[Atco]

Hi Guys - I bought a Philco 38-15 a few weeks ago and want to bring it back to life. Thought I'd start by ordering the capacitors. Now in the schematic there are two double electrolytic caps, one with the original cap in a can on the top of the chassis. The other one is wired in the bottom of the chassis. The schematic shows two electrolytic 2uf and a 4uf and I assume that cap was wired on the bottom of the chassis. But, right now the cap is shown as two 30uf 150v caps (a double) in stead of what the schematic shows. By looking at the solder, it's not the original cap. Maybe that was the only one the prior repairman had. So, I want to replace all the caps, and especially from the double 30uf, to two single caps, 2uf and 4uf to make the schematic match. Only problem though, I don't know for sure what voltages is needed for that 2uf and 4uf caps. I'm afraid to buy 160v incase that's too low. Does anyone know what the correct voltage needed for those 2uf and 4uf electrolytic caps? I'd appreciate the help! See ya -- Atco

[morzh]

The sch shows:

http://www.nostalgiaair.org/PagesByModel...013239.pdf

Cap 31 - 12uF+10uF
Cap 30 - 4uF
.

What sch are you looking at?

PS. Keep in mind, Cap 31's minus (can) should be insulated from the chassis and its 10uF part has its PLUS connected to the chassis.

[David]

Good Morning, When I worked on my 38-15 I used the fellowing  12uf-450volts, 10uf-50volts, 4uf  used 4.7uf-450volts, 2uf used 2.7uf-450volts. The 10uf was orginal 25volts the 50 volts replacement was like 4 cents more. I ordered seperate caps from mousser(sp). I did not restuff the old caps just left them in place, put the new ones under the chassie. Yes I am a sinner for not restuffing the old caps!!!!.  I am going to do a seperate post and try and show a picture of one page of my notes with regards to polarity of the 12uf and 10uf. David

[klondike98]

Welcome to the Phorum!  Lots of folks here to help you with your project. When you have a project, it helps to post the link to the schematic as well.  In this case you can find one here.  When those can electrolytic caps seen on the top of the chassis failed, the repair was often done by clipping the old leads and then putting the new caps under the chassis or by replacing the can with another one but often of different values than the original because it wasn't critical what the value was.  If the cans are still present on the chassis you can cut them open and stuff new caps inside to retain the look of the radio.  A nice write up on recapping can be found on Phil Nelson's site.  I'd use 450v caps for those electrolytics since the schematic shows almost 300v at those points. (other folks please chime in if I'm wrong).  You also have a bakelite block capacitor which holds the two 0.01uF line capacitors that will need to be changed out.  Morzh has a great thread on how to do the change out.  Data on how they are wired up can be found here. Those should be safety caps.  Some info on safety caps can be found here.  

(Mike...cap #30 is a 2uF + 4uF. )

[David]

Found my notes resistor number 24 orginal 190,000 (190k) replaced with a 200k 1 watt the 190k was fried, resister number 25  490k  was fried replaced with 1 watt used 470k the 490k is not a standared value today. The resistors in your set do not use the samr color code as todays parts. The picture attachment shows 4 little squares that is a terminal strip with numbers I used not part of the orginal radio, the most inportant thing is the polarity of the 2 caps!!! Will not allow me to attached the file to big contact me by email. David

[morzh]

Oh...yeas, the is that 2uF also.


The filter caps should probably be 500V rated as (I am not sure, been a long time since) 290V DC is under load, so without a load I would think it could reach over 450VDC for 3-4 seconds when the rectifier starts and other tubes are not hot yet as it should be the peak voltage which is 290V*3.14/2 = 455V.

[Atco]

Welcome to the Phorum!  Lots of folks here to help you with your project. When you have a project, it helps to post the link to the schematic as well.  In this case you can find one here.  When those can electrolytic caps seen on the top of the chassis failed, the repair was often done by clipping the old leads and then putting the new caps under the chassis or by replacing the can with another one but often of different values than the original because it wasn't critical what the value was.  If the cans are still present on the chassis you can cut them open and stuff new caps inside to retain the look of the radio.  A nice write up on recapping can be found on Phil Nelson's site.  I'd use 450v caps for those electrolytics since the schematic shows almost 300v at those points. (other folks please chime in if I'm wrong).  You also have a bakelite block capacitor which holds the two 0.01uF line capacitors that will need to be changed out.  Morzh has a great thread on how to do the change out.  Data on how they are wired up can be found here. Those should be safety caps.  Some info on safety caps can be found here.  

(Mike...cap #30 is a 2uF + 4uF. )

Thanks Bob. I never heard of a bakelite block capacitor before, but was wondering what that was. I looked at Morzh's thread on how to change out the caps. Very well done. I will have to do that myself.

[Atco]

Good Morning, When I worked on my 38-15 I used the fellowing  12uf-450volts, 10uf-50volts, 4uf  used 4.7uf-450volts, 2uf used 2.7uf-450volts. The 10uf was orginal 25volts the 50 volts replacement was like 4 cents more. I ordered seperate caps from mousser(sp). I did not restuff the old caps just left them in place, put the new ones under the chassie. Yes I am a sinner for not restuffing the old caps!!!!.  I am going to do a seperate post and try and show a picture of one page of my notes with regards to polarity of the 12uf and 10uf. David

Thanks Dave, that's just what I needed!

[Atco]

Oh...yeas, the is that 2uF also.


The filter caps should probably be 500V rated as (I am not sure, been a long time since) 290V DC is under load, so without a load I would think it could reach over 450VDC for 3-4 seconds when the rectifier starts and other tubes are not hot yet as it should be the peak voltage which is 290V*3.14/2 = 455V.

Thanks Morzh - I didn't know about those bakelite caps before. Glad to see your thread about them. Guess I'll need to do that as well.

[morzh]

Atco

Only in case you want to do that, this is "a little closer to original" measure that does not require you to go to extraordinary efforts (like some folks here do when they actually replicate old resistors) but still bring the chassis a bit closer to what it used to be like.
In case of quick and dirty approach, old caps may be disconnected and new soldered instead, like backelites can have the leads coming from inside cut, and then the new caps can be soldered to the remaining posts as the holders.

Personally I restuff backelites and lytics.

[David]

Made a error the 10uf was 450volts not 50volts sorry David

[morzh]

The 10uF cap can be 150V. The rest 475-500V.