technics 1210 - speed fault number 1

[deburgh]

hi there

i repair technics around town for bars clubs djs etc and i have a deck that speed up (way past the strobe limits) and then when u press stop it takes about a minute to slow down

i replaced the drive and the control chips with new ones (ic101 + ic201) but the same thing still happens ??

deck is ollllddddddd, from the eighties !

any ideas

thanks

[singa]

Hi, It is possible that the Hall effect element sensor (one of them) is malfunctioning.Most probably showing a low resistance or short across a pair
of pins.There are 4 leads for hall effect element.Whereas hall effect switch
has three.

Hall effect element sensors are not the same as Hall effect switches which are commonly found when you do a search ,where the former is basically a sensor without the switching circuitry.They may be hard to get as most hall effect sensors are designed into the switches for ease of use and economy.( Audio industry has technically retired the record player/turntable.)

Hall effect sensors are positioned under the motor coils to sense the
strength of the magnetic field passing which generate a voltage which is
used to control motor speed.However do check other components linked
to this elements. singa

[deburgh]

thanks singa

so how do i go about fixing / checking this problem ? this may be outwith my skills but if u can talk me through it .... ??

[singa]

Hi, When you said you repair technics turntables I assumed you are knowledgable in electronics which means having a schematic you would
know how to find your way to whatever section of the schematic that is
suspect.

Anyway if you want to try, the hall effect elements are located on
a pcb underneath the spindle motor which means either you turn the table
upside down, of course first removing the platter to see or check it with a
meter( be careful not to damage the tonearm).Again I assume you have the schematic for this model or similar,if not go to vinyl engine to find the service manual.For this kind of work it's better to make a jig to hold the table
leaving your hands free. Good luck.

[deburgh]

Originally Posted by singa

Hi, When you said you repair technics turntables I assumed you are knowledgable in electronics which means having a schematic you would
know how to find your way to whatever section of the schematic that is
suspect.

im not too knowledgeable electronics, more so the mechanics of the machine

if anyone can tell me which part to check on the main pcb that would be a great help