old technics turntable goin' bonkers
kevin farmer
technics SL-5200--direct drive, quartz-controlled--has seemingly lost its
ability to regulate speed, turning fast enough to spin the stylus out of
the groove.
an occasional, and momentary, respite can be had via removal of the
platter from the spindle. i have also cracked open the chassis and tried
to blow the dust out as best i could, and that actually cleared things up
for about a week.
then one day the thing just took off running again.
what's up?
Gary Woods
ltl...@mindspring.com (kevin farmer) wrote:
>technics SL-5200--direct drive, quartz-controlled--has seemingly lost =
its
>ability to regulate speed, turning fast enough to spin the stylus out of
If I had to guess (I've seen this behavior in pro video recorders),
you've lost a tach signal that tells the servo how fast the platter is
turning. Probably magnetic; look for a pickup under the platter,
check for continuity, scope wherever it goes. If you have _no_ tach
and the servo isn't particularly smart, it will just keep calling for
"more power; I'm too slow..." until the motor can't run any faster.
(newer stuff would announce, "error xxx; no tach sense."
Gary Woods, acting interim web guy, and technician at LARGE
Neil Leipziger
On 3 Dec 1997 19:58:59 GMT, ltl...@mindspring.com (kevin farmer)
wrote:
>technics SL-5200--direct drive, quartz-controlled--has seemingly lost its
>ability to regulate speed, turning fast enough to spin the stylus out of
>the groove.
>an occasional, and momentary, respite can be had via removal of the
>platter from the spindle. i have also cracked open the chassis and tried
>to blow the dust out as best i could, and that actually cleared things up
>for about a week.
>
>then one day the thing just took off running again.
>
>what's up?
Hi Kevin... I've repaired many of these. Usually is caused by an
erratic speed selector switch. Spraying the switch doesn't alway cure
it. I've disassembled the switch and clean contacts using an eraser
and reassembling the switch.
Regards.... Neil
Sam Goldwasser
The fact that it is intermittent suggests a bad connection or dirty switch or
connector. Loss of the feedback pulses - possibly from a magnetic pattern
inside the platter - would likely result in the runaway condition.
So, check for bad connections, cracked solder connections, dirty mode switch,
etc.
--- sam : Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Lasers: http://www.geocities.com/CapeCanaveral/Lab/3931/lasersam.htm
Usually latest (ASCII): http://www.pacwest.net/byron13/sammenu.htm
Jim Lagerkvist
kevin farmer wrote:
>
> technics SL-5200--direct drive, quartz-controlled--has seemingly lost its
> ability to regulate speed, turning fast enough to spin the stylus out of
> the groove.
> an occasional, and momentary, respite can be had via removal of the
> platter from the spindle. i have also cracked open the chassis and tried
> to blow the dust out as best i could, and that actually cleared things up
> for about a week.
>
> then one day the thing just took off running again.
>
> what's up?
Check for dirty contacts of the 33/45 rpm switch.
This was an exact problem on a Pioneer model.
Nigel Cook
> technics SL-5200--direct drive, quartz-controlled--has seemingly lost its
> ability to regulate speed, turning fast enough to spin the stylus out of
> the groove.
> an occasional, and momentary, respite can be had via removal of the
> platter from the spindle. i have also cracked open the chassis and tried
> to blow the dust out as best i could, and that actually cleared things up
> for about a week.
>
> then one day the thing just took off running again.
>
> what's up?
please contact e-mail or telephone me the proprietor of
Diverse Devices,Southampton,England;telephone (+44) (-0)1703 584680
(Shop stocking obscure/obsolete components,second hand test equipment,schematics etc)
Postal: 75 Priory Rd,St Denys,Southampton,England SO17 2JQ.
email div...@tcp.co.uk
repair briefs and hints/tips on homepage http://www.tcp.co.uk/~diverse/
Sale now on......15 per cent off all equipment and components
regards, Nigel
kevin farmer
thank you all for the advice!
i've narrowed my application area, vis-a-vis compressed air, to the magnet
under the platter, and have had a greater success rate affecting normal
playback speed, though reversion to high speed continues.
clearly a better cleaning is in order.
someone suggested an eraser. any other tips?
thank you, again-
-kevin
Sam Goldwasser
What are you calling a magnet? I was suggesting that there may be a
magnetic pickup - sort of like a gross version of a playback head. If
so, try adjusting it so that it is closer (BUT NOT TOUCHING) the platter.
