Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: Prev 1 [2] 3 Next   Go Down
  Print  
Author Topic: Al-811  (Read 1420 times)
W9IQ
Member

Posts: 3241




Ignore
« Reply #15 on: July 17, 2019, 10:41:43 AM »

I was not happy with the fan noise from my Kenwood transistor tx/rx (no model number given to avoid dissing a good radio).  I simply added a series dropping resistor in the fan circuit.  The resistor value selected to reduce noise, but with reliable start-up,  This did not seem to affect the radio.  The over-temp thermistor still operated normally, but not called on to protect the finals.

[sarcasm]
A similar approach would be to put a variable resistor in series with the AL-811 fan. Keep dialing up the resistance until the amplifier fails. Quickly sell this amplifier as "checked out fine last time it was on the air".

Then when you buy your new AL-811, just keep the fan resistor value slightly lower than on the failed amp. Also make certain you don't change the room temperature, the duty cycle, the atmospheric pressure, the load impedance, the input power, the finals, the line voltage, the position on the bench or the band and you should be good to go.
[/sarcasm]

- Glenn W9IQ
Logged

- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
AC7CW
Member

Posts: 1339




Ignore
« Reply #16 on: July 17, 2019, 02:00:10 PM »

I was not happy with the fan noise from my Kenwood transistor tx/rx (no model number given to avoid dissing a good radio).  I simply added a series dropping resistor in the fan circuit.  The resistor value selected to reduce noise, but with reliable start-up,  This did not seem to affect the radio.  The over-temp thermistor still operated normally, but not called on to protect the finals..

Good old cut-n-try engineering. I'm happy for somebody when it works for them, I'm happy when it works for me for that matter but do I want to buy the modified gear? Not too much maybe... One ham became my permanent enemy because I duct taped a gel cell to a rig and fed it from a car cigar lighter with only a surge protecting resistor. It worked fine actually, i got the batteries from a surplusser for $7 so i didn't care if they only lasted a year or whatever but it triggered the guy's perfectionism-resent-hatred thingy permanently. I always made sure I let him know that I was working the world from my car of course and how well the battery did on keydown; he would blow up and it was fun to watch Smiley
Logged

Novice 1958, 20WPM Extra now... (and get off my lawn)
KM1H
Member

Posts: 5109




Ignore
« Reply #17 on: July 17, 2019, 05:17:39 PM »

Good old cut-n-try engineering. I'm happy for somebody when it works for them, I'm happy when it works for me for that matter but do I want to buy the modified gear? Not too much maybe... One ham became my permanent enemy because I duct taped a gel cell to a rig and fed it from a car cigar lighter with only a surge protecting resistor. It worked fine actually, i got the batteries from a surplusser for $7 so i didn't care if they only lasted a year or whatever but it triggered the guy's perfectionism-resent-hatred thingy permanently. I always made sure I let him know that I was working the world from my car of course and how well the battery did on keydown; he would blow up and it was fun to watch Smiley


There are always a very small few that I watch self destructing when they are questioned and/or dont get their own way no matter how wrong they are. Sorta sad but can also be entertaining.
Logged
KM4AH
Member

Posts: 945




Ignore
« Reply #18 on: July 17, 2019, 05:20:48 PM »

When there is not a lot of fan noise in my shack I feel like something is wrong.
Logged
K4RVN
Member

Posts: 261




Ignore
« Reply #19 on: July 17, 2019, 09:15:49 PM »

Michael,
I thought my 811 fan was a little noisy not from a defect just a noisy fan selection. It is such a small fan diameter that the rpm is high
making it  more noisy than my AL 80 A or B fans I owned. Not much you can do because of the opening diameter on the back where the fan mounts. Glenn is right on saying it will operate on its' fan curve and it won't be zero static pressure. It will do an adequate job as Tom designed it for the cooling needed even if it is a little noisy.
The better mfgs will give you a fan curve showing CFM@ static pressure or resistance along with a DB noise rating. Most axial fans are rated at 0 inches SP for max CFM which certainly won't happen on the AL811 amp blowing through the cabinet with tubes and other components. The center tube on that amp runs hotter than the other two so be careful just putting a quieter fan on it without knowing the CFM and static pressure.
I used a headset for the 811 and still do for my existing amps which makes most fans tolerable.

