philips ga 212 restoration

[klamsoss]

Hello all! I'm in the process of fixing up a 212 for a good friend of mine and I'm stuck on step 4 of the electrical adjustments outlined in the service manual.
Let's back up..
I started by checking the function of the 'table when I got it... The power switch, of course was broken and wouldn't stay on. Next, one of the touch lights was very dim and sometimes flickered, plus neither of the 45 or 33 touch lights would stay on. The motor spindle at least turned when you held your finger on 45 or 33, but it wouldn't stay on if you took your finger off the touch button. As usual, the stop control bulb was completely burnt out. And of course the melted drive belt. Yuck!
So i did the following:
Cleaned out the melty belt and replaced that after cleaning the surfaces well with alcohol. Then I put a new power switch in (watch that wiring! check it with an ohmeter first so you know what to connect where. The switch I used had a different setup). After that, I got a set of LED replacement bulbs for the touch buttons and end control.... All 4. those went in without any drama other than that the 33 bulb socket had been damaged. I replicated the lead-soldered-to-bulb-base setup that had been in there, and at least lit the bulb. Clearly someone has had this 'table open before me...

So now I'm trying to get the electrical adjustments done properly. I got the speed and supply voltage set correctly, but on step 4, it indicates that the voltage across R404 (the light dependent resistor, LDR) should be set to 0.75V b adjusting R465. I can't get anywhere near 0.75V b adjusting R465. I'm 90% sure I am measuring it correctly... there are two grey wires that come out of the LDR and connect to the main board. I have my probes between those two wires. I can get maybe down to 4.5V, but that's it.
So I did some searches on here and vinylengine and I see that it's perhaps impossible to get 0.75V across that LDR. Okay... but the issue I am having here is that the auto-stop happens before the end of the record.


Additionally, the touch buttons for speed are... iffy. If you leave your finger on there or rub it across the button a bit, it'll stay lit, but otherwise, it just switches back to 'Stop'. This is something I can live with, but it would be nice to fix. I've tried swapping the old bulbs back in, which did nothing, and i've cleaned the contact surface with alcohol. It doesn't seem to improve anything.

Any ideas?

 

[jobrewer1983]

Hello all! I'm in the process of fixing up a 212 for a good friend of mine and I'm stuck on step 4 of the electrical adjustments outlined in the service manual.
Let's back up..
I started by checking the function of the 'table when I got it... The power switch, of course was broken and wouldn't stay on. Next, one of the touch lights was very dim and sometimes flickered, plus neither of the 45 or 33 touch lights would stay on. The motor spindle at least turned when you held your finger on 45 or 33, but it wouldn't stay on if you took your finger off the touch button. As usual, the stop control bulb was completely burnt out. And of course the melted drive belt. Yuck!
So i did the following:
Cleaned out the melty belt and replaced that after cleaning the surfaces well with alcohol. Then I put a new power switch in (watch that wiring! check it with an ohmeter first so you know what to connect where. The switch I used had a different setup). After that, I got a set of LED replacement bulbs for the touch buttons and end control.... All 4. those went in without any drama other than that the 33 bulb socket had been damaged. I replicated the lead-soldered-to-bulb-base setup that had been in there, and at least lit the bulb. Clearly someone has had this 'table open before me...

So now I'm trying to get the electrical adjustments done properly. I got the speed and supply voltage set correctly, but on step 4, it indicates that the voltage across R404 (the light dependent resistor, LDR) should be set to 0.75V b adjusting R465. I can't get anywhere near 0.75V b adjusting R465. I'm 90% sure I am measuring it correctly... there are two grey wires that come out of the LDR and connect to the main board. I have my probes between those two wires. I can get maybe down to 4.5V, but that's it.
So I did some searches on here and vinylengine and I see that it's perhaps impossible to get 0.75V across that LDR. Okay... but the issue I am having here is that the auto-stop happens before the end of the record.


Additionally, the touch buttons for speed are... iffy. If you leave your finger on there or rub it across the button a bit, it'll stay lit, but otherwise, it just switches back to 'Stop'. This is something I can live with, but it would be nice to fix. I've tried swapping the old bulbs back in, which did nothing, and i've cleaned the contact surface with alcohol. It doesn't seem to improve anything.

Any ideas?

Have to start off by saying I’ve never worked on this table, but I had one that I gave a buddy who was successful in getting it working. No real experience with this table personally.

That said -

one suggestion would be to spray R465 with some deoxit, the actual “variable resistor” may be bad... I’m taking a guess. ??

Have you tested any of the actual resistors in that circuit? Who knows a resistor could be bad. Any leaking caps on the PS? That may be the cause of the dim lights.

Good luck with it man!

