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Rescued 650 needs help - Printable Version

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Rescued 650 needs help - OZ4 - 03-18-2019

Ron you seemed to think the chassis  that I rescued  was a 650.

The Ryders index  6-37 is the closest version that I can find, the tube layout is correct but the component layout is very different.

Might this be something other than a 650? Of course the sticker is missing.

Thanks

RE: Rescued 650 needs help - Ron Ramirez - 03-18-2019

How is it different? Photos of the chassis (above and below including a frontal view showing the dial) will help.

RE: Rescued 650 needs help - OZ4 - 03-18-2019

So here is the chassis. Looks pretty good. until you look underneath.
Here is a good example of how it is different. Looking at the under side the drawing shows four bakelite blocks in the lower right corner
and mine only has three. I don't see any spots where one is missing.

RE: Rescued 650 needs help - Ron Ramirez - 03-18-2019

It's a 650 chassis, no question about it.

Check and see if there is a tubular capacitor connected from the screen grid of the 78 RF tube to ground. If not, either a tubular cap will need to be added there, else you will have to get a replacement bakelite block and restuff it with a .047 uF, 630V capacitor.

Maybe someone removed the bakelite block and never replaced it.

Maybe someone replaced it with a tubular cap.

I looked in the Philco Changes in Models sheets and found no such factory change. Which doesn't mean much since Philco often made undocumented changes during production as well as documented changes.

RE: Rescued 650 needs help - LarryFS - 03-18-2019

I think I had the same dilemma when I refurbished my 650X.  I ended up using the 655 info in Rider's 7-114 to 7-116.  Although the parts drawing still shows that bakelite block, it is not identified in the parts list and wasn't in my chassis either.  I always wondered if I had a 655 chassis in a 650 cabinet.

   

RE: Rescued 650 needs help - OZ4 - 03-18-2019

Screen grid I assume you mean the AVC line or do you mean the control grid. The AVC has a .047 on it.

I can see now that the cathode bypass resistor and caps for the 78 IF are missing with the cathode straight to ground. that's why the bakelite block is missing. There are four components that are missing
R43, C44a and C44b, and R45. The primary of the second IF connected straight to the b+

But they did leave the 5K resistor on the shadow meter.

RE: Rescued 650 needs help - OZ4 - 03-18-2019

I see the 655 has all the cathodes straight to ground. The lower right corner layout matches. But with only has three wafer switches. Mine has four wafers with four positions.
Thanks Larry the 655 drawings will help.

RE: Rescued 650 needs help - Ron Ramirez - 03-18-2019

BIG difference between a screen grid and the AVC line. The screen grid carries B+, albeit lower than plate voltage.

The screen grid is pin 3 in a 78 tube.

RE: Rescued 650 needs help - OZ4 - 03-18-2019

Yes Ron your right that #2 grid does have b+ on it. It's not AVC and it has a .047uf on it.

I can never get the names right. Let see there is control grid, screen grid, accelerator grid, suppressor grid, and on the 6A7 there are a couple more.

So It looks like this radio is a hybrid between the 650 and the 655. It has the RF selector section of the 650 with the IF and detector section of the 655.