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  #1  
Old 10-20-2017, 03:15 AM
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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/
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Old 10-20-2017, 10:16 AM
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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.
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Old 10-20-2017, 11:58 AM
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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?
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Old 10-20-2017, 03:23 PM
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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.
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Old 10-20-2017, 04:34 PM
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Quote:
Originally Posted by Electronic M View Post
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.

Last edited by Jon A.; 10-20-2017 at 04:37 PM.
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Old 10-20-2017, 05:30 PM
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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.
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Old 10-20-2017, 05:48 PM
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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.

Last edited by Jon A.; 10-20-2017 at 05:59 PM.
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Old 10-20-2017, 06:26 PM
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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).
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Last edited by Electronic M; 10-20-2017 at 09:16 PM.
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  #9  
Old 10-20-2017, 10:14 PM
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Quote:
Originally Posted by Electronic M View Post
Somewhere on youtube I once saw a video on using a scope to find the outside foil of a cap.
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!
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  #10  
Old 10-21-2017, 01:18 AM
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Quote:
Originally Posted by Electronic M View Post
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).
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.

Last edited by Jon A.; 10-21-2017 at 01:25 AM.
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  #11  
Old 10-21-2017, 01:24 AM
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Quote:
Originally Posted by MadMan View Post
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!
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.

Last edited by Jon A.; 10-21-2017 at 04:26 AM. Reason: Need resistor advice.
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  #12  
Old 10-21-2017, 10:51 AM
madlabs madlabs is offline
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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.
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  #13  
Old 10-21-2017, 11:34 AM
old_coot88 old_coot88 is offline
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Quote:
Originally Posted by Electronic M View Post
....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...
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.
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  #14  
Old 10-21-2017, 11:49 AM
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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.
Attached Images
File Type: jpg DSC_0258.jpg (86.7 KB, 11 views)

Last edited by maxhifi; 10-21-2017 at 11:53 AM.
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  #15  
Old 10-21-2017, 02:15 PM
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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..
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