Yamaha CA-800, whooshing sound?

[rjsilva]

I have a Yamaha CA-800 and it has a sort of whooshing noise noticible when it’s on and not playing any music. It’s a noise that ‘moves’. I run it mostly in AB mode.

I had been considering recapping it, cleaning switches, and replacing some parts and wondered if anyone has any thoughts as to what might cause this moving noise.

Thanks.

 

[mbz]

Long shot would be TR605 on the heatsink of the power amp. these are 2SC458LG's which have a bad history of going noisy. Replace with KSC1845.
Do you still get the noise if you set the coupler switch to OFF?

 

[mbz]

The CA-800 is a decent amp but a PITA to refurb. As a minimum I would suggest,
- replace main filters, these are 50V items and the rails run anywhere 49-53V. United Chemicon SMH or KMH series
- recap power supply/relay board
- refurb power amp boards ie, recap and multiturn trimmers
- replace class A/AB snap switches
- dismantle and clean coupler switch
- deoxit etc... other switches

The amp uses polar tantalum caps in phono and preamp stages. These also have a history of going noisy.
Replace with either Nichicon UKL or wima mks

Many other things to do, it is a PITA but worth the effort.

 

[avionic]

- dismantle and clean coupler switch

All slide switches..

 

[mbz]

Should add "check fisible resistors are within spec" as a must do

 

[rjsilva]

Thanks for replies! And also for some part numbers.

I actually redid my CA-1000 years ago and was really enjoying it. Then either I did something to it one day or some other problem that creeped up on its own, but it started humming. I tried to figure it out and asked for help on this forum but was never able to solve it. I actually bought the CA-800 because of that, as a temporary solution (it’s been a few years now...).

I would have loved to fix the 1000 but I wasn’t able to afford to send it to someone more knowledgeable than me to fix. It’s probably something simple, I just don’t have enough knowledge of circuits to work it out.

 

[mbz]

I actually redid my CA-1000 years ago and was really enjoying it.

The CA-1000 has a strong following being noticably better than the CA-800, both share the same mechanics so both = PITA.

Then either I did something to it one day or some other problem that creeped up on its own, but it started humming

Hums are one of the most difficult problems to repair with a wide range of causes. A good start is to determine if it's 50/60Hz mains hum
or rectified 100/120Hz hum, apparently a mobile app is useful here. Also is hum on both channels, does it increase with volume, is it still
present when you turn off the coupler switch. Also, there is a track on the function board that's known to burn out, just lift the shield off...



I've included a pix of the coupler switch, these do get tarnished.

 

[rjsilva]

Since you made some suggestions mbz... I looked back to the thread (from 2013) and this was my condensed list of observations about the hum from the CA-1000:

“1. The hum is normally at 120hz, very audible, equally in both speakers.
2. Touching the pre-out/main-in plugs with my finger causes the hum to reduce a little bit.
3. Disconnecting the grounding wire at the rear panel circuit board and chassis causes the hum to increase in volume by about 50%.
4. Decoupling the preamp/amp causes the hum to reduce in volume a lot (maybe 70% quieter?).
5. Unplugging the function board from the preamp changes the hum to 60hz.
6. Using different outlets and reversing the plug doesn't change anything.”

Several members, including avionic, were assisting and giving suggestions. I tried my best but unfortunately while mechanically competent I am not especially knowledgeable about circuits.

 

[mbz]

Little busy at the moment but I will have a look at the CA-1000 hum (remember to check function board for burnt track) issue/track down the original thread and post there
rather than go off post, keep this for the CA-800 issue.

Do you still get the noise if you set the coupler switch to OFF?

Would confirm is pre or power amp problem

 

[Roboturner91]

I had a CA-810 with this exact problem and traced it to the bass turnover switch. Have you cleaned that at all?

 

[avionic]

The CA-1000 has a strong following being noticably better than the CA-800, both share the same mechanics so both = PITA.


Hums are one of the most difficult problems to repair with a wide range of causes. A good start is to determine if it's 50/60Hz mains hum
or rectified 100/120Hz hum, apparently a mobile app is useful here. Also is hum on both channels, does it increase with volume, is it still
present when you turn off the coupler switch. Also, there is a track on the function board that's known to burn out, just lift the shield off...

View attachment 1225392

I've included a pix of the coupler switch, these do get tarnished.
View attachment 1225393

Awesome photos .. mate.

 

[rjsilva]

I will be looking into this today and keeping in mind the suggestions. And also the CA-1000. Thanks