I have a Pilot 403 that needs a capacitor replaced. The mica compression capacitor seems to be associated with tuning the MW band. Does anyone have any specifications, brand or details for the capacitor used in the 1936 Pilot 403 5 valve superhet SW/MW receiver?

Is it this American model?

http://www.radiomuseum.org/r/pilot_403_2.html.

If so and answer is forthcoming here, you might find that info in Riders or SAMS, or ask on an American vintage radio forum.

Well it is built in USA but is 240V and was bought originally by a New Zealander.

That has a multi tap transformer from 115VAC upwards, so all that matters is that it is on the right one.

It would appear that it can have two different speakers one permanent magnet the other electrodynamic so there is a variation in the PSU to accommodate this.

If it has still got old paper caps & electrolytics in it, get rid of them. That cap may be the padder for the oscillator? It is often set first.

Its in "Rider": Alignment data is on the sheet. SW coils have the least wire. Align the IF first. re-trim later, changing RF parts throws the RF settings off.

http://www.nostalgiaair.org/PagesByModel/404/M0014404.pdf.

Marc

Hi Marc, thanks for the circuit drawing and the alignment details. The radio works OK with quite a bit of interference on MW. I have replaced all paper caps. I have fitted safety caps as AC filter caps between Neutral and Active as well as between Active and Ground. I did not have the alignment procedure so have not done that. I did notice that some of the noise (not all of it) can be removed by adjusting the mica compression cap, and that the volume of the stations on MW can be adjusted using this cap, so I suspect (and it's location seems to support this) that it is a trimmer that adjusts the match to the antenna for MW only. I suspect from its appearance that it would be a candidate for replacement, mica caps also tend to suffer from over-compression of the mica I believe.

In over 40+ years I may have replaced / repaired about 3 mica trimmers and that's several hundred radios. People do like to screw the guts out of these things and I have had them with stripped screws & torn out threads. If some thing goes wrong they will adjust anything that moves.

If it still adjusts there is the possibility that the coils have changed over time. The Airzone had an open Aerial coil, which I repaired. as a result I needed to add 20pF across the aerial trimmer. Be prepared to have to do things like that. Sometimes they actually fracture the Mica & short the trimmer. I have repaires some of those with Mica out of the "window" (not door) for a Microwave magnetron.

As said this week an Airzone here was deaf due to IF & changes I had to make.

There will be trimmers for each band. It is important for the IF's that the generator is accurate and more particularly stable. I set mine with a frequency counter, should you do that, turn the modulation (tone) off to set it. Those look like top trimmer IF's, beware one is in the plate circuit & live, do not use a metal shaft.

I prefer to adjust the high end of the aerial coils using actual antenna signal.

Switch mode power supplies & Compact Fluorescent lights are the main enemy. Interference regulations no longer seem to exist. I have had an SM PSU get into a 175kHz IF.

It should go better aligned. I normally use an Oscilloscope to watch the signal when I align. Do not direct couple the sig gen to a valve, you only need around 12uV at the antenna not Volts. Series cap may be specified but is essential.