1- I don't see where you stated if a load was connected or not??? there should be at least a 8-10 ohm resistor connected across the speaker terminals. without a load you may see some DC.
2- the output cap could have a lot of leakage. if you are using old caps for the output cap they could be bad but measure ok and work ok for typical power supply use just not as an output coupling cap. for testing you can use just about any cap there. try a 10,000uf or whatever else you have that may be newer.
Zc
2- the output cap could have a lot of leakage. if you are using old caps for the output cap they could be bad but measure ok and work ok for typical power supply use just not as an output coupling cap. for testing you can use just about any cap there. try a 10,000uf or whatever else you have that may be newer.
Zc
bad Pa ;
'twas your blessing
Now, musn't blame Nelson for my omission.
For the sake of others:
If one tests with a dummy load (as one should) the coupling cap discharges rather quickly through the load.
Since speakers don't always like this sort of thing, we use a 100 Ohm or so resistor connected from the output to ground to bleed off the cap when there's no load connected. This can potentially save you or your speker from a shock.
Now, musn't blame Nelson for my omission.
......
why not ....... I'm really enjoying in that
Attachments
I think the problem lies with my version of 'grounding'. I'm waiting on a replacement VFet. As soon as I know for sure I'll post a detailed and well illustrated report.
Regards,
Dan
I went back and looked and said to myself that being the big dummy that I am I would need to wire it up and do a double check on it. But I have to agree with you Michael - upon a 2nd look it does look correct. OTOH - I am all to familiar with the term "smoke test".
Now, musn't blame Nelson for my omission.
For the sake of others:
If one tests with a dummy load (as one should) the coupling cap discharges rather quickly through the load.
Since speakers don't always like this sort of thing, we use a 100 Ohm or so resistor connected from the output to ground to bleed off the cap when there's no load connected. This can potentially save you or your speker from a shock.
The reason I came across this is I'm in the habit of checking for DC offset on the outputs of new amplifiers. With one slight deviation in the grounding scheme I know my wiring is perfect and an exact duplicate of the original schematic. That said, when my new VFets arrive I'm going to install a 100 ohm resistor across the output terminals of my amp. Hopefully this will prevent my speakers (or myself) from seeing any DC.
Regards,
Dan
ilizmn is trying to clue you in on why you're measurement is wonky. Your cap is hanging in space.
The 100 ohm resistor will improve your measurement situation as well as bleed the cap, but I'd like to emphasize that you should always test with a load resistor. There's one in the schematic, and if you had you'd probably be listening to an amp right now.
The 100 ohm resistor will improve your measurement situation as well as bleed the cap, but I'd like to emphasize that you should always test with a load resistor. There's one in the schematic, and if you had you'd probably be listening to an amp right now.
I probably mistook the load resistor as representing a nominal speaker load. That aside, I'll do all my next startup tests with a resistor load in place. Thanks for the heads up.
Regards,
Dan
Hi Dan,
we are mostly used to the capacitor free outputs and check the offset.....
I was in the last days also in the situation to be in panic with the F3 clone and my newly implemented 15 x 1000uF Silmic ... it is easy to forget what ilimzn wrote...
especially when building a new project.....!
but what was the reason your SIT was blown?
we are mostly used to the capacitor free outputs and check the offset.....
I was in the last days also in the situation to be in panic with the F3 clone and my newly implemented 15 x 1000uF Silmic ... it is easy to forget what ilimzn wrote...
especially when building a new project.....!
but what was the reason your SIT was blown?
besides bad cap , there is missing bleeder resistor on speaker side
that's the price when Pa is in a hurry to please everyone
it can be a problem when connecting speaker to still excited cap
not first and not last subject , beaten to death
there is no need to take it from wrong side .........
you can find mistakes in Pa's manuals , left there most probably because life isn't serious thing , so there is no need that electronic must be ........ and what Greenhorns can catch , if not own mistakes
(sez Mighty Moi , who scorched more than few mosfets and just later found that Pa was laughing all the time )
there is no need to take it from wrong side .........
you can find mistakes in Pa's manuals , left there most probably because life isn't serious thing , so there is no need that electronic must be ........ and what Greenhorns can catch , if not own mistakes
(sez Mighty Moi , who scorched more than few mosfets and just later found that Pa was laughing all the time )
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