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From: Artek Manuals <>
Date: Tue, 16 Apr 2019 21:06:29 -0400
List-post: <>
OK as I feared apparently no one knows what the specs on the TL-922 fan are. Or has a 1:1 cross replacement for it. Lots of meaningful links to dozens of sources for "similar" fans with CFM rates from 25CFM to 160 CFM, and noise ratings from 30dba to 0ver 100dba. I even found a couple of folks with TL-922 cadavers, but they were unwilling to unbolt the fan and sell it to me at offering prices above comparable retail for a new ones.

So undaunted here is what I did find out by direct measurement

1) My next door neighbor is a very knowledgeable HVAC guy and he had a air flow meter, that he uses to ascertain air volume in duct work when balancing a new system. We used that to measure the output rate from the fan (about 650 ft/min) . The cross sectional area of the fan orifice is about 11 sq in ( .077 sq ft) . [4.25 inch outside diameter less the 2" diameter of the fan motor) gives a CFM of 49.8 ... so we have a 50-CFM fan !

2) Not sure how to actually get a the noise spec for the fan . There are many free apps for your phone that will allow you to use it as Sound Level Meter. Calibrating those and then applying that to a actual specification measurement of stock fan seems to be fraught with too many variables. OF three apps I used all give different absolute values for the noise level ( no surprise my Moto phone is far from being a lab grade microphone anyway)  They were however consistent in that the shack which is very quiet to begin with and each sound meter app showed an increase of 12db in the noise level at the operators position when the amp is switched on

So here is the plan ...I will initially search for 50-60 CFM , 120x120x38mm, 110VAC  fan with the lowest noise spec and try that. Once in place I can measure the noise compared to the original and that will give me some correlation to what the sound level of the original fan is/was

Finally another interesting data point  the exit temperature of the fan air. The ambient air in the shack today was around 25-26 C, the exit air from the amp is around 31C at idle . Key down at 750 watts CW for 2  minute into a (big old Bird Termaline) dummy load produced a rise in the exit air to 36.7 C ,  a rise of 5.7 C degrees. I have no idea if this is good or bad but it gives a data point to evaluate the future fans against.

Check back in a month and I will report on my first substitute fan

Finally the inability of many respondents to follow the instructions in the original email just underscored my assertion that as hams many of us have ADD disproportionately so from the rest of society. I know I do 8^)


-----Izvorno sporočilo----- From: Artek Manuals
Sent: Thursday, April 11, 2019 1:10 AM
Subject: [Amps] TL-922 FAN REPLACEMENT

OK I searched the archives and though the question was asked a couple of
times over the last two decades I did not see  a direct answer to this
question and what little info I did find is almost 10 years old.

My 35 year old TL-922 will likely need a fan in the not too distant
future, the original is  nosier than I remember it ( been in the box for
5 years). and as we TL-922 owners know there are no longer ( as near as
I can find)  any genuine factory replacement parts for this beast.

The voltage and the dimensions fro the fan are given known or easily
measured items but what I have not been able to find is what the
specified CFM rating or RPM specs for the are. Does anyone know the CFM
for the original fan and/or has anyone found a drop in replacement in
recent times from the likes of Mouser or Granger, etc. ?

Just to keep this thread focused ( I think as I read the archives that
as ham a required personality trait is to have Attention Deficit
Disorder (ADD) ...I know I qualify) .....I AM NOT INTERESTED in
modifying the unit for a 12V fan or a squirrel cage, etc... I am looking
for a DROP IN REPLACEMENT for the ORIGINAL FAN. My fan still has a label
on that says "CENTAUR CT3D55F 7.5 watts". So far a USA google search has
not produced anything useful  near apparent possible replacements all
seem to draw 2 to 3 times the wattage (18-25w vs 7.5w) . I have not
looked at the circuit to decide if that is a problem but I suspect not

tnxs in advance


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