to align tomorrow.
RE: Kirk's Philco 40-145 - sam - 04-16-2016
kirk kirk kirk it`s always about kirk
nice ME
RE: Kirk's Philco 40-145 - morzh - 04-16-2016
He's the only one whose radios I got.
RE: Kirk's Philco 40-145 - Radioroslyn - 04-21-2016
Hey Mike,
What did they use before Y caps???
Terry
RE: Kirk's Philco 40-145 - morzh - 04-21-2016
Regular high voltage caps. You know, in Philco they used that backelite block of two 15nF 600V ones.
And at the time that was the only right thing to do.
Again, with grounded chassis that would not present any hazard to the user though considering absence of fuses could create fire if broken down between Line and Earth.
The danger was real, the cap of a similar function used in audio amps got the moniker "death cap" as some people were electrocuted as a result of the cap shorting, including musicians touching mike and guitar at the same time etc, and one famous Russian dissident poet/song writer Alexander Galitch who died in France electrocuted by his tape-recorder (though conspiracy theorists say the KGB arranged for that to happen).
Y-cap guarantees failure in "open mode". Which does not entirely eliminate electrocution from various devices where they are used, but it usually is not due to them, but other components. Like that girl killed in China (I think) about 2 years or so ago while using an Apple iPhone plugged into an outlet. Y-cap there is in parallel with the transformer shorting the primary to the secondary for the common mode AC current to stem the EMI (otherwise it won't pass the radiated EMI FCC/CE certification), so if the transformer breaks down, that will kill ya the same way the death cap would.
Or for that matter, any tube radio transformer internal short of primary to the case if the radio is not grounded and the user is.
In short, any good extra measure of protection if available should be used, and Y-cap is one of those essential ones. I always use them.
RE: Kirk's Philco 40-145 - Radioroslyn - 04-22-2016
So I'm thinking on a transformer set why do you need them at all? Certainly if it's to block or filter rf noise from the ac line the relativity large inductance (at rf frequencies) of the primary should eliminate that issue right? With caps on both sides of the AC line no matter which way you plug it in to the socket there is some small leakage or coupling so if the chassis isn't at earth ground there is some low voltage AC there which can give you a little tingle.
On an ac/dc set (transformerless) I presume that it is there to filter rf from the ac line. Have built many p/s over the years and don't think I've ever used any caps on the line on transformer's primary. So enlighten this untrained long time hobbyist.
Terry
RE: Kirk's Philco 40-145 - morzh - 04-22-2016
Terry
Having tried to model it in my mind I do not see how not having Y-caps would hurt the reception much for transformer radios. In fact many 40-s and 50-s radios, both US and European lack the caps.
Let's say the chassis is not grounded. Any noise then induced upon the primary (yes you are right about inductance but then there is the through parasitic capacitance which common mode noise will use to get through) will appear as also common mode noise at the secondary. But since it IS common mode it does not matter much for the reception as it does not create any signal anywhere relative to the chassis.
Now if you do ground the chassis it is possible that what was common mode before after getting through the xfmr parasitic capacitance (and still is for everything other than the chassis which is now grounded) becomes a signal towards the chassis and thus gets amplified and heard. Partly this is taken care of by decoupling and bulk capacitance, though electrolytics are not really that good at radio frequencies being a bulk storage, so some low capacitance ceramics/paper/polyesters could help when used as decouplers.
Should you however use some Y-caps this becomes less of an issue in the first place.
Now in today's devices Y-caps are there mainly to protect the Mains from the noise generated by the equipment itself. I short it shorts out high frequencies between the device's common and the point where the Mains' earth enters it so not letting the noise escape in the Mains and cause interference for other people. This tale care only of really high frequency component.
Applying the same idea back to 30-s radios (though I doubt that was the intent, I think FRC/FCC at the time did not bother that much about these things) - well, the Y-caps can possibly filter out oscillator noise that would leak otherwise in the Mains.