Pressing the power button gets relay click and power LED flash (on volume
control) but all shuts down immediately.

Looked for infamous "pink cap" on "sub power supply" (there is one) and
replaced but no change in symptoms.

Jumpered the relay contacts and using a Variac ran voltage up full (while
watching main transformer secondary voltages): all seems normal but still no
signs of life. Transformer voltages are as expected (2 pairs of windings;
each pair share a common center tap, total: 4 windings, all voltages increase
linearly with increase of primary V). Still no display or control
functionality at all.

Pressing the power button (with jumpered relay and full mains voltage
applied) gets same symptoms.

So far I think I can rule out a shorted output device.

How best to proceed with the troubleshooting?

Ideas?

I have the service manual.

Thanks.

Bob E. wrote in message
...
Pressing the power button gets relay click and power LED flash (on volume
control) but all shuts down immediately.

Looked for infamous "pink cap" on "sub power supply" (there is one) and
replaced but no change in symptoms.

Jumpered the relay contacts and using a Variac ran voltage up full (while
watching main transformer secondary voltages): all seems normal but still
no
signs of life. Transformer voltages are as expected (2 pairs of windings;
each pair share a common center tap, total: 4 windings, all voltages
increase
linearly with increase of primary V). Still no display or control
functionality at all.

Pressing the power button (with jumpered relay and full mains voltage
applied) gets same symptoms.

So far I think I can rule out a shorted output device.

How best to proceed with the troubleshooting?

Ideas?

I have the service manual.

Thanks.


voltages increase linearly and match + and - ?
Any SIL protection device eg (uP)C1237 , get the data on it and work around
its inputs and outputs , could be IC failure or genuine bad/erroneous bad
input

N_Cook wrote in message
...
Bob E. wrote in message
...
Pressing the power button gets relay click and power LED flash (on
volume
control) but all shuts down immediately.

Looked for infamous "pink cap" on "sub power supply" (there is one) and
replaced but no change in symptoms.

Jumpered the relay contacts and using a Variac ran voltage up full
(while
watching main transformer secondary voltages): all seems normal but
still
no
signs of life. Transformer voltages are as expected (2 pairs of
windings;
each pair share a common center tap, total: 4 windings, all voltages
increase
linearly with increase of primary V). Still no display or control
functionality at all.

Pressing the power button (with jumpered relay and full mains voltage
applied) gets same symptoms.

So far I think I can rule out a shorted output device.

How best to proceed with the troubleshooting?

Ideas?

I have the service manual.

Thanks.


voltages increase linearly and match + and - ?
Any SIL protection device eg (uP)C1237 , get the data on it and work
around
its inputs and outputs , could be IC failure or genuine bad/erroneous bad
input




If microcontroller based, then similar sort of skirting around process, but
not so easy working out the relevant inputs/outputs

"Bob E." wrote in message
...
Pressing the power button gets relay click and power LED flash (on volume
control) but all shuts down immediately.

Looked for infamous "pink cap" on "sub power supply" (there is one) and
replaced but no change in symptoms.

Jumpered the relay contacts and using a Variac ran voltage up full (while
watching main transformer secondary voltages): all seems normal but still
no
signs of life. Transformer voltages are as expected (2 pairs of windings;
each pair share a common center tap, total: 4 windings, all voltages
increase
linearly with increase of primary V). Still no display or control
functionality at all.

Pressing the power button (with jumpered relay and full mains voltage
applied) gets same symptoms.

So far I think I can rule out a shorted output device.

How best to proceed with the troubleshooting?

Ideas?

I have the service manual.

Thanks.



If that's one of the ones with the little sub PSU, there's also a 4013 chip
on there that is a good place to monitor the supply volts. Those volts feed
another little circuit on the board that generates the reset pulse for the
system control micro. Unless that pulse is sharp and of sufficient
amplitude, the micro never boots. When you checked for the bad cap that's
notorious in those models, are you absolutely definitely sure that you
picked the right cap ? I only say that because there are several slightly
different versions of that sub board, and on more than one occasion, I've
just gone for the obvious looking one without checking, and it has in fact
been another one entirely that has been the bad one. You can usually be
pretty sure that it is the cap, if you check the supply volts to the IC. Use
its pin 7 as the ground, and then check pin 14. Should be about 8 volts.

