A nice big piece of Pye
 

I'm preparing to electronically restore this diamond in the rough for someone else who's going to restore the cabinet. The biggest issue is I'm not sure how to select quality replacements for the paper capacitors. Also, I don't have instructions for re-stringing the tonemaster and wave change indicators and the dial pointer is long gone. At least I know the chassis is going to clean up well and is complete except for the dial pointer. Oh, I'd like to upgrade the dial lights as well, the originals work but who knows for how long.

https://www.flickr.com/photos/154129...h/37787128011/

Wow, that's a unique and cool radio!

If you need specific help definitely ask here, for paper capacitors in radios I like to use the Chinese orange drop knockoffs which are cheap and plentiful on eBay, 630V everywhere.

Very nice! I've always been a fan of those big British radios. Very sensitive, great sound, and the spacious chassises are easy to work on.

Was yours made at the Ajax plant or actually imported from England?

I'm partial to brand new parts from proper vendors Like Allied Elect, Digikey, Just Radios (of Canada), Mouser, etc. If you do enough recap work most of those parts houses offer steep discounts if you buy by the 100 on caps.

I've been reluctant to order from JustRadios due to the lack of information on manufacturers. What would you say about their parts? Also, what would I look for on sites like Mouser and Digikey?

So I suppose polypropylene orange drops are the best to use hm? Antique radio work is still very new to me.

I've made one large order from Just radios (~5 years? ago), the shipping cost and wait time to get their stuff into the states makes me usually pick other parts houses, but the quality of parts was plenty good for tube radio and TV work. They mostly stock Orange drop types and those generic Chinese yellow caps.

Some folks here (such as the captain) look down their snoot at yellow caps but I've been raised on them if you will. The professional tube TV and radio repairman who mentored me in my first few years repairing radios the better part of 2 decades ago used them and I have on and off (depending on what I could get my hands on) ever since. I've never had a bad one and aside from the possibility of destroying them by holding a soldering iron to the plastic (made that mistake ~5 times now) there are no drawbacks to them.

When I'm not restuffing caps (which is where the yellow ones shine), I prefer Panisonic caps like these since I can't melt one soldering. http://www.mouser.com/ProductDetail/...n1p2vhg7KKs%3d

Basically for the papers you select "film capacitors" and for the lytics you select "aluminum electrolytic" in the bigger parts houses catalogs then you use the filters to select capacitance value and DC voltage rating and sort by manufacture and or price. You want to look for parts with long leads if available (saves the work of adding wire on to the cap). You don't have to go with Panisonic or any specific brand...Anything that meets specs (even the cheapest) should work. Old capacitance values like 5, 2, 3 and powers of then multiples there of are not made affordably, best to pick the nearest modern standard value 4.7, 2.2, 3.3 etc.

I'll buy whatever when I'm low on funds or have a HUGE order. I just spent close to $400 on about 60 different part numbers most of which I ordered 10-200 pieces for each part number...most films were panisonic, but I've mixed in some Illinois Capacitor and some Wima, and even more brands if I go into lytics...

Here are a couple of starter pages for mouser.
http://www.mouser.com/Passive-Compon...x371?P=1yp7zip
http://www.mouser.com/Passive-Compon...5hqt?P=1yx4ard

Last tip: be sure to check the in stock box when searching, you don't want to order a non-stocked part with a 3 month lead time/back log.

Ah, I was just looking at Panasonic film caps on Mouser. I've ordered a bunch of electrolytics from them - all 105 degree Nichicons so far - but just a couple of film caps. I've had to re-order a few caps a couple of times, mostly because I got ones too big to fit in a can, but the experience of course is invaluable.

Ugh, that non-stocked chestnut is so annoying, I often forget to check that box. It's usually when I get a lot of results that I remember to use it; it thins out the results big time.

There's one more thing that's throwing me; all paper caps I've looked at indicate their working voltage in DC, but I seriously doubt they're polarized, at least not like electrolytics.

This radio isn't mine but it will be restored to the same exacting standards as anything I own. I'll aim for affordability but there's no way I'm cheaping out. Besides, it isn't me who's paying for the parts. :)

Paper caps have DC working voltage. Film caps on most sites often have Both AC and DC working voltages*. It is the DC that matters. (IIRC on my links I added a 630VDC filter for the film and a 450V for the lytics so you won't see a DC voltage selection column unless you nix that criteria in those links). You can always go higher voltage on film and to a point lytics as well.

