What is everyone using to replace the filter caps on the Philco model 20's?
I finally found the values "thanks Nostalgia Air"
1.0/1.0/1.5/0.13 at 1200v/1200v/1200v/1200v respectively. WOW look at those V's and there
not electrolytic but paper caps in that big can?
Any ideas where to find replacement or something close would be greatly appreciated?
Feel free to email me if you wish.
shawn.d.phillips@us.army.mil
:Hello ALL:
:
:What is everyone using to replace the filter caps on the Philco model 20's?
:
:I finally found the values "thanks Nostalgia Air"
:1.0/1.0/1.5/0.13 at 1200v/1200v/1200v/1200v respectively. WOW look at those V's and there
:not electrolytic but paper caps in that big can?
:Any ideas where to find replacement or something close would be greatly appreciated?
:Feel free to email me if you wish.
:shawn.d.phillips@us.army.mil
:ADVICE FROM THE RADIO GODS ?!?!?!
:
::Hello ALL:
::
::What is everyone using to replace the filter caps on the Philco model 20's?
::
::I finally found the values "thanks Nostalgia Air"
::1.0/1.0/1.5/0.13 at 1200v/1200v/1200v/1200v respectively. WOW look at those V's and there
::not electrolytic but paper caps in that big can?
::Any ideas where to find replacement or something close would be greatly appreciated?
::Feel free to email me if you wish.
::shawn.d.phillips@us.army.mil
However, as for the voltages, I do not know where you got 1200 volt ratings for those condensers. Your radio has a 650 volt center tapped high voltage winding in the transformer. When this center tapped winding is used with the full wave rectifier #80 tube, as shown in the schematic, the effective DC voltage is about 325 volts. You could be fine with 350 WV (working volts) condensers. I would choose 400 or higher, though, as 350 is cutting it close. You really don't need anything more than 400 or 450 WV. Some paper condensers (to-day mylar and certain metalized film condensers replace the unreliable paper antiques) come in 600 volt sizes, which will work quite well. If you wish to reduce hum in the radio even more, you may try electrolytics in place of the paper condensers. Try values of 8 or 10 MFD each. You must have your polarity correct with electrolytics. With paper condensers, polarity is not a concern, but with electrolytics, it definitely is. If you install them backwards, you can burn up the supply. Basically anything coming off the cathode of the 80 tube is positive, and anything coming off of the center tap in the high voltage winding is negative. The condenser (terminals 1 and 3 on the original unit) that connects from the center tap to the bank of resistors, should have its negative side towards the center tap and its positive side towards the resistors, if an electrolytic is chosen.
If you would like to try electrolytics in your set, between 1 and 2, and 1 and 3, use 10 MFD units. 1 and 4 can be an 8 MFD unit. 2 and 6 should be left at its original value, and can remain an unpolarized paper condenser. Try the paper units at the original values, first. If you're not satisfied, try the electrolytics at the above mentioned values. Use 400 WV condensers.
Thomas
Well I was going to cut and paste the info that I had found here explaining where I got those values but I couldn't find them tonite. I'm pretty sure they came from PHILCORADIO.COM site.
I have since found that the 1200 volt ratings were test voltages not working voltages. So I ordered some 630 volt "Yellow" caps from AES they have test ratings at the 1200 v range. Those should look real authentic under the chassis. Maybe I'll take the can apart and see if I can hide them in there. Anything to get rid of that LOUD HUM. If these don't keep it clean I'll go the electrolytic route.
reading your post though I wonder could it be a bad coil causing the hum............ hummmmmmmmmmmmmmmmm.
By the way the model 21 did start incorporating electrolytics into the filter cap section. They were
truly new back then.
