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What are the correct electrolytics for a 41-280 chassis? - Printable Version

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What are the correct electrolytics for a 41-280 chassis? - Art Hoch - 02-02-2011

Last evening I was snooping around in this recently acquired 41-280 chassis and found the one large double electrolytic cap tucked in the corner of the chassis. It is a large black cardboard version with 40 and 50 microfarad markings on it.

As I looked at the schematic from both Rider's and Beitman's (they are the same), I read the schematic to say they should be a 12 uf and an 8 uf. (# 62 and #27) Am I correct? The one in it now looks like, from the soldering, it has been replaced at some time. So I'm seriously doubting it is correct. Also it has 3 red leads into it as well as the one black ground. I usually replace doubles or triples with separate caps so I'm a little confused why there would be 3 red positives going into a double cap. Are they tied together inside? If so, why would that be?

Thanks Philco guys.

Art

Re: What are the correct electrolytics for a 41-280 chassis? - Ron Ramirez - 02-02-2011

This model actually uses three electrolytics; as shipped from the factory, two were in the same container (27 & 27A), with the third one (62) in a separate cardboard tube, but mounted alongside part (27 & 27A).

This is probably why the cap in your set has three positive leads. However, it would not have worked correctly in that configuration - the negative of (62) needs to go to B- (center tap of the power transformer's high voltage winding), while the negatives of the other two go to chassis ground.

(27) had an 8 uF and a 16 uF cap inside, while (62) had one 12 uF cap.

Owing to the wide tolerance range of electrolytics in the 1940s, you can use a 10 uF, 450 volt cap to replace (27), another to replace (62), and a 22 uF, 450 volt cap to replace (27A).

Re: What are the correct electrolytics for a 41-280 chassis? - Art Hoch - 02-02-2011

Thanks Ron,

That's (1 40uf and 1 50uf) probably the reason someone ditched the chassis. I don't see 27A on the schem. Am I blind or just can't see it!! ;)

Re: What are the correct electrolytics for a 41-280 chassis? - John R - 02-02-2011

Art,
27A is the 16 UFD in the power supply section. What you can't find on the schemo is #27 the 8ufd. It is located on the left side of the schematic near the XXL tubes and is for addtional B+ filtering for the plates of the 1st det. and oscillator tubes. It more than likely has been removed from your chassis when someone changed out the electrolytics.
Good luck, John

Re: What are the correct electrolytics for a 41-280 chassis? - Art Hoch - 02-02-2011

@ John,

I saw the 8 ufd near the XXL tube (tied to a 33K resistor (#26) and an 18K resistor (#28) that you refer to, but neither my Rider's or my Beitman's schem shows a 27a nor in the "Part Locations underside" drawing. My wife accuses me of being blind in one eye and not able to see in the other but I just don't spot it...even with a magnifying glass. I looked on Nostalgia Air site but can't see it there either, fuzzy or no. Can you tell me what the 27a is tied to on the schem? Ron says it goes to ground chassis.

Thanks,
Art

Re: What are the correct electrolytics for a 41-280 chassis? - John R - 02-02-2011

Art,
I know what you mean by using a magnyfying glass.. I have to use one all the time Icon_crazy Cap 27 is the 8 ufd which ties to the two resistors near the XXL tubes and the negative to ground. Cap 27A is the 16 ufd tied to the ouput DC side of the field coil and is located on the schematic just to the right of the power supply and field coil. The NA site shows this on the 41-280 (code 121) schemo which is a Riders Vol. 12, Philco page 63.
Below the 16ufd value is a circle with the # 27A within it. It shows typically ~ 180VDC across this cap. The negative of 27A does go to ground.
The negative of the #62 cap, as Ron said, goes to the center tap of the high voltage transformer secondary winding. Icon_thumbup
John

Re: What are the correct electrolytics for a 41-280 chassis? - Art Hoch - 02-02-2011

@ John,

I'm embarrassed. I finally found the 27a cap on the schematic --- while I was looking for something else. Waiting now to see if I can get a correct speaker for this so I can power it up after I change caps and resistors..

Re: What are the correct electrolytics for a 41-280 chassis? - Art Hoch - 02-10-2011

Electrolytics are replaced as of today (2/10/11). Now on to the small caps. And resistors which are out of tolerance....not too many, thank goodness. Found a braided copper wire out of the variable capacitor broken. It was grounded to the chassis. So soldered it back together where it went through a hole in the deck. About the only thing I could do because of crowded locations. Have continuity so think that is solved. Speaker repair done today also. Hopefully will know soon whether this baby is going to play!

Re: What are the correct electrolytics for a 41-280 chassis? - Art Hoch - 02-12-2011

It plays on all three bands! Have to figure out why 2 dial lamps aren't lighting. Then the dial stringing....won't be fun. Icon_rolleyes Does anyone have a spare pointer for this radio?

Re: What are the correct electrolytics for a 41-280 chassis? - Glenn Roberts - 02-12-2011

I think I might. let me look. It will be today or tomorrow.

Glenn

Re: What are the correct electrolytics for a 41-280 chassis? - Art Hoch - 02-12-2011

glennpr Wrote:I think I might. let me look. It will be today or tomorrow.

Glenn
************************
Thanks Glenn. I got one of the 2 dial lamps to work........bad bulb!! Icon_sick Any body know where the "pushbutton" lamp wire connects to underneath the chassis?? Impossible to see due to the crowded area where it comes through the deck.

Preset buttons are all working...tuned them today. Lots and lots of shortwave reception last night on both SW bands. I was pleasantly surprised.

I appreciate all your help.

Re: What are the correct electrolytics for a 41-280 chassis? - Glenn Roberts - 02-13-2011

Art,

Art Hoch Wrote:Any body know where the "pushbutton" lamp wire connects to underneath the chassis??

It slips onto a flat piece of metal on the front of the chassis. It almost looks like a support, except it doesn't support anything...except the bulb Icon_smile . I asked the same question when I was putting my 300 back together, I'm sure it's the same type of setup.

Glenn

Re: What are the correct electrolytics for a 41-280 chassis? - Art Hoch - 02-13-2011

glennpr Wrote:Art,

Art Hoch Wrote:Any body know where the "pushbutton" lamp wire connects to underneath the chassis??

It slips onto a flat piece of metal on the front of the chassis. It almost looks like a support, except it doesn't support anything...except the bulb Icon_smile . I asked the same question when I was putting my 300 back together, I'm sure it's the same type of setup.

Glenn
************************
Glenn
I think you must be talking about the bulb socket. Yes a hole on the backside of the dial housing holds it. But I'm referring to its wire which goes through a hole in the chassis deck and disappears UNDERNEATH the chassis deck. There's so much "stuff" under there, like the band switch and other things. that hide the wire. It's impossible to see where it connects to. I assuming the band switch but can't wiggle the wire enough to spot it.

Art

Re: What are the correct electrolytics for a 41-280 chassis? - Ron Ramirez - 02-13-2011

The wire for the "pushbutton" lamp goes to the band switch, contact B9 on the schematic.

Re: What are the correct electrolytics for a 41-280 chassis? - Art Hoch - 02-15-2011

Ron Ramirez Wrote:The wire for the "pushbutton" lamp goes to the band switch, contact B9 on the schematic.

IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
All done Ron. Culprit was a bad bulb socket.
Art