[Amps] FOLLOW UP DATA 0n TL-922 FAN REPLACEMENT

Tue Apr 16 21:06:29 EDT 2019

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^)

Dave
NR1DX

>
> -----Izvorno sporočilo----- From: Artek Manuals
> Sent: Thursday, April 11, 2019 1:10 AM
> To: amps at contesting.com
> 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
> Dave
> NR1DX
> manuals at artekmanuals.com
>
>

-- 
Dave
Manuals at ArtekManuals.com
www.ArtekManuals.com

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