The schematic I got from NostaligaAir shows a lead going from the center tuning condenser to the cap of the 6A8 1st converter and also from there to the first section of the tuning condenser, this second wire is missing but if I add it the radio doesn't work..without it the radio works but doesn't get more than about 5 BC stations. Why not much sensitivity? I have about a 7 foot antenna.

First, the schematic itself shows each section of the tuning condenser as a separate unit. The only connection between the three is the frame, which links them to the chassis. There is no connection between any of the stators (stationary part that is insulated from the frame). The wire you see going from one to the other in the PICTORAL diagram, which is basically a tube layout diagram, is an error, if that, because I think that it is actually supposed to be something else. At any rate, this drawing means absolutely nothing electrically. It just shows the physical layout of the parts. There are other pictoral diagrams of other radios that show the resistors and condensers drawn under the chassis, and wires will go anywhere, not necessarily where they should. This is simply an artist's rendition of the underside of the chassis with no concern for wiring accuracy. On occasion you will see a schematic that uses pictoral representations of the various components and how they are connected. This is different. Here any wires shown are accurately represented unless the manufacturer has made a mistake. I will show you one such example. Anyway, disregard the wire in the pictoral layout diagram.

As for sensitivity in your set, if noone played around with any of the trimmer condensers in the set (little items with adjustment screws--you'll find some on the tuning condenser itself...others will be porcelain devices with plates that compress when the screw is tightened on each), then they should be fine. You should be using an antenna of 25 feet or longer, and it should be mounted in your attic or outside, insulated from all other objects. You may use insulated wire if you wish, which will help the situation.

In order for your set to perform properly, all condensers (not trimmers or the main tuning, but the round paper ones and the large electrolytics) must be replaced. Resistors that have drifted high in value must also be replaced. All of the above components can only be accurately tested by removing them, one at a time. All you really need to do is remove one of the two leads for each component in question. The entire device does not have to be removed. If you'd like the procedure for testing condensers with a multi-meter, ask. I'll tell you how. It is a critical but simple operation. Lastly, weak tubes should be replaced--that is, if a good tube improves operation. Just because a tube tests weak does not mean that it is necessarily bad, though new tubes always improve a set's operation to a degree, even if small.

It is possible, though somewhat rare, to obtain a set that has all of its original components, and to find them all in perfect working order. If you wish, before you go replacing all of the condensers, you may test each one for leakage, and electrolytics for ample capacitance as well as leakage. If the components do not leak now, however, they very well may with time. Unless you like working on your radio as a continuing project, I recommend replacing all of the condensers. Sometimes when they short, they destroy other components that are far more expensive. All of the condensers within a set will likely run you no more than $20.

Many people simply butcher the underside of their radio with unattractive new components, but if you have concern for the appearance of your chassis, purchase the metalized film condensers (small yellow units found at www.tubesandmore.com). They may be slipped inside of the old paper tubes that once housed the original condensers. Electrolytics are more difficult to restuff. You may simply disconnect the old units if they are mounted to the chassis, and then connect new units below the chassis. Restuffing takes time, however, so if you'd simply like to see if the set will work, the old condensers may be removed and saved for later.

If this does not improve reception, then you must obtain a good quality signal generator in good working condition (purchase recommended anyway, even if set works well). Use this to align the various circuits within the radio.

Thomas

Thomas,

Actually, I would like to know what the proper procedure is for testing condensers with a multi-meter. I've never been real sure I was doing it correctly.

Larry

:If you'd like the procedure for testing condensers with a multi-meter, ask. I'll tell you how. It is a critical but simple operation.

:Thomas

This is for the Simpson 260 meter. Use the highest resistance check setting on your meter.

************************************************

Do not touch both leads at the same time while making a test. Use the 10,000 ohm setting on your meter. Remove the condenser from the radio circuit. For electrolytics, connect the positive lead to the positive condenser terminal, and the negative lead to the negative condenser terminal.
Electrolytics larger than 1 or 2 MFD should cause the meter to deflect all the way to zero, set at the 10,000 ohm setting. Then the needle should fall back all the way to infinity. If, after a while, the needle does not fall back all the way, then the electrolytic is either leaky and bad or it needs to be rejuvenated. To rejuvenate, attach the condenser to a DC source that supplies the rated working voltage listed on the condenser (375 volt condenser should be put on a 375 volt source). Connect a 5K ohm resistor in series. Power it up slowly and allow to run at full voltage for 20 minutes. If the resistor starts to smoke, then the condenser is likely shorted, and should be replaced. If the condenser gets hot, this is also a sign of a short. The condenser should not get hot. This is dangerous, as steam pressure could explode it. If, after 20 minutes, nothing has smoked, and the voltage at the condenser is where it should be, then turn off the power and carefully disconnect the condenser. Connect a 30K resistor across the condenser and allow it to slowly discharge. Retest the condenser. If the needle will not fall above 10meg, then the condenser is leaky. Leaky condensers are not good. Generally 1 meg resistance or higher is acceptable, but I do not like to use electrolytics with a leakage resistance less than 10meg.

As for testing paper and mica (and other materials) non-polarized condensers, use the same setting on your meter. With condensers smaller than .001 MFD, you will not likely see a deflection at all. When connecting your meter, watch the needle closely, and as said before, DO NOT touch both leads at the same time. When the meter is connected, the needle will swing up just a small amount. Then it will fall back down. It MUST fall right back to where it started (the infinity mark). Any leakage at all is NOT ACCEPTABLE. If a condenser smaller than .001 MFD is tested, and the needle swings up, make sure it falls back down. Any condenser with leakage will cause the needle to swing up even if it normally wouldn't, so pay close attention. Leakage in the 10s of millions of ohms does not usually cause equipment damage, but tubes operate under extremely sensitive high impedance conditions. 10 meg leakage is just enough to pass some of the high voltage B+ from one stage to the grid of the successive stage. This positive voltage will throw off the slightly negative grid voltage of the succeeding stage, and cause distortion in the audio as well as inefficient amplification.

Thomas