I've just had a squint at the schems for a couple of models from the same
series, and the cap is called C4 on one of them, and C405 on another. I also
have a note on the diagram saying that it's called C3015 on yet another
version.

A long time ago, I did have a few of these big Yammy AV amps that had faulty
5 volt regs in them. They are located on a heatsink running across the front
of the amp, and facing the back as I recall. They are 'oddballs' I seem to
remember, with 4 or 5 pins on them, and the faulty ones I had, produced low
output, rather than none at all. I'm sure Mark Z will be able to confirm all
of this, as he has worked on them a lot.

Arfa

I removed the temporary jumper from across the relay contacts. And:

I've just had a squint at the schems for a couple of models from the same
series, and the cap is called C4 on one of them, and C405 on another. I also
have a note on the diagram saying that it's called C3015 on yet another
version.
Arfa

Let's talk function and not label... The obvious "pink cap" (0.01 uF/50v) is
across the ~12v secondary of the small transformer near the AC input. It is
an AC filter cap. I measured 4 vac across it. Replaced with a mylar and it's
a reasonable 12 v now.

Here's that little PCB:

http://www.tinyuploads.com/images/8O0dYH.jpg

I replaced C312.

Any other suggestions?

The supercap (0.047F / 5.5v) on one of the function PCBs is obviously leaking
and corroded. I removed it (it caused no further damage to the PCB) and will
get a replacement today. Shouldn't the unit boot if this was the cause of
pulling down the 5v line (I'm guessing at this -- haven't found it in the
schematic so don't know what, exactly, it's hooked to...)?

Symptoms remain unchanged with new filter cap and removed super cap.

Ideas welcome.

Thanks.

What do the extra labels mean next to many of the components on the
schematic?

Next to a transistor is its label "Q302" and next to that is "s10".

Just on this small board there are these extra labels from "s10" through
"s37".

http://www.tinyuploads.com/images/8O0dYH.jpg

What is this "s" designation for?

Thanks.

Bob E. wrote:
Just on this small board there are these extra labels from "s10"
through "s37".

http://www.tinyuploads.com/images/8O0dYH.jpg

What is this "s" designation for?

Looking at the schematic, it might indicate a part whose value changes
(or is/is not installed) based on which version of the board is being
used. Note that parts with the "s" labels don't have a specific value
listed - compare C308, marked just "s14", with C307, marked "1000/25".
Also note that the fuses and transformer all have "s" labels; these
parts often are different for a power supply with 120 V vs 240 V input.
Also, it doesn't make sense to have J301 and Q302 installed at the same
time; J301 would just bypass Q302 in that case. Both J301 and Q302 have
"s" numbers. Somewhere on the schematic or in the manual there should
be a table of "s" number to part number based on the version of the
board.

To your original problem, have you tried unplugging CB304 and measuring
the voltage across +MB and G, or across C307? Those should be pretty
close to 12.5 V DC. If you have a scope, also measure the same place
for AC ripple; if you don't, put your multimeter on AC and measure the
same place - you should have much less than 1 V AC. If there is a lot
of ripple, check C307 and C308.

Matt Roberds

"Bob E." wrote in message
...
I removed the temporary jumper from across the relay contacts. And:

I've just had a squint at the schems for a couple of models from the same
series, and the cap is called C4 on one of them, and C405 on another. I
also
have a note on the diagram saying that it's called C3015 on yet another
version.
Arfa

Let's talk function and not label... The obvious "pink cap" (0.01 uF/50v)
is
across the ~12v secondary of the small transformer near the AC input. It
is
an AC filter cap. I measured 4 vac across it. Replaced with a mylar and
it's
a reasonable 12 v now.

Here's that little PCB:

http://www.tinyuploads.com/images/8O0dYH.jpg

I replaced C312.

Any other suggestions?

