Unusual LED behaviour on WD88VA XL, advice needed

[tobzman]

Hi All
This is my first post on the forum, I've owned my WD88VA for about three years now and I have to say I've enjoyed every second of it.
It does however have a potential problem which I first noticed around a year ago. The problem may have always existed but it was a year ago when my system was moved into a dedicated room and I was therefore able to use it at much higher power levels for extended periods.

The problem manifests itself as a flicker on the power LED usually during bass heavy passages. I have also noticed it to be quite prevalent on passages containing large mid range excursions. The problem is usually only present once you get above 2 o'clock on the volume dial. Up until now I have managed to live with it (although that flickering LED can be annoying in a dark room) however the other night the flickering became really extreme to the point the LED was flashing on and off in time with the music. I actually had to turn it down as far as 9 o'clock before the flickering stopped. Strangely the amp behaved itself during the next album I played and the flickering was barely noticeable (I had reduced the volume for about 20minutes in the intervening period). The central PSU Tx did seem to be a good few degrees hotter at the end of the evening than it would normally be as well.
Another thing that is probably worth mentioning is that when it's in the LED flickering condition the blue glow in the power valves is also flickering in time. It therefore leads me to suspect the HV rails may be bouncing about during times of high current demand.
The LED never actually changes colour just flickers.
Is this a common problem which has a known cause?
My first thoughts would be HV rectifier diodes or possibly a reservoir cap?

I suspect some may recommend I cut the wire on the LED but if it is trying to warn me of impending doom I'd rather know.

Other things that might be worth mentioning are:
- the sound quality is never affected by the LED flicker.
- the amp is still running the original Winged C KT88's, I have no idea of age as I bought the amp second hand.

Sorry for the rambling post, any advice would be greatly appreciated.

Cheers
Toby

[bikerhifinut]

just ignore it, mine has always done it. its just the cathode voltage varying as the signal. I personally have considered wiring the green end to the heaters and just having it as a power indicator. You'll sharp know if the HT failed!

Andy.

[Richard]

Yes, you could cut it or wire a single colour led to the DC heaters instead but if the anodes are pulsating I wonder if you're thrashing it a bit without realising? Music with strong bass will show this first.

What speakers are you using? I've had pulsating blue power valves thrashing a number of push pull amps. They'll be clipping but they clip softly just sounding a little compressed and maybe not noticeable.

[bob orbell]

Agree with both Andy and Richard, it would handy to know your speakers and your source, ie CD etc, if you are using CD or other digital sources, these have about 2 volts output, and your amp. requires .5 of a volt for full power, so with your volume control past the half way point, you may be over loading the input, the only thing that will suffer in this case will be the speakers, be warned. BOB

[tobzman]

Hi
Thank you all for your replies.
Ok so the general consensus seems to be that I shouldn't be overly concerned but at the same time I should be aware that I'm being a little unkind to my amp at times.
In answer to the questions about my system:
My speakers are PMC FB1+ and my source is currently a Marantz CD50 being used as a transport running through a Rega DAC.
I do listen to a fair bit of bass heavy music and as my system is in a purpose built room in the garden I have guilt free listening at high volume levels hence it is usually pushed hard.
My room is 16'x13' (pitched ceiling 8' at the ridge and 6' at the eaves) and at the time of building it I was a little concerned that the space may be a little large for the amp to fill. I would say the amp is definitely capable of filling the room (it shakes the lights on the ceiling) but maybe only just

Cheers
Toby

[Richard]

Hi Toby, very nice, mind your ears

[Chris]

The Winged C KT88's may need changing if you have used the amp for 3 years and the original owner had a couple of years use with them.

Chris.

[tobzman]

I have been thinking for sometime that it would be sensible to have a spare set of KT88's in hand just in case one goes down at any time. However due to the winged C being totally unavailable these days I cannot decide on what to plump for. Originally I was going to pick up a quad of regular Svets but I have read that the ones available nowadays are likely to be from the dregs at the end of production and potentially a bit slack in the tolerance department.
I know it's a very subjective topic but what has everybody else switched to these days?

Cheers
Toby

[pre65]

See what HotRox (UK selller) have available.

http://www.hotroxuk.com/matched-valv...6l6-909-0.html

[bob orbell]

Agree with Philip on Hotrox, I myself use a set of JJ's at the moment, don;t forget that you can also use 6550's in your amp, so that makes your choice a bit wider, don't be tempted to go for the KT120's, the power supply may just be overloaded, on another note, my chum, who I sold a KAT 6550 to, still uses the valves supplied with the kit which must be 15 years old, and it still sound good. BOB