Im slightly confused by the electronic symbol used for C82 so I started probing around for the right capacitor.
In the amp which measures as C82 is a standard capacitor.
There is a 50v 47uf cap inside within tolerance
In the amp which measures as C82 is a standard capacitor.
There is a 50v 47uf cap inside within tolerance
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The component masking is vanished because it is placed on a trace.
There is a C82A which totally does not match the diagram.
This is the only cap that matches the diagram C82100/16v
Q52, R57, R56, D51 has the same markings and are placed next to eachother.
The 47ųF 50v cap is placed next to it as well.
I'm sure it's the right one.
There is a C82A which totally does not match the diagram.
This is the only cap that matches the diagram C82100/16v
Q52, R57, R56, D51 has the same markings and are placed next to eachother.
The 47ųF 50v cap is placed next to it as well.
I'm sure it's the right one.
I'd replace the 47uF cap with a 100uF. That should increase the delay.
If you want to experiment, decreasing R55 to 10k and replacing D51 with a 10v Zener should also help increase the delay for the driver ICs.
If you want to experiment, decreasing R55 to 10k and replacing D51 with a 10v Zener should also help increase the delay for the driver ICs.
Ok so, I put in a 100uf cap, changed D51 to a 10v zener, replaced R55 to a 10k resistor.
It helped a lot already.
When the amp started up after laying on the bench for 10 minutes, its hard to see but it seems like it does not fully wait until full rail is applied.
If I pulse the remote once every 2 seconds it waits a second before it starts oscillating. So in that case it seems to work.
Rail voltage is dumped again after powering off
It helped a lot already.
When the amp started up after laying on the bench for 10 minutes, its hard to see but it seems like it does not fully wait until full rail is applied.
If I pulse the remote once every 2 seconds it waits a second before it starts oscillating. So in that case it seems to work.
Rail voltage is dumped again after powering off
If you still have the jfet connected to the 2 legs of Q52 and the 1N4148 connected to D22 (driving the gate of the jfet gate via the resistor) try removing the cap that was connected across the 10v zener.
Does it still drain the rail caps?
Does it still drain the rail caps?
Confirmed, it does prevent oscillation.
I'm thinking, should I maybe make a remote/optocoupler circuit where the remote directly drives the Jfet's gate via an optocoupler?
I'm thinking, should I maybe make a remote/optocoupler circuit where the remote directly drives the Jfet's gate via an optocoupler?
I was trying to keep it as simple as possible to make it a practical modification. If it's too complex, it would need a small circuit board to make it practical. The 21844s will likely become available to make this unnecessary.
If you look at the gate-source voltage in differential mode, do you see the gate voltage drop immediately when the remote voltage is removed.
If you look at the gate-source voltage in differential mode, do you see the gate voltage drop immediately when the remote voltage is removed.
It's hard to check excactly since the scope is a bit delayed.
But it drops voltage as good as immediately.
One thing I noticed is that it does not drop to 0v instantly, it sinks from 10 to 5v in about 600ms.
From 5 to 0v takes about 25 seconds
But it drops voltage as good as immediately.
One thing I noticed is that it does not drop to 0v instantly, it sinks from 10 to 5v in about 600ms.
From 5 to 0v takes about 25 seconds
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Connect a 100k resistor between the gate and source. Does that make it immediately drop down to 0v?
What sort of optocoupler are you going to use?
In what type of configuration?
What sort of optocoupler are you going to use?
In what type of configuration?
No, voltage between gate and source does not immdeiately drop to 0v
If I pulse the remote, the oscillations starts after a nice delay, and the rail voltage does not drop a bit.
When I turn off the remote when the oscillation is present for less then 700ms there is not a single rail voltage dump.
When I turn the remote off after more then 700ms of oscillation it dumps rail voltage.
I have 6n137, HCPL3180, FOD3120
Just a basic dc voltage 'relay' function
If I pulse the remote, the oscillations starts after a nice delay, and the rail voltage does not drop a bit.
When I turn off the remote when the oscillation is present for less then 700ms there is not a single rail voltage dump.
When I turn the remote off after more then 700ms of oscillation it dumps rail voltage.
I have 6n137, HCPL3180, FOD3120
Just a basic dc voltage 'relay' function
The ±700ms rail dumping is strange.
Where are you going to connect the output of the optocoupler?
Where are you going to connect the output of the optocoupler?
I wanted to connect the output at the Jfet's gate.
But, I forgot that the Optocoupler should have a steady VCC as well. But the VCC will never be quicker then the generated voltage at D22.
So I don't think the optocoupler will work...
Yes, the 700ms is strange, like a capacitor or induction capacitance is charged up and then releases?
I took out the Jfet to test.
Without Jfet the amp waits with oscillation until full rail voltage is reached nicely.
But, I forgot that the Optocoupler should have a steady VCC as well. But the VCC will never be quicker then the generated voltage at D22.
So I don't think the optocoupler will work...
Yes, the 700ms is strange, like a capacitor or induction capacitance is charged up and then releases?
I took out the Jfet to test.
Without Jfet the amp waits with oscillation until full rail voltage is reached nicely.
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I think in this case the muting circuit works faster than the power supply shutoff time.
Is there a way to directly connect it to the remote? With a mosfet/transistor to keep it isolated?
Is there a way to directly connect it to the remote? With a mosfet/transistor to keep it isolated?