changed the resistor to 4.7 k -no change-batteries connected ,its reading zero, ,on the output.relative to ground.
but a constant 2.54 volts when i disconnect the negative 9 volt battery..
gonna catch up on a bit of sleep.

thanks Allen will give it a go,

 

i am connecting to the 15 volt rails now.
joe, did you get a delay on the simulator?.
it might need the other RC circuit as well.

cant help thinking this could have been achieved with a 555 and a couple of resistors and caps....oh well.

 

just in case anyones viewing, where is everybody,? in case it comes up again,
at mute voltage below 3.5, mute is on.
above. 3.5 volts mute is turned off . i think.

i take back all i said about livewire, brilliant! set up the whole circuit into a bi colour led,
as i wasnt too sure about the output polarity ,
and its showing as joe stated about 9 volt (,rail voltage less the zener voltage) and with a delay....which is largly produced by the extra rc network at the audio chip, so the original circuit is probably ok, which begs the questiion, what does it do?
stiil puzzled about the standby function, if anyone can help on this, it would be appreciated.

 

i donno if it's what you need

- perhaps you should reference the opamps to positive rail instead ...

 

well i cant believe ive been so stupid,
early on, i cut the mute wire just after the zener, and was still getting speaker pops......
without power, the mute on the chip should be on, and no sound,
that should have suggested to me, that the RC network at the audio chip is getting power from somewhere else.
or that the audio output chip on both speakers are faulty.,

i naturally assumed that what i thought was the delay circuit was at faullt ....a red herring.?

thank you c1139, will have a look after tea.

 

my thinking now is to cut the mute/standbye pins at the audio chip and splice in the
new rc circuit,.bypassing the existing.
could be tricky, or dare i say with half a dozen componants, build a new output amp,
any thoughts or suggestions welcome.

 

thank you c1139, will have a look after tea.

-- ! hei i don't quite get where your delay timer output is (supposed to be) going
-- on your diagram it shows likely the midpoint in between ±Vs that perhaps are charged from positive rail
. . . i don't know your stuff -- i just posted some examples , in a hope these helps you to clear your thinking

you have to be critical -- a large capacitor likely discharges through OpAmp's input - you can't do such in real -
- unless you know such safe for the particular occasion . . . i might've been passed more errors
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? , your stuff works fine . . . in simulator
in you grid you can set the longer delay by mostly increasing the C16 , C17 and/or adjusting threshold point by R24 , R25

 

Doug,

Did you see the Engineering revision B note on the diagram located on page 16 of the pdf? Do you have that revision on the circuit board you are troubleshooting?

 

The Power Up Mute is on page 16 of the diagram. The three circuits Doug is looking at are on two different diagrams. Disregard the items encapsulated by the red rectangles. They represent either a POS/NEG voltage indicator or a typical 10M ohm DMM.

And a video .... The power switch was energized one second after the start.

 

i have decided to take a chance that the existing op amp mute section is ok, and build a new LF output amp circuit, based on the tda7296,
the pins on the hf amp chip are a bit easier to get to, so i can easily cut the mute pin and solder in the mute wire etc,

i would like to express my thanks to all who helped with what turned out to be tricky post,
particularly joe., who gave up his time to help on this,
thanks again
doug

 

Did you confirm that revision B, was accomplished in your speakers?

You can build a simple test circuit to ensure there is a visual indication of the delay at power up. It will take two LEDs (different colors) and one resistor. It's on the schematic in my post #29.

 

joe
you might have saved my life..., i had a quick look for the note yesterday and didnt see anything,
but i ve just looked again before ordering parts, and found it-- my monitors rubbish, and my
eyesight isnt much better,
ive found the resistor on the schematic, its miles away from the mute circuits....

 

the mute circuits are still favourites though, as something is killing audio for many minutes when first switched on,
on both speakers and on both LF and HF,after being stood unpowered for a couple of days, could be something else causing this, but as i mentioned in my previous thread, the mute sections on the amp output board were the most badly affected by the water ingress.

checking that resistor now, .its a miniscule difference though..49.9 to 54.9 are those values even available?
51k plus 3.9k ?

its reading 50 k in circuit.

 

and my
eyesight isnt much better,

trivia https://en.wikipedia.org/wiki/Lutein#Role_in_human_eyes
http://www.centrum.com/centrum-silver-adults-50-plus
the general boosters of your health is sufficient drinking preferreably pure mineral water and fresh fruits vegges
also vitamin c,b-complex and potassium and iodine omega-3
also sufficient physical exercise(, sauna / hot shower improves cappilar blood flow) , good night sleep
also massaging your ears-head and neck - also holding your breath and while redirecting your blood flow to dumb parts of your body !!! you must know how to do this and also know how not to faint if it is about to occur (to not fall over causing damage !!!) - it's however everything you can do by yourself

thouhg i have individually dev. this it might be something muscle yoga i'm not into finding out exactly now . . . a starting point , maybe - https://yogainternational.com/article/view/heal-your-neck-shoulder-pain

now that it came to thought - neck pain killer is strong coffee no or little sugar + another half a lemon juice (liquidzes your blod - improves also capillary flow - cosult your doctor first if you have ??? high blood pressure ! i gess !) (+ green tea concentrate + artichoke) or other antioxidants

while i'm attempting to find the precursor of this thread . . . . http://forum.allaboutcircuits.com/threads/help-please-rokit-8-powered-speakers.126690/

 

have ordered the resistors, 51k and 3.9.k cant wait.....the law of the sod, its in the worst place on the board .
54.9 k are rare. but a couple of companies do them- but prohibitive p p.
joe, the datasheet for the tda7296 does show the required wave forms on the mute pins, quite complex, but very similar to your oscilloscope display .( even has instructions for building the amp.)
thanks for that c1139.

 

As far as those resistors go, they are probably 1℅ tolerance. See the attachment below. E96 is 1℅.

Your resistors might not work, but since you already ordered them, make sure they are within the specified tolerance.

 

You said the speakers are muted for many minutes before sound is available?

That sounds like something is amiss in the power supply.

 

'You said the speakers are muted for many minutes before sound is available?

That sounds like something is amiss in the power supply.' sorry joe i cant do quotes,

i was hoping it was going to be the amp, as the HF was coming on immediately
on power on,-on the speaker im working on-.but the LF was taking many minutes to come on.--what do you think?

the other speaker was the same, but after being powered off for a few days. no audio at all.
perhaps thats a job for another day.,

 

Ok...start by taking pictures of the boards, front and back in indirect light and make sure your glad is off.

What test equipment do you have and what are the model numbers?

Once I have that info, we will walk through the troubleshooting process together.

 

thats weired i just put these pics on just on a whim at the exact moment you were sending the request.
you said the speakers are muted fo many minutes before sound is available?

That sounds like something is amiss in the power supply.'

i was hoping its an amp problem as the HF comes on immediately on the speaker i'm working on, on power on.- but the LF takes around 5 minutes, what do you think?

the other speaker cab was doing the same, but after being powered off for a few days,
now has no audio at all-.but perhaps thats a job for another day...

'You said the speakers are muted for many minutes before sound is available?

That sounds like something is amiss in the power supply.'

i was hoping its an amp problem as the HF comes on immediately on the speaker im working on, on power on.- but the LF takes around 5 minutes, what do you think?
the other speaker cab was doing the same, but after being powered of for a few days,
has no audio at all.


a couple of pics of the boards, the resistor is next to the two orange ceramic caps top right of the preamp board
.