[Ben-Jamin]

hi my name's ben and i just picked my first tube radio yesterday at a local flea market for virtually nothing. looks like its complete. i had to re-cord it as the old one on it had pretty much rotted away. i started out trying to rehabilitate this little guy; cleaning some connections with deoxit along with the power/volume pot.

i really just want to get this philco back up and running again just to challenge myself. i've never worked on anything with tubes nor have i worked on anything this old before.
i started out in the home audio scene about 6 years ago when i was 13 and bought my first stereo receiver, a pioneer sx202. i've stepped up a bit over the last couple of years, acquiring some of my favourite vintage pioneer stereo equipment from the 70's including a very nice (and powerful) sx-950.

anywho back to the PHILCO 8)

when i first plugged it in the backlight would flicker a bit sometimes staying on for about 5 seconds then turning off again. today i've managed to get the light to stay on and im getting a low hum/buzz from the speaker. the sound im getting doesn't seem to be affected by either the volume or the tuner know, its just a consistent sound im getting.

i then noticed a loose wire (see pic) coming off one of the tube terminals.

i have found a schematic for this radio. i've found one for what i think is sorta of like the american version of mine which is some thing like model 42-PT-25 or something along those lines.
heres some pictures.

Note from site admin: Sorry, but the photos which were attached to this post are no longer available.

[codefox1]

Very well. The first thing you should do is not plug in the radio until several steps are taken. The first thing is to replace the electrolytic capacitors which are the large value polarized ones in the power supply. In a radio this old, they are certainly unreliable/dangerous, and are part of why you get ony a hum. You should post your schematic here so we can refer to it.

After that you will want to replace all the paper capacitors (those gummy wax covered beasts,) with modern ones. These you don't measure, you just replace. You will also measure the resistors and those found more than 20% out of tolerence must be replaced. I usually replace all the small carbon resistors because it is easy and cheap to do so.

Once you are certain your schematic is the correct one for your set, you can use it to create a parts list for your order. Best buy everything at once to avoid delay and another shipping charge.

A great source for parts (happens to be in Canada) is http://www.justradios.com/

if you don't have one, get an inexpensive digital meter that reads volts and ohms, etc... They're available for less than $20.

[Ben-Jamin]

thanks codefox. im very new to repairing/diagnosing electronics so i appreciate your help. correct me if im wrong but the capacitors act as "filters" correct? they help to remove the "hum" that i am now getting?

what about the electrolytic capacitors? are these the giant looking paper "cylinders"
in my radio? do they serve the same purpose as the other capacitors? and i assume since they're polarized they must be installed a certain way correct? how do you know which way to install them?

i was up late last night watching radio repair vidoes on youtube and scouring ebay and kijiji for old tube radios... does this mean im officially addicted?

heres the schematic i found (not very good at reading them...)

[Image: http://i40.tinypic.com/av2d69.png]

[Arran]

If it's a Canadian made philco it should have a brass tag rivoted to the back of the chassis with the model number, serial number, and the power requirements, there may also be a paper lable elsewhere like the inside or bottom of the cabinet. The Radio College of Canada manuals should have a diagram for this set, that is if it differs from the American models in any way, usaully they are the same save for using cloth covered rather then rubber covered wire under the chassis. Both Canadain and American models still have rubber covered wire going into the IF transformers so be careful not to disturb those.
The large cardboard tube that has a bundle of wire sticking out one end, in the first photo is the electrolytic filter condenser/capacitors, and will likely need replacement. There will be two capacitors inside that one unit sharing a common negative lead, it's probably easies and cheapest to replace this two section cap with two seperate electrolytic caps. If you like you can clean out the old cardboard tube by melting out the innards and install the new ones inside with new wire leads for esthetics, functionally it doesn't matter, the components in these sets are pretty tightly packed so just going all new without restuffing is understandable . Even if you don't choose to restuff save the old filter condenser anyhow in case you change your mind later or want to use the shell in another radio, same story with the old paper caps.
Regards
Arran