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Impossible to undo pcb screws, never had this one before

I suspect they deliberately used non-matching threads,ie cross-threaded, despite disassembly ideograph of a screw on the pcb overlay and red nail-varnish anti-shake lock. Even 2 minutes of soldering iron tip on the head will not free the locking . And of course buried deep in the case surrounded by all sorts, that block access, to grind flat blade slots in the screw heads or pairs of flats for mole-grips etc. Before grinding off the heads of these screws , any ideas to try.? Good mechanical holding of this pcb is via a large bolt through the main bridge rect, that came away easily, then glue on the shanks of the original screws would do for remounting. The retaining pillars for these pcb screws are welded to the case bottom. Before attacking wiht a grinder I'll try an impact driver, but that is guaranteed to butcher the cross-head slot. It might be easier to grind through the pillars as better access for that angle, not decided yet. Then sleeve over the existing half pillar for reassemble and glue to stop any rattling.

Reply to
N_Cook
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Going by the slight hex shape under the case, these pillars must be Hank Bush (TM) press fitted pillars , not welded. Rather than silicon wafer colateral damage possibility from impact driver shock, I'll try grinding into the base of one of those pillars, to free the pillar with pcb screw. That keeps grinding dust out of the elctronics. Then reassembly may be just countersunk head screw into the pillar at the other end.

Reply to
N_Cook

That worked surprisingly well, just hoping the punch through shock of each pillar moving impulsively did not do any electronic damage. Not seen the pillars yet as will be marking the 30/40 or so headers and crimps and photoing before disconnecting that rat's nest. So method used. Clearly mark the hex shadow in the outer case paint. Dremmel and .5mm grinding disc (no breakage) 3 cuts diametrically to the corners of the hex, about 3 minutes per pillar . The centre will then take a 3mm ball bearing. Then use a board over the amp and a clamp to squash between board and ball. The ball punches through leaving a small disk on the end of the pillar which hopefully will grind off easily when I get the now loose pcb out of the case. The cuts reduce the metal and allow seating of the ball. Another impossible task in my portfolio, still learning about all this stuff.

Reply to
N_Cook

Incompetent or deliberate filling the tapped pillars with proper threadlock before screwing in , correct threads, then blinder blobs of antishake lacquer on the heads. Needs more than 50W soldering iron, due to heatsinking of the steel casing via the pillars.

Reply to
N_Cook

Might be worth reading the; "Best Philips screwdriver" thread.

Could be the crosspoint in the screw head is too shallow for the pointy end of your screwdriver and the cross blades are only part engaging.

Screws can be tight, and a poor fit screwdriver will ruin the head.

Unless there's an overhead obstruction, you should be able to seat a drill bit in the crosspoint recess and drill the head off. Removing the threaded bit with only the thickness of the PCB to get hold of might be fun.

If you haven't chewed the heads up too much, drilling down with a pilot drill smaller than the thread core diameter might allow you to turn it with a regular Philips screwdriver. Or you could graze the pointy end of the screwdriver a little with a grinder.

Reply to
Benderthe.evilrobot

Use a reversible drill and left-handed drill bits. then theres a pretty good chance you'll unscrew the screw before you get done drilling. So you only have to replace the screw. Otherwise, you can glue it back together later.

Also, there is another kind of screwhead/screwdriver in with crossed slots, other than Philips. It's supposed to eliminate the need for more than one size of such a screwdriver. I don't know any place these scdrews are used by maybe you found one.

(Yes, I read the thread and know you finished this one but for next time.)

Reply to
micky

I can't find this. I looked back to before last June in SER, so where can I find it?

Also the screw style I meant was Pozidrive. Could that have been the difference?

Use a reversible drill and left-handed drill bits. then theres a pretty good chance you'll unscrew the screw before you get done drilling. So you only have to replace the screw. Otherwise, you can glue it back together later.

Also, there is another kind of screwhead/screwdriver in with crossed slots, other than Philips. It's supposed to eliminate the need for more than one size of such a screwdriver. I don't know any place these scdrews are used by maybe you found one.

(Yes, I read the thread and know you finished this one but for next time.)

Reply to
micky

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