vintage amplifier circuit board with TDA2010 with this tone/volume control circuit

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Hi dear friends!
I need your precious support to realize a project that means a lot to me.
So I hope to get your very important support.
I've this old and simple amplifier based on two horrible TBA 810 (maximum power output for each channel about 4-5 watt (picture n.1)

Well, in the second picture, you can see the complete "naked" circuit board.

So my project is to take only all the frontal circuit board with the vu-meter, headphone/speakers switch, source switch and, of course, the tones and volume controls sliders (picture n.3).
Obviously I want to use only the frontal "pre" circuit board, removing the terrible and bad-sounding power amplifier circuit board, replacing it with a better (really hi-fi) amplifier circuit board based on a pair of TDA2010 (power output for each channel:12 watt rms/18 watt) (picture n.4, in the picture the two chips are without their original big heat sinks, but I'll add them when the project is complete).
Now my doubt is: is it possible to connect a very simple tone/volume control to an amp circuit board with two hi-fi chips like the TDA2010 ?
Now I'll add two pictures where you can see the electronic components welded on the "pre" circuit board, between the two pairs of sliders for the tone and volume control.
Very important:please note that the tone control is unique (I mean: there isn' t a bass and a treble separated control, but just a single tone control for the right channel and another one for the left channel, the same system for the volume control: one slider for the right channel and another slider for the left channel).
The picture n.5 are the sliders for the tone controls (note the component in the middle of the two sliders, but there are other two ceramic capacitors up on the first slider(picture n.6), that are solded on the back of the circuit board with the audio signal input cable (picture n.7)
And, finally, the last picture (n.8), where you can see the electronic components between the two volume control sliders.
I know how to connect the two circuit boards...but my question is:
does this union of these two circuits works?
Plese help me! I need your support.:worship::worship::worship:
Thank you in advance for your kindness and your patience;)
Best regards
 

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It may be possible but you are going to have to 'busk' it (make it up as you go along).

One very important piece of information would be to knowing how the tone control is configured. It may be wrapped around the TBA810 as part of the feedback network, and if that is so then it can not be used independently.

If it is a passive network then it can be used.
 
Hi Mooly!
First of all, thank you very much or your reply.
I'm a newbie, but a friend of mine explained to me the functions of the most important parts of this "volume-tone" control circuit board.
As you can see, this is the back of the circuit in question.
Note that, in this picture, you're seeing my second exemplar of this circuit board, so don't worry about the damaged parts where some the copper tracks are missing (for example the connection pins of the speakers, including the ground pin, in the middle.
In reality, I use this exemplar of this circuit board only for experiments and to photograph it to show it here.
In fact, I own another unbroken and undamaged exemplar of this circuit board that I keep in a drawer due to the fear that I can damage it:I will use it only for the final project.
However, I need to know your opinion about the union of these two circuits.
I hope so much the picture of the back of this volume-tone control unit can help you to advice me. I'm so confused :(:(:(:
That said, thank you very much for your kindness;)
Best regards
 

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It is difficult just working from pictures... not the same as having it in front of you.

I think you need to take this in stages.

1/ Rig up a suitable volume control, power amp (any power amp) and speaker. Feed it with a line level signal and make sure it works.

2/ Now add your tone/volume board before the volume control and make sure it works as intended.

The descriptions your friend has put on the board look reasonable so use the turntable input which appears to be the thin two core wire + shield in your second picture.

3/ Take the output from where you have marked 'to amplifier'.

Test it and make sure tone and volume work. That is the first step.

Your second picture also seems to show what appear to be two zener diodes near the meter. I can't say what they are from just pictures. Are they power supply related ? or simply part of a passive VU rectifier (and maybe not zeners).

A lot of unknowns I'm afraid :(
 
Ah Mooly, I was forgetting your question about the two components under the vu-meter.
I've removed the vu-meter from the circuit board (the second exemplar for the experiments) and I've discovered the two components you was talking about, are two "1N4"...they are "silicon power zener diodes" (I've just read it!)-
They are connected to the vu-meter's pins.
Please be patient with me, dear Mooly: could you explane to me their fuction?
I'm just a newbie but I love this world!;);
Thank you very much!
regrds
 

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Yes, I would concur with PRR having looked at the second image although you typically need two diodes per meter......

