Hello,
I have the same problem with one of my 1210s.
Both speed indicator (33 and 45), ON/OFF and stylus LEDs flicker accompanied with fluctuating platter speed.
When the stylus light is turned on or off, platter sometimes stops completely.
Aside from that, almost inaudible mechanical noise is heard from under the platter and is correlated with LED flicker.
Any ideas?
I have an access to a quality soldering station and an oscilloscope, and could try all of your suggestions.
Both turntables were used in a room without air conditioning and sometimes it would get hot and humid in it.
The other one works perfectly.
Serial number is NH1AH27484
I have the same problem with one of my 1210s.
Both speed indicator (33 and 45), ON/OFF and stylus LEDs flicker accompanied with fluctuating platter speed.
When the stylus light is turned on or off, platter sometimes stops completely.
Aside from that, almost inaudible mechanical noise is heard from under the platter and is correlated with LED flicker.
Any ideas?
I have an access to a quality soldering station and an oscilloscope, and could try all of your suggestions.
Both turntables were used in a room without air conditioning and sometimes it would get hot and humid in it.
The other one works perfectly.
Serial number is NH1AH27484
Thank you for your reply.
I'm confused because the sticker says I shouldn't connect the unit to AC without platter present on the motor shaft.
If that is true, is there some other way to access the main board while keeping the platter on?
Actually that's the main thing that's bothering me; I already have schematic and voltages printed out
I'm confused because the sticker says I shouldn't connect the unit to AC without platter present on the motor shaft.
If that is true, is there some other way to access the main board while keeping the platter on?
Actually that's the main thing that's bothering me; I already have schematic and voltages printed out
So, how is it possible to measure the running values for example on IC201 ?
I have to fix a 1210SL with intermittent problem : the motor is not starting and moving 1/10 of turn forward and back (like a washing machine). If I push it a little forward it's running but with flutter.
80% of the time it's running fine.
I have to fix a 1210SL with intermittent problem : the motor is not starting and moving 1/10 of turn forward and back (like a washing machine). If I push it a little forward it's running but with flutter.
80% of the time it's running fine.
Hi, Please somebody can check this video to tell me if he already got the same problem?
https://www.youtube.com/watch?v=Irg5CWHJ2JQ
Changed already:
Full Pitch unit
AN6680
Q201, Q1, Q2 et Q3
D3
Zener diode D301
https://www.youtube.com/watch?v=Irg5CWHJ2JQ
Changed already:
Full Pitch unit
AN6680
Q201, Q1, Q2 et Q3
D3
Zener diode D301
that looks like washing machine platter rather then "weird speed problem". I read on another website this can be sometimes caused by capacitor C210 coming unsoldered or broken leg. http://www.futureproducers.com/foru...hing/technics-sl1200-washing-machine-74294/6/
Last edited:
Replacement of R307 with a 10K resistor worked for my speed issue as well. Very pleased.
Trying to understand the fix now.... so I noticed the voltage at the zener actually dropped after the fix, which is the opposite of what I expected. The same point is supposed to the supply to IC302, so I'm wondering if IC302 needs to be seeing less voltage to be working properly.
If anyone has any clue as to why this fix works I would greatly appreciate your feedback
Trying to understand the fix now.... so I noticed the voltage at the zener actually dropped after the fix, which is the opposite of what I expected. The same point is supposed to the supply to IC302, so I'm wondering if IC302 needs to be seeing less voltage to be working properly.
If anyone has any clue as to why this fix works I would greatly appreciate your feedback
Interesting.. In terms of current flow, I guess that means that R307 was pulling too much current from AN6680's FO output?
Any idea why it only affects the falling edge of the square wave?
Do you think swapping the diode for a "better" one achieve the same effect? Not such what diode characteristic would constitute "better".
Very nice scope output btw, also curious which one that is.
Any idea why it only affects the falling edge of the square wave?
Do you think swapping the diode for a "better" one achieve the same effect? Not such what diode characteristic would constitute "better".
Very nice scope output btw, also curious which one that is.
That's the same conclusion I came to too.
AN6680 and AN6682 are supplied with 9V from AN6680's internal reference and Q201.
For some strange reason (Anyone with an explanation let me know! Did they plan for TTL and finally go CMOS?) IC302 (4011) is supplied at 5V from R304 and D301.
It would make sense that the AN6680 "FO" is an open collector or open drain output and that R307 is the pull-up resistor allowing for a 0-5V output, if R307 is pulling too hard "FO" cannot drive low correctly.
I just checked the I/V curve of AN6680 "FO" relative to GND on a spare IC, it appears symmetrical, so possibly not open drain type output, it would be nice if someone could confirm that by measuring "FO" with R307 open. (I no longer have the turntables.)
I would not bother fussing with D301, either the 4011 could / should be supplied straight from the 9V and / or they messed-up on their R301 pull-up / level-shifting scheme, in any case they messed-up.
