Tim Schwartz wrote:
> RuF wrote:
>> valhealey wrote:
>>> Tim Schwartz wrote:
>>>> RuF wrote:
>>>>> Hi Experts,
>>>>>
>>>>> I have finally managed to get my 1219 going again, this time with a
>>>>> new Shure M97xE.
>>>>> It feeds into a Sony STRAV260 amplifier via RCA cables.
>>>>>
>>>>> The right channel is working fine but the left one has a very weak
>>>>> output. I swapped the
>>>>> RCA connectors at the amplifier and output behavior also swapped,
>>>>> so the problem is at the turntable.
>>>>>
>>>>> Under the turntable there are four connector prongs beside the
>>>>> muting switch. Two of the connectors are between one and two inches
>>>>> above the others. The pair closest to the axis of the turntable are
>>>>> attached to ends of the RCA cables. One of the other prongs has
>>>>> nothing connected and the fourth prong is connected to a ground
>>>>> lead that goes to the amplifier case and to the ****elds of the two
>>>>> wires that carry the output from the cartridge.
>>>>>
>>>>> Without taking the arm off, it's not easy to see into that area
>>>>> under the shell. Is it likely that there is a bad contact there?
>>>>>
>>>>> Comments appreciated.
>>>>>
>>>>> RuF
>>>>
>>>> RuF,
>>>>
>>>> It is possible that the muting switch is causing the problem,
>>>> but not the first thing I'd suspect.
>>>>
>>>> Dual used among the worst RCA cables in existence, so if you have
>>>> not already tried new ones, I would. The factory ones used
>>>> crimped connections, and the grounds commonly go bad causing hum and
>>>> bad connections.
>>>>
>>>> There is a similar problem with the head shell leads These can be
>>>> resoldered, but you have to be VERY careful not to damage the head
>>>> shell contacts. Both the cartridge and head shell ends of the 4
>>>> wires are suspect. You might want to consider a new head shell if
>>>> they are still available. A new old stock head shell may have the
>>>> same problems as your existing one, as the crimps have been around
>>>> for many years.
>>>>
>>>> The contacts in the arm itself, where the head shell connects can
>>>> often be corroded. Don't use a rough abrasive, as you'll remove the
>>>> plating. I'd start with a cotton swab moistened (not dripping) with
>>>> a contact cleaner. Do the head shell side of things too. I would
>>>> then use a dry q-tip to remove as much of the cleaner as possible.
>>>> To be really residue free, you could clean with alcohol.
>>>>
>>>> Of course, first start by being sure that the head shell leads are
>>>> all going to the right places, and make sure the lugs going onto the
>>>> cartridge pins are snug. If they are loose, squeeze them GENTLY
>>>> with needle nose pliers or tweezers to tighten them up a bit. Be
>>>> careful, if you over-tighten them, then they won't fit the pins on
>>>> the cartridge any more. They can also break.
>>>>
>>>> Lastly, are you sure that the new cartridge is good? If you have an
>>>> ohmmeter, then measure the left and right windings of the cartridge.
>>>> The readings should be similar. This needs to be done with the head
>>>> shell removed from the turntable, but the cartridge can still be
>>>> mounted in the head shell.
>>>>
>>>> Regards,
>>>> Tim Schwartz
>>>> Bristol Electronics
>>>
>>> Thanks Tim.
>>>
>>> As you suggested I cleaned up all the contacts near the pickup and
>>> then reinstalled
>>> but it didn't do any good. Next I tweaked the contacts at the rear of
>>> the shell and reinstalled.
>>> That did the trick. Thanks again for your help.
>>>
>>> RuF.
>>
>> Seems like I spoke too soon. After copying 4 records to the HD, the
>> right channel
>> has now become the very weak one and the left is ok. I have tried
>> several different
>> records to make sure they were stereo and they were. I tweaked the R
>> and RG contacts
>> at the rear of the shell but that was no help.
>>
>> I made some measurements across the 2 RCA connectors and there was
>> symmetry in
>> the resistances. For example, across the two skirts the resistance was
>> 0. From the black
>> prong to the red prong the resistance was 2.8 ohms. From the black
>> prong to the red skirt
>> and from the red prong to the black skirt the resistance was 1.35 ohms.
>>
>> Comments appreciated
>
> RuF,
>
> If those measurements were made with the turntable in the off
> position, then you are measuring what should be a near short across the
> cables. If that is so, then you likely have a dirty muting switch or bad
> cables. If that measurement was made with the unit on and the arm above
> the record, then you've got the lowest resistance measurement I've ever
> heard of on a cartridge.
>
> Regards,
> Tim Schwartz
> Bristol Electronics
Thanks again Tim. Your help is much appreciated.
This time the measurements were made with the
pickup on the record about
mid point in the tracks.
The results of the measurements were exactly the
same as before, which would
appear to suggest that there may be a problem with
the mute switch. The RCA
cables were installed a few months ago to replace
the old 5-pin DIN plug and cable
and were soldered to the same connections that
were used previously. The original
ground cables from the turntable are still used
and are attached to the chassis
of the Sony amplifier. The ground from the arm
wiring is also attached to the same
wires. I guess I could replace the original ground
cables, if necessary.
Today I'll check the muting switch and clean up
the terminals and anything else I
can see in that area.
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