JVC 4VN-880 issue with channel 3 constant hiss.

[Qwadrafoniq]

Hello everyone,

New guy here that's been reading the forums for a while and now needs some advice. This JVC 4VN-880 has been in the family since new (1973) and has been used on a daily basis. I currently have it set up with a pair of Wharfdale Lintons and an SMSL SU-9n DAC and it sounds glorious....well, it did until last month.

It's used at the moment in stereo mode (rear switch set to 2 speaker setup) and it's alwasy been whisper quiet with zero hiss on either channel. Suddenly turning on one day recently channel 3 now has a faint but annoying hiss that's getting slightly worse over time. The hiss is like the background static and is constant. No crackling or other noises. It is not volume dependant or input dependant, it is constant. It doesn't matter what input you're using, what source your'reusing or what speakers you're using, the sound is constant. The cables are good grade and I've swapped them with no change.

I called Robert at Excel Audio Services (SM6) who has vast experience with most things Hi-Fi related and whilst he was familiar with this amp, he did say that he'd never come across a hiss like this before that he will take a look at it but recommended I ask about first to see if there are any other 4VN-880 owners that have had this issue or if there are any JVC specialists on this forum who might have an opinion?

Does anyone have any ideas whagt the source of this hiss could be? Channels 1,2 & 4 are perfectly quiet, it's just 3 that has this issue. I will say that the amp is a bit of a family heirloom and I absolutely love its sound with these Lintons. I'm happy to try and fix any issue.

Many thanks for any advice offered.
Rod

 

[Qwadrafoniq]

probably a noisy transistor

thank you inductor, that would be good and simple to fix. I think the audio engineer chap I was speaking to was most concerned by the fact that the hiss noise level didn't increase or decrease with the volume and was prevalent through all the inputs / outputs. He was concerned that this might indicate an problem with that specific channel's power amp or it's power supply.

 

[Ebondazzar]

Hello Rod,

have you solved that issue yet?
I'm having the same problem on my 4VN-880. Would be interesting to know, if you were able to fix it.

Greetz
Holger

 

[Qwadrafoniq]

Hello Holger,

Not yet! I tried to get help from a few vintage audio specialists, alas, they showed little interest in helping, or they just didn't know the cause.

The amp is currently with a local repair specialist who's giving it a good internal clean up and upgrading the power cable and a few capacitors whilst working his way through the schematics to try and find the culprit. I now have the subtle hiss on channels 2 & 3.

I'll let you know on here if he manages to track down the cause. As a last resort I'll buy the capacitor package available on eBay from an Australian seller, including the power capacitors and swap everything out. I'm keeping the original power capacitors for now simply because the replacement modern capacitors are so tiny in comparison!

Kind regards, Rod

 

[Ebondazzar]

Hello Rod,

thank you for your quick response.
My 880 already had that noise when I bought it 4 years ago, that's why I'm only using it as a switch for now (feeding the multichannel inputs of my AV-Receiver).
I have some other devices waiting to be fixed before I can concentrate on the 880, still I'm already collecting informations wherever I can.

According to this thread the 2SC458 transistors could get noisy. According to the wiring diagram there are a couple of these on the circuit board.
I also found a discussion about these transistors in a german forum, they really seem to be known as troublemakers. Maybe this would be worth considering.


Cheers
Holger