.50 Caliber PCB standoff fix - Pictures!

[joepopp]

I just bought an old .50 caliber but most of the PCB standoffs are cracked and falling apart. I found a replacement for the originals but I was thinking about changing them to the stainless steel hex type. I am just concerned that if the amp takes a big hit I could crack the circuit board. Any thoughts?

I hate plugging a 12AX7 into the socket and feeling the circuit board flex!

The chassis has the sus-4 shock mount so that may provide enough shock resistance against cracking the PCB.

Also, The preamp tube cover has some plastic parts that I can't seem to source. Any help greatly appreciated.

Joe Popp

 

[Boogiebabies]

A Metal standoff with a lock washer is a much better design than a .10 cent plastic version. Mesa used the plastic standoffs as far back as the II's on the Fliter Cap board and they get yellow, brittle and wiggle.
On the other hand, my 93 SLO uses metal standoffs for all the boards and they are perfect. I think you are apt to have more problems when a plastic standoff breaks and you have no idea what the board or components are going to short to. When I have to work on the filter supply board on an old Boogie, I cringe and pray that I do not break the plastic. They also have a bad memory and do not like to snap back into the holes without prying the barbs back. As long as you get the right hight and don't bump into anything you will have a better hold on your circuit boards. For larger boards, they are easier to work on as well. Instead of having to pry and lift 10 plastic barbs for 20 minutes, you could have removed 10 screws in seconds.

 

[joepopp]

Thanks Boogiebabies! I will post pics and info of the mods here. I measured carefully and it looks like an .875" standoff will do the trick. I think I'll throw some nylon washers on there too to relieve a little stress on the PCB.

 

[Boogiebabies]

Good Luck.

 

[joepopp]

After a bunch of crazy measuring here is what I came up with. The .875 spacer is just too short so I went up to 1". The grommet should add a little shock resistance. Drawn with ConceptDraw V on a Mac. I will have Digi-Key part numbers very soon (after I am sure it works)!

 

[Boogiebabies]

****, I have three Mac's and I have never heard of that program.
It's killer. Good Job.

Current Gear -

2004 I-Mac G5 21 Inch
2006 Mac Book Black 2.0 Duo Core 1GB
2007 I-Mac 2.16 Duo Core 1GB 24 Inch

 

[joepopp]

Thanks BB.

It's up to version VI now. It's really cool because you can drag jpegs right into a design doc. Great for illustrating signal path in guitar set ups.

http://www.conceptdraw.com/en/

 

[joepopp]

Here are some pics of the completed standoff replacement. It was a total pain! I had to take the entire circuit board out. I don't think I would do it again. It came out nice though, and I have not worries about cracking the circuit board when pushing in new tubes.


Note: I revised the drawing above to reflect what I actually did.

Sorry for the blurriness on some of the shots.

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[Boogiebabies]

Good Lord !!!

Metal Standoffs and Nyloc Washers !!!

That's Awesome. That board is going nowhere.

 

[joepopp]

Thanks BB! The grommet is the key. It adds a little shock resistance. I used the Nyloc nuts so that I don't have to crank it all the way down on the grommet. The board can wiggle just the slightest bit when bumped but has a much more positive firm feel.

I am sure there are at least 3 inuendos in the previous paragraph.