Engenius phones, again, Jeff L...

I'm a victim of circumstance, Jeff.

I _must_ use the Engenius Durafon 4x system because of the wierd physical
topology of a fireworks factory. No other product on the market (that we
can afford) comes close to the features and range it offers.

But, like so many others, I'm having problems that Senao and EnGenius
deny happens to anyone else but us.

EVERY handset we've bought (except the one run over by a truck...<G>) has
failed about four or five months out of warantee. The microphone fails.
Squeezing or twisting the case lightly makes the problem come and go for
a while, then it fails hard.

Obviously, it's a cracked run, broken feedthrough, or SMT component that
breaks under normal handling and battery changing stresses to the case.

Unfortunately, without PCB maps or schematics, and with that damned 5-
layer board, finding a broken run is a fruitless activity.

But they won't acknowlege the problem exists. Seems to me it would be
easier to say, "We'll look into it" or some other pap designed to
satisfy; but no. "You're the only person who's ever had that problem."

FWIW, there is no common factor of use that might explain it. Some
phones are used outdoors, some in the factory buildings, and some in air
conditioned desk service. All fail the same way, at about the same
interval.

They'll all work for another month or two with an external headset, but
that ultimately develops the same symptoms. Then it's rebuild or re-buy
time.

The two we've recently sent in for repairs developed the same problem
less than a month after they came back.

LLoyd

On Thu, 10 Jul 2008 14:55:08 -0500, "Lloyd E. Sponenburgh"
<lloydspinsidemindspring.com> wrote:

>I'm a victim of circumstance, Jeff.

Yeah, that's what they all say.

>I _must_ use the Engenius Durafon 4x system because of the wierd physical
>topology of a fireworks factory. No other product on the market (that we
>can afford) comes close to the features and range it offers.

<http://www.engeniustech.com/telecom/products/Category.aspx?id=7>

Have you considered using two-way (licensed) radios with a phone
patch? My guess(tm) is that most of the communications is between
handsets, which makes commercial radio a viable option.
<http://www.midians.com/pdf/sales_brochures/Interconnect-Brochure.pdf>
Any ham radio repeater controller with a phone patch interface should
also work.

>But, like so many others, I'm having problems that Senao and EnGenius
>deny happens to anyone else but us.

Hmmm.... this is starting to sound familiar.

>EVERY handset we've bought (except the one run over by a truck...<G>) has
>failed about four or five months out of warantee. The microphone fails.
>Squeezing or twisting the case lightly makes the problem come and go for
>a while, then it fails hard.
>
>Obviously, it's a cracked run, broken feedthrough, or SMT component that
>breaks under normal handling and battery changing stresses to the case.
>
>Unfortunately, without PCB maps or schematics, and with that damned 5-
>layer board, finding a broken run is a fruitless activity.

Yep. Welcome to the throw away economy.

>But they won't acknowlege the problem exists. Seems to me it would be
>easier to say, "We'll look into it" or some other pap designed to
>satisfy; but no. "You're the only person who's ever had that problem."

Yep. Sounds like the same run-around I got.

It's really hard to fix things without a schematic. However, a fairly
simple failure, like a loss of microphone audio can be troubleshot or
traced. If you have one handset that still works, it should be fairly
easy to identify the applicable parts and walk down the signal path
with an oscilloscope. In effect, you're generating your own schematic
using reverse engineering.

Incidentally, one vendor (who shall remain anonymous) refused to
supply me with a schematic for troubleshooting an obsolete product. I
was a bit lazy, and announced to the support droid that if I had to go
through the effort of reverse engineering the product, I would either
post or sell the results on the internet. Faced with the prospects of
hanving literally everyone have a copy of the schematic, they faxed
sent me a barely readable schematic. I swear it had been reduced and
run through a fax machine several times before sending it, as it was a
really bad print. However, it was good enough to repair the piece of
junk. I later tried the same ploy with other vendors, all of whom
refused to even acknowledge that they had possession of a schematic.
That's what happens with an outsourced support service, that literally
doesn't care.

>FWIW, there is no common factor of use that might explain it. Some
>phones are used outdoors, some in the factory buildings, and some in air
>conditioned desk service. All fail the same way, at about the same
>interval.

I have a customer that blows up cell phones at an alarming rate. He
goes in and out of refridgerated meat lockers all day long. The phone
can't handle the thermal cycling. I reduced, but not eliminated, the
problem with an insulated phone holster. Have these phones been going
in and out of the sun or cold?

>They'll all work for another month or two with an external headset, but
>that ultimately develops the same symptoms. Then it's rebuild or re-buy
>time.

It may not be the board or the components. It could be the electret
microphone. I've had problems with those losing their charge in
commercial radios. If the headset works, but not the internal mic,
then the mic should be suspected. However, if both fail, then it
might be some common circuitry:
<http://en.wikipedia.org/wiki/Electret_microphone>
<http://www.hosiden.co.jp/web/english/web/products/pdf/e_pg01_kogata.pdf>

>The two we've recently sent in for repairs developed the same problem
>less than a month after they came back.

