Pre-Amp distortion

[Jolida]

Was working with the amp all day. The problem seems to be in the firmware of the amp I guess. When I switch on the amp, the problem starts as usual, the balance shifting totally towards the left channel, along with distortion. The amp has digital assigning of channels to the inputs. For eg. if I have connected my Cd player to the analogue input 1 on the amp, I need to go to the Menu & assign a Name for that input (like CD), & also the Mode (Stereo) etc. Now when I go to the set-up & assign the input for Cd as the Optical in , & immediately change it back to Analogue 1, the Amp functions alright (though with very less distortion). The Volume regains balance as normal. The problem remains upon each Restart, & has to be done as above each time I start listening. How do I resolve this??

 

[jitter]

From page 31 on, there's a service bulletin about updating the firmware if its older than version 2.4.

What version is displayed directly after power on?

 

[jaycee]

You might find that the analog switching chips 4051/4052 have gone bad. This looks like it's an oldish preamp and some of those chips were vulnerable. Nowadays there are superior pin compatible parts available.

 

[Jolida]

The version is 2.4E. So does that mean there is nothing that can be done to fix this ??

 

[Bonsai]

Sounds like a power supply issue to me, or an electrolytic cap failing, thats putting DC bias into a stage causing severe clipping.

Have you got a DVM - time to take some readings, write them on the schrmatic, and then post them up here so we can give you some advice.

 

[jitter]

The version is 2.4E. So does that mean there is nothing that can be done to fix this ??

No, it means that the firmware doesn't seem the likely cause of your problem.

I would say that jaycee's comment about those ICs is worth checking out and given the age of the preamp, so is probably also Bonsai's.
Other than these, I have no clue.

 

[Jolida]

Oh ok. I sure can take measurements of the power supply. Some guidance would be appreciated..

 

[Jolida]

Also, is this in any way harmful to the power amp it's connected to????

 

[Jolida]

Sounds like a power supply issue to me, or an electrolytic cap failing, thats putting DC bias into a stage causing severe clipping.

Have you got a DVM - time to take some readings, write them on the schrmatic, and then post them up here so we can give you some advice.

Page 63 of the service manual shows the Voltages to each Board. Is our prime
Area of interest only the Analog board? Will it suffice if I check the voltages on that page match the ones going to the Analog board?