Greetings folks

Has anyone yet got to the bottom of the StagePass300 intermittent sound
problem which seems to be endemic with the units these days.

Sound cuts out intermittently, although the leds continue showing a
signal which returns if the unit is switched off and on again. There
doesn't seem to be a mechanical cause such as dry joints etc. as tapping
the unit makes no difference. It seems to be possibly a problem with the
protection circuits.

Ron

Ron wrote in message
...
Greetings folks

Has anyone yet got to the bottom of the StagePass300 intermittent sound
problem which seems to be endemic with the units these days.

Sound cuts out intermittently, although the leds continue showing a
signal which returns if the unit is switched off and on again. There
doesn't seem to be a mechanical cause such as dry joints etc. as tapping
the unit makes no difference. It seems to be possibly a problem with the
protection circuits.

Ron


I've only ever seen blown channels. Beware antiphase outputs . Increase the
fan apertures while in there. Schematic as .rar probably on eservice.com ,
opens to
Yamaha-Stagepas300 pwrmix.part1
then pdf
I would drill open some of those tiny vent holes and open up the outlet side
of the "main " fan and see how it fares after that

On 04/12/2011 13:13, N_Cook wrote:
wrote in message
...
Greetings folks

Has anyone yet got to the bottom of the StagePass300 intermittent sound
problem which seems to be endemic with the units these days.

Sound cuts out intermittently, although the leds continue showing a
signal which returns if the unit is switched off and on again. There
doesn't seem to be a mechanical cause such as dry joints etc. as tapping
the unit makes no difference. It seems to be possibly a problem with the
protection circuits.

Ron


I've only ever seen blown channels. Beware antiphase outputs . Increase the
fan apertures while in there. Schematic as .rar probably on eservice.com ,
opens to
Yamaha-Stagepas300 pwrmix.part1
then pdf
I would drill open some of those tiny vent holes and open up the outlet side
of the "main " fan and see how it fares after that


It's not a heat issue, these units can fail on switch on or after any
indeterminate period of time, sometimes they don't fail at all for weeks
then fail several times in one gig.

Yamaha are quite aware that there is a problem yet don't seem to want to
share.

Blown channels are often caused by using metal bodied right angle jacks
in the mixer unit. If two plug bodies touch, or one touches the metal
handle it shorts out one of the amps.

Ron

Ron wrote in message
...
On 04/12/2011 13:13, N_Cook wrote:
wrote in message
...
Greetings folks

Has anyone yet got to the bottom of the StagePass300 intermittent sound
problem which seems to be endemic with the units these days.

Sound cuts out intermittently, although the leds continue showing a
signal which returns if the unit is switched off and on again. There
doesn't seem to be a mechanical cause such as dry joints etc. as
tapping
the unit makes no difference. It seems to be possibly a problem with
the
protection circuits.

Ron


I've only ever seen blown channels. Beware antiphase outputs . Increase
the
fan apertures while in there. Schematic as .rar probably on eservice.com
,
opens to
Yamaha-Stagepas300 pwrmix.part1
then pdf
I would drill open some of those tiny vent holes and open up the outlet
side
of the "main " fan and see how it fares after that


It's not a heat issue, these units can fail on switch on or after any
indeterminate period of time, sometimes they don't fail at all for weeks
then fail several times in one gig.

Yamaha are quite aware that there is a problem yet don't seem to want to
share.

Blown channels are often caused by using metal bodied right angle jacks
in the mixer unit. If two plug bodies touch, or one touches the metal
handle it shorts out one of the amps.

Ron



You would think Y would put some clear plastic sleeving over that nearby
handle, but I suppose its absence is a money earner
Someone phoned up 2 weeks ago for me to repair one where he had done that
with extension speakers, a snare drum brush bridging the 2 metal barrels of
the speaker lead plugs. Who in they're right mind would think that one
connector
barrel was at earth and the other is hot ?
Hopefully he's chucked it now .
Do you know of a forum/thread discussing that "protection" drop-out issue

Yamaha was about the first to adopt PbF , 2001 IIRC, so all Stagepas will
likely be PbF

Is it always preceded by a pop , ala
http://recording.org/controllers-aud...17-yamaha-stag
epas-300-problems.html

Then genuine or false protection issue ? pops due to protection cutting in
or preceeding the protection ?
Ignoring the internal to ps protection . Both the outputs are monitored for
protection and only the +rail , presumably an advantage of antiphase
operation. If no PbF issues and no blown amps then I suppose a stopgap
measure would be to downgrade the output end pick-offs by a half or so,
until a fully known cause is found

Assuming you have a working amp , is there an o/p pop if you trigger the 802
opto into protect mode?

