Yamaha HS8 suddenly stopped working

[adamrodgers]

Hi, I’m looking for help regarding my new pair of Yamaha HS8 studio monitors. I bought a pair of these in July this year and they have been great. However today I was playing music from them at a reasonable level and suddenly my right monitor cut out and the power light went off. There were no strange noises (pops, crackles etc.) and the audio just cut out completely.

I turned the monitor off and on again with the switch on the back, this did not help.

When the power is on, transformer humming can still be heard, indicating the fuse has not blown, and there is no power light or sound coming from the drivers.

I checked the fuse of the HS8 and it’s OK, and the fuse of the power lead which was also OK. I also tried powering it on with another power lead, which did not work.

There are no visual signs of damage on the circuits within the speaker, nor smoke/burning smells etc. I would be very surprised if the drivers had blown as these are known to get very loud with no problem.

Does anyone have any idea what this could be?

Thanks in advance,
Adam

 

[Bluejets]

Most power supplies these days are switchmode.
Sounds like yours has a failed output.
This could be due to any number of things and without your having any trouble shooting experience, I'd say possibility of your repairing it rather low.

 

[adamrodgers]

Thanks for your reply. I’ve contacted the supplier with hope of repair. Out of interest, how could you troubleshoot such a problem?

 

[Martaine2005]

Depending on the power supply, you might find a simple diode has gone open circuit in the bridge rectifier.
Can you supply photos of the board?

Martin

 

[bertus]

Hello,

When the units where bought in july, is there no warenty?
When the units are already opened, the warenty might be gone.

Bertus

 

[73's de Edd]

Sir adamrodgers . . . . .

Working with . . . .
When the power is on, transformer humming can still be heard, indicating the fuse has not blown, and there is no power light or sound coming from the drivers. (WHAT . . if the /a fuse is being located PAST the transformer ?)
AND
Most power supplies these days are switchmode.
Sounds like yours has a failed output.

I'll buy that . . . . hummmmming on the transformer aspect
I won't buy the SWITCH Mode PS aspect

Seems like they went to their surplus stock room and pulled out 3 . . .repeat . . .3 old stock transformers and tripled their input and output windings ( in phase) together to end up with the equivalent of a much BEEFIER transformer. That then gets the usual linear power supply treatment.
The linear power supply designed with that gets to put out a higher voltage and sub 15V + and - supplies to feed two 68 watt potted power modules ( LM3886 ), with one only being utilized up to its max watt level for the 8 in WOOFER / MID RANGE and the other power amp only taxed to the 35 watt level for the units TWEETER.

Looks like its having ABSOLUTE MINIMALIST controls . . . .a LEVEL control and two slide switches and the audio input is being a plug in option of 1/4 inch stereo phone plug or a 3 pin XLR audio connector.

So o o o o o o o you just might have a blown fuse on your now defunct unit . . . . .BUT . . . if so, you DON'T just jam in another like fuse . . . . . . or you are a bigger fool than I can give you credit for.
You sub in a wired in / clipped in 60-100 watt OLD SCHOOL repeat OLD SCHOOL Incandescent lamp for that fuse . ( NO LED's or CFL lamps )
Then, when you power up for testing, if you get but a mere glow or glow and dimming, it would then be safe to chance testing, by using a proper fuse.
OR . . . . if you get a BRIGHT lamp light up on power turn on . . . . THAT's BA A A A AD . . . . and you probably saved KNOCKING out $374 dollah and eleventeen cents in damaged component parts, had you just initially popped in a new fuse and plugged in.

Now go look for that blown PS fuse or send us some . . . HELP . . . . .HELP . . . ME . . . . . . .photos.



Just now caught . . . fuse of the HS8 and it’s OK . . .on a later re-read .

THEN . . . how about presence the POWER SUPPLY outputs +V supply across the large C430 or C401 E-capacitors or the -V supply across the large C431 or C402 E-capacitors .
Or the lower +15 V supply across C407 and the -15V supply across C408 .

Thaaaaaaaaaassit . . .

73's de Edd . . . . .

Statistically . . . . . . . 6 out of the 7 dwarves are not Happy.



.

 

[Bluejets]

Edd...the definitive word there was "most".