Fiberboard mounting

lmolter · 07-03-2008, 01:56 AM

Ok, it's time for another newbie (noob?) question: I have a nice 5F6A fiberboard and insulator, but I'm not sure of the recommended way to mount the board to the chassis. I imagine spacers are used between the chassis and the insulator board. What about between the insulator and the circuit board - spacers there, too? And do I have to drill my own mounting holes in the chassis? It seems that none of the pre-drilled holes match up.

Progress note on my Bassman replica: I have most of the parts loaded on the fiberboard; I have all my filter caps loaded on their own board; I have a commercial chassis from Hoffman; Have sockets; All pots and jacks mounted on brass plate with some wiring; No tubes yet; No trannies yet (see another post about which iron to buy); No cabinet yet. Needless to say, I have a ways to go.

Larry

MWJB · 07-03-2008, 10:17 AM

You don't need any spacers between the insulator board & chassis, nor between insulator board & circuit board.

"I have most of the parts loaded on the fiberboard" - Aaaah, I would have tackled the mounting hole problem BEFORE loading up the board, it's the first thing I do. You'll probably want to use the holes in the circuit board as your datum now. Transfer circuit board holes to the insulator board & drill thru, then dry mount the insulator on the chassis & drill new holes in the chassis if necessary.

Hopefully this will save you drilling thru the circuit board from the chassis side & possibly taking out a component? Though, working from chassis holes forward is the way that I would have gone, you could still do this if you have spare components/don't mind a bit of remounting if necessary?

Double check that board mounting screws do not short against ANY wires, even ground wires, on either side of the crcuit board.

lmolter · 07-03-2008, 10:02 PM

Thanks for the reply. Luckily, the components are not yet soldered to the board. I can pull them out easily and then follow your instructions. But... there seem to be a lot of holes in the chassis already, but all I have to mount yet is the PT, OT, and choke. The tranny holes are obvious, but I'm not sure where the choke gets mounted. I also have the holes for the cap cover accounted for. I just want to make sure any holes I drill for the board don't conflict with some other part that has yet to be mounted. I know, I'm too cautious. However, since I might sell this amp, I don't want a hack job.

Larry

lmolter · 07-03-2008, 10:44 PM

Well, I just looked at the chassis again and all holes are accounted for. That's a good thing. However, the board slightly overlaps the mounting holes for the OT and cap pan, so I'm thinking maybe a small spacer to lift the board up a tad to clear the nuts. And how many mounting holes should I drill? 2, 3 (2 ends plus middle in a line), or 4?

07-03-2008, 01:56 AM	#1
lmolter Member Join Date: May 2008 Location: Tampa, FL Posts: 101	Fiberboard mounting Ok, it's time for another newbie (noob?) question: I have a nice 5F6A fiberboard and insulator, but I'm not sure of the recommended way to mount the board to the chassis. I imagine spacers are used between the chassis and the insulator board. What about between the insulator and the circuit board - spacers there, too? And do I have to drill my own mounting holes in the chassis? It seems that none of the pre-drilled holes match up. Progress note on my Bassman replica: I have most of the parts loaded on the fiberboard; I have all my filter caps loaded on their own board; I have a commercial chassis from Hoffman; Have sockets; All pots and jacks mounted on brass plate with some wiring; No tubes yet; No trannies yet (see another post about which iron to buy); No cabinet yet. Needless to say, I have a ways to go. Larry

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07-03-2008, 10:17 AM	#2
MWJB Old Timer Join Date: Jun 2006 Posts: 1,926	You don't need any spacers between the insulator board & chassis, nor between insulator board & circuit board. "I have most of the parts loaded on the fiberboard" - Aaaah, I would have tackled the mounting hole problem BEFORE loading up the board, it's the first thing I do. You'll probably want to use the holes in the circuit board as your datum now. Transfer circuit board holes to the insulator board & drill thru, then dry mount the insulator on the chassis & drill new holes in the chassis if necessary. Hopefully this will save you drilling thru the circuit board from the chassis side & possibly taking out a component? Though, working from chassis holes forward is the way that I would have gone, you could still do this if you have spare components/don't mind a bit of remounting if necessary? Double check that board mounting screws do not short against ANY wires, even ground wires, on either side of the crcuit board.

07-03-2008, 10:02 PM	#3
lmolter Member Join Date: May 2008 Location: Tampa, FL Posts: 101	Thanks for the reply. Luckily, the components are not yet soldered to the board. I can pull them out easily and then follow your instructions. But... there seem to be a lot of holes in the chassis already, but all I have to mount yet is the PT, OT, and choke. The tranny holes are obvious, but I'm not sure where the choke gets mounted. I also have the holes for the cap cover accounted for. I just want to make sure any holes I drill for the board don't conflict with some other part that has yet to be mounted. I know, I'm too cautious. However, since I might sell this amp, I don't want a hack job. Larry

07-03-2008, 10:44 PM	#4
lmolter Member Join Date: May 2008 Location: Tampa, FL Posts: 101	Well, I just looked at the chassis again and all holes are accounted for. That's a good thing. However, the board slightly overlaps the mounting holes for the OT and cap pan, so I'm thinking maybe a small spacer to lift the board up a tad to clear the nuts. And how many mounting holes should I drill? 2, 3 (2 ends plus middle in a line), or 4?

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