On 04/12/2011 19:13, N_Cook wrote:
Assuming you have a working amp , is there an o/p pop if you trigger the 802
opto into protect mode?




I do own a StagePas myself, which has so far not exhibited the failure.
I`m not going to go poking around in it just for the sake of it.

I hear of faulty StagePas units all the time, I direct them to a local
Yamaha repair agent, but it would be nice to know what causes the units
to fail

Ron wrote in message
...
On 04/12/2011 19:13, N_Cook wrote:
Assuming you have a working amp , is there an o/p pop if you trigger the
802
opto into protect mode?




I do own a StagePas myself, which has so far not exhibited the failure.
I`m not going to go poking around in it just for the sake of it.

I hear of faulty StagePas units all the time, I direct them to a local
Yamaha repair agent, but it would be nice to know what causes the units
to fail


Especially with PbF inside, if it ain't broke, don't poke.

This is one of my repair briefs that may well be consistent with your query
symptoms, causation would seem to be PbF or electrolytic intermittent punch
through


intermittent then no left channel (no pan control on
this amp so L-R a bit specious), 150W per channel
in the blurb. Speakers measure 5.6 ohm so
probably 8 ohm.
Not possible to play around with it without disassembling as, all wrapped
inside one another.
Marked all the bits of celluloid and sub-assemblies before disassembling.
No obvious solder problems or wobbly bits under illuminated mag glass.
The power board with 2 fans is confusing because what looks like 2 channel
power amp farthest from the mains inlet filter chokes is a very distributed
SMPS, split into 2, especially with a thermistor on a vaned heatsink with a
7 pin TO220 device either side, that look like TDA... monolithic audio o/p
blocks.
But those devices are TOP249YN smps drivers.
The compact lump nearest the mains inlet, that looks like a compact SMPS,
contains 4 TO220 devices , ST P14NF12FP 120V 14A mosfets.
Generally i would say this was well constructed except for the conical
greyish silver solder points. Perhaps 1Kg of the overall 2.5Kg is the weight
of the thick steel top fascia plate and the robust black enclosure box of
composite/plastic/rubber or whatever thick and dense formulation.
One potential problem, is all the pots are pcb mount only with
no bush nuts to that nice steel fascia, i've checked the dual master one
with DVM but seems ok.
I don't know what the electrical/electronic term is but in nuclear power -
the "void coefficient " could be a problem. 2 fans , 1 1.5 inch and the
other 2 inch . If either of those stopped with all that power consumption in
a small space , I wonder what the result would be. Hopefully the thermistor
would initiate a shut-down procedure.
Because of the coil blocking removal of the bolt
through each pa heatsink. To remove the mosfets desolder the nut
side one, slackening off
the bolt enough to de-solder the heatsink and then remove
the other mosfet. My replacement were not insulated so
the mounting hole through the heatsink needed enlarging to
take a full depth insulating bush as well as mica.
Class D, but not unipolar design, and 2
"channels" of SMPS for + &-
2 neatly shorted D-S-G mosfets and 2 neatly o/c 0.056 ohm wide SM resistors
leading to each of the o/p filter electrolytics, no overheating, charring or
burning anywhere.
So assuming no leads to speaker or speaker problems what would cause this ?
I had previously desoldered one of the o/p electrolytics on the other more
accessible board to try and read the ident of the obscured mosfets and that
cap presumably only had marginal soldered contact via junk lead-free solder,
could that be a cause? the 2 off per channel 50V, 470uF HF filter caps
across the output.
http://www.diversed.fsnet.co.uk/solder.jpg
Here is a pic I took of what was probably tin pest.
Ignore the top pic as just a control showing normal silvery appearance of
pins after desoldering.
The black cap, the top pin could be pulled out and the bottom one needed
desoldering. It is just about possible to see the all grey dusty covering to
the top pin. So that 100 percent tin layer eventually turns to the grey form
, expanding in the process. So like a weed growing through concrete it
forces the solder apart as well as in itself being non-condusctive.
The solder joints on the caps and elsewhere
otherwise looked normal, only this surface layer tinning of the pin had
transformed to grey.
Located down to one of the power amps, permanent out rather than
intermittant now, nothing found twizzling. Both have indirect edge
connector pairs . It
would be nice to swap them over because the duff one is not very accessible
without making a pair of extenders, but probably not advisable,
as maybe not identical, the feeds are different.
With maybe 250KHz on these amps in operation I'm loathe to put a scope
around the mosfets and will try and diagnose cold.
find space on or off both pa to replace the 50V 470uF
pairs with something higher than 50V. They are part of the LC LP filter
straight across the output via the o/c Rs. As there is nothing wrong with
the speakers or leads then internal punch across these downstream of mosfet
electrolytics (test to 60V ok) is likely reason for blowing the 0.056 ohm
resistors on the outputs and then blown mosfets.

