I have an Eico HF87 I am refurbing into an HF89. The bias voltage wires are to short as they were clipped off for use in the HF87 which uses cathode bias. and the HV leads are just shot, can't pull insulation off without breaking the wire itself. So I've exposed the works and need to replace the leads.
The info in the Eico manual regarding transformer temperature states: transformers operate under 195'F with a safety margin to 221'F
That's pushing it for margin of safety with the 105'C wire I have.
I'll have to order something. Not sure what I should get. Any recommendations?
Thanks!
The info in the Eico manual regarding transformer temperature states: transformers operate under 195'F with a safety margin to 221'F
That's pushing it for margin of safety with the 105'C wire I have.
I'll have to order something. Not sure what I should get. Any recommendations?
Thanks!
Teflon wire will be fine, or silicone which seems easier to get in an assortment.
Do buy from a reliable source though.
TubeDepot.com | 18 Ga. Stranded, Silver Plated, Aerospace Grade, PTFE
Do buy from a reliable source though.
TubeDepot.com | 18 Ga. Stranded, Silver Plated, Aerospace Grade, PTFE
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Teflon insulation requires silver plated wire, and you'll need a good wire stripper.
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Why does PTFE insulation require silver plated wire? I use leftover fluorescent light ballast wire in my amps and it PTFE insulated copper wire. Of course it’s solid core, so maybe I’m just unaware with stranded.
The high temperature required to apply extruded Teflon insulation would damage the copper wire
and it would become difficult to solder, unless it is silver plated. Cheaper wire can use a lower
temperature wrapped and fused method.
and it would become difficult to solder, unless it is silver plated. Cheaper wire can use a lower
temperature wrapped and fused method.
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Because Teflon reacts with copper so they had to use silver plating to avoid the reaction and in the process get a better conductor as a bonus.
Thanks for the educational info! I looked back and the wire I have is PVC insulated with a nylon jacket, not PTFE. Only 105C/600V rated. I don’t know why I thought it was Teflon [emoji849]
I don’t buy any of those reasons. Teflon is extremely inert. The wire is silver plated because of the mil spec calling for it.
Teflon probably doesn't react with copper, but the high temperature extrusion required probably oxidates the copper if there are traces of oxygen present.
I have seen (rare) examples of direct teflon-insulated copper wires, and they didn't have the color of natural, freshly exposed copper: they were somewhat ambered, but this didn't affect the quality of contact or solderability. It was merely an aspect issue.
I have seen (rare) examples of direct teflon-insulated copper wires, and they didn't have the color of natural, freshly exposed copper: they were somewhat ambered, but this didn't affect the quality of contact or solderability. It was merely an aspect issue.
221F *is* 105C. Your wire is exactly what EICO designed for.
OK, it has failed after only 60 years. That seems long enough to me, but younger folks may see it differently.
Use Class F or H enamelled winding wire, used for motor winding.
Or fiberglass / mica covered copper wire, the kind used to connect industrial heaters, they work till at least 320 C reliably.
320 C = 608 F
Enough, I think.
Or fiberglass / mica covered copper wire, the kind used to connect industrial heaters, they work till at least 320 C reliably.
320 C = 608 F
Enough, I think.