Paper and film caps are not polarized, but if you want a rough idea of the DC polarity on them there is a convention....The 'outside foil' band on the end of paper caps is traditionally connected to ground. The outside foil wraps around the cap shielding it (thus why you want to connect it to ground when trying to optimize performance). Somewhere on youtube I once saw a video on using a scope to find the outside foil of a cap.

*In tube amp circuits the DC rating is what matters since most paper caps have ~200-600VDC on them and maybe 5 volts AC signal (until you get to TVs and sweep circuits then it jumps sharply). If on your tube set there is a cap between the two terminals of the power cord or between 1 terminal and the chassis then AC rating becomes important. Many film caps at made at paper cap ratings are made as line to line or line to chassis RF noise suppression/safety caps thus the AC ratings being available.

The non-stocked stuff can be annoying, but what sucks even worse is stuff with a low stock...I was going to buy IIRC 10 .0047uF 6KV caps for some electrostatic sets I want to finish (+ a few extra for the future) and at checkout found only 3 were in stock the rest would be back order....So I dropped it to 3 and now I've got my fingers crossed that it will be enough (or at least the 2 in series I used in a roundy as an emergency sub for a 2KV part are the right value and that I can take them and can come up with something different for the roundy).

Yeah I thought that was a great idea to make sure to minimize interference in my stuff when I'm recapping. But then I tried it, and came to realize that you need a super-accurate/sensitive scope to be able to figure out which lead is the outside foil. So like... I figure now if my scope isn't sensitive enough to tell the difference... why bother?

I've ordered from justradios before, their parts seem to be decent quality. But the $25 minimum sucks, so if you miss something in your order you're fucked.

I've used capacitorworld too. They definitely sell cheap shit. And they have a bad tendency to screw up my orders, and they have NO customer service to speak of. But anyway, the way I see it, most old paper caps have a tolerance of +/- 20%, and most modern film caps - even the cheap ones - are usually 10%.

Idk. Also - noice radio!

Right, I just realized they have a DC working voltage too, totally different from the AC ratings. I have a list tacked to the wall here that I've been referring to when adding to my shopping cart. I went with a slightly higher voltage for each one, and sometimes slightly different values as the originals were not available. One of the paper caps is rated at 0.0005 uF and the lowest value Panasonic poly film cap available is 0.001 uF so I guess I'll have to use two in series.

Hm, I see lots of people have made videos on how to find a cap's outside foil, but more importantly the video I saw a while ago shows that many with a band end have been marked incorrectly. I had to dig a little but I got it:

https://www.youtube.com/watch?v=BnR_DLd1PDI

This fellow mentions that one should be fine using a digital storage oscilloscope that goes down to 5mV per division but he demonstrates with an old Tektronix 547 so my BK Precision 1479A should work just fine for this application.

I noticed two caps in the parts list that were specifically marked AC, and they're going from line to ground so I selected Kemet X1/Y2 caps to replace those.

In my latest order my shopping cart was loaded up for a while and one electrolytic went out of stock in the meantime, but that was easy enough to replace.

Onto resistors now, and then I'll have to pull a Santa and check my list twice before placing the order.

As I said above there are quite a few videos on testing for the outside foil, but only one I know of is really useful, and from what I saw an older scope should work just fine.

Yeah, the minimum order thing sucks, that's even worse than missing a part and having to cough up the extra shipping charge.

As for Capacitor World, I'm not the least bit surprised.

Yeah it is a pretty cool radio. Most antique table radios I've seen are a lot simpler and a lot smaller.

Okay, now I'm pretty torn as to which resistors to choose. Someone recommended Vishay metal film resistors a while back but I'm not sure how to go about stepping up the wattage.

I like metal oxide resistors with the metal film ones for higher values. Just bump on wattage up, so for a 1/2 watt get a 1 watt etc. This is not for wattage but for physical size and voltage rating.

Not necessarily. If shielding is your concern, the outside foil needs to go to the lower impedance side, which is not always ground. For example, the coupling cap from plate of a 1st audio stage to grid of output stage. The outside foil goes to the plate because it's lower impedance (albeit higher DC voltage) than the grid.

