ISP IS 5022 Mk 2 Sound Enhancers : 2 x Faulty

On the Workbench 2  IS5022 Sound Enhancers

• Nr 1. : Is a modified version it was used by “Concert Radio” in the Neterlands, it has Glitch in the Audio
• Nr 2. : bought on Marktplaats, and it doesn’t seem to work, blinking LEDs

Nr1. Modified audio input and output circuit

More Modifications

Comparison Nr 1 vs Nr 2

close up Nr 1

Nr2, was quickly fixed, switched analog balanced to unbalanced , did a factory reset , it’s working fine . User error ?

made a backup of the ROM’s , you never know 😉

This Controlboard with the DSP has a problem , it is causing glitches on the Analog audio input, if is swap the Boards between Nr1 & Nr2 the problems move between units

The anoying glitch on the analog output audio only when i use the analog input, its appears 2 times in a second, and the glitch noise is around 22 KHz , is its 44.1/2 ..?, digital input is working fine, as all DSP functions.

I can see something strange on pin 17 ( I/O 4 )   of the LH2464 NMOS RAM Chips  ; RAM Sharp LH2464  when i use the analog inoput

Lets take a gamble and replace the  LH2464 NMOS dRAM’s ,

Oeps pin 2 🙁 , my mistake

That helped , problem solved