Beginner trying to fix Philips 212 turntable circuit - Page 1
Forum section: electronics / repair

author: CarlJacob
author_rank: Newbie
timestamp: January 24, 2018, 11:32:29 am
content: Hi. I am trying to fix a Phillips 212 turntable for a friend. I noticed that there was a lot of activity on this forum back i 2015 about this turntable, so I thought it would be a good idea to ask you guys for help. (I already have the curcuit diagrams and the PCB layout.)Problem:When I turn it on and play the first record (33rpm), it works fine for a few minutes! All the internal bulbs are working, and the speed is perfect. Then suddenly the speed control goes bananas. It changes to 45rpm and stays there. There is no reaction if I touch the STOP button, but if I leave my finger on it, the 45 bulb starts flickering and when I remove my finger, the 33 button gets active for a couple of seconds, and then the system goes back to 45 and stays there.The only way I can play records at 33rpm is to quickly put my my finger on the 33 button when it lights up an LEAVE IT THERE!Sitting in front of the turntable all night with a finger on the button is not that interesting, so I hope somebody out there can help me. Thanks.

author: retrolefty
author_rank: Super Contributor
timestamp: January 24, 2018, 12:20:51 pm
content: Vintage hi-fi gear of that era usually is built pretty well. Many problems come down to dirty switch contacts and/or bad electrolytic capacitors. If you have the schematic drawing then checking for proper DC voltages is called for.

author: cowasaki
author_rank: Frequent Contributor
timestamp: January 24, 2018, 12:24:18 pm
content: It's a bit difficult to diagnose without the schematics. Can you post them. It could be one of many potential issues..... Is the "speed" control via a bistable, micro processor controlled, a switch or a two position switch? Something else?

author: CarlJacob
author_rank: Newbie
timestamp: January 24, 2018, 01:29:37 pm
content: Hi. Thank you for responding. I attach curcuit diagrams.It might be a solution if we could find a way to make it run at 33 rpm and nothing else. That will solve the problem.Regards Carl JacobHortenNorway

author: cowasaki
author_rank: Frequent Contributor
timestamp: January 24, 2018, 01:41:44 pm
content: From a very quick look of just the first schematic a dirty way to do it would be to simply speednadjust the 45 section to 33. They appear to have the same components other than the pots but I haven’t had that good a look yet. It would also be reversible.

author: CarlJacob
author_rank: Newbie
timestamp: January 24, 2018, 01:44:05 pm
content: Hi again.This is how the switches look like.

author: CarlJacob
author_rank: Newbie
timestamp: January 24, 2018, 01:48:05 pm
content: I would highly appreciate if you could take a closer look at the schematics and maybe find a way to adjust the 45 to 33. That solution is more than good enough for me.

author: Andy Watson
author_rank: Super Contributor
timestamp: January 24, 2018, 01:52:04 pm
content: Have you verified that the power supply is stable and ripple free? In particular C734 is a prime candidate for having dried-out.

author: cowasaki
author_rank: Frequent Contributor
timestamp: January 24, 2018, 02:06:54 pm
content: Quote from: CarlJacob on January 24, 2018, 01:48:05 pmI’d suggest looking at the 33 & 45 sections as labelled. There are two pots in each and adjusting the pots in the 45 section to the same value as the 33 section could well do it but I haven’t looked in great detail and I would make a note of their current value before you turn them. If you stick an LP on at 45 and turn the one not marked as user to see whether you can get it to slow down then that might be a quick way of bodging it. Personally I’d rather fix the issue and as another member has said electrolytic caps are always a reasonable starting place!

author: CarlJacob
author_rank: Newbie
timestamp: January 24, 2018, 02:23:59 pm
content: Hi again.I have just disassembled the turntable and started measuring. The -9V from the power supply was - 13,9 !! What do you think is the most obvious reason ?

author: CarlJacob
author_rank: Newbie
timestamp: January 24, 2018, 02:31:31 pm
content: Thanks to cowasaki. It is pretty obvious that the power supply doesn't work properly, so I think I will start there and see what happens next.