Signal impedance is what you're shielding for.

I understand why one would want to buy the good stuff, like real orange drops. But the bulk ebay brown drop caps have saved me tons of money, and I haven't had a single failure. I wouldn't use them in something valuable, or critical, but for old tube radios, PA amplifiers and other such applications, they are great. It's also nice to have all the values I need in stock, all the time, for minimal cost.

See attached how I organized them (box not from ebay) . Everything in that box cost me under $50, I've refilled the 0.047s and 0.1s a couple times but the rest are still from the initial order.

Mouser is my go-to for caps. I usually order enough to get the price breaks, I don't think they have a minimum order, but I get enough to make the 8$ shipping worthwhile..

I looked up my old thread and it was Bob Andersen who recommended the Vishay metal film resistors and he posted the link below. If he likes them then they must be good. Besides, metal oxide resistors are a bit hard to come by in the values I need.

http://www.mouser.com/catalog/catalogusd/646/817.pdf

Okay, just a couple more resistor questions; this radio uses mostly 1/2-watt resistors so I have most picked out.

1. Is a 3-watt resistor of about the same physical size as a 1950s 1-watt a suitable replacement?

2. There's a massive 18k 2-watt, ~30mm long carbon comp in there, what can I replace that with?

3. What is the modern equivalent for a 1.6k, 4-watt power resistor?

https://www.mouser.com/ProductDetail...dji2uRYA%3d%3d

This should work for the 1.6K

https://www.mouser.com/ProductDetail...dji2uRYA%3d%3d

A little smaller than 30mm, 25mm.

Are you using 1 watters for the 1/2 watters?

That 1.62 looks good, thanks. Edit: Oh shoot, that's a non-stocked item.

The same link was pasted twice; I've made that mistake many times. Actually it's the 18k 2-watt carbon composition resistor that's about 30mm long; I have no idea what to replace that with. I'm using 2-watt resistors to replace the old 1/2 watters. Bob Andersen said he does this, they're approximately the same physical size.

To sum it all up I plan to use 2-watt metal film resistors in place of the old 1/2 watters and 3-watt to replace the old 1-watters as they're very close in size. I have no idea what I'll do about that 2-watt carbon composition fatty or the 1.6k 4-watt resistor.

I got a close-up of the circuit the 1.6k 4-watt resistor is in, highlighted it and identified the tubes in the area, hopefully that helps.

Dang. I thought I checked the non-stock option. Grr. I do see that Mouser has a 10 watt, 1.6 k in stock. If you can do 1.5K Mouser has plenty of in stock options and that is a less than 10% difference. What is the tolerance of the original part?

Here is a 18k, in stock and 25mm.

https://www.mouser.com/ProductDetail...reHfLvJIcaE%3d

No can do, tolerance is 5% and I wouldn't feel safe going lower. I believe it's a wirewound resistor; I suppose 1.8k 5w will have to do in this case, it's about as close as I can get. As for the 18k resistor I suppose I'll go with the Panasonic 3w metal oxide.

If that's all in order I now just need a source for dial string, 6.5V 0.3A indicator bulbs, tuning condenser grommets and a dial pointer like the one pictured which is the usual grossly overpriced eBay item. The ad says it's 4 3/4" long which seems appropriate for this radio and the carriage looks like the one in the dial stringing instructions.

It's just a piece of metal. Can't be that hard to make.

Yeah, some 18 gauge bus wire ought to do it. I just have to finish figuring out the bends needed to mock up a pointer carriage.

Now, is there a one-stop shop for the bulbs, grommets and dial string?

How about two 3.3k, 3W in parallel? That gives you 1.65k.

https://www.digikey.com/product-deta...W-3BK-ND/36825

I don't know, wouldn't that cause a drop in available power dissipation? I see they're only 3 watts each, and I just haven't been able to get a grip on series/parallel wiring for resistors.

2 3W resistors of equal resistance in parallel or series = 1 6W resistor for series it will have twice the rated resistance of each unit, for parallel it will be half the rated resistance.

Power = Voltage * Current In series each unit takes half the voltage of the pair, in parallel each unit takes half the current....This assumes the two resistors are of equal value....If different the math for power ratings gets more complicated.

It may be useful to do some practice ohms law math, and network analysis math to gain a better understanding.