That brief was from before I had a schematic for the 300 or the 500. PA
component level schematic with similar D class in the 500 manual.
The 470uF cap is not on the audio o/p filter but must have been one of the
main DC rails. What effect would intermittant non electrical contact of one
of those , due to tinpest, have on functioning of the amp when there is
plenty of capacitance at the ps ?

On 04/12/2011 21:19, N_Cook wrote:
This is one of my repair briefs that may well be consistent with your query
symptoms, causation would seem to be PbF or electrolytic intermittent punch
through


Well that's an actual component failure, the fault I`m on about is
intermittent and very common. It doesn't seem to be dry joint or heat
related, sometimes they come on then go off, sometimes they fail to
produce sound even tho the meters show a signal.

Switching of and on again generally restores operation. It's become a
common fault and a shame because the units are otherwise very useful for
small gigs and if not for this lack of trustworthiness would be
lucrative for hire purposes.

I imagine that the typical case of output device failure might be caused
by the unit being thrashed beyond its design limits (as so often happens)

Ron

Ron wrote in message
...
On 04/12/2011 21:19, N_Cook wrote:
This is one of my repair briefs that may well be consistent with your
query
symptoms, causation would seem to be PbF or electrolytic intermittent
punch
through


Well that's an actual component failure, the fault I`m on about is
intermittent and very common. It doesn't seem to be dry joint or heat
related, sometimes they come on then go off, sometimes they fail to
produce sound even tho the meters show a signal.

Switching of and on again generally restores operation. It's become a
common fault and a shame because the units are otherwise very useful for
small gigs and if not for this lack of trustworthiness would be
lucrative for hire purposes.

I imagine that the typical case of output device failure might be caused
by the unit being thrashed beyond its design limits (as so often happens)

Ron

I think I've repaired 3 different 300 Stagepas. Each one dealt with the
blown amp and while in there, drilled open those tiny inlet holes and
propped open the outlet vent. None of them have returned so may or may not
be relevant. One of them the smaller fan had stopped functioning so probably
contributory. One of them the owner had noticed the outlet air was hotter
than usual (same set and useage as normal),
Later versions had more holes in the outlet vent which suggests a heat flow
problem , then after that perhaps PbF problems. I'll have a look at the
thermistor/thermal protection area of the schematic some time

Ron wrote in message
...
On 04/12/2011 21:19, N_Cook wrote:
This is one of my repair briefs that may well be consistent with your
query
symptoms, causation would seem to be PbF or electrolytic intermittent
punch
through


Well that's an actual component failure, the fault I`m on about is
intermittent and very common. It doesn't seem to be dry joint or heat
related, sometimes they come on then go off, sometimes they fail to
produce sound even tho the meters show a signal.

Switching of and on again generally restores operation. It's become a
common fault and a shame because the units are otherwise very useful for
small gigs and if not for this lack of trustworthiness would be
lucrative for hire purposes.

I imagine that the typical case of output device failure might be caused
by the unit being thrashed beyond its design limits (as so often happens)

Ron

I would think thermistor TH810, Q801, Q805 and PS PWM controller IC804 are
just doing their job which is fine when amp is new but not when a bit of
dust and grime accumulates , component variation etc.