What did they do to fix them? I'll bet they replaced the mic element.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558 (E-Mail Removed)
# http://802.11junk.com (E-Mail Removed)
# http://www.LearnByDestroying.com AE6KS

Jeff Liebermann <(E-Mail Removed)> fired this volley in
news:(E-Mail Removed):

> I have a customer that blows up cell phones at an alarming rate. He
> goes in and out of refridgerated meat lockers all day long. The phone
> can't handle the thermal cycling. I reduced, but not eliminated, the
> problem with an insulated phone holster. Have these phones been going
> in and out of the sun or cold?
---
> What did they do to fix them? I'll bet they replaced the mic element.
>
>

They never tell you what they "did" (or didn't).

I'm competent and equipped to do everything you suggested, but there
isn't enough time in my whole life to go trouble-shooting crap hardware
just to avoid buying more crap hardware. sigh...

You're right about one thing. We are in Florida. It's HOT and humid
here, and the phones go in and out of AC all the time.

Nonetheless, I'm banking on a mechanical failure of the PCB or an SMT
part. We change batteries in the phones a lot, and it takes a great deal
of squeezing and hard pulling to open the case; Ten or fifteen pounds of
force. It's likely that stress on the hard-mounted board that is busting
something. They didn't grommet the mounting points; so the board twists
with the case.

The mics in the Durafons use a system I haven't encountered, and will
have to study more to understand. The mic looks like a standard electret
element, but has no electrical connection to the board. It's
mechanically pressed against an insulating (checked it) silicone pad
which is pressed against two coaxial rings of pcb land. The interface
appears to be made by varying the capacitance between the rings.

I've worked on a lot of things, but somehow I've missed that method up
til now.

LLoyd


LLoyd

On Fri, 11 Jul 2008 06:34:55 -0500, "Lloyd E. Sponenburgh"
<lloydspinsidemindspring.com> wrote:

>They never tell you what they "did" (or didn't).

Did you ask?

>I'm competent and equipped to do everything you suggested, but there
>isn't enough time in my whole life to go trouble-shooting crap hardware
>just to avoid buying more crap hardware. sigh...

Your decision. I have the same problem but tend to do it anyway, just
to satisfy my own curiosity. Such reverse engineering doens't make me
any money, but I find it interesting.

>You're right about one thing. We are in Florida. It's HOT and humid
>here, and the phones go in and out of AC all the time.

Bingo. The humidity also causes some circuit boards to expand and
contract. It also gets inside the mic elements. Ask around about
cell phone failures.

>Nonetheless, I'm banking on a mechanical failure of the PCB or an SMT
>part.

The first step to solving a problem is to assign the blame. In this
case, that's a fair guess, but lacking in one respect. You have no
direct evidence.

>We change batteries in the phones a lot, and it takes a great deal
>of squeezing and hard pulling to open the case; Ten or fifteen pounds of
>force. It's likely that stress on the hard-mounted board that is busting
>something. They didn't grommet the mounting points; so the board twists
>with the case.

Yech. Also look for cracked components and surface mount solder
joints. Why do you need to juggle batteries?

>The mics in the Durafons use a system I haven't encountered, and will
>have to study more to understand. The mic looks like a standard electret
>element, but has no electrical connection to the board. It's
>mechanically pressed against an insulating (checked it) silicone pad
>which is pressed against two coaxial rings of pcb land. The interface
>appears to be made by varying the capacitance between the rings.

That's commonly used on cordless phones and cell phones. The
concentric rings are the contacts. The ones with external DC bias
have 3 rings. The ones without an internal amplifier have two rings.
The mic fits in a molded hole in the plastic front panel. There's
usually a foam or rubber ring to provide tension. The assembly is
compressed by the board mounting system. The problem with this method
is that condensation from the speakers voice tends to make the
contacts rot. Gold plating is common. Mounting the mic element
directly on the board isn't very useful as the mic element will not
survive reflow soldering.

The electret mic elements aren't totally hermetically sealed and will
also condense water inside, causing the capacitor to discharge. If
you have any old Motorola flip phones floating around, each phone will
have TWO electret elements you can borrow.

>I've worked on a lot of things, but somehow I've missed that method up
>til now.
>
>LLoyd


--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann <(E-Mail Removed)> fired this volley in
news:(E-Mail Removed):

> The first step to solving a problem is to assign the blame. In this
> case, that's a fair guess, but lacking in one respect. You have no
> direct evidence.

Pretty fair indirect evidence, though: torquing the case (board)
temporarily fixes the problem. Even on a "hard-bad" unit, I can
sometimes get the mic to come back on for a second with some brutal
handling.

I'm pretty certain if the electret element had lost its charge, fiddling
wouldn't make the problem come and go.

>
>>We change batteries in the phones a lot, and it takes a great deal
>>of squeezing and hard pulling to open the case; Ten or fifteen pounds
>>of force. It's likely that stress on the hard-mounted board that is
>>busting something. They didn't grommet the mounting points; so the
>>board twists with the case.
>
> Yech. Also look for cracked components and surface mount solder
> joints. Why do you need to juggle batteries?

We work multiple shifts with common phones, and have a lot of talk time
and general broadcasts on most of them. They also run at high power a
lot of the time because of how spread out our facility is.

You've given me a lot of good tips, Jeff; thanks.

Maybe I will take a spare evening I'd have 'wasted' reading, and try to
fix this pile of junk on my desk.

LLoyd