 

[sregor]

What type of LED replacements did you use? One of the idiosyncrasies of this table is that the lamps are part of the switching logic, and if the resistance is too low or too high, then the logic won't hold correctly (logic is discrete transistors) Correct original bulbs work, I would guess adding some resistance in parallel to the LEDs would work. Original bulbs were 6 volt 50 mA, and if LEDs were at 10 mA, then about 150 ohms should work. I'd start higher but stay in that neighborhood.
The touch buttons are very sensitive to residual moisture, and if you clean them, they can take a long time to dry out. I find using a toothpick and some cloth or tissue and cleaning the area between the sensing "rings" usually works. (We had one which was cleaned with a cleaner that took a full day before it worked right. When cleaned with alcohol or Windex, still would take a few hours before it would work correctly. Were the old bulbs original. We used to see them with generic bulbs which were 6 volts, but not 50 ma and they don't work right (type 44 was a common won't work lamp)
My guess is that your shut off issue is mechanical - the arm that interrupts the LDR can be out of position. Good luck.

 

[mr_light]

"One of the idiosyncrasies of this table is that the lamps are part of the switching logic" this is why I eventually got rid of this table. Having functions not work if a bulb doesn't exactly match SPEC or just burns out, seems to be a terrible design...

 

[klamsoss]

I should have mentioned that I hit all of the trim pots with deoxit, and replaced the electrolytics with new pieces.
I dont know the specs on the bulbs. They came from the auction site. They were listed as working for the 212 and 312, but I know listing are only marginally more reliable than picking at random.

Close visual inspection of the boards doesn't show any resistors that look burned but I haven't tested any specifically.
Also, I did measure mechanical parts as outlined in the service manual and the "scanner" appears to be positioned properly.
I'm inclined to agree that this is a trick system for turning the motor on and off, but falls short of "good design" because of its complexity and potential for failure. That said, it would seem that the advent of LED lighting might be a saving grace for these 'tables since they never burn out, provided I can get them working properly.

I should be able to put a current meter in line with the bulbs to determine their draw. I suppose I would then treat the LED as a resistor to calculate the appropriate parallel resistor that will yield the proper current draw?

 

[ramjet]

I had a GA212 and currently have a GA312 and have worked on both. Here is what I know. The -9VDC is the critical voltage; no deviation. Always replace C734, the 470uf filter capacitor, they age. The 4 lamps used in the table are of two different voltage and current ratings; mix up their locations and all kinds of weird things happen. These are well designed and functional turntables for their time (introduced in 1971, almost 50 years old). I have not tried the led conversion but have had to replace the power switch. My GA312 is been in almost daily use for ten years with no problems.

 

[56RETROGRADE]

I owned a 212 for 30 years and the touch controls are that tables flaw imo.

 

[steerpike2]

"One of the idiosyncrasies of this table is that the lamps are part of the switching logic" this is why I eventually got rid of this table. Having functions not work if a bulb doesn't exactly match SPEC or just burns out, seems to be a terrible design...

Philips were primarily a light bulb manufacturing company. I'll bet they foresaw no problem whatsoever in making available replacement bulbs with precision specifications.

 

[klamsoss]

UPDATE:
The LEDs I got are just fine. I talked to the seller (very responsive, nice guy, I'll probably buy bulbs from him in the future) and he assured me that they are direct replacements. He has 100% positive feedback, and says he sells 3 or 4 of these kits a week and hasn't had any issues. I even talked to another one of his customers and they said that the same bulbs had worked for him in his 312, so I'm convinced he gave me the right bulbs.
Actually, after fiddling with things a bit, the touch sensors now DO seem to be working. I am thinking that @sregor hit the nail on the head with his thought about the contacts needing to dry out a bit. They are still a little finicky, but consistent enough that I think they'll work reliably once I stop messing with other stuff.

SO, now I'm just down to the auto-shut off mechanism. The bulb is working just fine, and I measured the distance between the scanner and the LDR itself. That is about 1mm which is within the 0.5-2mm range specified in the manual. However, I'm still getting around 4.something volts between A19 and A18, the contacts for the LDR on the circuit board, with the arm in the STOP position.
Additionally, if I just put the thing together and put a record on, the auto stop doesn't function when the tonearm gets to the end of the side.
If I manually move the tonearm across the record (like you would if you want to listen to the last cut on a side), the auto-stop function will activate and stop the record. That actually seems consistent with the design brief on the auto-stop function that is in the service manual. It describes the mechanism as basically only functioning when the arm moves quickly for the voltage across the LDR to increase more rapidly than it is bled off by the control network. (again, a sort of clever design.... IF it works...)

So, the mechanism is functional, just not functioning properly.

Here are my thoughts:
Maybe the LDR is dirty? I don't want to clean it with alcohol if that might kill it, but I do want to get this working properly. And since I can't get anything like 0.75V initially, maybe it's just not seeing enough light? I have tried shining additional light directly on the LDR, and I CAN drop the voltage down lower, but not down to 0.75V
It is possible that there is a bad resistor somewhere else on the circuit board, but I have no idea how I would go about finding it since I don't completely understand the schematic, or functions of each component and how they affect one another. I'm somewhat disinclined to simply replace all of the resistors. Any tips?
After reviewing the service manual section how the auto-shutoff mechanism works, I am thinking maybe I should replace TS426 and TS427 since those seem to be the transistors that control this mechanism.
Maybe target C726, R532 and R466 since those are the series circuit that bleed off the deltaE that normally comes from the advancing of the film across the LDR during record play?
(If it seems like the above is a ham-fisted 'replace everything near the problem' approach, it's because that's exactly what it is. I'm still new to this stuff, learning with each repair.)

