[amsat-bb] Elevation meter Rotor YAESU G-5500 stopped working

Norm n3ykf normanlizeth at gmail.com
Tue Jul 18 23:47:41 UTC 2017


Take EXTREME CARE working on equipment that has power applied.

You'll need a copy of the schematic. Preferably the one that came with
the controller/rotator. There are at least two different power op-amp
power supply layouts. One with a pass transistor and zener diodes, the
other a 75L10 regulator.

Unplug the control box.

Remove the top cover. Remove the front two screws from the bottom
cover. This will let the face (meters, circuit board and switches)
free. (still wired to the rest)

Get two books. Turn the front face down on top of the books, switches
between the books. (to allow the assembly to sit level and not
press/break the switches)


Q4 is one half of a 4558 op amp pair(two on one chip, the other runs
AZ output for the aux jack).

Find Q4.

You're mission is to check the various components making up the drive
circuit for the EL meter for trouble.

Could be:

Shorted capacitor

Open diode

Short or open via other means.


Use an Ohmmeter to look for capacitors that aren't open (Should look
close to it, at least the values in the circut. Electrolytics are a
different story...) Look for open diodes. Meter anything reasonably
accessable, starting from the wiper on VR2 on the back panel. Some
things are best looked at with respect to ground, others point to
point reading the components in between.


This part of the test requires making power on voltage measurements.
Here be dragons, or a trip to your eternal reward!!!

 Locate L2 and L4. Those components (each in their seperate circuit)
form the power supplies (rails) for the EL op amp. See C1 (the voltage
output) next to L2? C2 likewise next to L4?

Check the pins 8(C1) with respect to ground and 4(C2) of Q4. These are
the power supply rails (should be +/- 12 volts or so).

Before plugging it in to test, make sure no bare wires are touching
things they should not be.

Plug it in (you did leave the power switch on, didn't you??). Test

Have fun and don't break anything. A fire here is a failure.

Norm n3ykf

On Tue, Jul 18, 2017 at 5:56 PM, Albert van Deursen <avdeur at home.nl> wrote:
> Hi all,
> All of a sudden the elevation meter stopped working of my Yaesu G-5500 rotor
> controller unit .
> No issue with the AZ meter. Rotor itself keeps on steering / working
> without any problem in EL &AZ (via interface EA4TX ARS-USB) so all still
> working fine (fortunately !)  for satellite work.
> Looks like a component failure in the controller unit  or the meter itself ?
> A physical check (opening the controller unit) didn't show any anomaly.
> Being a not too tech ham was wondering if any of you Yaesu rotor users had
> seen this problem before / around ?
> Possibly anyone to hint/ indicate at a quick check in the schematic wire
> diagram to where to start looking for this failure ?
> Thanks beforehand for yr appreciated advice
> 73
> Albert
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