Discussion in 'Amateur Radio Amplifiers' started by N4EYZ, Jan 18, 2016.
Who said I was trying to cool the inside of the tube?
I guess you failed physics 101 big time or skipped class. While a tube radiates inferred energy from inside vacuum of tube, the rate at which it is transferred is dependent on ambient temperature around tube. It is very silly and improper to suggest that air flow around tubes have no effect on tubes.
I never said that. I said the stock cooling fan is sufficient. I see your assumptions about other peoples education are being gloriously displayed. Yet another one in the hobby who can't just enter civilized conversation without name calling and superiority complexes.
sigh... again here we go.... other people have said things besides you. I was responding to others. Just because you create a thread on this forum doesn't mean that every single reply is directed at you.
Not that it really matters to me but I was the one who started this thread. I am very grateful for all the good and thoughtful ideas on amp cooling and all my questions have been well answered. However I am extremely dismayed at some of responses back and forth between a very few of those who have replied. If I were a non-ham reading this thread I would almost think "If this is a representation of the attitudes among and between radio amateurs then I don't want any part of this hobby!" So please guys..........give it a break.
Practice what you preach. If you believe your BS take on this you would need zero air flow and tubes would be fine. It is VERY simple physics (to tuff for KM1H though) As ambient temperature around tube increases, the internal temperature of tube increases to try to get enough temperature differential for heat to flow at a rate high enough to remove heat being produced. Posters like KM1H though cannot begin to understand the Physics of this and want everyone to believe that a thermal transfer rate via radiation is the same regardless of temperature outside of tube envelope. Carl you need to tell Eimac and Amprex that they had it all wrong that no cooling fan is needed nor are chimneys because heat will get-out magically regardless of air flow or temperatures around tube according to KM1H's thermodynamics theories.
The ambient temperature around the tube (and entire amp) would need to be quite high to effect the transfer of heat significantly. And, BTW that is spelled infrared (or did you really mean inferred?) energy.
I have an old SB-200 and in all honesty the fan does not do much except circulate the air around inside of the RF box. About all it does is help transfer heat from the tube to the cabinet which is then transferred to the air around the cabinet. Most of the cooling for the SB-200 is based on convection (IMO). And, while this does not seem to be a very efficient method of cooling the amp it WAS sufficient. Most tube equipment I have used in the past got quite (very) warm during use anyway.
You might also consider the FACT that the Heathkit SB-200 has been around for many years now, with the original cooling fans, and there haven't been significant problems. How many guys out there ran SB-200's every day for years getting them extremely warm with no issues?
If you want to make your SB-200 type amp transfer heat more efficiently paint the inside of the RF Box flat black and put a small computer type fan blowing on the exterior of the amp. You could also set the fan on top to suck the heat out.....
Judging from the quality of the build I would not worry so much about cooling the tubes. The original builder knew what he was doing and would have provided for more heat removal if it was needed.
I was not able to see how the fan in your amp was mounted. Could be a lot of the noise is a result of a rigid connection between the fan chassis and the mounting. Perhaps some sound insulation is needed to isolate the fan chassis from the mount.
Good luck and have fun.....
Since the subject is about 572B cooling and you own a SB-200 Im very disappointed you are so ignorant about the subject. Maybe you should turn in that old timey Extra or at least tell us who actually took the test since your make believe knowledge of such a simple subject is slim to none. Any kid with a couple of 60's era ARRL Handbooks could understand what sort of cooling was required in different amps.
The subject is not about Eimac but since you brought it up have someone read the cooling specs of the 100TH, 250TH, 4-125A to you and then explain to you in simple words what radiation and convection cooling means.
The similar power 813 is another tube that needs only radiation and convection cooling in typical use.
When radiation and convection cooling are not sufficient then steps ranging from a simple SB-200 fan to forced air cooling for 24/7 operation of tubes such as the 4-250A's and larger.
Well Gee Golly bringing actual facts into a discussion violates some QRZ rule Im sure in order to prevent embarrassment of the poorly informed poster
With only about 20,000 SB-200/201's being sold (some say more) you wouda thunk that was a decent sample
Since Cetron suggested a small convection fan above 2000V for a 572B Heath did it correctly.
I cant wait for the next gem from JX!