Harman Kardon AVR 141 protect mode and volume issue

[srt1]

Hi i got recently AVR 141, it have two issues one is it going protection mode some times and its surround right channel have volume issue when i am increasing the volume it goes on increasing but suddenly lowering when i reach -42db then it have no change till -28db when reaching --27db it again increasing to a level which is same level of other channel ... i dont know what is causing for this volume issue even i did reset no changes, regarding the random protection mode , i checked the voltage out put at speaker terminal in front right channel its showing around 2.1 volt but other channel shows in milli voltae range so i suspect problem with front right channel. hope it can be fix, but i dnt have any idea about volume issue on surround right channel any one can help me

[srt1]

Re: Harman Kardan AVR 141 protect mode and volume issue

any one can help me

[jondoe]

Re: Harman Kardan AVR 141 protect mode and volume issue

Pictures on the insides will go a long way towards getting help

[srt1]

Re: Harman Kardan AVR 141 protect mode and volume issue

hi,,, i want fix the volume issue first , is it problem wit IC njw1197 (dogital volume control ic) only have problem with Right surround, this IC have two unused pins for Surround back channels , but how i can enable this pins to divert audio signal from SB right to this - schematic i attached here

[tibimakai]

Re: Harman Kardan AVR 141 protect mode and volume issue

Maybe, that channel has a bad component.

[srt1]

Re: Harman Kardan AVR 141 protect mode and volume issue

I deverted the signal to other channel but ,its same ..so i am.thinking problem with mcu or this digital volume ic .but i need to confirm it

[Piotr07]

Re: Harman Kardan AVR 141 protect mode and volume issue

Typical "Protect" problem on this model is bad transistors KTC3200 - the differential pair on the Power Amplifier circuit. You must to replace to 2SC1845 of all pair as Q514/519 ,Q818/819 etc.

[redwire]

Re: Harman Kardan AVR 141 protect mode and volume issue

Don't fix volume problem first, fix amplifier.
Capacitors C501,2,3,4,5 etc. shorted can blow up the DAC.

[srt1]

Re: Harman Kardan AVR 141 protect mode and volume issue

Typical "Protect" problem on this model is bad transistors KTC3200 - the differential pair on the Power Amplifier circuit. You must to replace to 2SC1845 of all pair as Q514/519 ,Q818/819 etc.

I measured voltages at points collector terminal of q876 & q886 its +3.2volt and 0.66volt respectively , but in other channel its +1.3volt and -1volt.. This protection mode only happening when i switch on in cold coundition after few times restart it will stay power on.. when i amm switch on cold condition its showing around 3 volt on speaker terminal , but after few minutes its lowering ,becaming 2 volt .. then receiver stay alive

[Piotr07]

Re: Harman Kardan AVR 141 protect mode and volume issue

Try to freeze the differential pair and you will see a change of the DC offset

[srt1]

Re: Harman Kardan AVR 141 protect mode and volume issue

Try to freeze the differential pair and you will see a change of the DC offset

i apply hot air to diffrential pair transistor section , then DC offset goes to 0volt . anyway i will replace c3200 transistors.

[srt1]

Re: Harman Kardan AVR 141 protect mode and volume issue

i need help regarding the volume issue also.. if it faulty NJW1197 ic , i want divert the audio signal to other channel which is unused as this ic has 8 channel volume control is ther now only its 6 channel used ,,hope i can use one channel out of 2 in remaining , but i dont know how to configure it..

[srt1]

Re: Harman Kardan AVR 141 protect mode and volume issue

HI, I replaced C3200 with C1845, now amplifier section is ok.. but i want fix the volume issue on Surround right channel.

[arnaoldus]

Re: Harman Kardon AVR 141 protect mode and volume issue

hi,

i wil try too explain my problem in my best English (i'am from Belgium)

when i switch on my HK VR 141, after few seconds, "protect" appair on the screen and the HK shut down.

someone can tell me the origin of the problem?

best regards

[srt1]

Re: Harman Kardon AVR 141 protect mode and volume issue

hi,

i wil try too explain my problem in my best English (i'am from Belgium)

when i switch on my HK VR 141, after few seconds, "protect" appair on the screen and the HK shut down.

someone can tell me the origin of the problem?

best regards

CHECK THE output volatge on speaker terminal before protect mode appear