Thanks again
Shawn
:Radios of the 1920s often used condensers of very low values in the filtering section. Electrolytics were very new, and I don't think they were invented until sometime in the late 1920s. Someone correct me if I'm wrong. I'm almost certain about this, though. The first electrolytics were liquid filled and very large. It wasn't until the late 1930s that "dry" electrolytics had been invented. These units have paper between the two foil electrodes, and the paper is soaked with the electrolytic. This reduces the size considerably by having the electrodes close together between paper, instead of being quite far from eachother in an electrolytic bath. As for condenser technology of the time, paper condensers were large when they got to values of 2 MFD. Because larger sizes were extremely inconvenient, elaborate filtering systems were devised that made use of these small values. Such things as phase cancellation and hum bucking coils on the speaker, and high resistances, cushioned the voltage and eliminated a lot of the hum. Hum bucking coils and various filter chokes (or field coils) remained in radios even after large value electrolytics had been invented, because of their great performance and ability to remove hum. The capacitances you have listed are the correct values for your radio, though.
:
:However, as for the voltages, I do not know where you got 1200 volt ratings for those condensers. Your radio has a 650 volt center tapped high voltage winding in the transformer. When this center tapped winding is used with the full wave rectifier #80 tube, as shown in the schematic, the effective DC voltage is about 325 volts. You could be fine with 350 WV (working volts) condensers. I would choose 400 or higher, though, as 350 is cutting it close. You really don't need anything more than 400 or 450 WV. Some paper condensers (to-day mylar and certain metalized film condensers replace the unreliable paper antiques) come in 600 volt sizes, which will work quite well. If you wish to reduce hum in the radio even more, you may try electrolytics in place of the paper condensers. Try values of 8 or 10 MFD each. You must have your polarity correct with electrolytics. With paper condensers, polarity is not a concern, but with electrolytics, it definitely is. If you install them backwards, you can burn up the supply. Basically anything coming off the cathode of the 80 tube is positive, and anything coming off of the center tap in the high voltage winding is negative. The condenser (terminals 1 and 3 on the original unit) that connects from the center tap to the bank of resistors, should have its negative side towards the center tap and its positive side towards the resistors, if an electrolytic is chosen.
:
:If you would like to try electrolytics in your set, between 1 and 2, and 1 and 3, use 10 MFD units. 1 and 4 can be an 8 MFD unit. 2 and 6 should be left at its original value, and can remain an unpolarized paper condenser. Try the paper units at the original values, first. If you're not satisfied, try the electrolytics at the above mentioned values. Use 400 WV condensers.
:
:Thomas
The filtering system in that radio was more tuned than a blunderbus filter as used later with the heavy duty electrolytics. When I say blunderbus, do not think of it in a bad way like the old blunderbus tone arms that ruined records. Just think of it as the modern filtering systems that strong arm the hum right out of the DC very effectively. Since they were using such small value condensers back then, the filtering had to be somewhat tuned to cancel hum. With the big value condensers of to-day, the hum can be completely wiped out. If the condenser across the choke is increased in value (with a big electrolytic) (or it shorts out), this may actually increase hum. Now, I know that you have no electrolytics in there at this time, so I know that isn't your problem, but I'm trying to give you an idea how that filtering system is slightly different. A large value electrolytic would actually allow hum to pass by the choke, as would a shorted paper condenser. The choke and original paper condenser were selected for their values so that they'd somewhat tune out the hum. Now, there are some radios with high value condensers across the chokes, but usually this increases hum. An example would be my 630TS television, which has some electrolytics across some of the filter resistors.
So, when looking through the filter section, look for more subtle things. Make sure that the filaments of the output tubes are connected properly across the center tapped filament supply, so that B- is applied in a balanced maner to the filaments. Make sure noone altered the wiring in any way. If you replace all filter condensers and hum is still present, you can try reversing the speaker voice coil leads. If they have not been tampered with, though, chances are they are connected as they should be. Some other critical filtering condensers are #14 and #22. Both filter hum out of the early audio stages. If hum is left present in these stages, it will be greatly amplified. Here, the values used are just fine, and do not need to be increased. Anything from .05 to .1 or perhaps .2 MFD will do quite well. Anything much larger than this really isn't necessary.
Also, another thing to look for is to be sure both sides of the high voltage winding are feeding the rectifier. If only one is feeding the rectifier, you will only be getting half wave current, which hums more. If you can connect across the plate leads with an AC meter, and get 650 volts, then all is well.
...And, using 600 volt paper (or other type of original value) condensers is fine. If you choose to go the electrolytic route later, don't go over 400 or 450 volts. Anything higher is much more expensive, unnecessary, and hard to find.
