Intermittent Static on ARC REF 3 Preamp - diyAudio
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Old 9th November 2008, 11:30 AM   #1
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Default Intermittent Static on ARC REF 3 Preamp

Hi,
I've recently started getting an intermittent scratchy sound (like static) through my left speaker. I've isolated the problem to my Audio Research Reference 3 preamp. I swicthed the 6H30P tubes (left with right) and the noise is still from the left channel only.
Any help would be appreciated.
Thanks.
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Old 9th November 2008, 11:58 AM   #2
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Can you post a schematic?
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Old 9th November 2008, 12:04 PM   #3
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Don't have one.
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Old 9th November 2008, 12:07 PM   #4
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Quote:
Originally posted by burnedfingers
Can you post a schematic?



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Old 9th November 2008, 12:12 PM   #5
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Maxzimum

Do you get this this both in balanced and SE mode? The sctratchy sound may indicate oxidated contacts of the tube sockets, bad connectors, bad solder joints. I'll be very surprised if it's something else. How good are you with a soldering iron?
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Old 9th November 2008, 12:13 PM   #6
chrish is offline chrish  Australia
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Had a situation where I thought the worst of some of my equipment. Turned out it was a cable problem. Always worth checking the cables before pulling the covers off equipment...
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Old 9th November 2008, 12:16 PM   #7
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Quote:
Originally posted by analog_sa
Maxzimum

Do you get this this both in balanced and SE mode? The sctratchy sound may indicate oxidated contacts of the tube sockets, bad connectors, bad solder joints. I'll be very surprised if it's something else. How good are you with a soldering iron?
I haven't tried in SE mode. Will try in a few hours and post back.

I have removed and reseated the the tubes, even replaced them but with no luck. Pretty good with a soldering iron.
I have Deoxit spray, should I try spraying the tube sockets?
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Old 9th November 2008, 12:18 PM   #8
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Quote:
Originally posted by chrish
Had a situation where I thought the worst of some of my equipment. Turned out it was a cable problem. Always worth checking the cables before pulling the covers off equipment...
Tried with different IC cables, didn't help. Will try with SE cables now and post.
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Old 9th November 2008, 12:31 PM   #9
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The SE test won't tell much. Unless you are lucky.

Start with the Deoxit and inspect all solder joints on the tube board. Seems there are always a couple of relays along the signal path, no matter what input is in use and relays are, annoyingly, also suspects.

If these casual measures don't help you would probably need to get your hands dirty, disconnect the amplifier board from the volume control section and test it using an external volume control, like a variable output cd player. This is not so straightforward as it sounds and probably involves lifting one side of the grid stoppers and providing grid leak resistors.
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Old 9th November 2008, 12:52 PM   #10
Dragon2 is offline Dragon2  Canada
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Hi Maxzimum

I am a repairman and i have repaired a Ref 3 some time ago.

First: do not put deoxit on tube socket!
At first, it will wok but after a while, it will isolate the contacts because of the heat.
The heat make a sort of gum...

This preamp is too young to clean the tubes sockets.


The problem sems likely to be the plates resistors: they have pretty high voltage on them and sometime they make noise. Look for red resistors.

It may be also a fet or a cap but it is unlikely and you will need to order the originals parts if it is the problem.

You will need a scope to fix this unit.
Be carafull: high voltage.

Good luck
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