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Source selector issues
Source selector issues
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Old 14th July 2018, 12:04 AM   #1
vandalfsens is offline vandalfsens  United States
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Join Date: Aug 2010
Location: Wausau WI
Default Source selector issues

Hello,

I am demoíing a MFA MAGUS A-2 preamplifier this weekend. Iím really blown away with the sound however it has a problem with the source selector. When I choose phono, the left channel suddenly becomes very finicky.

Thereís a little bit of crackling and an attenuated signal compared to the left; a little bit of pressure on the knob in the right places brings it back to normal. But itís always the left channel, the right is fine.

No such problems with the other sources. Iíve double and triple checked.

Iíve tried some deoxit from the inside and I tried flipping the knob back and forth a number of times periodically throughout the evening but it continues to act the same way.

This unit has been sitting for a while and has not been used. Is this something that will work its way through on itís own or is this something more serious?

Replacing the selector is likely beyond my skills, but I would pay to have it done if I decide I like the unit. How much is it likely to run?

Thank you in advance for your replies to this fairly simple issue.

Shawn
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Old 14th July 2018, 12:10 AM   #2
audiopro is offline audiopro  Canada
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Easy to replace the selector in these. I've done it at least a dozen times. Depending on the quality of switch used $40 -$80.00
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Old 14th July 2018, 12:15 AM   #3
vandalfsens is offline vandalfsens  United States
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Thank you for your quick response.

Does that mean that a moderate DIYer such as myself could do it?

It looks like this particular unit is two pieces of plastic held together with clips what I do well to try and pry them apart and get deoxy on the inside? Or is spraying deoxy in the center hole good enough?

Also, I should add, that I havenít bought it yet so I probably shouldnít be mucking around too much. LOL
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Old 14th July 2018, 12:19 AM   #4
Richidoo is offline Richidoo  United States
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If cleaning the switch doesn't help, then it could be a bad connection, resolder all the phono left leads. Or a bad part, like cracked resistor.
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Old 14th July 2018, 12:31 AM   #5
audiopro is offline audiopro  Canada
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If you try to pull that apart, you may make it worse.
The biggest issue with replacing, is getting the old one out without damage IF it is the version with the switch soldered directly onto the board. If it is a hard wired switch, it's pretty easy. Just have to make sure you get the contacts correct.
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Old 14th July 2018, 12:54 AM   #6
vandalfsens is offline vandalfsens  United States
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Join Date: Aug 2010
Location: Wausau WI
Thank you to everyone for your replies, I don’t spend a lot of time on this forum because I don’t know a lot about electronics and I’m not an electrical engineer, I just like to dabble with great sound.

I think it’s best if I take this through the weekend, see if it improves, and then have a discussion with the owner on Monday.
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Old 14th July 2018, 02:39 AM   #7
Bare is offline Bare  Canada
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There IS of course the question of: WHY? the unit needs a ~80$ parts fix/upgrade.... so it will even work as you expected it to... when you paid for the Stoopid thing.
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Old 14th July 2018, 02:46 AM   #8
rayma is offline rayma  United States
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Quote:
Originally Posted by vandalfsens View Post
I think it’s best if I take this through the weekend, see if it improves,
and then have a discussion with the owner on Monday.
Looks like a hard-wired, non-pcb-mounted switch.
The contacts are probably worn or corroded, and so
will not improve. It should be straightforward to remove
and replace with another switch. There are many options.
Attached Files
File Type: pdf magus.pdf (174.4 KB, 41 views)

Last edited by rayma; 14th July 2018 at 02:50 AM.
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Old 14th July 2018, 12:43 PM   #9
vandalfsens is offline vandalfsens  United States
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It certainly appears as if the deoxit worked its magic overnight. This morning I can switch back-and-forth from the other sources to phono without any issues at all.

I will continue to monitor this weekend.

Just to give everybody a little bit of background, I’ve always loved music and I’ve always been a budget audiophile. I went from an Adcom system to vintage Hafler, the preamplifier had been updated by musical concepts. I really loved it but I was tempted by all of the great reviews for Cambridge Audio’s 851a integrated.

I bought one and tried it for several weeks but I just could not get involved. I guess what they say about British audio is true, it’s very polite and reserved. I guess I’m looking for a little more energy.

I’ve gone back to a Hafler DH 220 which was upgraded by musical concepts and recently given a clean bill of health by same. My local audio store happened to have this MFA preamplifier on the used rack. It was traded in by a customer who purchased at Primo Luna. It had just been overhauled by United radio in New York.

It is really outstanding! I am hearing things from my records that I have never heard before! Amazing detail and very musical.

Again, I’d like to thank everybody for their replies with white is probably a newbie type issue.

Typically speaking I’m Type A enough that I want my power amplifier in preamplifier to match, at least to come from the same company. But this set up sounds so amazing I think I may stick with it.

My turntable is a Pro-ject 5.1 SE with the Sumiko Bluepoint Number 2 .cartridge

Last edited by vandalfsens; 14th July 2018 at 12:46 PM.
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