Recapping my 40-185 - Printable Version
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Recapping my 40-185 - scottwkurth - 11-10-2010
I'm finally getting around to working on the electronics of my 40-185 after a couple months of real life getting in the way. My next step is to order new caps and start doing replacements one-by-one.
I've come up with the following inventory of paper and electrolytic caps in the set.
Qty Part Value Voltage Schematic
2 30-4469 0.003 mfd 1000 V 50, 55
2 30-4572 0.01 mfd 400 V 46, 52
3 30-4479 0.01 mfd 200 V 30, 40A, 42
1 30-4444 0.05 mfd 200 V 8 (actual part in radio is 30-4441)
3 30-4123 0.05 mfd 400 V 10, 17, 31
1 30-4519 0.05 mfd 200 V 32
1 30-4536 0.2 mfd 200 V 33
2 (3903DG) 0.01 mfd 600 V 64 (bakelite)
1 30-2406 16 mfd 200 V 58 (electrolytic)
1 30-2405 12 mfd 350 V 61 (electrolytic)
Before I get started, I've got a few questions as my circuits knowledge is basic and 15 years old at this point.
1. As I look at ordering replacement caps I'm a bit overwhelmed by the different types. Looking at my options at Just Radios, depending on the values required I see Metal-Foil Polypropylene, Metalized Polyester Film, Metalized Polypropylene Film, Metalized Polyester Film, and Polystyrene Film. Yikes!!! Can someone give me some guidance on which type I should be using to replace the paper caps in this radio? (BONUS Question: Why one type over another?)
2. For working voltages it seems that the general wisdom is to standardize on 630V for the paper cap replacements and 450V for the electrolytic. Assuming I can work out the answer to #1, I'm all set except for the two Part 30-4469 caps. I found conflicting advice in my searches - some said replacing those with 630V would be fine, others said that they need to be 1000V since they are connected to the audio output tubes. Can someone please clarify?
3. Assuming that I need 1000V caps, I can't seem to find a 0.003 or 0.0033 mfd 1000V cap at Just Radios. What should I be looking for as a replacement?
4. I thought I had seen some tips on how to replace the electrolytics, but I can't seem to locate them now when searching. Are these wet caps and do I need to do anything special to replace them?
Thank you for any help you can share!
Scott
Re: Recapping my 40-185 - Ron Ramirez - 11-11-2010
If you're buying from Just Radios, here's what you should do (in my opinion):
1. Looking over the options at Just Radios, I would order metalized polyester film to replace every paper cap in the set, and use 630V rated caps to replace the 200, 400 and 600 volt caps. These are the yellow, axial lead caps. I see the smaller values (smaller than 0.01 uF) are metalized polypropylene film, so use those for any caps you need smaller than 0.01 uF.
Why one type over another? Some people prefer the Orange Dips (replacement for the old Sprague "Orange Drops") as the insulation is hard and not as easy to destroy with an errant soldering iron/gun. Touch a hot soldering iron or gun to the side of a yellow film cap, and you've instantly destroyed it.
2. Correct, 630V for all paper caps and 450V for the electrolytics. Yes, you will get conflicting advice on the two 1000V caps that go from the audio tube plates to ground. While 1000V caps were used to compensate for potential audio spikes, you can get by with 630V caps here. I use 630V caps on the plates of audio output tubes and have yet to blow one out. Of course, I don't crank my radios to full volume either and play them that way for hours on end...
3. If you feel you must use 1000V caps on the audio output tube plates, they do carry .0033 uF in 1600 volt Orange Dips.
4. It depends on whether you plan to restuff the old electrolytic cans or just mount the new ones under the chassis, disconnecting the old cans and leaving them in place for appearance.
Syl has posted an excellent how-to on restuffing can electrolytics here:
http://philcoradio.com/phorum/showthread.php?tid=1002
One more thing. I recommend you use X1/Y2 safety caps, .01 uF, to replace the two in the bakelite block (3903-DG). These are designed to fail open in case they do fail. Regular metalized film caps can be used here, but if they fail, they could fail shorted, which is not a good thing.
Re: Recapping my 40-185 - scottwkurth - 11-11-2010
Ron - I can't thank you enough. The breadth of your knowledge and your willingness to help are incredible! With my questions answered, it is time to place an order and dust off the workbench!
Thanks again.
Scott
Re: Recapping my 40-185 - scottwkurth - 12-11-2010
Victory! I've finished the recapping project, added a fuse and a polarized AC cord, and finally powered up the radio. After some tense moments slowly cranking up the variac I now have a fully operational radio! 70 years to the date, no less, from the day it passed final inspection at the Philco factory!
I'm happily listening to holiday music playing on a local German radio station, complete with ads in German. What a great morning! Thanks again for all the help.
Re: Recapping my 40-185 - Ron Ramirez - 12-11-2010
Congratulations!
Re: Recapping my 40-185 - DeckApe - 12-11-2010
Congratulations, Scott!
...Where on your cabinet/chassis did you find the final inspection label? I have a 40-190 that I honestly haven't had time or space to attack, that has a similar chassis to yours.
Re: Recapping my 40-185 - scottwkurth - 12-13-2010
>Inspection label
If you are looking into the back of the radio, it is attached to the right side in the upper compartment. It is easily visible in mine - not hidden away anywhere at all.
Now on my radio, there is one label that has clearly fallen off at some point that I don't know what it was - attached to the speaker mounting board in the upper right. Any ideas from yours? All I have left is a tiny corner of the piece of paper to tease me.
Re: Recapping my 40-185 - DeckApe - 12-13-2010
Scott--unfortunately, no such luck. I checked the mounting board from the 40-180 where I obtained my speaker and there was no evidence of a label whatsoever. The mounting board in my 40-190 was fabricated by yours truly, so I know there were no labels on it. If the original speaker and mounting board ever turn up in the in-laws' attic I'll report back to you.