Hello Community,

i have an audio mixer, the delay effect function works sometimes but not always, and i think i found the Problem, do you guys think the "NE571N" is the Problem of that? bc thats the only IC i found for the delay effect when im right.

 

It does not seem to me that the chip has much to do with delay. The datasheet describes is as a compander. Do you know what the purpose of a compander is?

https://en.wikipedia.org/wiki/Companding

 

It does not seem to me that the chip has much to do with delay. The datasheet describes is as a compander. Do you know what the purpose of a compander is?

Not so much

 

Not so much

See the link I added in Post #2

 

There are almost zero passive components on that side of the board. Please post an image of the other side.

The OKI part at the bottom looks like a RAM chip (a memory device). The Toshiba part comes back as a quad NAND gate. Missing (at a minimum) are the A/D, D/A, and memory address counters.

There were bucket-brigade audio delay devices back when. Maybe one of them is on the bottom side.

ak

 

See the link I added in Post #2

Ok i understand it know, but that was the only thing i found, i have another photo the other pcb

 

There are almost zero passive components on that side of the board. Please post an image of the other side.

The OKI part at the bottom looks like a RAM chip (a memory device). The Toshiba part comes back as a quad NAND gate. Missing (at a minimum) are the A/D, D/A, and memory address counters.

There were bucket-brigade audio delay devices back when. Maybe one of them is on the bottom side.

ak

This is the underside.

 

I don't see anything that jumps out at me for use as an audio delay device.

 

the delay effect function works sometimes but not always,

What do you mean by "but not always"? What do you mean by not working?

ak

 

What do you mean by "but not always"? What do you mean by not working?

ak

When i knock on the sound mixer with something the delay functions again.

 

I don't see anything that jumps out at me for use as an audio delay device.

The only chips i found are:
LM348M
HCF4053BE
and this board

 

The effect referenced as "Delay" was not actually a true delay in some devices, but rather a scheme to boost the gain as the signal faded. I think that was related to a "comply" function. The 571 IC was a gain controlled amplifier that could be made to provide that function. (It acted like a compressor to hold the output constant for a short time, much more like a sustain function.)
Unfortunately the 571 has been out of production for decades, with no exact replacement available that I have seen. Similar functions with much different circuits and more control are available from Analog Devices.)

 

Since that PCM54HP is a honking big 16-bit DAC I suspect the delay is digitally created so my first effort at repair would focus on the switch that controls it, assuming there is a hard switch.

 

The large square black IC in the 68-PLCC socket looks like a Motorola MC68HC11 MCU.
KM62256 is a 32KB RAM chip.
I am going to bet that the delay is done in MCU software.

 

Since that PCM54HP is a honking big 16-bit DAC I suspect the delay is digitally created so my first effort at repair would focus on the switch that controls it, assuming there is a hard switch.

I think that too that the delay effect is generated digitaly, i think the delay slider is the problem i orderd that gonna test it when it arrives.