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Philco 38-10 redo - Printable Version

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Philco 38-10 redo - Bob Andersen - 08-15-2014

This 38-10 is the first Philco radio I ever restored back in 2006. I just did a basic recap and tacked the new electrolytics underneath. A few years later it died Icon_sad and I'm just now getting around to taking a look.

[Image: https://farm4.staticflickr.com/3926/14635220670_bb88355863_c.jpg]

Note I've already started doing work so there are some loose parts in this photo.
[Image: https://farm4.staticflickr.com/3903/14635220050_348dbdb506_c.jpg]

I figure while I'm at it I might as well restuff the filter caps too.
[Image: https://farm6.staticflickr.com/5578/14675057238_e1bc56d4cb_c.jpg]

[Image: https://farm4.staticflickr.com/3882/14881553423_8fb31032da_c.jpg]

I finished up work under the chassis and powered it up. No smoke, but only a faint crackle output of the speaker.
[Image: https://farm4.staticflickr.com/3895/14925287401_d0803fa4e9_c.jpg]

[Image: https://farm6.staticflickr.com/5588/14741700469_20e421d118_c.jpg]

RE: Philco 38-10 redo - codefox1 - 08-15-2014

Looks like you know what you are doing, ask here before plugging her in.

RE: Philco 38-10 redo - gregb - 08-15-2014

Hey Bob:
You say it was redone and worked fine and then died a few years later, maybe a tube went south on you. Funny a working set that was recapped quit like that. I am sure you have done all the usual checks, B+, screwdriver on the volume control, throw some signal or IF at it??

Gregb

RE: Philco 38-10 redo - Bob Andersen - 08-15-2014

I just finished checking all the tubes and they're all good. Touching the grid caps does produce hum. Next up voltage checks then I'll inject some signals.

RE: Philco 38-10 redo - Bob Andersen - 08-17-2014

I found the problems Icon_smile First, this resistor should be 51K but I installed a 5.1K. So hard to tell the red from orange sometimes!
[Image: https://farm6.staticflickr.com/5587/14939150361_8489bb5b06_c.jpg]

Second, a plate on the cap was bent on the far right and shorting for a portion of the rotation.
[Image: https://farm6.staticflickr.com/5560/14941872892_f4d3feec15_c.jpg]

RE: Philco 38-10 redo - morzh - 08-17-2014

Bob

1. None of this to me explains "worked a few years and then quit". What, has the vane bent all by itself? Or Did the resistor burn out or cause something to quit?
2. Whenever I replace resistors, even though I pull them from Mouser marked bag, I ALWAYS measure it bedore installing. I never read the code, why bother when you have a meter. Plus colors on all but beige/white are distorted.
3. What is that small yellow cap next to your open electrolytic? Is this what you are putting in? Looks too small for a main filter cap.
4. this blue electrolytic potted with green stuff: cannot claim 100% correct opinion but all light blue coated ones I ever saw are cheap GP caps and have ripple in low tens of mA. If it is a main filter one, not enough usually.
5. After I thougt awhile, I only pot the lead/bottom part and leave the barrel clear, the potting degrades temperature performance and this is what kills them faster. Especially main filter where ripple is high.

RE: Philco 38-10 redo - Bob Andersen - 08-17-2014

1. No, it doesn't and we'll never know why the performance faded then died because I did a lot of work on this radio before powering it back up. That included replacing the three electrolytics, some tubes and all the resistors. The capacitor vanes likely were bent when I unmounted the tuning cap to replace the rubber shock mounts during this second restoration.

2. I think this may be a first for me after several decades of working in electronics both as an engineer and a restorer. I had been using blue bodied resistors and recently switch to the reddish types. Tough to tell orange from red.

3. It's a cap about to be thrown away that just got caught in the photo.

4. It's not potted and it's not blue. That's just some green bubble wrap to keep it from flopping around and some blue heat shrink tubing I put around it.
It's a PZ series Nichicon rated for long life, high ripple current and 105C. I only use top quality components.

5. I rarely pot anything and never a filter cap. Just makes it harder for the next guy to work on.

RE: Philco 38-10 redo - ccomer1955 - 08-17-2014

Bob! Good to see you on this forum. Having never seen one in the flesh or even in a photograph, I have to ask. Is that squashed funnel-like thing on the tuning cap a shadow meter? If it is, how does it work?

RE: Philco 38-10 redo - morzh - 08-17-2014

It is not the meter, it is a lamp.

As for the meter , it is a simple version of Darsonval/weston galvanometer (as in regular arrow analog meter) attached to a vane that shades the lamp behind it shining through a small opening. Depending on the current (in AVC circuit) the vane rotates making the shade narrow or wide.

RE: Philco 38-10 redo - ccomer1955 - 08-18-2014

Thanks, that makes sense. The Philco version of the tuning eye?

RE: Philco 38-10 redo - Arran - 08-18-2014

Shadow meters were not a feature exclusive to Philco, but they probably used more of them in more models, and used them for a longer length of time,
then anyone else, 1932-1938 if I remember correctly. They never did go with the magic eye tube idea, which was just as well, probably in part because RCA held some of the patents, the last thing that Philco would do is pay royalties to RCA if they did not have to.
Regards
Arran

RE: Philco 38-10 redo - mikethedruid - 08-21-2014

I have an old Zenith model 411 from 1933 I restored years ago, complete re-cap. It has one of the electro-mechanical shadow meters. They are nifty and work as well as the magic eye tubes ever did.

RE: Philco 38-10 redo - morzh - 08-21-2014

...and they do not get dim. But then they can get demagnetized, or worse yet, the coil gets open.

RE: Philco 38-10 redo - Bob Andersen - 08-30-2014

I finally found the time to do an alignment and put it back together. It's playing like new Icon_smile
[Image: https://farm6.staticflickr.com/5596/14899015310_25a3fc5616_c.jpg]

RE: Philco 38-10 redo - mikethedruid - 08-30-2014

Congratulations, Bob, absolutely beautiful ! I bet it sounds as good as it looks too.