[captainclock1988]

CEO to the marketing Department we need to sell more 35W4 tubes. Yes Sir. Production this is the marketing Dept start using 50UF & 50UF no more 30UF & 50UF this is from the top!!!  Not trying to be a wise @&$ but do what  mike suggest.

Well like I said, Seeing as they don't make 40 or 50 MFD Capacitors anymore since they redid the capacitor values in the 1970s the next best capacitor that uses the modern capacitor value system is a 47 MFD which is what I ordered, if you tried to use a 33 or a 39 MFD it would be under rated for what the radio needed, if you tried to use a 68 MFD (if what you and morzh are saying is actually true) then a 68 MFD would be over rated, so I think a 47 MFD is fine in this application since the values they would of used back when this radio was built no longer exist since the capacitor value system redesign in the 1970s.

[David]

C2 33UF, C3 47UF current production Ecaps +20% -50%  This is all I have to say. Stay safe. David

[morzh]

Engineers go by datasheets and abs max ratings. NOT by the schematics that use parts. At least the good ones do.

[captainclock1988]

Engineers go by datasheets and abs max ratings. NOT by the schematics that use parts. At least the good ones do.

Yes, but those schematics and service datas that Beitmans and Riders used came from the factory that made those respective radios, so those scematics in those service manual were originally drawn up by those very engineers that you said go by tube data sheets and max ratings, unless you're suggesting that perhaps the engineers at Westinghouse who designed this radio were morons? 

So I would tend to trust that the data given in the Riders (with exception of known manuals that have known typos), has the correct information, coupled with the fact that my radio which was untouched from what I could see matched the Riders and Beitmans service Data exactly right down to the component values, which makes me think that those electrolytic caps were NOT a mistake and were put in there for a reason.

I have ordered 2 47 MFD 250 WVDC electrolytics to replace the old 50 MFD 150 units that were in there originally.

I have also ordered the rest of the caps to replace the paper caps that I wasn't able to replace previously, and I also ordered a replacement output tranny so hopefully we can get some action out of this unit again.

[captainclock1988]

C2 33UF, C3 47UF current production Ecaps +20% -50%  This is all I have to say. Stay safe. David

So you're still suggesting that I put in caps that are undersized for the task?  

If I would of done that and my radio ended up blowing up or catching on fire, then I would of blamed you and morzh for giving me shoddy information! 

I've already got two 47 MFD caps ordered for this radio and that's what I'm going with.

[morzh]

Yes. You should trust that the information is correct as far as the as hematics are given.
No. The usage of the componets in some schematics is incorrect. The schematic is faithfully tells us that.
And....no, many schematics have mistakes. Philco in particular. Like missing tiedots. So if you followed say 60 sch while rewiring the chassis, it would not work.

It helps when one understands schematics, not just blindly follows one. Even the one that correctly represents the circuitry. Because the circuitry may be flawed.

Ok, I'm out.

[captainclock1988]

Yes. You should trust that the information is correct as far as the as hematics are given.
No. The usage of the componets in some schematics is incorrect. The schematic is faithfully tells us that.
And....no, many schematics have mistakes. Philco in particular. Like missing tiedots. So if you followed say 60 sch while rewiring the chassis, it would not work.

It helps when one understands schematics, not just blindly follows one. Even the one that correctly represents the circuitry. Because the circuitry may be flawed.

Ok, I'm out.

I wasn't saying that ALL service information is going to be accurate, notice how I said in my previous post that Riders is notorious for mistakes in their service manuals, but I studied the schematic and the pictured they had of the underside and upper side of the chassis on this radio and and compared it to the unit I have which like I said was an unmolested example as it had all of its original paper and electrolytic caps intact yet as well as all of its original carbon comp resistors (Allen Bradley style and the old style carbon comps that had the rougher surface than the newer style Allen Bradley Style Carbon Comp Resistors), and the radio I have matched the schematic and the photo representation of the chasis that showed the physical location of each part on the chassis perfectly even the parts list matched the parts that were in the unit I have.

That's why I was saying that my radio as it sits was exactly as it was when it left the factory over 70 years, right down to the filter cap values, plus there were manufacturers during the tube era that were known to drive tubes well above their rated specs to get more power out of their units, for example I had gotten from my church several years back an old Newcomb Pathfinder PA Monoblock Amp that that was rated for 75 Watts max, using 7027As in Push-Pull Configuration which 7027As in push-pull configuration are good for about 65-70 Watts MAX and Newcomb drove the 7027As extremely hard in their Amplifier setup in order to milk an extra 5 watts out of the them by upping the B+ voltage on the plates of those 7027As from their max rating of 450V to aroud 650V using a special Voltage Doubler Circuit that utilized a 6V6GT tubge as a Voltage Regulator Tube for the circuit. 

My guess is that when Westinghouse designed and built this radio they were designing it in a way that drove the tubes in it beyond their limits in order to get the most out of the circuit that they could, seeing that this is a fairly minimal circuit compared to other comparable AM/FM tabletop radios from this time period (such as the ones that Zenith made like this).

[John Bartley]

I think it's necessary to keep in mind that most (with a few exceptions) tube data sheets show "typical" operating values, not maximums. When I look at other schematics and most spec charts, I see "typical" of 40uF in the specs, but many schematics with more than 40uF, and I have seen and replaced some of these myself, usually with 47uF caps. Keeping in mind that these sets have operated for several decades like this, it is my opinion that this 40 vs 50 is a tempest in a teapot and unworthy of much debate. I believe the schematics are correct as drawn and are not errors, and I personally will continue to NOT second guess the engineers who designed the radios in the first place.

