N-800-G High-frequency Malfunction

[kimchi2]

My N-800-G crossover has stopped sending any high-frequency signal. The high-pass leads show as open on my multimeter. The 806a driver works OK and lows pass to the 416a woofer with no problem. The pot is also OK and is perfectly clean. The crossover has never been opened before. I just opened the crossover to find everything encased in shiny, black tar, so it's a bit hard to locate anything. Any suggestions as to what, specifically, may be at fault? Anybody have a schematic for the N-800-G?

[kimchi2]

Does anyone have any suggestions regarding what solvent to use to clear away the tar in the crossover? It still smells fresh after 47 years, but it covers nearly everything, making it impossible to really see what's inside.

[voice of the theater]

A lot of the vintage Altec crossovers have that tar-like substance inside the crossover. I've owned several. If I recall correctly, the best way to remove it is to warm the crossover up in an oven at 200 degrees for 15-20 minutes (and no more than that) and that will make the "tar" soft enough to remove. There are members here who've actually done this with success--perhaps one of them will chime in as well. That's the best way to soften the "tar" as far as I know....

[GM]

Never tried the stove, just a commercial 1 kW heat gun that requires a 20 amp outlet. Anyway, these XOs are way past old enough to need their caps replaced and I assume one has blown.

GM

edit: Maybe this cheap heater or similar will work without resorting to smelling up the oven: Heat Gun - Dual Temperature Heat Gun, 1500W

[Alien_Shore]

If you do go through the effort to excavate the XO from the tar pit, please post pics - I'd love to draw a schematic and get it posted up.

[kimchi2]

Thanks guys. Heating slightly made the tar peel away easily, revealing 2 chokes and what I assume is a box of ELPAC capacitors. Here are some preliminary pictures. 001.jpg