The scope is a Lecroy 93xx series, nice scopes to use, I now use an RS232 link rather than digital camera
Its 2am in Australia, i have been starring at my strobe now for over 2 hours after swapping out R307 with a 10k ohm resistor, there have been a few moments i could swear i detected an oscillation, but.. thats probably because i have been trying to fix this issue for 3 days. short of buying an oscilloscope and learning how to use it, there has no suggestion i have not tried to fix the erratic pitch at -8. thanks for sharing your knowledge so openly. In a few days time, i will be baby sitting my mates very early 1200 mk11, i can't wait to pop the hood and throw a meter across R307, i bet its 10k.. that thing has not skipped beat in 25years
i will get back to you as soon as i get the early model on the bench. Did you try putting a heat sink and thermo past on IC 201, even though the 10k resistor resolved the problem ? i am considering it, just to be sure.. just have to give mounting some thought, i would rather not drill through the board.
cheers
cheers
Hi JohnSnell,
Indeed, R307 was 2k7 OEM.. unfortunately, i do not have the technical skill or understanding to document why replacing R307 with a 10k solved my issue. Payed a lot of attention the the entire pitch circuit, swapped out the resistors you mentioned, despite them reading correct values across a multi while cold and at running temp. i replaced the zener diode and electrolytic cap. i even popped a brand new AN 301, reflowed AN6680 and Q201. Given that i had good DC power at all Test points, zero light fluctuations, steady pitch at reset and correct voltages off AN 201 legs, i did not look at Q1 2 or 3. i also replaced D3 zener (because i had one handy and was at the point of guessing ) No love. SDS's findings above and KAB's input led me to trying the 10k sub for r307. Over the past 2 days, i have run the decks for several hours at a time.. i figure more time will tell, as it stands.. the deck is performing flawlessly and the AN 201/301 are running at least x4 cooler than fault condition
Indeed, R307 was 2k7 OEM.. unfortunately, i do not have the technical skill or understanding to document why replacing R307 with a 10k solved my issue. Payed a lot of attention the the entire pitch circuit, swapped out the resistors you mentioned, despite them reading correct values across a multi while cold and at running temp. i replaced the zener diode and electrolytic cap. i even popped a brand new AN 301, reflowed AN6680 and Q201. Given that i had good DC power at all Test points, zero light fluctuations, steady pitch at reset and correct voltages off AN 201 legs, i did not look at Q1 2 or 3. i also replaced D3 zener (because i had one handy and was at the point of guessing ) No love. SDS's findings above and KAB's input led me to trying the 10k sub for r307. Over the past 2 days, i have run the decks for several hours at a time.. i figure more time will tell, as it stands.. the deck is performing flawlessly and the AN 201/301 are running at least x4 cooler than fault condition
Thanks for the update on the vintage turntable.
Other (good) repair technicians I know have fixed this issue heat sinking IC201, I would not bother.
The .PDF service manual I have states both 2k7 and 10k ohm for R307.
I spent a while investigating on that fault, charged quite a bit of cash, I've had no feedback from my customer who uses his turntables intensivley, I take that as good news knowing that I would have heard from him if there had been a problem.
I only settled for that solution because the service manual mentioned 10k for R307 and the measurements agreed, I'm also convinced it's the most reliable fix suggested so far although the waveform could be cleaner.
Switch the oscilloscope on, improve further...
Other (good) repair technicians I know have fixed this issue heat sinking IC201, I would not bother.
The .PDF service manual I have states both 2k7 and 10k ohm for R307.
I spent a while investigating on that fault, charged quite a bit of cash, I've had no feedback from my customer who uses his turntables intensivley, I take that as good news knowing that I would have heard from him if there had been a problem.
I only settled for that solution because the service manual mentioned 10k for R307 and the measurements agreed, I'm also convinced it's the most reliable fix suggested so far although the waveform could be cleaner.
Switch the oscilloscope on, improve further...
Hi everyone,
I'm having a some issues with an MK2 SL-1200 lately.
First of all, the platter wasn't starting by itself when I was pressing the start button, but it was actually spinning after a little push forward : I solved that by replacing the AN6675 IC.
After that I still had speed variation and instability on the LED driver. Solved it by replacing the AN6680 IC.
Now, I still have a last problem : Platter running fine and pitch responding correctly wether it's on 33 or 45 RPM but when I press stop it actually takes a little while to completely stop and even makes a little backward spin before actually stopping (even with the brake adjustment set to maximum clockwise). Furthermore, everytime I turn the deck ON, the platter slightly moves backwards...
Does anyone have an idea of what it could be ?
I was (randomly) wondering if it could be an erratic D204..?
Thanks !
I'm having a some issues with an MK2 SL-1200 lately.
First of all, the platter wasn't starting by itself when I was pressing the start button, but it was actually spinning after a little push forward : I solved that by replacing the AN6675 IC.
After that I still had speed variation and instability on the LED driver. Solved it by replacing the AN6680 IC.
Now, I still have a last problem : Platter running fine and pitch responding correctly wether it's on 33 or 45 RPM but when I press stop it actually takes a little while to completely stop and even makes a little backward spin before actually stopping (even with the brake adjustment set to maximum clockwise). Furthermore, everytime I turn the deck ON, the platter slightly moves backwards...
Does anyone have an idea of what it could be ?
I was (randomly) wondering if it could be an erratic D204..?
Thanks !