I'm in the process of refurbishing an RCA BP-10. I have it working, but I'd like to tweak the alignment. I noticed that all four of the filter caps are tuned by threaded rods that terminate in ends that are half-circles. It's almost as if they were originally screwdriver slotted ends but one-half broke off - except that they are all the same and too cleanly cut to be broken. So i'm assuming this is by design.

I've attempted to attach a crude sketch of what I mean.

Does anyone know the name of the appropriate tool for this type of tuning rod?

Thanks,

Doug

I think you are getting you terminology mixed-up here. Filter caps are not "tuned". I think you meant " IF transformer ".

Anyway, I am not aware of a specific tool for that purpose. As you have said most of the threaded rods (if used in an IF transformer) have a screwdriver slot or a nut for making the adjustments. Even if RCA used a special tool for the purpose, it is highly unlikely that you will be able to obtain one now, so you will have to improvise. Try needle-nose pliers to gently turn the threaded rods to align the radio. Some of the IF transformers have powdered iron cores which are moved in or out of the coils to change their resonance and often times they are "stuck" and using too much force can make them crumble, thereby destroying them.

Yes you are right. According to the schematic, it's the coils of the IF transformers that are tuned, not the caps. And also physically that's what it looks like. Don't know what I was thinking.

OK, I'll use needle-nose pliers, and I'll be careful not to apply to much force.

Thanks!

Depending on the diameter of the slugs and the size of the hole in the can, an old radio knob might work.

I've also improvised tools for turning slugs out of different plastic scraps. Heat up a barrel from a cheap ball point pen until it's pliable on one end, then stretch it a bit to make it thinner. Once you get the diameter right to fit into the opening for the slug, re-heat just the end of the barrel and press it down into the opening with the slug. Hold it firmly in place for a few seconds until the plastic hardens, and it should have taken on the shape of the slug enough to turn it.

These plastic tools are less likely to damage the delicate slugs, and when they loose grip from wear, just reheat them and reform the tip.

If you have a slug that is sticking, it's best to apply a drop or two of light oil and let it sit for an hour or so. If it still sticks after a few applications of oil, a small amount of heat might help, but be very careful not to overheat the coil. Sometimes the wax used to seal the coil will clog the threads and seize the slug. Set your iron on a low setting and apply it to the slug a few seconds at a time, trying to free it with your tool between times.