Thomas
Thank you for the reply! You have given me a lot to think about. I am going to print this out as well and
see what I can come up with. Honestly hoping I don't
have to go past the filters. But I have to wait until next week for them to arrive via mail.
It is nice to have such knowledge to turn to on this board. I will reply later as to which or what fixes the nasty hum.
Shawn
:You could have a coil problem or some other problem. Perhaps a shorted or leaky condenser, such as the one across the choke (27) or somewhere else. Paper condensers do not often open up. They usually get leaky or completely short out. It is slightly possible that they have opened up, however.
:
:The filtering system in that radio was more tuned than a blunderbus filter as used later with the heavy duty electrolytics. When I say blunderbus, do not think of it in a bad way like the old blunderbus tone arms that ruined records. Just think of it as the modern filtering systems that strong arm the hum right out of the DC very effectively. Since they were using such small value condensers back then, the filtering had to be somewhat tuned to cancel hum. With the big value condensers of to-day, the hum can be completely wiped out. If the condenser across the choke is increased in value (with a big electrolytic) (or it shorts out), this may actually increase hum. Now, I know that you have no electrolytics in there at this time, so I know that isn't your problem, but I'm trying to give you an idea how that filtering system is slightly different. A large value electrolytic would actually allow hum to pass by the choke, as would a shorted paper condenser. The choke and original paper condenser were selected for their values so that they'd somewhat tune out the hum. Now, there are some radios with high value condensers across the chokes, but usually this increases hum. An example would be my 630TS television, which has some electrolytics across some of the filter resistors.
:
:So, when looking through the filter section, look for more subtle things. Make sure that the filaments of the output tubes are connected properly across the center tapped filament supply, so that B- is applied in a balanced maner to the filaments. Make sure noone altered the wiring in any way. If you replace all filter condensers and hum is still present, you can try reversing the speaker voice coil leads. If they have not been tampered with, though, chances are they are connected as they should be. Some other critical filtering condensers are #14 and #22. Both filter hum out of the early audio stages. If hum is left present in these stages, it will be greatly amplified. Here, the values used are just fine, and do not need to be increased. Anything from .05 to .1 or perhaps .2 MFD will do quite well. Anything much larger than this really isn't necessary.
:
:Also, another thing to look for is to be sure both sides of the high voltage winding are feeding the rectifier. If only one is feeding the rectifier, you will only be getting half wave current, which hums more. If you can connect across the plate leads with an AC meter, and get 650 volts, then all is well.
:
:...And, using 600 volt paper (or other type of original value) condensers is fine. If you choose to go the electrolytic route later, don't go over 400 or 450 volts. Anything higher is much more expensive, unnecessary, and hard to find.
:
:Thomas
:
:
Thomas
: Are you sure this is a filter cap? I've never heard of a filter cap with values that low or voltage that high in a radio receiver.
:
:
::ADVICE FROM THE RADIO GODS ?!?!?!
::
:::Hello ALL:
:::
:::What is everyone using to replace the filter caps on the Philco model 20's?
:::
:::I finally found the values "thanks Nostalgia Air"
:::1.0/1.0/1.5/0.13 at 1200v/1200v/1200v/1200v respectively. WOW look at those V's and there
:::not electrolytic but paper caps in that big can?
:::Any ideas where to find replacement or something close would be greatly appreciated?
:::Feel free to email me if you wish.
:::shawn.d.phillips@us.army.mil
For example- to get 1-mfd @ 1200V put 2 2-mfd 600V caps in series. Use same idea for other three.
PS- some may suggest bridging each cap with 100K equalizing resistor.
:ADVICE FROM THE RADIO GODS ?!?!?!
:
::Hello ALL:
::
::What is everyone using to replace the filter caps on the Philco model 20's?
::
::I finally found the values "thanks Nostalgia Air"
::1.0/1.0/1.5/0.13 at 1200v/1200v/1200v/1200v respectively. WOW look at those V's and there
::not electrolytic but paper caps in that big can?
::Any ideas where to find replacement or something close would be greatly appreciated?
::Feel free to email me if you wish.
::shawn.d.phillips@us.army.mil