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just when you think it is nearly done....


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As my new room thread pointed out, I have reset up my room and I have been enjoying the 2 ch more than I have been in a long time. Last night, I turned the system on then left the room for a few minutes, well about 10 but that shouldn't have been a big deal. When I went back in the room, there was a fricking 60 cycle hum out of both speakers!

I have never had one before and I have an isolation transformer and power filter on both the amp and the preamp so there should be nothing but clean power going in. I turned off everything but the amp and I still had a hum though I did not disconnect from the transformer. I will do so tonight but I am pretty sure I have a filter cap going bad on my power amp. A Sonic Frontiers Power 1, 55 wpc push / pull 6550 tube amp. It was made in the late '90s to early '00s if I remember right.

Stuff happens for sure but dag nabbit, I never expected an issue with this amp. I have an email out to a service tech in Burbank (near L.A.) as I really don't want to send the unit x country to Craig but it may come to that. This guy has worked on some nice gear if his repair photos are real, more Gutiar amps than Stereo but then there are a lot more of them than tube home stereo units out there.

What ball park should this recap/ tune up run?

Also, anyone know anything about this guy? Good tech? Hard or easy to work with??

http://glasssoundlab.com/

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I think your instincts are spot-on. That is a balanced push-pull design, all the way out to the output transforms, so you have B+ and B- in the primary windings. If you have power supply ripple, it's going to be on the secondary to the speakers. And, a deteriorated power supply filter capacitor is the obvious way that can happen. I suspect the fix maybe a pretty straight-forward DYI. The caps will have their specs printed on the sides. Just type whatever that is into mouser.com and I be the exact replacement part will pop right up. Just change them all, it won't be that expensive. Good luck.

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Thanks for the reply.

I fix most everything else but I have never been inside this amp. Thanks for the link to mouser,

it has been a very nice amp and they are still selling on Audiogon for around $1200 give or take a little, so it really is worth taking care of this issue.

Funny, I have no problem working with steel at 2000F but a little electric inside the amp and I am looking to have the work done[:S]

I guess I will open it up this weekend, it isn't like it is a long weekend with nothing to do but listen to music!

I am guessing that the filter cap is likely a surface mount al can type mounted somewhere close to the input Xformer, am I even close?

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The filter caps will be BFC's (big fat capacitors ;-), and will be leaded, near the power transformer and rectifying diodes (or maybe that amp uses rectifier tubes). They will have high voltage ratings like 200V, 300V, maybe higher. They will also have high capacitance values like 22uF, 33uF, maybe higher. Usually there are 2-4 of them on the plus and minus rails. It is also possible you will see physical damage to them. Of course, they are polarized electrolytics with a "+" terminal marking. They should be easy to find.

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That does not sound quite as scarry!

I think you are right with the blue caps.

I just 2 minutes ago recieved an email from the local tech, he said filter caps, depending on how hard the board and solder joints are to reach take about 1 to 2 hours to do, $50 an hour and he will check/clean any controls, tighten all tube sockets and burn in at 80% power just to make sure there are no other issues.

For $100 plus parts (and parts markup) it is nice to have someone else to yell at if things go sideways! I will take a closer look and see just what is involved but I am giving serious thought to taking it in, it is about an hour drive to the shop.

Thank you again for taking the time to look things up and provide a little hand holding. You clearly know a lot more about this than I do! Regardless, of where it's done, it needs to be repaired. BUMMER!

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That's about the same price I got from a "tech" up here in Sacramento, to replace a leaky cap in a subwoofer I bought on CL.

If he sounds trustworthy, let him do it and go through the rest of it, to make sure it is all up to spec.

Good luck and keep us posted,

Dennie

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Before I would start 'operating' on the amplifier, I would make sure I don't have a ground loop somewhere. If you completely changed your room (Not sure what you did), you may have introduced a ground loop somewhere. BTW - 'Clean power going in' does not remove ground loops at all.

The usual procedure.

Unplug and disconnect everything until you hear the offending componet. See if a cheater plug on the amp solves the problem.

In my new room I finally had to add a GFCI on the amp circuits to safely add a permanent cheater plug on the amplifers.

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Well I did find the offending piece of gear when I swapped in my SS amp from the HT to serve as a main amp for 2 ch.

The hummmmmmmm followed onto the new amp so I knew the tube amp was not the issue. I did move each piece of gear in turn to find the ground loop and it was from the last thing I would have guessed. In my pic of the setup, you see a monitor, I put it there so I could watch DVD concert recordings while listening to 2 ch, the issue was with the monitor, through the composite VIDEO inputs as there was NO audio in to the monitor from the DVD/ SA/HD DVD player.

The HDMI input had come loose on the monitor so I was using the composite inputs as the HDMI had failed, it must have shorted something out in the monitor and though it works fine on it's own, when connected into the audio system, it caused a ground loop.

So....... I replaced the monitor and all is well now, even with the tube amp, no issues with hummmmmmmmm at all.

The monitor I picked up was in the return/ open box shelf at my Sams club. I picked up a 40" 1080P screen for $280. It had been returned and supposedly it had been "repaired" and it was also missing the remote (I have lots of universal remotes so that wasn't a big deal) and the price was $100 off the cost of a new one.

Upon getting it home, I had one HECK of a time with it. While it was playing in the store, when I got home I could not get any pass through audio (or from the TVs speakers either) from my source that I knew worked properly when checked against another monitor. Longggggg story short, the audio section of HDMI 1 isn't working but there still are 2 other.. working, HDMI inputs to use so for the price, it works out well.

I have a week to take it back, no questions asked so I am putting it through it's paces for the next week to make sure it has no other issues. As my viewing distance is about 8 feet, I have about the same images size as my 60" is when viewed from that sets seating distance so it works out nicely.

$100 off the price for the loss of one HDMI port, when the set was made in 12/2011 isn't so bad of a deal.... three HDMI inputs minus one, retail price of ~$300 minus $100 it's a fair cop!

I also moved in my new gaming PC into the 2 ch room and it is under the power amp. I still have the Xbox 360 and the PS3 in the TV room but this gives me a place to play games when the wife wants to watch the big screen. So I guess this is now a 2 ch HT/gaming room LOL!

post-14862-13819800479188_thumb.jpg

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