author: cowasaki
author_rank: Frequent Contributor
timestamp: January 24, 2018, 04:51:05 pm
content: Quote from: CarlJacob on January 24, 2018, 02:31:31 pmLook at the last diagram, the power supply. The transformer's secondary windings give 14v which is basically what you get. If you are measuring in DC then that pretty much shows that the 4 rectifying diodes are also working. That would then give you 14v DC from the top to the bottom. The components between the top rail and bottom rail should pull that down to 9v. Look at what you have between these rails.......So start looking at these components, as you are a beginner just checking everything will come as good experience.....Check C734 and if you don't have an ESR meter or another way of checking it but do have a 470u of the right voltage then I'd stick it in.Diodes and resistors are easy to check with a multimeter leaving just the Zener diode and transistors to look at.Let us know once you get to this point if it isn't already working by then.

author: CarlJacob
author_rank: Newbie
timestamp: January 25, 2018, 12:01:05 am
content: Thanks. I have already ordered a new 470/25v and i will come back to you when it is in and then I will test the rest of the components.I am very grateful for trying to help me.Carl.

author: cowasaki
author_rank: Frequent Contributor
timestamp: January 25, 2018, 06:49:27 am
content: If you plan on repairing things then there are certain components you need to keep a stock of :-)

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: January 25, 2018, 10:25:11 pm
content: The Philips GA212 is a strange one. It has been many, many years since inside one.Touch (capacitive) switches were unique at the time. The problem many times with these is that when the bulbs for the switches burn out, someone replaces them with the wrong type, and this circuit WILL NOT TOLERATE it. Notice in the parts list shown, there are two types of bulbs listed. One type for the STOP switch if I recall, and the 33/45 switches use the other type. Good luck finding these.

author: CarlJacob
author_rank: Newbie
timestamp: January 27, 2018, 02:38:15 pm
content: HiI have put in a new C734 (470µ) and the voltage between the rails dropped form -13,6 to -7VDC. The pot R472 did not work properly, but after I cleaned it (CRC elec. cleaner) it worked fine and I could adjust the voltage to -8VDC, not more. That indicates that some other components don't work properly.Anyway, I left the power supply like this, cleaned the other pots and adjusted R 466 and R467 slightly to get the voltages as close to the ones on the curcuit diagram as possible.Then I cleaned the capasitive switches, and NOW THEY WORK PERFECTLY! The turntable is as good as new.Thank you for your help!

author: cowasaki
author_rank: Frequent Contributor
timestamp: January 27, 2018, 03:07:58 pm
content: Excellent news. It always feels good when you can fix something like that. If you are doing this regularly I would suggest putting an order in for an electrolytic capacitor kit. They are one component which has a life span and you will replace quite a few. Having them in stock is always helpful. Likewise having. Kit of resisters etc is also helpful but resistors tend to be a little less likely to go bang.

author: appsman
author_rank: Contributor
timestamp: February 11, 2019, 11:39:12 pm
content: I know this is an old thread, but if anyone is still struggling with Philips 212 repair, take a look at this approach to solving the problem - an Arduino controller retrofit:https://lensprojects.wordpress.com/2019/01/08/philips-212-turntable-controller-upgrade/

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 14, 2019, 01:04:22 pm
content: I dont usually have a shotgun approach to electrolytic capacitors but in this case there are only 2 and these blue Philips axials are usually past their date by now.I would also at least check C730 on the tacho feedback you may gain some speed stability replacing it.If the bulbs are still good don't bother playing with this, if they do need changing some time it should be possible to replace them with LEDs, changing series resistor of course.Stop circuit hysteresis may need readjustment due to the change.The Arduino approach is funny, I must be too old school, I find the original design such a neat design in discrete logic that it seems a shame to toss it away.

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 14, 2019, 05:46:09 pm
content: Due to a recent post about repairing a Telefunken S 500 HiFi turntable I had a look at the schematics for the S 600 HiFi model.It's amazing how close the motor speed servo sections are on the Philips GA212 and Telefunken S600, identical on the schematic level, very close on component values too.