The Fine Things are Always Hand Made

Replacing Capacitors in a Box and Finding B+ build-out resistors

I was replacing capacitors on my Philharmonic until I ran out. I am now awaiting an order.

So, I decided to mess around and attempt to open up that soldered box (Rider symbol 74, Scott p/n 1321, see p. 14-46 of Rider). Someone mentioned that they did it with a Dremel so I gave it a try starting with the bottom plate which you see opened here and labeled 'May 4, 1339'.

I found that there are two layers of metal, a box within a box. Then there is cardboard that oozes black tar. Any suggestions on what to do next?...dig it out, open another side (don't like that), cut the wires and make a new box?

Different topic, same radio: someone suggested that I replace all 1K B+ build-out resistors. Would they be R9? I see about 11 of them on the circuit drawing, several of which attach to a B+ feed. It also looks like there is one in each of the IF coil cans (left side of receiver looking down from top; don't know if I am naming them correctly). So far I only found one under the radio; those colored bands are not in good shape.

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Permalink Reply by Norman S Braithwaite on January 5, 2015 at 7:03pm

I have not had any problem with the 1k resistors in Philharmonic receivers. In fact, I have found them to be very precise and reliable. On the other hand I have had early production AW-23 sets where I had to replace every one but the problem in the AW-23 was not limited to the 1k resistors.

Norman

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Permalink Reply by Bill Liers on January 5, 2015 at 8:05pm

Ken,

I was able to open the can with lots of heat along the seams with a large iron while using a small screwdriver to hold the seams apart. Under the cardboard is a block of capacitor innards held in place with tar or similar. A heat gun will soften the tar so you can get the cap block out. It's going to be tough unless you have the bottom completely off. Good luck.

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Permalink Reply by Ken Carr on January 5, 2015 at 10:38pm

Thanks for the responses, Norman and Bill.

I tried a soldering iron on the box first. No luck. I'll try again with more watts.
And hopefully my resistors will test good too. The one that I did check was spot on.

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Permalink Reply by Norman S Braithwaite on January 5, 2015 at 11:03pm

Ken:

I use a prying tool and a torch to heat the entire side after finding the single side that can be separated. Great care must be exercised to avoid any of many possible injuries!

Norman

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Permalink Reply by Ken Carr on January 5, 2015 at 11:13pm

If an injury is possible I'll make it probable.
I have the scars to prove it.
Urgent care is where I met an old college friend. We caught up as he stitched me up.

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Permalink Reply by Norman S Braithwaite on January 5, 2015 at 11:41pm

If I had worn gloves and used a vice to hold the capacitor block about 80% of the risk would be mitigated but I had conducted the operation bare handed on the garage floor where the hot capacitor block and melting solder were free to roam. Next time I believe I will wear gloves and use a vice to hold the capacitor block!

After a heart attack when 750 miles from home, my brother learned that his excellent emergency care heart surgeon is our cousin! Neither knew the relationship before hand. What a way to meet extended family.