Although I have not tried PSUD, I agree with you using the RMS value as it is the DC equivalent value of AC. Max ripple peaks or pulses occur right after the rectifier bridge which are 100 or 120 times each second...the RMS value will be harder on the caps as this is a continuous value like DC. These ripples become smaller as they go thru each filter cap.
Well, I spent a bit more time with the cylinder head F5 tonight. I reckon I can confirm that the cylinder head is a good enough heatsink..... I'm using silpads - which I just feel are not as good as the mica for heat transfer - BS maybe, but there ya go.
So Bias is at 0.59V both sides, DC offset is <3mV and the amp has been running for 2 hours. Temperature right on the body of the mosfets is 85 degC. Temp on the cylinder head 3mm away from the mosfets (1/8") is 53-55 deg C. Temp about 25mm (1") away is down to 50 degC - at the extremeties its down to 45 or so. So it seems that the head does spread the heat fairly well. Now I think the body of the mosfets are too warm - but when I get my mica spacers, I intend fitting them and hopefully that differential will drop. That differential is not there on my other F5.
In all likelihood, the 85 degC won't harm the mosfets - I understand they are pretty hardy and will work till they glow! And because the case is open, heating the case isn't an issue.
Pics yet to be taken.....
Fran
So Bias is at 0.59V both sides, DC offset is <3mV and the amp has been running for 2 hours. Temperature right on the body of the mosfets is 85 degC. Temp on the cylinder head 3mm away from the mosfets (1/8") is 53-55 deg C. Temp about 25mm (1") away is down to 50 degC - at the extremeties its down to 45 or so. So it seems that the head does spread the heat fairly well. Now I think the body of the mosfets are too warm - but when I get my mica spacers, I intend fitting them and hopefully that differential will drop. That differential is not there on my other F5.
In all likelihood, the 85 degC won't harm the mosfets - I understand they are pretty hardy and will work till they glow! And because the case is open, heating the case isn't an issue.
Pics yet to be taken.....
Fran
Yes - I really think its the pads I'm using...... will experiment a bit more and report back soon. Amp sounds like it should and the bias is stable.
well, its surely not the same kind of aluminium
could be it has slightly higher thermal resistance
could be it has slightly higher thermal resistance
thermal resistance of a cylinder head (as investment cast) is probably something on th order of T3 alloy. I dont know but I think thermal mass may be pretty substantial as a cylinder head may weigh in excess of 20 lbs. Once thermal equilibrium is reached dissipation is the next factor.
E
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Yep, ill post photos later.
I'll do some more figuring out on the differential of the temp too.
Fran
I'll do some more figuring out on the differential of the temp too.
Fran
many Members of this Forum don't want the details, don't want the knowledge, don't want to invest the time, don't care about nor respect others.
All they want is a quick fix.
"Tell me how to do",
don't bother me with the work, I want it all for free.
We now live in a new age. Respect seems to have gone out the window. That is respect for self as well as respect for others.
That is only your opinion. I see lots of people trying to understand electronics, and do so with much gratitude.
I too see lots of Members that show gratitude and a willingness to share the workload.
That does not negate my observation.
Agreed. Of course they come here (as I have) for a quick fix...its totally understandable. What seems strange to me is someone knowledgeable here complaining about helping someone out. If that's their attitude, then why comment here at all? If they come here to get there *** kissed they are probably in the wrong place anyway. I thought it was about information, and the trading of it. Lord knows I've come here often enough looking for answers, my apologies to any offended.
I think of this place as a great source of expertise. A wonderful place.
I have absolutely no formal electronics training at all. Through forums like this I taught myself enough about tube amps to repair a few, then to build them out from scratch. Here, I taught myself to build an F-5 and B-1. I could not have done that without the help of many here, way more knowledgeable than I. For that I am greatful.
That said, I understand how irksome it is to have participated in a large thread, and have people ask basic questions that would have been easily answered if they had read the entire thread. Its just a fact of life that people start out everyday, and the same questions keep getting asked. This is part of the way it is.
Again, what a great place! I wouldnt have this killer F-5 and B-1 had it not been for this forum, Nelson Pass, and all the participants here! I would encourage all new starts to ask away, this hobby needs new participants, and no one starts if they cant get enough information to proceed.
To the knowledgeable ones out there who helped me, I thank you more than can be told. For those knowledgeable here who came to get "respect"....well you might question what your motivations really are.
Russellc
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I would say that having patience solves many problems, and goes a long way, for everyone
nothing new in that, really
and the general posting tone seems ok , considering almost 160000 members
nothing new in that, really
and the general posting tone seems ok , considering almost 160000 members
AndrewT,
I respect you, so lighten up...😉
..and if you ever get to Kentucky I'll try to teach you something about bourbon, beautiful horses and fast women, even if you know nothing to begin with...😀
I respect you, so lighten up...😉
..and if you ever get to Kentucky I'll try to teach you something about bourbon, beautiful horses and fast women, even if you know nothing to begin with...😀
it's necessity to mix them , in every part of the world .....
after enough bourbon , womans aren't more part of equation
fast horses are enough .....
😀