Good luck and you may find a thicker fan design of the same diameter provided you know the CFM and static pressure of the original fan plus the DB rating so you can purchase one less noisy.

Frank

Frank
Logged
OZ8AGB
Member

Posts: 553




Ignore
« Reply #20 on: July 18, 2019, 01:54:44 AM »

When there is not a lot of fan noise in my shack I feel like something is wrong.

It tells you you are operation QRP  Grin Grin
Logged
KM1H
Member

Posts: 5109




Ignore
« Reply #21 on: July 18, 2019, 08:35:26 AM »

Michael,
I thought my 811 fan was a little noisy not from a defect just a noisy fan selection. It is such a small fan diameter that the rpm is high
making it  more noisy than my AL 80 A or B fans I owned. Not much you can do because of the opening diameter on the back where the fan mounts. Glenn is right on saying it will operate on its' fan curve and it won't be zero static pressure. It will do an adequate job as Tom designed it for the cooling needed even if it is a little noisy.
The better mfgs will give you a fan curve showing CFM@ static pressure or resistance along with a DB noise rating. Most axial fans are rated at 0 inches SP for max CFM which certainly won't happen on the AL811 amp blowing through the cabinet with tubes and other components. The center tube on that amp runs hotter than the other two so be careful just putting a quieter fan on it without knowing the CFM and static pressure.
I used a headset for the 811 and still do for my existing amps which makes most fans tolerable.

Good luck and you may find a thicker fan design of the same diameter provided you know the CFM and static pressure of the original fan plus the DB rating so you can purchase one less noisy.

Frank

Frank

I use EBM Papst for all my fan replacements and find the 4600X size which is used on most amps of the AL-80 family size to be ideal for lower noise and long life. Cant help with the little ones, havent had a bad one thru here yet.

Carl
Logged
N1RND
Member

Posts: 56




Ignore
« Reply #22 on: July 18, 2019, 04:37:57 PM »

The fan used by Ameritron years ago on this amp was made by Pabst, a German company.  They went to a cheaper Chinese manufacturer that had the same cfm but more noise.  I was able to find an nos Pabst fan from a supplier that I can't remember right now. 
I don't have the part numbers of the old and new fans right now.

Another alternative that I want to engineer is a remote blower box with ducking to the amp that would make it almost silent!
Logged
WY7CHY
Member

Posts: 957




Ignore
« Reply #23 on: July 18, 2019, 08:28:20 PM »

You want a quiet fan for the AL-811/H that pushes air efficiently?

AC Infinity AXIAL 8038.

It will come with an AC plug on it; just cut off the plug. That's what I did. My original fan worked fine, but it was a little noisy. The Axial moves about the same amount of air, but it's half as quiet as the original. (To the human ear). I got it on amazon. Airflow: 23 CFM | Noise: 28 dBA | Speed: 2000 RPM. Costs $17.99. If you have prime, it's FREE Shipping. If you don't do amazon, you can go to acinfinity.com and get it from their website. Same price.

Some might say that 23 CFM isn't that much. But, considering the stock fan in the AL-811 is around 18 CFM, the AC Infinity is fine. Some amps used the Papst 8800 fans. They have a 28 CFM flow 2500 rpm fan. "Some" people say if I run 572b tubes, that I "Should" run at least a 35 CFM fan. It's not that important. If I was doing AM/FM/RTTY or even CW a lot, I might have thought of a 35 CFM fan. "MIGHT" is the key word. I do exclusively SSB VOICE. I also run the 572b tubes at the same power that I ran the 811A and G-811 tubes; around 750w PEP. So the duty cycle of my amp isn't that high. The 23 CFM AC Infinity Axial 8038 works perfectly. And because it's slightly slower, it's much quieter. But again, as long as the air is circulating in/out of the amp, it will be fine.

Remember, the fan in the AL-811 is creating positive pressure. The anode in the tube is not exposed to the airflow. It's in a vacuum. You can have the highest CFM in the world, and it's not going to cool down the tubes any more than any other fan. All you have to know, is if the amp is powered up, and you put your hand near the vent holes on the left side cover, and you can FEEL the air flow, the fan is doing what it's suppose to do. Positive pressure. Pull in colder air and push out hotter air. Cooling the amp is for the other component's health. Not the tubes.

