Old Audio Mixer / Delay Effect IC

Thread Starter

Ernst Eiswürfel

Joined Oct 29, 2018
16
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.
 

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AnalogKid

Joined Aug 1, 2013
10,113
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
 

Thread Starter

Ernst Eiswürfel

Joined Oct 29, 2018
16
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.
IMG_20220714_215306.jpg
 

MisterBill2

Joined Jan 23, 2018
12,696
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.)
 

Ya’akov

Joined Jan 27, 2019
6,263
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.
 

MrChips

Joined Oct 2, 2009
26,790
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.
 

Thread Starter

Ernst Eiswürfel

Joined Oct 29, 2018
16
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.
 
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