806, 807, 808 disassembly

[luksich]

I have several very beat 800 series drivers I'd like to have rebuilt. I want to clean the corrosion out of the innards and screen, but can't figure out how to take it apart. Any suggestions before I get out the big hammer? Thanks!

Regards,
John

[GM]

A screwdriver and putty knife works for me!

Remove the rear cover, VC wire leads, and loading cap (if supplied). Note that the loading cap has a rubber gasket that bonds pretty good over time, so a thin, yet fairly stiff putty knife comes in handy for removing it. Mine is 1" wide that I've honed to a sharper edge. The diaphragm is now exposed. It's dowel alignment pinned in place and very tight tolerance, so the putty knife is normally required to gently work the VC loose around its perimeter and up n' out of the gap evenly. Some really corroded ones have required spraying with WD40 or equal, but all of it must be cleaned off before reassembly. Since the dowel alignment is asymmetrical, it's a good idea to make a mark on the VC casing/driver so you'll have no trouble figuring out which way it goes back. I use nail polish, though many folks just scribe a line on both with a sharp tool.

The word 'fragile' doesn't really do the VC's construction justice, so be forewarned when removing/handling/cleaning/re-installing it. Double ditto if it's an early aluminum one.

Anyway, if you have dry, compressed air available then you can blow out loose non-magnetic debris, use a fine scotchbrite pad to scrub off corrosion, and spray electronics cleaner to finish up. Now you're ready to clean the gap with strips of folded masking tape to pick up any magnetic or other stubborn debris. Repeat until the tape comes out clean.

If the VC is damaged/corroded then it normally has to be replaced.

FWIW, if these are going to be used in a HIFI app, me and many others much prefer the increased HF response with the bug screen removed. This can easily be done with an Xacto knife after disassembly.

To plagiarize most repair manuals, assembly is the reverse of disassembly.

Once the VC's are back in place it's a good time to check polarity. Using a 1.5V battery, just tap the leads to see which way makes the VC move down towards the phase plug and mark accordingly (if not already done previously), so you'll know for sure how to reconnect the leads. I've seen them reversed, I assume due to someone not paying attention the last time they were assembled.

HTH,

GM

[luksich]

Thanks, GM. Good advice indeed. Any need to separate the sections of the magnet structure? I'm not sure I'm getting the inside clean enough (it's hard to see in there!).

Regards,
John

[GM]

I never have, never heard of it needing to be done or anyone having done it, and I assume you can't without damaging/destroying it.

BTW, I forgot to mention to make sure the terminals are angled in enough not to short against the rear cover.

GM