I did see one AL-811 that wasn't cooling properly. The person had taken the cover off for whatever, and accidentally stepped on the cover. Dented it in about 5 places. He "THOUGHT", that the cover was only for safety for the operator, and as long as the cover closed the rear interlock, that's all that mattered. Well, there were like 5 or 6 big gaps in the cover against the rest of the case. So the air flow wasn't flowing properly. The amp didn't over heat or anything, but you could tell it was a LOT HOTTER than normal. I took the cover off for him, took it into the garage and straightened it out with a hammer. Repainted it and put it back on. The positive pressure was back, air was flowing through it properly, and it never got warm again. 

If you want a quieter fan, get the AC Infinity Axial 8038. If you want the same air flow; 28cfm/2500rpm, then you're going to have to deal with the increased noise. A lot also depends on your shack. I live in a brick home. In the middle of summer, even if it's 90 degrees outside, the basement of my house is always around 67-70 degrees. Summer or winter. That's where my shack is. Mine never gets warm.

Also, go to this site and you'll learn everything about the AL-811/H cooling system. "From the man who designed and invented the AL-811/H amp. https://www.w8ji.com/al811h%20fan%20speed.htm



Logged

Born Wild - Raised Proud: 73
Cheyenne, Wyoming
K7KBN
Member

Posts: 3677




Ignore
« Reply #24 on: July 19, 2019, 12:10:19 AM »


AC Infinity AXIAL 8038.

It will come with an AC plug on it; just cut off the plug. That's what I did. My original fan worked fine, but it was a little noisy. The Axial moves about the same amount of air, but it's half as quiet as the original. (To the human ear).

"...half as quiet...?"  That tells me that it's twice as loud. Huh
Logged

73
Pat K7KBN
CWO4 USNR Ret.
W9IQ
Member

Posts: 3241




Ignore
« Reply #25 on: July 19, 2019, 04:27:00 AM »

Also, go to this site and you'll learn everything about the AL-811/H cooling system. "From the man who designed and invented the AL-811/H amp. https://www.w8ji.com/al811h%20fan%20speed.htm

As I have stated, it is not the spec fan CFM or dB rating that determines the fan selection. It is the CFM at the pressure on the fan curve that determines the fan selection. W8JI on the linked site states the same thing:

Quote
  The AL811 and 811H use a fan that follows curve 5 below at about .07 inches backpressure

So picking out a fan with no published curves or not consulting the published curves may "work" for some situations but if you wish to do it correctly and not risk your amp or waste your time, consult the published curves to make the proper selection.

- Glenn W9IQ
Logged

- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
WY7CHY
Member

Posts: 957




Ignore
« Reply #26 on: July 19, 2019, 07:52:39 AM »


AC Infinity AXIAL 8038.

It will come with an AC plug on it; just cut off the plug. That's what I did. My original fan worked fine, but it was a little noisy. The Axial moves about the same amount of air, but it's half as quiet as the original. (To the human ear).

"...half as quiet...?"  That tells me that it's twice as loud. Huh
You knew what i meant. Don't be anal.
Mike
Logged

Born Wild - Raised Proud: 73
Cheyenne, Wyoming
KM1H
Member

Posts: 5109




Ignore
« Reply #27 on: July 19, 2019, 09:37:09 AM »

Using 572B's in any of the AL-811's does not even require air as they are loafing.

Quote
Also, go to this site and you'll learn everything about the AL-811/H cooling system. "From the man who designed and invented the AL-811/H amp. https://www.w8ji.com/al811h%20fan%20speed.htm

And thankfully he was canned and that amps reliability has gone way up.
Logged
N6PJB
Member

Posts: 72




Ignore
« Reply #28 on: July 19, 2019, 03:30:52 PM »

That was uncalled for....
Logged
W9IQ
Member

Posts: 3241




Ignore
« Reply #29 on: July 19, 2019, 03:44:40 PM »

Using 572B's in any of the AL-811's does not even require air as they are loafing.

Carl,

Is that really true? The amp still needs to dissipate more than 300 watts of heat. I would think the cabinet and related electronics would reach a significantly high temperature.

- Glenn W9IQ
Logged

- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
Pages: Prev 1 [2] 3 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!