This is why working from images is difficult :)

This shows the basic passive VU circuit (its crossed out in red because it is considered a bad design).

C1 blocks any DC present.

D1 is a clamp and conducts on the negative part of the waveform, effectively removing it by shorting it out.

D2 passes the remaining positive peaks to capacitor C2 which charges up to the peak voltage. This voltage drives the meter.

The trouble with these simple circuits is that they are very insensitive and do not work at all with low level input voltages.

Hope you are feeling better soon :)
 

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PRR

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...you typically need two diodes per meter......

Good metering wants more than I see here, sure.

But dancing needle to dress-up a low-price set, fed the large output at a speaker, is usually resistor, one diode, and a soothing cap. Given 8V signal and 1mA meter, a few K resistor, a diode, and ~~50uFd cap so the needle is not too jumpy. Efficiency is not needed. Precision is not warranted at this price.
 
Yes, I would concur with PRR having looked at the second image although you typically need two diodes per meter......

This is why working from images is difficult :)

This shows the basic passive VU circuit (its crossed out in red because it is considered a bad design).

C1 blocks any DC present.

D1 is a clamp and conducts on the negative part of the waveform, effectively removing it by shorting it out.

D2 passes the remaining positive peaks to capacitor C2 which charges up to the peak voltage. This voltage drives the meter.

The trouble with these simple circuits is that they are very insensitive and do not work at all with low level input voltages.

Hope you are feeling better soon :)

Hi Mooly!
please forgive me for the delay replying to you!:(
Observing the amp board, I've just noticed that there're two diodes more on the circuit board: please take a look at the amp board and you'll notice two diodes behind the two grey ELNA capacitors (They're 1000uF 16V and they're the biggest ones)...on the body of the these two diodes there's a code: 1N4001 (and in the lower part of their body there's another code: 710).
Well, my question is the following: are they the two missing diodes of the vu-meters system? or they don't have any connection with the vu-meters?
Thank you very much for your patience;)
Best regards
 

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I'm not sure what those diodes are tbh, at least not without seeing how they connect. The grey caps appear to be for speaker coupling and so I suppose it is possible they are meter related.

Yu would have to see where each end of the diode goes and trace the circuit out.
 
OH Mooly!thank you for your fast reply, first of all;).
I can confirm that one pole of each diode is welded to a side of the Elna caps (speakers coupling).
In another thread about this object, my friend Anti supposes that those diodes are a sort of "anti-pop" circuit. In fact the two Elna caps are connected to the positive poles of the speakers(and the of the vu meters) and the negative pole (I mean the ground) is provided from the power supply (I mean from from the
rectifier negative pole).
This is the other thread where we're talking about this argument:

TCA940 vintage IC:distortion please look!!!

So please, dear Mooly, could you take a look at this topic and tell us your opinion about the function of those two diodes?:)
What do you think?: could they be a sort of an "anti-pop" system?
I know that your opinion could be an interesting contribution to our theories.
The only thing that I can confirm is that the two vu meters worksb when I've connected the other amp circuit board based on the TDA 2010 (you can see it in the pictures) without these two 1N4001 diodes mounted on the original TBA810 amp board.
Let me know what do you think about their function, please!:) I'm so confused, unfortunately:ashamed::(:confused:
Thank you once again for your support:):)
Regards from Italy
 
you need to get a schematic or draw one from the board connections then drop the 2010 into the correct pin positions.
it looks like the 810 has a gain of 100 ( 40 db ) so the 2010 needs to be set for this.
then wire in the pins to the correct holes. mount to copper plate around 810 and add extra heat sink if nesscessary
meter diodes are usually Germanium for low level sensitivity.
 
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Hard to say what the diodes are for without seeing them drawn in on a correct circuit diagram. The devil is in the detail and you would have to draw it out.

Pop or thump suppression seems unlikely as I can't think of a way it could be configured to do anything.

Another possibility is a 'clamp' to the power supply to prevent inductive loads causing voltage spikes and possible chip damage... but its a bit tenuous on something like this.
 
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