14-11-2016, 04:33 PM
It's worth saying that the protection circuits are all very well when everything is working correctly, but they might not protect new output devices when there is a fault prior to them.
If in doubt, in addition to using a lamp limiter, perhaps try the initial power-up with only one pair of devices fitted (minimises the cost of any blow-ups!). Or even use a "sacrificial" pair of transistors - something that has sufficient voltage rating, but costs a lot less than the correct originals. They only need to work well enough to establish the correct DC conditions are present and deliver a sine wave a low power. Once past that, a full set of "proper" devices should work with no drama, and full-power testing can be done at that point.
Can't see the schematic, BTW. Would love a copy - if you can't get it uploaded on the forum, email it to me and I'll see what I can do... If it's a PDF, we have a very generous allowance on the file size for those.
If in doubt, in addition to using a lamp limiter, perhaps try the initial power-up with only one pair of devices fitted (minimises the cost of any blow-ups!). Or even use a "sacrificial" pair of transistors - something that has sufficient voltage rating, but costs a lot less than the correct originals. They only need to work well enough to establish the correct DC conditions are present and deliver a sine wave a low power. Once past that, a full set of "proper" devices should work with no drama, and full-power testing can be done at that point.
Can't see the schematic, BTW. Would love a copy - if you can't get it uploaded on the forum, email it to me and I'll see what I can do... If it's a PDF, we have a very generous allowance on the file size for those.
