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Musical Fidelty A5 amp - small problem (I hope)

 

Gold Member
Username: My_rantz

Australia

Post Number: 2202
Registered: Nov-05
My MF A5 integrated amp is displaying a small problem. Usually I leave it and the cd player turned on for a while before playing. When playing a cd, if I turn the volume knob by hand (or covered hand) I get a static type sound or even a loud nasty snap (or crack if you like) through my speakers. No such noise is apparent wherever I leave the volume setting.

Now, if I use the remote to adjust the volume (a motorized control that turns the dial) there are no noises. Also after playing for an hour or so there is no problem either adjusting by hand or remote control.

My dealer/serviceperson (though not an MF dealer) was a bit baffled when I explained this by phone. His first suggestion was muck in the volume pot but the fact that using the remote caused no problem swayed him against that thought. He suggested bringing it in which of course is the obvious thing to do, but I just wondered if Jan or anyone had any ideas.

As I said, it's no big problem as I usually use the remote anyway, my worry is: could it be something that could worsen and turn into a big problem?

I also have a connection from the pre-out of our Marantz receiver into the HT (or pre-in) connection of the A5, but that is turned off (well in standby) when I play a cd. Speaker and IC connections checked also.
 

Platinum Member
Username: Nuck

Post Number: 12450
Registered: Dec-04
MR, try touching a good ground before you touch the amp.
Avoid the gear cases, but rather something else, just as a test, the screw in the middle of an outlet cover should do.
Wild guess.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 13637
Registered: May-04
.

I'm not familiar with the MF gear and they do some "unusual" engineering at times. I would take wild guess that there is a loose connection at the motor for the vc.

This could be a static electricity problem but such problems don't tend to go away after an hour's playing time. Occasionally, such a problem exists just due to a person's body chemistry. Just out of curiosity, does the same thing happen when your wife works your controls?

.
 

Gold Member
Username: Artk

Albany, Oregon USA

Post Number: 9663
Registered: Feb-05
Both my Unison and Creek amps do that as well and it's static with them.
 

Platinum Member
Username: Nuck

Post Number: 12452
Registered: Dec-04
JV, you could have it. The mechanical motion inducing voltage acting against the VC's motor circuit creating stray voltage that feeds back to the guts.
Quick check would be to unplug the motor, MR.
 

Gold Member
Username: My_rantz

Australia

Post Number: 2204
Registered: Nov-05
Just out of curiosity, does the same thing happen when your wife works your controls?

Well, it doesn't make me snap :-)

But, a good suggestion to try.

Thanks for the responses guys. I won't tamper with it myself (except for Nuck's grounding suggestion) but I'll pass the info to the service guy when I take it in. I just recently had to replace 2 prs of inputs (they come on a plastic plate of two or four pairs) as I must have been too heavy handed removing those Merlin I/C's and cracked a solder join.

I thought 'static' myself that's why I tried turning the volume with some cloth around my hand - so it seems if it is, it wasn't coming from me.
 

Gold Member
Username: My_rantz

Australia

Post Number: 2206
Registered: Nov-05
Nuck, I tried your suggestion of first touching a screw on the rear panel.

Luckilly the paramedics arrived just in time. Phew!




























heh, heh!

Yep, no noise. However, I'm not yet about to say it worked, if I get the same result tomorrow and the next day, then I'll say it worked and state what a smart fella you are.

 

Gold Member
Username: Mike3

Wylie, Tx USA

Post Number: 1970
Registered: May-06
For years I have worked around server racks where there is a grounding strap one should have in hand prior to pulling cards from slots.

I am not trying to diminish the beauty of your set up but it is a pain in the butt to disassemble kit and bring it to a dealer. I would at least loosen a screw on the A5 and strip a thin run of wire and wrap it around the screw, tighten the screw and then run the wire to the outlet screw Nuck mentioned above. Loosen that screw as well, strip that end of the wire and wrap it around the outlet screw then tighten again.

What have you got to lose?
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 13643
Registered: May-04
.

"What have you got to lose?"

It's not so much what he has to lose but what he has to gain. Since chassis ground is not electrical ground in all components, there is the possibility of a ground loop when you hard wire a ground cable to any electrical outlet ground - even more so if the elctrical outlet is not run to a true Earth ground. But it is not life and death and if it solves the problem, then it's worth the effort. If it doesn't, just disconnect the cable.


