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Thanks Jim, It's a lot easier than installing a new tach.
Dave Leonard
Dave,
Here is the fix for the RMI Tach problem that you are having.
1. Remove R82 (61.9Kohm resistor) on the CPU board. It is located in the
lower right hand corner of the pc board
2. Replace with a resistor of about 34K-36K.
I used a 34.8K as it allowed me to operate up to 7500RPM (as advertised) .
The exact value is not critical as this is in an RC circuit that controls a
one shot that filters the tach signal.
It works by preventing any ringing or spurious pulses from getting through.
You should be able to source the resistor from Radio Shak or any other
electronics outlet.
Another option which was suggested by Ron Mowrer at RMI is to leave the
existing resistor in and solder another resistor of about 86.6K in parallel
with R82, This has the same effect of putting a 36K resistor without having
to remove the existing one.
Either way it will solve your RMI tach problem.
Jim Maher
-----Original Message-----
From: DaveLeonard [SMTP:daveleonard@cox.net]
Sent: Sunday, May 23, 2004 10:03 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Two problems solved, 2 more pop up...
Jim, that is awesome. You are the one who clued me in to the fact that the
tach may not be reading right. I even tried changing the setting to "two
pulses per rev" to see if it might just work with half the value showing on
the display. No good, the half-values still maxed out at 2300 RPM.
Anxiously awaiting your fix, as I really don't want to install a separate
tach.
Thanks a billion.
Dave
-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]On
Behalf Of Jim Maher
Sent: Sunday, May 23, 2004 3:08 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Two problems solved, 2 more pop up...
Dave,
The RMI Tach circuit has a glitch filter which will prevent RPM readings
above about 4500.
On mine I changed a resistor value to allow readings up to 7500 RPM.
It is a simple change.
I don't have the schematic here at home so I cannot tell you how to fix it
until I go to work and review what I did.
I will send you the fix tomorrow.
Jim Maher
-----Original Message-----
From: DaveLeonard [SMTP:daveleonard@cox.net]
Sent: Sunday, May 23, 2004 2:15 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Two problems solved, 2 more pop up...
Snip
New Problem: RMI tach no good. According to my RMI engine monitor I have
about 4300 RPM at 24 MAP. At 29 MAP I still only have about 4500 RPM and at
35 MAP I am still at 4500 RPM static. I dont buy it because it sure sounds
different (faster). So I have to install an accessory Tachometer....
Snip
>> Homepage: http://www.flyrotary.com/
>> Archive: http://lancaironline.net/lists/flyrotary/List.html
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