Hi,
I have a retail amp unit that was shipped to me. It must have gone through a storm since all the mounting screws for the amp board/heatsink came off.
One of screw head broke off in the heatsink thread.
My question, the standoffs were of the nylon plastic type. Were these used to save on costs or to isolate the heatsinks from the chassis ground?
If I replace them with brass standoffs, that would connect the heatsinks to the chassis ground via the screw to some degree of contact between metals.
Is this ok? Do you see any issues with the heat sink as part of the chassis ground connected electrically?
I have a retail amp unit that was shipped to me. It must have gone through a storm since all the mounting screws for the amp board/heatsink came off.
One of screw head broke off in the heatsink thread.
My question, the standoffs were of the nylon plastic type. Were these used to save on costs or to isolate the heatsinks from the chassis ground?
If I replace them with brass standoffs, that would connect the heatsinks to the chassis ground via the screw to some degree of contact between metals.
Is this ok? Do you see any issues with the heat sink as part of the chassis ground connected electrically?
If there is no insulating plate between the chassis and sink, then the nylon bolts were just an unfortunate choice,
since they are more likely to break in shipping than not. I'd replace them with metal bolts. Are there insulators
under the output transistors? Hopefully they don't use nylon bolts there also, those would soon loosen and fail.
Most heat sinks are grounded, but there is better thermal conduction without power device insulators.
So, some do float the sinks, but then the sinks have to be fully enclosed inside the chassis (including
the fins) to avoid shock and shorts. This is rarely done with large sinks, and is much more common
with small, board mounted sinks.
Consider making a damage claim on the amplifier, especially if it was shipped in the original carton.
since they are more likely to break in shipping than not. I'd replace them with metal bolts. Are there insulators
under the output transistors? Hopefully they don't use nylon bolts there also, those would soon loosen and fail.
Most heat sinks are grounded, but there is better thermal conduction without power device insulators.
So, some do float the sinks, but then the sinks have to be fully enclosed inside the chassis (including
the fins) to avoid shock and shorts. This is rarely done with large sinks, and is much more common
with small, board mounted sinks.
Consider making a damage claim on the amplifier, especially if it was shipped in the original carton.
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Hi
The amp board/heatsink is raised off the chassis by 4x 10mm(height) nylon standoffs. There are mica insulators between heatsink and output transistors.
I bought it used so cannot claim ship damage. It was double boxed. I suspect the nylon plastic just over time became too brittle to support all that weight.
I will replace with brass ones I just ordered.
I was not sure about the isolation between grounded chassis and heat sink was intentional or if it posed a problem.
Thank you 🙂
The amp board/heatsink is raised off the chassis by 4x 10mm(height) nylon standoffs. There are mica insulators between heatsink and output transistors.
I bought it used so cannot claim ship damage. It was double boxed. I suspect the nylon plastic just over time became too brittle to support all that weight.
I will replace with brass ones I just ordered.
I was not sure about the isolation between grounded chassis and heat sink was intentional or if it posed a problem.
Thank you 🙂
Very odd for a commercial product using nylon hardware to joint heavy metal parts together.
Hopefully nothing was damaged otherwise.
Maybe they had noise/instability problems with the sink grounded. Be careful powering it up.
Normally those sinks are grounded, since floating sinks can cause noise/instability as well.
Hopefully nothing was damaged otherwise.
Maybe they had noise/instability problems with the sink grounded. Be careful powering it up.
Normally those sinks are grounded, since floating sinks can cause noise/instability as well.
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I suspect isolating heatsink from chassis was done for some reason, not just cost.
Just in case and in absence of continuity or voltage tests, I would rebuild factory original.
I think you will not subject them to air flight turbulence or UPS/FedEx torture in he near future.
FWIW there was a thread here just 2 days ago about an amp which would oscillate when grounding heatsinks 😱
Just in case and in absence of continuity or voltage tests, I would rebuild factory original.
I think you will not subject them to air flight turbulence or UPS/FedEx torture in he near future.
FWIW there was a thread here just 2 days ago about an amp which would oscillate when grounding heatsinks 😱
Measure the Continuity of the heatsinks & output drivers.
If they are isolated, go for the brass or use a screw with 3 or 4 washers for standoffs.
I know a manufacturer who uses glue-able furniture anti scratch felt for securing the amp boards to heatsinks on the opposite side of the board with the output drivers.
The other side is secured by the output driver's bolts.
If they are isolated, go for the brass or use a screw with 3 or 4 washers for standoffs.
I know a manufacturer who uses glue-able furniture anti scratch felt for securing the amp boards to heatsinks on the opposite side of the board with the output drivers.
The other side is secured by the output driver's bolts.