Sorry for the newbie question... I've been searching and have not yet achieved enlightenment... or maybe this is so basic no one talks about it?
But I have a new signal generator in one hand and a tube radio in the other, and they need connecting.
I understand that at a minimum I need to put a capacitor in line with the "hot" lead to avoid toasting the signal generator.
Fine, but what's a good way to do this?
- I doubt that a string of alligator clips and caps flopping around on the workbench is right.
- Could make up a lead with a cap soldered in, but the idea of a solid-lead cap with no strain reliefs flopping around in a cable doesn't sound right either.
- And if this is SOP, wouldn't there be ready-made test leads for this? Not finding any...
Depending on the radio and the band being aligned there are different cap values called for in alignment instructions. Don’t know how much difference it can make however. I just use the alligator clip approach.
As long as you touch the right place, maybe little importance. Slip and touch B+, that won't do the generator any good!
I may need to learn about alignment, for starts I just want to inject signals ..
klondike98 Wrote:I just use the alligator clip approach.
So do I, but have made my own with very short leads and booted small clips for such purposes.
For the record, here's the advice from Elements of Radio Servicing (1947):
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Pat, I’m using an old Heathkit SG-8 that was my dad’s. I reworked it by replacing the original connectors on the front of the cabinet with BNC type which is more compatible with newer test leads. While doing that, I inserted a cap to the center pin or hot side so it’s always there and I don’t need to worry about cobbling together anything before connecting to a radio. If I remember, I think I used a .01 mfd/630 volt unit. Works great on anything I’ve used it on so far!
Ron
462ron Wrote:I’m using an old Heathkit SG-8 that was my dad’s. I reworked it by replacing the original connectors on the front of the cabinet ...
About 40 years ago I used a number of pieces of vacuum-tube EICO and Conar test equipment that my father built from kits in the '60s when I was young. I eventually replaced almost all of them with GR and Heathkit instruments, but still use two of them (EICO 625 emission tester and 950A LCR bridge) - the rest are shelf queens. Some of them used the 2-conductor button mic jacks that were so common on EICO and Heathkit equipment in the '60s. I never replaced any of those jacks because 40 years ago parts jobbers were still common all over the country and I could get those plugs easily and cheaply for making custom cables.
I use the loosely coupled approach. I feed the generator signal to a coil of wire through a .1mfd cap. Then move the coil close to the radio to get the correct signal strength. When I have to inject the signal I use a .05mfd cap with an alligator clip soldered to a lead.