Hi,
I have found a Lenco 830 DD turntable and it seems to have an issue with the speed.
The 45 runs fine, but it is the 33 that is not stable. That is, when you switched from 45 back to 33, or
when you turn the power off.
If the speed is set at the correct pace, and you let it run, nothing seems to be wrong. But it is when you either turn off the power or
change the speed that the problems occur.
After an action like that, the 33 is either slower or faster than it was. It does rotate at a constant speed, not fluctuating during the rotation of the platter.
The motor control drive circuit isn't that big but it has the AN620 Matsushita chip on it.
It tried to clean the trim pot, but that did not solve it.
I swapped it out for a new one but that did not do the trick either.
With noting that I have a basic understanding of elec. I want to ask for help with this.
Could it be a faulty AN620 or maybe a resistor gone bad?
The servicemanual I managed to find on the net has a fault in it also, in the parts section it shows that the VR 1 an 2 are both 5K Ohm pots.
The diagram shows 20KOhm, but what's in there are 30K if I am correct. (303 code on both of them)
I have found a Lenco 830 DD turntable and it seems to have an issue with the speed.
The 45 runs fine, but it is the 33 that is not stable. That is, when you switched from 45 back to 33, or
when you turn the power off.
If the speed is set at the correct pace, and you let it run, nothing seems to be wrong. But it is when you either turn off the power or
change the speed that the problems occur.
After an action like that, the 33 is either slower or faster than it was. It does rotate at a constant speed, not fluctuating during the rotation of the platter.
The motor control drive circuit isn't that big but it has the AN620 Matsushita chip on it.
It tried to clean the trim pot, but that did not solve it.
I swapped it out for a new one but that did not do the trick either.
With noting that I have a basic understanding of elec. I want to ask for help with this.
Could it be a faulty AN620 or maybe a resistor gone bad?
The servicemanual I managed to find on the net has a fault in it also, in the parts section it shows that the VR 1 an 2 are both 5K Ohm pots.
The diagram shows 20KOhm, but what's in there are 30K if I am correct. (303 code on both of them)
Nice find
Not much information on the web about this one (vinylengine.com has the service manual).
Can you check if there is a controller on the back of the motor ?
Definitely would benefit from a refresh specially electrolytic capacitors.
PS: did you replace the caps on the motor control board ?
Not much information on the web about this one (vinylengine.com has the service manual).
Can you check if there is a controller on the back of the motor ?
Definitely would benefit from a refresh specially electrolytic capacitors.
PS: did you replace the caps on the motor control board ?
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I already had the SM as I described, that's where I saw the fault in the values of the trim pots, and it´s uploaded here.
There is a controller with the AN620 IC
And the caps are just being replaced but made no difference.
I also swapped the resistor that connects to the 33 RPM trim pot, resistor R8, 82 KOhm and replaced that with another, but that resulted in spinning at high speed on only the 33 rpm mode.
45 runs normal
Swapped the new back for the old and the speed is normal again but with the problem.
The SM says it is a metal film resistor I could only find a carbon lying around at the moment, maybe that is why it spun at high speed, adjusting the trim pot
had no effect on this.
Update, both the trim pots were replaced as one fell apart (age?) They were replaced by 2 15K Ohm.
The R7 and R8 should be both a 82K Ohm resistor according to the SM but the actual ones that were in there was the R8 being a 75K Ohm, and the the R7 a 82K Ohm. I replaced both ones for 100K Ohm. The set up seems to be stable now without fluctuating speed after switching off power of swicthing between 33 and 45 RPM.
The only thing that could be better is that the 33 RPM is difficult to get to speed. The timing is very precise, it really is precision adjustment, a tad too far and the speed is either too fast or too slow. Don't know if that is the reason that there was a lower value resistor on R8 in the first place.
Maybe the C12, tantal capacitor was an option to check / replace too, did not notice that it is in the path of the VR's to the IC AN620.
The R7 and R8 should be both a 82K Ohm resistor according to the SM but the actual ones that were in there was the R8 being a 75K Ohm, and the the R7 a 82K Ohm. I replaced both ones for 100K Ohm. The set up seems to be stable now without fluctuating speed after switching off power of swicthing between 33 and 45 RPM.
The only thing that could be better is that the 33 RPM is difficult to get to speed. The timing is very precise, it really is precision adjustment, a tad too far and the speed is either too fast or too slow. Don't know if that is the reason that there was a lower value resistor on R8 in the first place.
Maybe the C12, tantal capacitor was an option to check / replace too, did not notice that it is in the path of the VR's to the IC AN620.
