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 Post subject: tuner drifting?
PostPosted: Sun Aug 14, 2016 1:18 pm 
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Joined: Sun Apr 05, 2009 7:06 pm
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Location: hawkesbury, ON, CA
hello, I have a McIntosh mx 110 I like it very much , I few years ago a problem accured and ounce it a while it come and go.
the tuner sound great, and station pull in very good. I have a rooftop antenna, ounce I a while the station althought it is coming in good, the station start drifting like if the signal was lost and then it come back just fine like it was before. I wonder if it can be a bad tube in the tuner section. I have replace many tube. sometime the trouble go for month, then it come back for a little while, tubes component for the tuner are as follow
6ds 4 for RF 1 amplifier nuvistor
12 at7 for rf 2 mixer
6ab 4 for oscillator
6au 6 for if 1
6au6 for if 2
6au6 for if 3 limiter 1
6cs6 for if 4 limiter 2
12 at 7 for muting L+R amplifier
6 hu 6/em87for tuning indicator
6 d 10 for fm audio left and right 1 st audio amplifier
6 u 8 for mpx amplifier and 19 kc separator
12au 7 for mpx 38 kc oscillator

now those are for tuner section I think, and a few other tube but for pre amp section,
I know the tuner section is the problem because pre amp work flawlessly.
anybody add the same problem with a mx 110 or other tube tuner, that sound similar to my problem, was it tube related?
should I look elsewhere for my problem.
I know most of you will say change all tubes, or go to a technician. who will probably change all tube wich is something I can do myself, but would cost twice as much and might not fixe that problem.
I have many bad experience trying to find a technician that know what he is doing with tube tuner.
so my question is, which tube should I replace next I already change more than half of those tube.
in all those tube I describe wich one is the most likely to give me that kind of trouble.


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 Post subject: Re: tuner drifting?
PostPosted: Sun Aug 14, 2016 1:33 pm 
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Joined: Tue May 21, 2013 12:54 pm
Posts: 4700
Location: Dodge City, NB, CA
Zon,
Do you have another tuner you can sub in when this happens?. If it happens every now and then it could be due to atmospheric conditions and not a tuner issue at all. If another tuner does the same thing at the same time, blame Mother Nature.
Ken.

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 Post subject: Re: tuner drifting?
PostPosted: Sun Aug 14, 2016 2:54 pm 
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Joined: Sun Apr 05, 2009 7:06 pm
Posts: 942
Location: hawkesbury, ON, CA
KJT1 wrote:
Zon,
Do you have another tuner you can sub in when this happens?. If it happens every now and then it could be due to atmospheric conditions and not a tuner issue at all. If another tuner does the same thing at the same time, blame Mother Nature.
Ken.

sorry I don t have another tuner to try out, but I add a mx 112 before using the same antenna,for 4 years and i never did add that problem before. and I also used the mx 110 for the first 2 years with no problem, it just started 2 years ago.

-- 14 Aug 2016 23:00 --

I did change the 12 at 7,6 ab 4,6 d10,12 au 7, and 6 ds 4 tube 1.5 years ago, the problem disappeared for about 6 month, but came back. I cleaned all socket.and the 6 ds 4 rca tube (new) look weaker than the old McIntosh tube I add on , so I put the old one back. also when I wiggle that 6ds4 tube a little bit. problem will go away for an hour but will come back after. should I replace the other tube I did not replace, they are harder to find.


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 Post subject: Re: tuner drifting?
PostPosted: Sun Aug 14, 2016 3:24 pm 
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Joined: Tue May 21, 2013 12:54 pm
Posts: 4700
Location: Dodge City, NB, CA
Zon,
I think that if you can get it to come back by wiggling the tube that it is not likely the tube. I would switch the tube with one of it's mates just to confirm this. If the tuner works properly after you do this I would be more likely to believe that you might have either a cold solder joint under the socket or that the socket itself is faulty. I do not have a ton of experience with tubes but I have worked in electronics for forty years and have found that things like tubes and transistors do not alternate between working and not working. However, things like solder joints and tube sockets will as they react to heat and vibration.

Another thing that comes to mind even though I don't think this is your problem but it couldn't hurt is when was the last time this tuner was aligned. Tuner tubes are not high current like a power amp and tend to last a long time but if the bias has gone off the tuner section itself will not be working as well as it could. I'm sure there are other possibilities as well but these are the ones that are coming to mind at the moment.
Good Luck,
Ken.

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 Post subject: Re: tuner drifting?
PostPosted: Sun Aug 14, 2016 4:00 pm 
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Joined: Sun Apr 05, 2009 7:06 pm
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Location: hawkesbury, ON, CA
you are right, I should try to re-do all soldering on that socket, but it is very small,tube is only 1/4 inche in diameter,and made of metal.hopefully it might be easy to access.


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 Post subject: Re: tuner drifting?
PostPosted: Sun Aug 14, 2016 5:12 pm 
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Joined: Sun Dec 28, 2008 7:49 am
Posts: 1625
Location: Fairport Beach (in Pickering), ON, CA
FWIW:

I have a similar issue with my recapped McIntosh MR65B. I was talking to the tech at Bay Bloor Radio a couple weeks ago and he said ... check the tubes as it's not an alignment issue.

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Collecting vintage tube Pilot (Pilotone) HiFi gear.


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 Post subject: Re: tuner drifting?
PostPosted: Sun Aug 14, 2016 5:24 pm 
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Joined: Tue May 21, 2013 12:54 pm
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Location: Dodge City, NB, CA
Tom_r wrote:
FWIW:

I have a similar issue with my recapped McIntosh MR65B. I was talking to the tech at Bay Bloor Radio a couple weeks ago and he said ... check the tubes as it's not an alignment issue.


Well, did you?. Was it a tube or something else?.

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 Post subject: Re: tuner drifting?
PostPosted: Mon Aug 15, 2016 3:38 am 
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Joined: Sun Apr 05, 2009 7:06 pm
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Location: hawkesbury, ON, CA
I also dought that it is an alignement issue, because alignment would drift ALL the time, it would not be intermittent.
I listen to it for 3 hour last night, no problem? it comes and go, just like if the antenna, was moving and loosing channel, but when happening, all channel go. welding issue or bad socket, is something I will have to check.
allignement on these look like very complicated, many adjustment, and I do not know ANY technician that I would feel confident to give that kind of job to. he can end up making more trouble than good.
let s face it, when it come to INTERMITENT issue, I have spent more than MY fair share of spending with NO result.
and this one is no exception.


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 Post subject: Re: tuner drifting?
PostPosted: Wed Dec 21, 2016 6:14 pm 
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Joined: Sun Apr 05, 2009 7:06 pm
Posts: 942
Location: hawkesbury, ON, CA
I did check all welding first . no issue.
fixed my problem. it was a bad tube. I narrow down the tube for the tuner only, and they are
1 x 6ds4
2x 12at7
2x 6au6
1x 6ab4
so I look up for those tubes and could only get them from 3 different places, so I dicide to start with the cheapest one
the 6ds4 . it was not that one
so I odered 2 x 6au6 and the single 6ab4 put them on and bang now the tuner signal is over the roof. it come in so good the tuning indicators never went that strong. I think it was the 6ab4 tube suppose to be for oscilator, because when I was touching it, it would cut signal immidiatly.and comeback but always very low signal. now it is perfect.
I should now consider changing my phono stage tubes . if I change those tube for better or different ones would it change the tonality of the cartage? I will start that tread .


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