[Guest]

Hi everybody, thanks for activating my membership Ron !

well, I finally took the plunge and decided to repair a tube radio for the first time

I don't quite understand how the number coding works on these units so I'll show you what I got ... the inside label says 650 and from what I can tell this unit was made in Toronto around 1938, and is of the super heterodyne style - in the lower LHS of the paper sticker appears 39-4208 - does this mean anything ?? useful for tuning guides or something ?

[Image: http://www.lynx.net/~jc/Philco650.jpg]

[Image: http://www.lynx.net/~jc/Philco650label.jpg]

[Image: http://www.lynx.net/~jc/Philco650dataplate.jpg]

when I got the radio it worked at first, I did get some audio and I could tune into stations albeit with relatively poor reception - of course with no antenna connected to the hookups on the back side of the chassis ...

I took the tubes out to clean them, applied compressed air to get dust and stuff out of the chassis and tuning fans - had a quick look around ... I re-inserted the tubes in and got no reception, the third time I fired it up I got some smoke ...

the first thing I'm going to do is change the electrolytics - I have no way of testing the tubes so I'll assume they're ok for now ... I noticed some of the electro's in the schematic lie around 8uF/450 and I'm wondering if there's any risk going to 22uF/450 instead of 8uF or 10uF ?? will this send the tuning range way off or something ?

I checked the bias on the power tubes and measured -35v to chassis on the coil resistor.
I'm assuming I'm measuring the right voltage ... see pic below:

[Image: http://www.lynx.net/~jc/Philco650chassis.jpg]

[Image: http://www.lynx.net/~jc/Philco650schemCrop.jpg]

Also, the speaker chord appears to be intermittent at the connector end ...
any advice for rewiring that part ??

[Image: http://www.lynx.net/~jc/Philco650spkr.jpg]

I've downloaded a bunch of tuning directives and getting ready for that eventually ...

thx for any help
~jc

---

[exray]

Hi JC and welcome. A few notes...

1. The 39-4208 I believe is simply the part number for the label.

2. Since you were getting some reception even with no antenna I'd also guess the tubes to be in reasonably good shape.

3. Definitely replace the electrolytics. You really should stick with 10uf to replace the 8uf. 22 won't kill it and you could use them temporarily but it may add a bit more load on the rectifier tube. In fact, count on replacing all the paper caps including the ones enclosed in the Bakelite boxes. There's a number of easy methods there that we can talk about later.

4. The speaker plug. That merits pronto attention. The main power supply routes thru the plug and a short there is not a good thing to have. (the intermittent could actually be something shorting out and may even account for your smoke). Mark the wires in some fashion, cut and start from fresh.

Here's a site with some good generic advice for first-timers.

http://www.antiqueradio.org/begin.htm

Have fun...and be careful!

-Bill

[Guest]

Thanks for the welcome and the helpful reply Bill,

took a while to get back to this project after moving my shop
first thing I did was fix the speaker plug - after a study of the circuit I see how all that works
I'm gonna get a rivet gun and snap it back together when I get a chance

so, I replaced as many capacitors as I was able to - the attached pics give an idea:

[Image: http://www.lynx.net/~jc/philco650-before.jpg]

[Image: http://www.lynx.net/~jc/philco650-after.jpg]

I tied three 0.082uF/400v film caps together to replace the 0.25uF cap ... there's a mystery cap in the Lower RHS that I couldn't find in the schematic, what was there was 0.1uF/400v and I replaced with the same ... I stopped at the signal caps around the volume control as they looked ok ... I didn't get to 30 and 32 - how the heck do you change those things ?? I imagine one would have to remove the giant rotary switch ... here, I wanted to disturb as little as possible - so I left those for eventual replacement if need be ... I'm curious if I should try going after them while the chassis is open ??

lucky me, the Radio works again and the intermittent popping is gone ...

and I get fairly loud volume when I stick my arm near the top of the chassis - so yeah, tubes appear strongly emissive !

next questions :

(i) what kind of antenna does this radio need ?
(ii) what's the fine-tuning procedure ?

cheers
HR

[exray]

Hi HR, sounds like you've got a good handle on it

Caps 30 and 32 are in relatively 'safe' locations if they are slightly leaky so don't fret much over them. Can't help on the mystery cap. Its not unusual to find an extra cap tagged on by a serviceman or even the factory to cure some minor ill.

For an antenna all you need is a length of wire. Nothing specific, just as long as possible and preferably outdoors. You'll notice a huge improvement with anything over 20 feet or so.

For "fine tuning" do you mean alignment of the radio? The details are on page 6-38 here.
http://www.nostalgiaair.org/PagesByModel...013824.pdf I don't know if you want to jump into that or not if the radio is working well as-is.

GL,
Bill