The supercap (0.047F / 5.5v) on one of the function PCBs is obviously
leaking
and corroded. I removed it (it caused no further damage to the PCB) and
will
get a replacement today. Shouldn't the unit boot if this was the cause of
pulling down the 5v line (I'm guessing at this -- haven't found it in the
schematic so don't know what, exactly, it's hooked to...)?

Symptoms remain unchanged with new filter cap and removed super cap.

Ideas welcome.

Thanks.



OK. You can forget everything that I said, looking at that schematic. It's
not the sub pcb that I was expecting. Many of these Yammy AV amps have an
'eco' sub pcb, and there is a polyester cap on them used as a wattless
dropper. It is very common for this cap to lose value, and you then get
symptoms in those amps, very similar to what you are describing. Sorry to
have misled you ...

Arfa

"Bob E." wrote in message
...
Pressing the power button gets relay click and power LED flash (on volume
control) but all shuts down immediately.

Looked for infamous "pink cap" on "sub power supply" (there is one) and
replaced but no change in symptoms.

Jumpered the relay contacts and using a Variac ran voltage up full (while
watching main transformer secondary voltages): all seems normal but still
no
signs of life. Transformer voltages are as expected (2 pairs of windings;
each pair share a common center tap, total: 4 windings, all voltages
increase
linearly with increase of primary V). Still no display or control
functionality at all.

Pressing the power button (with jumpered relay and full mains voltage
applied) gets same symptoms.

So far I think I can rule out a shorted output device.

How best to proceed with the troubleshooting?

Ideas?

I have the service manual.

Thanks.



I can try to help. You can email me at:



and reverse labolgcbs to read "sbcglobal"

Mark Z.

Replaced the supercap (0.047F/5.5V), no joy. Same symptoms.

The "+MB" 12v line coming from the "sub power supply" board is 14.2v with
very little (0.05V) ripple.

The "switch on" signal (PRY) that runs the mains relay comes from the main
controller, IC1 (HD643361-A49P).

I jumpered manually the PRY signal from the 12v (actually 14) to the PRY
line. This gives the same symptom as pressing the power button: mains relay
clicks, volume control LED lights and goes out.

Not being to check DC voltages at the pins on this IC (we're not powered on
yet) the schematic does call out 2 scope checks to do on IC1: the oscillator
signal for; and the RESET signal which triggers when the mains input cable is
connected (and, curiously, NOT when the power switch is pushed). I'll check
these tomorrow.

Thanks.

Schematic of IC1 and "power down detect" circuit is he

http://www.tinyuploads.com/images/AtpXB5.jpg

Bob E. wrote:

Replaced the supercap (0.047F/5.5V), no joy. Same symptoms.

The "+MB" 12v line coming from the "sub power supply" board is 14.2v with
very little (0.05V) ripple.

The "switch on" signal (PRY) that runs the mains relay comes from the main
controller, IC1 (HD643361-A49P).

I jumpered manually the PRY signal from the 12v (actually 14) to the PRY
line. This gives the same symptom as pressing the power button: mains relay
clicks, volume control LED lights and goes out.

Not being to check DC voltages at the pins on this IC (we're not powered on
yet) the schematic does call out 2 scope checks to do on IC1: the oscillator
signal for; and the RESET signal which triggers when the mains input cable is
connected (and, curiously, NOT when the power switch is pushed). I'll check
these tomorrow.

Thanks.

THis maybe a stupid suggestion but, I've found this many times in sub
micro processor units that get moved, hit, vibrated etc... Have you
check to see if the processor has a xtal and is so, is it operating?

Many times the crystal will break loose from their connections inside,
due to vibration...

Also, I saw another piece of equipment that monitors the elimination of
a florescent display, if no light, no processor. Basically if that part
of the circuit fails, the rest will wait. That makes perfect sense
because you don't want to be operating blindly on some equipment.

Jamie

THis maybe a stupid suggestion but, I've found this many times in sub
micro processor units that get moved, hit, vibrated etc... Have you
check to see if the processor has a xtal and is so, is it operating?
...
James

Not stupid at all. As a matter of fact the Yamaha factory service manual says
that this is one of the first steps to take when diagnosing (I now see after
rereading this section...)

I'll look at that next.

Thanks.