What kind of component is this?

[bluzmn]

My '59-'60 Premier Twin 8 has a "dog bone" component in it, and I'm not sure if it's a resistor or capacitor. By comparing the circuit with the schematic(s) I have, my guess is that it's a capacitor, but then again, this circuit doesn't conform 100% with any of the 6 schematics I have for this model. Is there any way to know for sure? And does anyone know how to read the color code? The body is olive drab (I don't know if that matters); on the body there's a black dot, then a red dot, a black dot, an orange dot and a silver dot on the end. I will, of course, include a picture. Thanks.

[loudthud]

It looks somewhat like the capacitors you used to be used in Tektronix scopes.

[dai h.]

it's a ceramic cap

[Jazz P Bass]

Here is a capacitor DOT code link:CAPACITOR CODES

[bluzmn]

According to that ceramic code link, this would be a 2pf capacitor! There is no 2pf capacitor anywhere on 6 different schematics for this model, and I'm no EE, but I can't imagine what it's purpose would be in this circuit.
I have seen another page (of course I can't find it now) that said the first dot on a dog bone capacitor represented the temperature co-efficient (what the hell is a temperature co-efficient?) and the next 4 dots were the same as the resistor code. That would make this cap a 20,000, but 20,000 what? That's what I'm trying to find out; 20,000pf would make it a coupling cap.

[bluzmn]

I guess that page wasn't so hard to find after all - Color codes for Capacitors

[Enzo]

I sure wouldn't read that as 2pf.

I'd read:
Black for temperature coefficient

Then red-black-orange for 2-0-000 pf, or 0.02uf.

Silver as tolerance.

You have the schematics? Where is this component wired between? What does the schematic say it ought to be? In case I got lucky, could it be a .02uf? I see a bunch of .02uf on the schematics at Schematic Heaven.

[bluzmn]

The plot thickens...

@Enzo - I meant that according to the link Jazz P Bass directed me to, I would have read it as 2pf. But I believe that code applies to those capacitors that are shaped like dominoes. I had already decided that my cap was 20,000 something, I just wasn't sure if it was pf or something else. The coupling caps are .02mfd (or .022), but that would make the mystery too easy; I looked at some closeup pictures of the wiring I took for MWJB, and this cap appears to be part of the tone stack. But, according to all the schematics I have, that means it should be a .002 or .003mfd cap; but then again, according to the schematics, the other cap in the tone circuit is supposed to be a .0047 or .005mfd cap and the one on this amp is a .006mfd. Now I'm totally confused.

[Enzo]

Well, don't look at the pictures, look at the amp.. WHat two points does the part connect together? If we know tube pin and type, then we can identify plate to grid or whatevr.

[bluzmn]

I examined this part thoroughly when I was first trying to figure out what it was; it's connected to both of the 270K resistors in the tone circuit and to the tone pot at one end. It's nowhere near the tube sockets; it's up close to the instrument panel, between the volume and tone pots. I shouldn't have even mentioned coupling caps.

[Enzo]

OK, connected to the tone pot. Tube socket was merely a possible example. Looking at the selection of schematics for this amp over at Schematic Heaven, that cap appears to be .002uf in a couple versions, and .003uf (or .0033uf) in others. Not a large difference. It doesn;t agree with the .02uf code, but we could be misinterpreting that, or it could be a legitimate change they made. But there it is in the drawings, coming into the lower end of the tone pot.

I only have five drawings, so I can;t say what is on your sixth.

Chances are that ceramic cap is OK electrically. Are there other similar looking caps in the amp? If so, then this may be stock rather than someone's later mod. In any case, the amp should work OK with it, and once all the rest of the restore work is done, you can decide if you'd prefer a different value cap by simple substitution.

[bluzmn]

Thanks, Enzo. If ceramic caps don't tend to drift much in value, I guess it's a moot point; I won't be changing it anytime soon. Do they drift a lot? It is the only cap like that in the amp, but it appears to be just as old as all the other components. There's another cap that's the only one of it's kind in the amp, and it's in the tremolo circuit; it's a "Micamold" that looks like a chocolate domino, and it looks partially melted (that's probably part of the reason the tremolo doesn't work). The colors in the dots have worn off, so that's going to be a hard one to figure out.

[Enzo]

I don't worry much about drifting value, but I DO worry they get leaky over time. The ceramics are the least likely to get leaky of the various types of cap.