Lightstar humm/buzz when powered on

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nemodog
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Lightstar humm/buzz when powered on

Post by nemodog » Sun May 24, 2015 2:47 pm

I have Lightstar Reference #35. When powered on it has a faint hum. This transfers to the ribbons if using balanced connectors to the Sunfire Classic. I dose not transfer to the ribbons using RCA connectors. Any ideas?
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radioeng2
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Re: Lightstar humm/buzz when powered on

Post by radioeng2 » Sun May 24, 2015 3:06 pm

First thought would be that the unbalanced input is providing a ground path that is lacking on the balanced.

So...Is the amp using the same power outlet connection as the rest of the equipment? When you go balanced, is it from a balanced source or is it via some adapter? Does that amp have a 3 pin power cord and if so is it properly grounded?

Hmmmm...gets real old.

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nemodog
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Re: Lightstar humm/buzz when powered on

Post by nemodog » Sun May 24, 2015 3:24 pm

My mistake, Lightstar Reference #14. How do I post an image here?
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Re: Lightstar humm/buzz when powered on

Post by nemodog » Sun May 24, 2015 3:35 pm

The Lightstar has two three prong power cords plugged into a Monster Reference Power Center along with the Sunfire Classic Vacuum Tube Control Center. Strangely, It was all good with the balanced connectors and then one day when I turned every thing on I got the hummmm. Bummer!
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radioeng2
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Re: Lightstar humm/buzz when powered on

Post by radioeng2 » Sun May 24, 2015 3:45 pm

Then I'd temporarily substitute a power strip for the Monster and make sure it's not in play. If it isn't, then it'd sound like your Lightstar or the Sunfire is aged and wanting to be refreshed.

Maybe somebody else will throw in some experience...

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radioeng2
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Re: Lightstar humm/buzz when powered on

Post by radioeng2 » Sun May 24, 2015 3:50 pm

nemodog wrote:My mistake, Lightstar Reference #14. How do I post an image here?
I stash a photo to Photobucket and then use put a link here into the forum.

http://photobucket.com/

Photobucket is free (only have to clear a few annoying ads out of the way) and use the bottom of the set of prebuilt links and drop it directly in here without using the Img or URL stuff from the top.

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Re: Lightstar humm/buzz when powered on

Post by Snoop65 » Sun May 24, 2015 4:32 pm

Is your Lightstar quiet with nothing plugged in? Also your Lightstar shouldn't be plugged in to a power conditioner, it should be plugged straight into the wall. The Lightstar does it's own conditioning.
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nemodog
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Re: Lightstar humm/buzz when powered on

Post by nemodog » Mon May 25, 2015 6:50 am

Thank you Mark and others. I'll isolate some stuff and see what happens, Hopefully a grounding issue. Don't really want to ship this heavy mug for repair.
Hi-Tech did a thorough update of the Sunfire tube preamp about a year ago.
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Re: Lightstar humm/buzz when powered on

Post by TNRabbit » Mon May 25, 2015 8:00 am

Welcome!

Where in NoVA? I'm in the Fredericksburg area.
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Re: Lightstar humm/buzz when powered on

Post by nemodog » Mon May 25, 2015 9:06 am

Listening in Alexandria neighbor.
OK I've disconnected everything from the Lightstar but the power cords. Even moved the beast to connect to a different outlet. With both power cords pluged in I switch on one and get the hum then switch the second on and hum increases slightly. These outlets could be on the same circuit. Next plan is to test the electrical circuit for proper grounding.
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Re: Lightstar humm/buzz when powered on

Post by Robert R » Mon May 25, 2015 9:30 am

I'll throw some experience in, as Mark says: That's quite a warm-running unit (those transformers run quite surprisingly hot, even at idle), and the original factory capacitors were not the best. If that 20 year old Lightstar has never been recapped, every little electrolytic in there is suspect - they are all starting to fail at this point. Crappy capacitors often cause hum, and ultimately complete operational breakdown.

Actually, I'm surprised it lasted this long - perhaps it's had low hours of use.

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nemodog
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Re: Lightstar humm/buzz when powered on

Post by nemodog » Mon May 25, 2015 10:40 am

If that turns out to be the case Robert, where would you send it from Northern VA? I had a good experience with Hi-Tech in Oregon with the Sunfire tube pre-amp.
Just thinking of the shipping tonnage on the Lightstar.
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Re: Lightstar humm/buzz when powered on

Post by Snoop65 » Mon May 25, 2015 10:57 am

nemodog wrote:If that turns out to be the case Robert, where would you send it from Northern VA? I had a good experience with Hi-Tech in Oregon with the Sunfire tube pre-amp.
Just thinking of the shipping tonnage on the Lightstar.
It would be worth it. The Lightstar is a excellent amp. If I had to ship mine I would build a wood crate for it.
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Re: Lightstar humm/buzz when powered on

Post by jjptkd » Mon May 25, 2015 11:03 am

I believe Tom at Vintage hifi in Pittsburgh can help out:

http://vintagehifishop.com/
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Re: Lightstar humm/buzz when powered on

Post by Robert R » Mon May 25, 2015 11:27 am

Shipping an 80 lb. Lightstar really requires a special crate, and freight to the West Coast ain't cheap. Oregon - that would be Roland Barr, and last I heard he wanted a flat $600 to fix up a Lightstar. That was a couple of years ago.

The Vintage HI FI guys in Pittsburgh used to do these, then their repair work went on hold a long time while they moved everything to a new shop. Lately nobody hears from them on the forum - perhaps others know more of that situation. Much closer to you, if you can hook up, and they do good work.

If it were mine, I'd do it myself, but I'd cuss a lot - all in all the most miserable amps to work on I ever messed with. Another option would be to get it all apart and just send the circuit boards to someone. But actually, that leaves you to do the hardest part - the recapping is tedious, but relatively straightforward compared to R&R of the boards. You need to be pretty handy to get these amps apart - just getting one board out requires [AFAIR] three different size little hex wrenches, each of just the right length. All (8?) power transistors must be unscrewed, and then they are just hanging there by their leads and thus are subject to trauma. Add to that, whether it's that heat or old age or just crappy material to start with, the plastic connector plugs on the interconnects are extremely brittle, and require very gentle handling or they'll crumble. Even if the plugs don't break, getting everything back together is hard enough - you need to take notes and maybe pictures as you pull it apart.

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