In other news that part that was low stock turned out to be NO-Stock...I had to call Mouser and ask about it for them to send me the rest of my order....Which apparently they were not going to ship till I asked...

Tom, you got that backwards - Two equal resistors in parallel halves the resistance and doubles the wattage. Two equal resistors in series adds the resistance and the wattage remains the same.

So Jon, no problem with the two resistors in parallel. I would make sure there is a little air gap between them for heat dissipation

Got it, thanks.

Any leads on the bulbs, grommets and dial string? Once those are secured I'm all set.

The wattage rating for the pair would double, wouldn't it? For example, with two equal-value half-watters in series, the wattage rating for the pair would be 1 watt, seems like (since the working voltage across each will be halved).

Whereas a pair of half-watters in parallel also has a 1 watt rating because the current through each is halved.

Nope. With the resistors in series each resistor still has to handle all the current flowing through it. So the wattage rating remains the same. With two equal resistors in parallel each is taking half the current so the wattage rating doubles.

Yup. All the current.
Since they're in series, each resistor sees only half the voltage. So the wattage rating of the pair hasta double.

Just for example - two 20K half-watters in series makes a 40K @ 1 watt rating.

Just as two 20K half-watters in parallel makes a 10K @ 1 watt rating.

Alrightie, I finally got motivated enough to compare the original parts list, my list of parts to replace and the contents of the Mouser shopping cart, all is good there.

Once I get info on a source for tuner capacitor grommets, dial string and bulbs I'm all set. Nevertheless it's good to have the info on the resistors, that was a tough nut to crack. I clipped out the 1.6k 4 watt resistor and smashed it apart just to see how it was made. It had a white cylindrical ceramic core with stranded leads going all the way through each end, was wrapped with very fine wire and topped off with a thin green coating. I have doubts it was one of the more reliable designs.

Now, can anyone point me in the direction of the last things I need? That would be great, a one-stop shop would be best. I'm finalizing a list and an estimate for the owner.

This guy is a local cap vendor (I buy from him at swap-meets) and stocks dial cord and dial lamps as well as yellow film caps and lytics. http://www.radioantiques.com/

Some hardware stores stock rubber grommets if you look through the drawers (IIRC Ace hardware is one).

Madlabs: I fixed the series parallel resistance value thing, I noticed I got it backwards (sometimes I have to finish typing fast and skip a proof read) before I read your post...However I agree with old coot the effective wattage of the pair doubles in both configs. In college I proved that mathematically a few times and can do it again if you doubt us.

Tom, I knew it was a typo. And I sit corrected and thank you and old coot for setting me straight!

Oh cool, that's one site I stumbled on, just needed confirmation of a good source.

Oh okay, so I don't need special tuner grommets, just the right size. I already added one grommet to my cart for the power cord. Got to replace the cord too, the insulation was falling apart.

The owner thought it might explode if powered up as-is; maybe not explode but I'm pretty sure the end result wouldn't have been pretty.

I'm sure there's no short answer to this, but can this radio tune FM stations? I can't make head or tail of this dial.

http://videokarma.org/attachment.php...1&d=1509043570

No. This radio is broadcast band, and "general coverage" shortwave. It will be amplitude modulation only, no FM.

M c/s = MHz, and K c/s = KHz.

Gotcha, the frequencies in MHz looked unfamiliar to me and I didn't know what influence the markings on the right of the dial mean.

Anyway, I totaled up the cost of all the parts and supplies needed to restore this radio - the parts being a fraction of the cost - and at this point it looks like the owner doesn't want to bother with it so worst case I'll be hanging onto it as a long-term project. He wanted to use it regularly but there are no AM stations around here. No big deal, there must be something to listen to in the decent parts of the country.

The markings on the right, at the top is BC, which means broadcast, and under that is the wavelength in meters. Wavelength is inversely related to frequency, and is commonly used in short wave and amateur radio.

As for parts count, there isn't really any reason to change all the resistors, and you can use cheaper capacitors. That's a really cool radio and it would be nice to see it work, but I agree without any use for it it's a tough sell.

May not be any daytime AM, but there should be some decent stations at night....I've regularly been able to tune AM stations from better than half way across the continent at night.
I don't know what to expect with short wave up there, but if somewhat close to the east coast there should be plenty of European stations.