Zenith b511b
 

I found this radio today in a thrift store. The older lady that helped me said Looks pretty old but we test everything that comes in so how about a Dollar? So this being my first tube radio I quess I should change the caps and out of spec res. have tubes tested but what else? Heck for a buck even if it sits on a shelf Im good LOL

Nice little set!

I've attached a schematic - just by looking at the pics I'd change both those wax caps and that .01 that looks cooked. Then disconnect the filter caps (black tube on top of chassis) and solder new ones in underneath.

I wouldn't worry about the tubes yet - they're probably good. Address those capacitors and you'll probably be fine.

The rectangular device towards the right in your underchassis view is an audio couplate, contains a cap or two and a few resistors. These were common for a few years in radios starting in the mid fifties. It's probably OK. After you change the wax caps and electrolytics that Audubon suggested, check the power cord and plug, change if bad. Check that you have continuity through the loop antenna back to where it connects to the tuning cap. Then plug 'er in. If the tubes all light, 90% of the time it'll work right off. If they don't light, probably only one of them is burned out: use your ohmmeter to check heater pins on each tube: you can see which pins go to the heater looking through the side of the tube. Tubes are usually pretty reliable and don't need changing in a "found" radio.
Reece

Ok question I went to the local electronics store today They dont have multi section cans the one on the radio is 20/80mfd @150vdc they gave me a 22@150vdc (tiny thing) and said they couldnt even get close to the 80mfd in anything higher then 50vdc so I checked rat shack same deal there to

There are quite a few mail order places that can supply them. One of which is http://www.justradios.com/capacitors.html

John

You'll have to use two caps to replace the can - sometimes you'll need to mount them on a lug underneath if the cap doesn't reach where it needs to go.

Sadly, most of this stuff is strictly mail order these days. I use justradios.com - sometimes the mail is slow getting out of Canada, but their cap shopping cart is very easy to use and they've given me good service. I think there's a $15 minimum order though.

I can't remember if they have a minimum order, but also check Antique Electronics Supply.

thanks for the link but I have a question since they had 22mfd@160vdc cant you use 4 in parallel I will order the right one but I have been reading about caps in parallel does this work well?

If, when you get all caps replaced, tubes checked, and out of value resistors changed, the radio still has issues (such as a staticy sound or the volume not being constant), suspect the IF transformers. This set uses the small ones that are prone to the silver mica corrosion.

The cure is to carefully take them apart. Then remove the old caps and replace them with new ones of 100pf or so. It is a tedious process, but the radio will play fine once this is finished.

It would work. It would just look a little messy.

John

This problem is due to the manufacturer placing two caps on the same mica wafer. silver can migrate from one cap to the other, creating a leakage path. If the wafer is easily gotten to, just scraping the surface of the mica between the two caps will interrupt this leakage path, thus solving the problem. However, many IF transformers have this cap wafer buried under plastic pressure plates, and it becomes a bigger PITA to get at it. If you have to drill out a big rivet to gain access, at this point I'd use the 100pF mica caps as replacements. See halfway down http://www.geocities.com/wa2ise/radios/repair.htm for more info.

About 80% of old radios like yours won't have this problem.

As for the filter cap, it looks like the better grade of cap (electrolytic with a metal can, with cardboard over the can). It may still be good. The cheaper grade of filter caps often used in radios were just the electrolytic cap inside a cardboard "can". Those are always bad, as the cardboard lets the water in the electrolyte dry out. If you don't hear a lot hum when you try the radio, it should be okay.

A source of suitable caps could be had by taking apart something that used a switching power supply, like TV sets, DVD players, newer VCRs and computer power supplies.

wa2ise,

You have some really useful info on that link. Thanks!

John

Beautiful Zenith AA5. I have one in a nice dark red rounded cabinet, needs work as not only is the low end of the AM band quiet, but the tuning capacitor is severely stiff.