.
 

Platinum Member
Username: Nuck

Post Number: 12464
Registered: Dec-04
MR, I am not familiar with Aussie electrical code.
I am assuming that you use standards closer to North America as compared to the funky Brit stuff?
 

Gold Member
Username: My_rantz

Australia

Post Number: 2208
Registered: Nov-05
Funny thing is guys, since I tried your suggestion Nuck, the problem has not reoccurred. This doesn't make sense as I touched the screw on the rear panel only once two days ago.

Mike, Jan - I'll follow through with Mike's suggestion when and if the problem reoccurs. I'm at loss though why it hasn't without following Nuck's tip each time I power up the amp and cdp.

Oh, and because it hadsn't happened again, I haven't had the better half try. Stay tuned.

Edit - I just tought of this:

Since chassis ground is not electrical ground in all components, there is the possibility of a ground loop when you hard wire a ground cable to any electrical outlet ground - even more so if the elctrical outlet is not run to a true Earth ground.

Then why didn't this problem occur from the beginning?

The amp and cdp have 3 prong (1 earth) plugs that go into an 8 point belkin power board with surge protection powered from a wall outlet that should be correctly earthed (since the electricals in the box have an earth to a copper rod in the ground. That's about as far as my electrical knowledge can tell you - and we're 240volts here.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 13646
Registered: May-04
.

"Then why didn't this problem occur from the beginning?"

Don't know. Sometimes that's the only answer to such problems. You just have to hope it doesn't return since the same fix then sometimes proves not to have been anything more than coincidental.


.
 

Gold Member
Username: My_rantz

Australia

Post Number: 2209
Registered: Nov-05
Fair enough.

Thanks for all the tips guys. If the problem returns I shall try all suggestions and post results back here. Otherwise I'll leave well enough alone.
 

Platinum Member
Username: Nuck

Post Number: 12480
Registered: Dec-04
Buy Nuck a drink.
Buy Nuck a drink.

See above.
 

Gold Member
Username: My_rantz

Australia

Post Number: 2210
Registered: Nov-05
The bar don't extend to Ca, but I'll have one or four in your stead my friend. In fact I'm gonna do that right now!



Oh, and your'e a smart guy :-)
 

Gold Member
Username: My_rantz

Australia

Post Number: 2211
Registered: Nov-05
I take the drinks back, Nuck and you're smart title :-)

The problem returned this afternoon and I think I may know the cause. The week I picked up the amp from the service to replace the inputs, was very precipitous and it was a little showery today so I believe the problem can be put down to moisture. So, if that is the case, what to do about it ?????

Any more suggestions?
 

Platinum Member
Username: Nuck

Post Number: 12488
Registered: Dec-04
Then it seems to go back to the motor controller, MR, putting feedback into the amp.
Service shop time?
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 13647
Registered: May-04
.

Yep, go back to the shop and see what they can figure out. This could be a cold solder joint that is open when cold and then fades away as the unit warms up. Any recent repair would give that a good chance. The worst case would be a cracked board. Your best chance of success in the repair would be to do as much homework as possible before handing it to the etch, being able to provide accurate clues will give the tech somewhere to begin. Once it's on the bench it could take awhile for intermittent problems to show up.


.
 

Platinum Member
Username: Nuck

Post Number: 12492
Registered: Dec-04
And the meter is ticking...
 

Gold Member
Username: My_rantz

Australia

Post Number: 2212
Registered: Nov-05
Hmm okay, but I did not try your grounding tip again yesterday Nuck, I'll do that later just to double check. If that solves it again, then I try Mike's tip. Having the amp sitting in the tech's place is the last thing I want, but que sera sera I guess. I'll check back later guys with any new developements, thanks.
 

Gold Member
Username: My_rantz

Australia

Post Number: 2216
Registered: Nov-05
Well, I took the cover off the A5 as I was going to follow Mike's tip: to attatch a wire from an outlet screw to a screw on the chassis.

I cramped myself down behind the speaker again, cursed numerous times trying to undo the speaker connections etc without knocking the speaker (you do not want speakers spiked to slate) and manouvered the almost 40lbs off the isolation board and got it onto the kitchen bench.

