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04-09-2024, 10:49 AM
Hi Guys
Note that some PTs have insulated bolts holding the laminations together - although, once the unit is vacuum varnished, the varnish is what holds the laminations together and the bolts are just for mounting. If there was tape over the threads through the lams and/or nylon bushings and/or fiber washers at either end, these should all be incorporated with the new longer bolts.
An alternative to the long bolts is to use long threaded standoffs screwed onto the stock bolts. Then use short bolts to secure the card. A quick look at the Keystone catalog shows threads up to 8-32 and lengths up to 2". PT bolts are often #10, so this may not be an option. Only short threaded spacers are threaded the entire length; from 1" up the thread at each end are about 3/8" deep.
The PSU card in The Standard carries the fuses and bias supply and is more or less full. How is your card empty?
Regarding the toothed lug for use as a chassis ground: In my amps and kits I use a flat washer over the lug, then the nylock nut. This way, the teeth on the lug does not interfere with tightening the nut.
In many of the amps I've built where a board sits over an OT, say, I add "captive bolts" to the card. These are comprised of a 3/8" long bolt with a nylock on the underside of the card facing the standoff. I tighten the nylock then release it very slightly so the bolt can turn in the hole in the board - not wildly, but with a screwdriver. This also works nicely when there is a stack of cards.
Note that some PTs have insulated bolts holding the laminations together - although, once the unit is vacuum varnished, the varnish is what holds the laminations together and the bolts are just for mounting. If there was tape over the threads through the lams and/or nylon bushings and/or fiber washers at either end, these should all be incorporated with the new longer bolts.
An alternative to the long bolts is to use long threaded standoffs screwed onto the stock bolts. Then use short bolts to secure the card. A quick look at the Keystone catalog shows threads up to 8-32 and lengths up to 2". PT bolts are often #10, so this may not be an option. Only short threaded spacers are threaded the entire length; from 1" up the thread at each end are about 3/8" deep.
The PSU card in The Standard carries the fuses and bias supply and is more or less full. How is your card empty?
Regarding the toothed lug for use as a chassis ground: In my amps and kits I use a flat washer over the lug, then the nylock nut. This way, the teeth on the lug does not interfere with tightening the nut.
In many of the amps I've built where a board sits over an OT, say, I add "captive bolts" to the card. These are comprised of a 3/8" long bolt with a nylock on the underside of the card facing the standoff. I tighten the nylock then release it very slightly so the bolt can turn in the hole in the board - not wildly, but with a screwdriver. This also works nicely when there is a stack of cards.
