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Help trouble shoot Scott combo

69.255.251.215
Posted on March 28, 2020 at 09:35:03
Cpwill
Audiophile

Posts: 1096
Location: DC
Joined: December 22, 2003
Contributor
  Since: October 24, 2008
 I having been using a Scott 310-D tuner/335 multiplex combination for quite a while. Lately it has been going as berserk as my 2-ish year old pit bull pooch. It will play fine for a while and than go to total loud static with the meter pegged to the right. Rotating the tuning dial has no impact; nothing but static as the meter remains pegged. Because of the meter issue, I assume the problem is with the tuner, not the multiplex, but I could be wrong. Sometimes, if I disconnect the antenna, it will return to normal and I can pick up my favorite station, which is 50K watts and less than 2 miles away. Other times the meter pegs to the left and I get nothing but a softer static. If it returns to normal and I reconnect the antenna, sometimes the problem returns right away, other times, it plays fine for a while before the problem returns. I can never try to listen for more than say 20 minutes +/- before it goes haywire. I have double checked the antenna connections and all tubes are well seated and glowing. Beyond that, I know nothing about tuner maintenance/repair compared to amps, preamps, etc.

So, any suggestions of what I could look for before trying to find a reputable repair service.

Thanks in advance.


"Anyone who understands jazz knows that you can't understand it. It's too complicated. That's what's so simple about it." - Yogi Berra.

Cpwill

 

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RE: Help trouble shoot Scott combo, posted on March 28, 2020 at 10:57:16
fredtr
Audiophile

Posts: 1987
Location: Phoenix
Joined: January 4, 2005
 Touch the tubes, coils and tuning capacitor when it is in static mode. Dirty tube sockets, pinched coil wire and dirty tuning capacitor grounds can all cause what you are seeing. If you localize to touching just one thing and affecting the problem you can then deal with it by cleaning the tube socket, insulating coil wire or cleaning wipers.

It could also be a heat component related problem, but more likely when it warms up, the thermal expansion causes one of the above.

 

RE: Help trouble shoot Scott combo, posted on March 28, 2020 at 16:41:21
fredtr
Audiophile

Posts: 1987
Location: Phoenix
Joined: January 4, 2005
 BTW, the coils I mentioned are in the squarish cans, next to the tubes. Scott tuners, the 6U8, be sure it is a 6U8 and not 6U8A. The construction is different, it doesn't matter in most applications, but it does here.

 

RE: Help trouble shoot Scott combo, posted on March 29, 2020 at 14:48:15
eds65gto
Audiophile

Posts: 196
Location: Mt Pleasant SC
Joined: December 29, 2003
 Hi:
I think that the trouble with your tuner is that you are too close to the transmitter.
Try hooking up a two or so foot piece of wire to the antenna terminal, just stick the end of the wire into the center of the F "Antenna" connector and see what happens. Or if using the 300 ohm twin lead connections , hook the wire to just one of the screw connections.
Since you are so close to the station you may be overloading the antenna input.
Hope this helps
Ed

 

RE: Help trouble shoot Scott combo, posted on March 30, 2020 at 07:49:15
Cpwill
Audiophile

Posts: 1096
Location: DC
Joined: December 22, 2003
Contributor
  Since: October 24, 2008
 Thanks, however, It doesn't correct itself when using the tuning dial to tune to a more distant or weaker station. Also, why now after working fine foe a long while. Neither the tower or my home have moved.

Thanks


"Anyone who understands jazz knows that you can't understand it. It's too complicated. That's what's so simple about it." - Yogi Berra.

Cpwill

 

RE: Help trouble shoot Scott combo, posted on March 30, 2020 at 12:58:11
Cpwill
Audiophile

Posts: 1096
Location: DC
Joined: December 22, 2003
Contributor
  Since: October 24, 2008
 I listened for over 2 hours this morning, and could not replicate the problem. That is the longest it has played without going bonkers. All tubes seem tight.


"Anyone who understands jazz knows that you can't understand it. It's too complicated. That's what's so simple about it." - Yogi Berra.

Cpwill

 

RE: Help trouble shoot Scott combo, posted on March 31, 2020 at 13:27:23
fredtr
Audiophile

Posts: 1987
Location: Phoenix
Joined: January 4, 2005
 Intermittent problems can be like that. Temperature and/or vibration is the catalyst that causes the problem to come and go.

I have had the coil problem I mentioned on a 310d and 350b. I reread your first posting, the affect of disconnecting the antennae, that is different than what I saw with the coils, but it didn't take much vibration to cause the problem to come and go. One thing you can do, is to order a 6u8 and a 6bs8/6BQ7A. They are inexpensive tubes and particularly the 6u8 can cause similar symptoms. You won't need to re-align, if the problem continues, swap the tubes in one at a time and see if it helps.

 

RE: Help trouble shoot Scott combo, posted on April 3, 2020 at 17:02:02
6bq5
Audiophile

Posts: 4385
Location: SF Bay
Joined: August 16, 2001
 one other issue you may wish to consider is to get the tuner aligned
this needs to be done by a tuner tech- but most McIntosh service centers are capable (and competent) -
Happy Listening

 

RE: Help trouble shoot Scott combo, posted on April 6, 2020 at 19:09:01
Steve O
Audiophile

Posts: 12362
Location: SE MI
Joined: September 6, 2001
 Sounds like a case of the dreaded leaky silver/mica caps internal to the IF cans. Results from silver migration across the mica insulator discs. Typically sounds like you're receiving an intermittent thunderstorm with hisses and crackling punctuated by loud crashes. Heat and moisture can make things worse. If this is the case, the defective can(s) can be removed, opened up and the offending caps replaced but its not a procedure for the faint-of-heart. A realignment will also be required in most cases

 

RE: Help trouble shoot Scott combo, posted on April 9, 2020 at 06:57:07
fredtr
Audiophile

Posts: 1987
Location: Phoenix
Joined: January 4, 2005
 That's interesting, I have never seen those silver mica caps fail in the Scott. Thank-you for posting it. I have seen twice now, the coil leads shorting against the can at the base, giving the symptom described by the OP. The pegging of the needle has been for me a common symptom of the coils and other problems in the IF and upstream.

 

Some closure. . . , posted on April 14, 2020 at 06:42:43
Cpwill
Audiophile

Posts: 1096
Location: DC
Joined: December 22, 2003
Contributor
  Since: October 24, 2008
 . . .at least for now. So the problem returned after I last wrote, and continued intermittently. I decided to swamp a few tubes, the 6U8, 6BN6 and the 12AU7 fell out. It's bottom was cracked and two pins were still in the socket. Perhaps one of those was loose during the problem period. I don't have a schematic so I don't know if its function could have caused the problem. Anyway, with new tubes in those positions, the tuner has played consistently well for nearly two weeks.

I just hope I haven't jinxed it by writing this.

Thanks all, stay safe.


"Anyone who understands jazz knows that you can't understand it. It's too complicated. That's what's so simple about it." - Yogi Berra.

Cpwill

 

RE: Some closure. . . , posted on April 14, 2020 at 06:58:12
fredtr
Audiophile

Posts: 1987
Location: Phoenix
Joined: January 4, 2005
 12au7 is mono audio output, wouldn't cause the problem. 6U8, 6BN6 could have certainly been the cause.

 

RE: Help trouble shoot Scott combo, posted on May 11, 2020 at 08:24:28
Mr_bill2
Audiophile

Posts: 2178
Joined: September 17, 2002
 Foster Blair is the guy you want to talk with. Way back when he was the guy doing the Mapleshade mods. He did the work on my H.H. Scott 310E. I've got contact info if needed.
Good luck


 

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