This is my earlier observation about the outlet fan , first air is directed
at a wall 3/8 inch from its blade, then forced through a very small grill
http://www.luthermusic.com/images/pr...1-original.jpg
The outlet grill , on this presumably later version, is under the master
control in the pic orientation.
This pic shows about twice the number of slots as the one I have here, so in
recent years they have punched more slots. This one is just the slots in the
black area of that pic, not the continuation towards the master control. I'm
not in the position to retrofit slots, but can bend and lift that corner
with a
standoff and elongated fixing hole.
The inlet holes are a line of 1.8 mm holes , directly under the top handle
in
that pic, so obscured."

On 05/12/2011 14:08, N_Cook wrote:
wrote in message
...
On 04/12/2011 21:19, N_Cook wrote:
This is one of my repair briefs that may well be consistent with your
query
symptoms, causation would seem to be PbF or electrolytic intermittent
punch
through


Well that's an actual component failure, the fault I`m on about is
intermittent and very common. It doesn't seem to be dry joint or heat
related, sometimes they come on then go off, sometimes they fail to
produce sound even tho the meters show a signal.

Switching of and on again generally restores operation. It's become a
common fault and a shame because the units are otherwise very useful for
small gigs and if not for this lack of trustworthiness would be
lucrative for hire purposes.

I imagine that the typical case of output device failure might be caused
by the unit being thrashed beyond its design limits (as so often happens)

Ron

I would think thermistor TH810, Q801, Q805 and PS PWM controller IC804 are
just doing their job which is fine when amp is new but not when a bit of
dust and grime accumulates , component variation etc.

This is my earlier observation about the outlet fan , first air is directed
at a wall 3/8 inch from its blade, then forced through a very small grill
http://www.luthermusic.com/images/pr...1-original.jpg
The outlet grill , on this presumably later version, is under the master
control in the pic orientation.
This pic shows about twice the number of slots as the one I have here, so in
recent years they have punched more slots. This one is just the slots in the
black area of that pic, not the continuation towards the master control. I'm
not in the position to retrofit slots, but can bend and lift that corner
with a
standoff and elongated fixing hole.
The inlet holes are a line of 1.8 mm holes , directly under the top handle
in
that pic, so obscured."


Mine doesn't have the slots in the lighter grey area, but the slots in
the dark area are longer than those in the pic and follow the lower edge
of the tapered grey screen print.

Any road up, it's not a thermal problem as it can happen on switch on.

Ron

None if the ones I've seen for repair have been used inside the speaker ,
excessive vibration causing your symptom from being used as powered speaker?
Any amp hiss from the speakers when the amp dies?
As far as I can see all the protection measures kill all power rails so no
long term continuing of any level LEDs. So what is common to both ch in the
preA ?
As there is no stereo controls with this amp , presumably the fault is
between where the inputs are commoned and where they are divided into the 2
PAs

I have seen the following problems occuring on StagePas 300 :

People change cables w. "standard issue 10m cables, 6,3mm Jack ends" because they need longer cables. This won't ever work; Most industry standard cables having 6.3mm jacks are meant for guitars and other relevant instruments,Conductors inside are thin and coaxial having enormous capacitance and very large resistance.

You need to order your technician or build yourself a pair of REAL Loudspeaker (twin-lead and sufficient thickness for 150W power handling) cables having mono 6,3mm jacks end to end. You won't burn your amp that way.

also -

I have noticed a problem w. my set that showed after 15 mins of operation the following problem:

Sound cut off, replaced with low frequency hum (thus amplifier is still active), Limiter led (red on bar graph) stuck ON, Turning it off and after a few minutes back on solves the problem.

That problem was traced down to an 7915 voltage stabilizer on the main preamp/psu board, having an output of -8V instead of -15 on normal operation and after 15 minutes that voltage fell to 0 volts. Replacing the 7915 with another fixes the problem (solid -15V on output). My Stagepas 300 has an 7915 with plastic casing (too large heat resistanse to heatsink, I guess, and a semiconductor fatigue resulted to that problem). It looks that using a metallic 7915 is possible as the heatsink is electrically isolated from the rest of the circuit on my revision, if in doubt use some mica - plastic ring isolator there.

Cheers.