--- sam : Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Lasers: http://www.geocities.com/CapeCanaveral/Lab/3931/lasersam.htm
Usually latest (ASCII): http://www.pacwest.net/byron13/sammenu.htm
kevin farmer
In article <SAM.97De...@colossus.stdavids.picker.com>,
s...@stdavids.picker.com (Sam Goldwasser) wrote:
>What are you calling a magnet? I was suggesting that there may be a
>magnetic pickup - sort of like a gross version of a playback head. If
>so, try adjusting it so that it is closer (BUT NOT TOUCHING) the platter.
i'm calling something a magnet that clearly is not a magnet.
i do see something that resembles a playback head, only there are three of
them, located at equidistant intervals surrounding the spindle. that is
where i concentrated my eforts with the canned air.
and it seemed to help, though a permanent solution still eluded me.
oddly enough, last time the thing started cooking at a gazillion rpms i
just let it run. after about fifteen or twenty minutes it reverted back to
proper speed and hasn't sped up since.
?
-kevin
Tech Guy
It sounds like you are referring to the permanent magnet rotor on the platter below the spindle. If this is not damages, leave it alone.
If this is correct, you may need to clean or replace the variable speed control especially common on 1200 series.
( it looks like a very large volume control - about 5" long )
Sam Goldwasser
Well, as they say, "If it ain't broke (any longer), don't fix it" :-).
Not having seen that model, I sm still not clear on what you are describing.
Is there anything near the perimeter of the platter underneath?
--- sam : Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Lasers: http://www.geocities.com/CapeCanaveral/Lab/3931/lasersam.htm
Usually latest (ASCII): http://www.pacwest.net/byron13/sammenu.htm
Asimov
s...@stdavids.picker.com said the following to All on the subject of
Re: old technics turntable goin' bonkers (15 Dec 97 13:10:24)
sa> From: s...@stdavids.picker.com (Sam Goldwasser)
sa> Subject: Re: old technics turntable goin' bonkers
sa> Well, as they say, "If it ain't broke (any longer), don't fix it" :-).
sa> Not having seen that model, I sm still not clear on what you are
sa> describing.
sa> Is there anything near the perimeter of the platter underneath?
>What are you calling a magnet? I was suggesting that there may be a
>magnetic pickup - sort of like a gross version of a playback head. If
>so, try adjusting it so that it is closer (BUT NOT TOUCHING) the platter.
sa> i'm calling something a magnet that clearly is not a magnet.
sa> i do see something that resembles a playback head, only there are
sa> three of them, located at equidistant intervals surrounding the
sa> spindle. that is where i concentrated my eforts with the canned air.
sa> and it seemed to help, though a permanent solution still eluded me.
sa> oddly enough, last time the thing started cooking at a gazillion
sa> rpms i just let it run. after about fifteen or twenty minutes it
sa> reverted back to proper speed and hasn't sped up since.
sa> ?
sa> -kevin
Just remembered a problem I was working on recently concerned a monitor
blowing hot's intermittantly. When in failure mode the horizontal
frequency was some 10 times higher than it should be. Turned out it was
a 100uF 10wv electro that was occasionally shorting out the oscillator's
supply. This 10 volt part was undoubtably mistaken for a 16 volt unit to
filter a 12 volt line. Even the silkscreen outline had a larger
diameter. I replaced it with a 25 volt unit at hand and this cured it.
As you probably know, typically oscillation frequency goes higher as the
supply voltage decreases. This is what was happening each time that cap
broke over pulling down the supply and resulting in a higher frequency.
Perhaps your reference oscillator's supply voltage is being pulled down
by a shorting or leaky electro?
--
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