Buzzing sound of a SHARP VZ-2000

[Funkateer38]

Hello to the Group,

I need your help in resolving the buzzing sound of a SHARP VZ-2000.
I made the following repairs:
- Change of the electric transformer
- Cleaning of the REC bar
- Cleaning of potentiometers
- Verification of IC and REC BAR welds

The hum is reduced by increasing the volume of the internal speakers. And less loud by connecting an external speaker.
I have made an attached video.

Any idea to resolve this hard buzzing ?

Thanks for your help

 

[hopey]

My favourite new topic, it is probably related to the position of cables when reassembled, they are power or grounding circuits are injecting into the audio path. Open the box up and try to separate all the cables and turn it on and check. The audio cables from the Tape head to the Main PCB are also a source of hum. Were you playing that reggae from tape? This is know as ground loop.

 

[Funkateer38]

21/09/24:
I changed all the capacitors on the power supply but the buzzing problem continues. Checking the electrical resistances shows that only R705 is at 40K for 100K.
Any idea to resolve this hard buzzing ?
Thanks for your help

 

[Wes125]

it sounds very much like a mains hum..take it apart and turn it on. see if this heat sink gets scolding hot. there might be more smoothing caps further up on the main circuit board where the 12v supply plugs in. that will be a secondary stage..or it could be a voltage regulator chip gone bad.. BUT FIRST OFF its got a 15v external power input plug. plug a 12v dc power supply into that..make sure the polarity on the plug matches the input plug on back of box as in plus & minus. then see if it still buzzes

 

[Funkateer38]

Thank you WES for your advice and photo.
The heat sink is missing. However, the power supply unit does not heat up.
With a 15 V electric adapter, the buzzing is always present.

 

[Radio raheem]

i suspect a faulty amplifier. does it hum on batteries. if it doesn't just run of dc

 

[Wes125]

Thank you WES for your advice and photo.
The heat sink is missing. However, the power supply unit does not heat up.
With a 15 V electric adapter, the buzzing is always present.

make same video and turn up the volume again. but dont play any music this time. thats not helping us

 

[Wes125]

so we've ruled out the power supply. look further on the main board where power goes in. there might be a dodgy cap there. but i doubt that. that's wishful thinking.but check it out.. i had a record player what buzzed like this and that was a rectifier chip gone bad ...now as said bad amp chip. that would mean the amp chip is one self contained chip coz it buzzes out of both speakers..now ive never seen that in any sharp box. they use two single chips for left & right. and if a chip goes bad..you will only get a buzz on one speaker or that side will be dead. now i think its rectifier chip causing the buzz

 

[Funkateer38]

Cannot check with batteries because one of the springs is broken.
I checked the voltages of the MULTI AMP. CONTROL (Q406) and two two IC 401 and 402, they are good.