Voltage Regulator replacement

jmk wrote:

General statement: The Zeftronics unit is more accurate and more
reliable... and cheaper. In general, replacing the old unit (rather
than repair) makes a lot of sense.

Specific: However, some aircraft will experience electrical noise
problems in the avionics after replacement. The digital Zeftronics
puts out continuous broadband RF (as opposed to the old mechanical
units that put out various pops and clicks at random times). A lot of
older Piper's especially tend to have the wiring for the VR (up under
the dash) bundled with antenna wires and power lines to the avionics.
The result is a "frying bacon" sound on the ADF on the lower bands -
especially when tuned to a weak NDB. [The needle will also probably
track somewhere well OFF the station.]

I have had exactly the opposite experience. It is easier to suppress an
electronic regulator than it was to suppress the mechanical
regulator...

ADF (and Loran, remember those?) operate at low-rf frequencies between
100Khz and 500Khz. The "frying bacon" noise that effects these is
usually generated by arcing as the brushes jump across the segmented
commutator in a generator, or arcing as the brushes rub on the
slip-rings in an alternator. This happens regardless if the regulator
is mechanical, electronic or is not there at all...

Preventing the brush RFI from radiating to the ADF/Loran is
accomplished by putting a RFI suppression filter (usually just a
coaxial HyPass capacitor) on the output terminal of the gen/alt.
http://www.lonestaraviation.com/prod...tor%20Filt er
shows such a capacitor. BTW, contrary to what Lonestar claims, putting
such a filter on a gen/alt does nothing to cure alternator whine in
aircraft audio/intercom systems; only in "bypassing" RFI which would
otherwise radiate from the gen/alt and its wiring to the ADF or Loran
antenna. Also note that if the aircraft doesn't have an ADF or Loran,
then a filter is not even necessary, because the gen/alt brush hash
doesn't effect VHF/UHF/GPS receivers... Putting a filter between the
gen/alt and the aircraft electrical bus is not without consequence,
see:
http://www.ntsb.gov/ntsb/brief2.asp?...FA284& akey=1

Shielding the Field wire running between the regulator and the gen/alt
is usually sufficient to prevent radiation off the field wire. It
matters not if the reg is mechanical or electronic.

mikem wrote:
I have had exactly the opposite experience. It is easier to suppress an
electronic regulator than it was to suppress the mechanical
regulator...

ADF (and Loran, remember those?) operate at low-rf frequencies between
100Khz and 500Khz. The "frying bacon" noise that effects these is
usually generated by arcing as the brushes jump across the segmented
commutator in a generator, or arcing as the brushes rub on the
slip-rings in an alternator. This happens regardless if the regulator
is mechanical, electronic or is not there at all...

I don't think we actually disagree. First off, the
alternator/generator noise is independent of the regulator... If it's
arcing and sparking, then that needs to be addressed regardless.

Second, the mechanical regulator does put out higher amplitude "spikes"
- but they tend to have less power in the higher frequencies than the
digital regulator, and they are MUCH MUCH less frequent. [Basically,
the mechanical regulator only "adjusts" in a few discrete quantum -
whereas the digital unit is constantly switching.] The result is that
the pops and clicks from the mechanical regulator don't tend to
interfere with the ADF and Loran, whereas the higher constant noise
ground floor from the digital unit does.

None of this matters if the regulator has proper grounding and
shielding, and minimal care is made to not run sensitive antenna wiring
and radio power/audio lines bundled with regulator wiring... but in
older planes with mechanical regulators they *could* (and hence *did*)
get away with it.

jmk

jmk wrote:
mikem wrote:

Here's an interesting story for you guys to ponder... Years ago, some time after
I installed my Stormscope (and with a fairly new alternator), the anal retentive
electrical engineer in me decided to get one of those solid state Zeftronics
voltage regulators. It created a phantom storm on the Stormscope. I checked
all the grounding, etc, and tinkered with it for a few days, then I re-
installed my mechanical regulator. It's been fine ever since. I still have
that solid state regulator around somewhere. I'm going to try it again, when
I get a chance.

--- Jay


--

Jay Masino "Home is where the critters are"
http://www.JayMasino.com
http://www.OceanCityAirport.com
http://www.oc-Adolfos.com

Jay Masino wrote:
jmk wrote:
mikem wrote:

Here's an interesting story for you guys to ponder... Years ago, some time after
I installed my Stormscope (and with a fairly new alternator), the anal retentive
electrical engineer in me decided to get one of those solid state Zeftronics
voltage regulators. It created a phantom storm on the Stormscope. I checked
all the grounding, etc, and tinkered with it for a few days, then I re-
installed my mechanical regulator. It's been fine ever since. I still have
that solid state regulator around somewhere. I'm going to try it again, when
I get a chance.

Hi Jay, your experience with the solid-state regulator supports jmk's
thesis, ie that the mechanical regulator switches infrequently, and
generates less interference to your Stormscope than the Zeftronics
regulator, which switches on/off at a much higher rate.
I recently experimented with a solid-state regulator which switched at
about 20 to 40Hz.
I also recently tested FAA-PMAed solid-state "linear" regulator, which
doesn't switch at all. It is a class A amplifier which smoothly changes
the alternator's field current from zero to full-on (about 3A). Maybe
you should get one of those to keep your Stormscope happy.

mikem wrote:
I also recently tested FAA-PMAed solid-state "linear" regulator, which
doesn't switch at all. It is a class A amplifier which smoothly changes
the alternator's field current from zero to full-on (about 3A). Maybe
you should get one of those to keep your Stormscope happy.

What's the brand name?

--- Jay


--

Jay Masino "Home is where my critters are"
http://www.JayMasino.com
http://www.OceanCityAirport.com
http://www.oc-Adolfos.com

Jay Masino wrote:

What's the brand name?

It was a Lamar. I didn't write down the model number. It was for a 14V
aircraft, probably a Piper, meaning that the regulator sinks the field
current.

mikem wrote:
Jay Masino wrote:


What's the brand name?


It was a Lamar. I didn't write down the model number. It was for a 14V
aircraft, probably a Piper, meaning that the regulator sinks the field
current.

Piper electrical systems source the field current. The other side of
the field winding is connected to ground.

mikem wrote:
The digital Zeftronics
puts out continuous broadband RF (as opposed to the old mechanical
units that put out various pops and clicks at random times

The mechanical regulator operates like a buzzer. I have a
couple of sim setups here I use to teach the systems, and in a dark
room with the alternator operating you can see the small but constant
arcing between the regulator contact points. A capacitor across field
and ground kills most of the noise. The inductance of the field winding
and the resistors in the regulator maintain a semblance of constant
current flow even thought the points are bouncing, and the capacitor
reduces the arcing that makes noise and burns the contacts. Works
pretty well, even though it's primitive. I do like the constant-current
regulator idea, though failure is more likely to be instant and without
warning. Worn mechanical regulators will start dropping the output
voltage or might stick occasionally.

Dan