Next I undid the numerous screws holding down the top plate and had a look inside; big capacitors, huge toroidal transformer, decent looking wiring and so on. Mike's tip is a no go and Nuck's advice was about the same in usefulness in this situation, so when the noise disappeared for a couple of days must have been a coincidence as Jan stated.

The outlet screws themselves thread only into the plastic/nylon input cartridges hence having no effect to grounding whatsoever. The rear plate and chassis are correctly grounded from the point where the power supply wires are connected (earth to the chassis). Apart from a minor amount of dust which I lightly brushed off and blew out, nothing seemed wrong - yes I know, I wouldn't be able to see such things as a cracked board, cold solder joint and so forth.

At least it was an interesting hour or so if nothing else - thanks Mike, my friend :-)

So, it seems if the problem persists it will definately be taking a trip to the techie and I'll relate everything stated here.
 

Platinum Member
Username: Nuck

Post Number: 12601
Registered: Dec-04
Where do you stand now, MR?
Did it maybe just go away from handling the amp?
 

Gold Member
Username: My_rantz

Australia

Post Number: 2227
Registered: Nov-05
No such luck, Nuck (could be a poem starting here).
It's a matter of timing - when I have the time, the tech is busy, I may try again tomorrow. It's a case of my not wanting to leave it with him unless absolutely necessary - hoping he can find the reason while I'm there.
 

Gold Member
Username: Dmitchell

Ottawa, Ontario Canada

Post Number: 2651
Registered: Feb-07
a poem... or a dirty limerick.
 

Gold Member
Username: My_rantz

Australia

Post Number: 2228
Registered: Nov-05
Well, yesterday and today the problem didn't occur - we're having very dry weather here at present - and I don't want to take it in if there are no signs. Could it be moisture problem perhaps?

Anyway . . .

There once was a lad called Nuck
and he was having a bit of bad luck
When his Mac made a groan
Nuck began to moan
Then all he could do was yell "Oh darn!"

Something like that, Dave?
 

Gold Member
Username: Dmitchell

Ottawa, Ontario Canada

Post Number: 2652
Registered: Feb-07
lol. That's perfect M.R.
 

Platinum Member
Username: Nuck

Post Number: 12609
Registered: Dec-04
Hallmark cards might be hiring, MR!
 

Gold Member
Username: Mike3

Wylie, Tx USA

Post Number: 1993
Registered: May-06
M.R., seemingly the problem is intermittent (another word for hourly technical types to triple to time it takes to identify the issue).

You have indicated that it makes itself known on days that the weather is not dry.

So instead of taking the amp to the shop for an indefinite time and with no guarantee a problem can even be found wouldn't it make more sense to just replace your amp stand with a dehumidifier?



No comments about me not being wired right most appreciated.



Just kidding about the amp stand, you could put the dehumidifier anywhere close to the Integrated amp you wanted to, it just seems that right under the amp would be the most effective deployment.
 

Gold Member
Username: My_rantz

Australia

Post Number: 2232
Registered: Nov-05
Mike, I was thinking along those lines - except I thought about a cheaper option like a bag of silicon to draw the moisture. It really isn't a problem at all providing I use the remote, but I do like things to be right. More testing in the dry and I'll see how it behaves when the weather changes again.

And you know I wouldn't comment about your wiring Mike. BTW, how was your stay at Bellvue?

 

Gold Member
Username: My_rantz

Australia

Post Number: 2254
Registered: Nov-05
The problem with the A5 has been fixed. The volume pot needed more lubrication. It took the tech a while and finally something gave and presto - no more noise. Thought this problem wasn't evident using the remote, it was the slight pressure on the spindle when turning the volume knob manually.

So it's good fo now at least!
 

Platinum Member
Username: Nuck

Post Number: 12728
Registered: Dec-04
Stick with the remote, MR, the shaft might be a little thin to react like that.
Good to know its fixed, that was some bit of postulation we had there, hehe!
 

Gold Member
Username: My_rantz

Australia

Post Number: 2257
Registered: Nov-05
No it's not thin at all Nuck, it could be it wasn't lubed well enough in the factory to begin with. The remote turns the control quite slowly and without any pressure so that could have something to do with it. All still seems good now.
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