For yourselves ..... ??? ..... do as you wish.

[morzh]

John

About Typ/Max.
See below.

   

[John Bartley]

Yes, I have already seen that.

Did you read my post where I said "with a few exceptions", show typical, not max?

One sheet showing "max" beside a cap value does not negate a whole bunch of spec sheets showing "typical" for the same value. If you wish I can show you one to off-set yours, then we can keep arguing, but why waste our time? I'll keep following schematics and OEM installations and you can keep re-engineering if you wish.

[morzh]

John

I am not a life-long tube designer and so I do not keep the tubes' datasheets the way I keep semiconductor ones, and so I have to go by what what I find, and so fat what I find has the words "maximum" and "40 uF" next to each other.
I saw one sheet showing 40uF undet "typical" but then it did not show maimums.

So, if you produce a datasheet that says explicitly "maximum 50uF" I will agree with what you say.

Meantime, here's another one for the same tube I found.

   

And....speaking of "several decades of operating like this", we do not know how many time this tube was replaced.

PS. I am not saying the tube will immediately go up in smoke because of 50uF. Or even 100uF. It might last for years and, given today's "once in a blue moon" operation, might live forever. But to me this is a wrong way to do things. Even if it works.

[Eliot Ness]

OK captain, your pair of 47's will (more than likely) be fine and last a long time.

But instead of everyone getting in a p$ssing contest let's use this as a learning experience.  I applaud Mike showing how to use tube data sheets to determine the max (recommended) value of the 1st filter cap.  Often folks will randomly jack up the value of that cap trying to eliminate hum, but if one looks at the data sheet they can see the max value they should typically use.  BUT, the 2nd capacitor is the one you can jack up the value on w/o damage to the tube.

The tube data sheet is also helpful when you aren't sure what the value of that capacitor should be, such as the label is not legible or some hack stuck in a ginormous filter cap at some point in time and the schematic is not available or capacitor values not labeled.

I like to have a couple hard copies of RCA's tube books around, but there are several that are available for download or you can just do a search for an individual data sheet for a specific tube. 

Thanks Mike, for introducing the value of the tube data sheet for collectors who might not have been aware of their usefulness.

[morzh]

John,

Thanks.
Also another effect of jacking up the first filter cap (yes I agree about the second as that one could be ...just about anything reasonable; the datasheet only specifies the first one), even within the specifications, is increase of the output voltage.
So, if one were to increase the value from 50uF to 100uF (and the radio was designed for 50uF value so all the tubes and their operations relied on that) the B+ voltage then would rise and the tubes would operate at unnecessarily high voltage thereby running hotter and having less useful life. Even if we disregard the ill effects of increasing the first cap directly on the rectifier tube.
That also has to be kept in mind.

[captainclock1988]

I think it's necessary to keep in mind that most (with a few exceptions) tube data sheets show "typical" operating values, not maximums. When I look at other schematics and most spec charts, I see "typical" of 40uF in the specs, but many schematics with more than 40uF, and I have seen and replaced some of these myself, usually with 47uF caps. Keeping in mind that these sets have operated for several decades like this, it is my opinion that this 40 vs 50 is a tempest in a teapot and unworthy of much debate. I believe the schematics are correct as drawn and are not errors, and I personally will continue to NOT second guess the engineers who designed the radios in the first place.

John, I agree 100% with what you just said, that's exactly what I was trying to say this whole entire time but everyone was just ignoring my comments because they think that just because I'm a 31 year old that's only been fixing radios and record players for 20 years that I don't know what I'm talking about.


I've repaired over 20 radios so far using the values spec'd in the service data for the radios (or going off what was originally in the radios) and I have yet to have a radio fail on me.

And....speaking of "several decades of operating like this", we do not know how many time this tube was replaced.

PS. I am not saying the tube will immediately go up in smoke because of 50uF. Or even 100uF. It might last for years and, given today's "once in a blue moon" operation, might live forever. But to me this is a wrong way to do things. Even if it works.

morzh,

Just so you know, this radio still has its original Westinghouse branded Rectifier Tube in it with a date code of 8-13 (13th week of 1948) and it tests around 95 out of 100 on my tube tester so that just tells you that the original filter caps that they used in there (50/50 @ 150) didn't overdrive the rectifier tube in this radio at all. even the original 35B5 output tube measured about a 90 out of 100, there were only 3 tubes in this radio that were replaced over the years (well actually 2 the 19T8 was replaced by me because it was the original Westinghouse branded tube in there when I got it and was measuring weak on two of the 4 sections of the tube) the other two tubes that were replaced in its history was the 12BA6 and the 12AT7 the rest were all original Westinghouse tubes that still tested between 85 and 95 out of 100. 

So with that in mind I think this radio's design was just fine as is.

[Jayce]

The 12AT7 and 19T8 tubes don't really surprise me that they needed replaced. Depending on how the radio operates, the 12AT7 is always almost DOA and I have heard talk of the 19T8 tubes being part of a trio of 'snap crackle pop' tubes that can go bad or short just because they want to. I've had 19T8 tubes that have tested great in radios before being recapped only for them to conk out or develop shorts a short while later after the radio has been restored. The 12BA6 might have been due to a bad bypass capacitor as I rarely run into bad examples of those in radios. Not impossible though!