The GA 212 does NOT include a tonearm lift mechanism (I believe the 312 does). I'm wondering what the benefit is of having the record stop spinning while the stylus is still down? Doesn't that actually pose a risk of damage to the stylus should the record somehow spin even slightly backwards after it has stopped? My Pro-Ject, my dad's Rega, and most of the other turntables I have dealt with don't have any auto-stop or auto lift mechanism (other than my Dual 504, on which all the automated functions work flawlessly). Maybe it's okay for it to not auto-stop, and I can just disable that mechanism altogether. I don't like the idea of an incomplete repair, but I'm starting to wonder about the fundamental necessity and validity of the mechanism, to begin with.

 

[sregor]

It appears the "flag" which interrupts the LDR is out of position and blocking the LDR prematurely. I don't recall the exact nature, but it is relatively simple to adjust.

 

[klamsoss]

Well, this project has come to a successful conclusion!
This was a real pain in the ass to figure out because the issue with the stop mechanism was inconsistent and there's no easy way to make adjustments to it in real time. Everything is under the 'table, and you have to flip it, or turn it on it's side to get at any of the adjustment screws. Since the voltages related to the LDR never did line up with what the service manual says, I was basically having to make an adjustment, then partly reassemble to see if it improved things, made them worse, or had no impact. Then flip it back over and make another adjustment... Rinse. Repeat.

@sregor was at least partially right about the 'flag' that moves in front of the LDR being out of position.
I was able to gt the 'table to work flawlessly a few times, but it would screw up once it was completely reassembled. WHY?
Well, eventually I identified that the tonearm had a bushing that was out of place, and was allowing it to wobble slightly on the mounting board, which, in turn, moved the scanner which traverses the LDR. This was not immediately obvious. I assumed that the slight movement of the tonearm was because I am missing one of the transport screws so the suspended deck inside the chassis moves a bit each time I turn the 'table on it's side to make an adjustment. Once I figured that out, and pushed the bushing back into place (from the top of the deck), things got MUCH easier.
From that point it only took two rounds of the guess-and-check adjustments to get it working properly.

@ramjet was also fairly accurate in saying that the critical voltage is the supply -9V. I always checked it coming off the rectifier and it remained rock-steady at -9.02 V after the initial adjustment.

The owner's manual mentions use of some kind of alignment jig for setting up the cartridge. I am no expert with cartridges, and have never heard of such a jig, so I checked the alignment with an ortofon 2 point protractor and it looked quite good. I've only set up a few cartridges, and in contrast to what I see and hear form people, none of them seemed terribly difficult. In fact, it has never taken me more than 15 minutes to set them up, including adjusting tracking force and anti-skate. Admittedly I have never attempted to muck with VTA, but I have also never felt like there was a need...
Anyway, the cart on here is a Shure v15 with vn23he cartridge. I don't know what version of the V15 it is. (Can anyone help with how to identify that? Right now I'm assuming it's a Mk3 because that seems to fit the era, but I have no idea.) I set tracking force to 1.5g and set the anti-skate equally per the owner's manual instructions (observing that this is an elliptical stylus shape).

Then, it was time for a test drive! I pulled out a few reference records and gave it a short listen. My initial impressions were all positive. I'd love to give it more of a test, but it goes back to the owner today.

I see him regularly, so if I learn more about it or if anyone weighs in and makes some recommendations, I can always make adjustments for him.

As always, I appreciate the input from folks here, and hope that people in the future find this thread useful for their own troubleshooting and restorations. I'm happy to answer questions.

Photos:
1. The 212 before final reassembly but after the last repairs/adjustments were made. Cleaning the melted belt out took a lot of diligent work with rubbing alcohol on pipe cleaners, qtips, and some stuff called 'gear floss', which is sort of like a string pipe cleaner used to clean bicycle cassettes. There's always crossover! In fact, I used one of my special bike lube mixes for the platter bearing.
2. Clean pulley, new belt, clean subplatter.
3. The cartridge
4. Most of the electronics are hidden on the other side of that circuit board, but you can see the "scanner" coming from the tonearm mount pointing towards the lower left corner of the circuit board. The LDR is mounted on the brown phenolic piece to the left of where the terminal block for the tonearm wires is located. It is partially obscured by the bulb, mount and film that act as the light source for the control mechanism. You can also see the beefy new power switch that was installed up top.
5. I've taken to writing a short summary of the work I do on equipment somewhere inside said equipment. That way a future tech doesn't have to wonder and try to decipher what has changed.
6. Playing.
7. And stopped!!!
8. Tested it out in my main system (which features some B&W CDM1NT bookshelfs for right now, while my dad borrows my tektons.

 

[KristerSv]

I´ve just bought a DUX Sound Project 8540, which is the same as the Philips GA212. Having problem with the autostop function I found this thread being very helpful. The bushing on the tonearm is needs to be put back in place and this maybe helps the scanner finding its right way over the LDR. However, which I didn´t recognize at first, the film on the scanner is missing. I am looking for any help or ideas on how to replace it.

 

[klamsoss]

@KristerSv I see this is your first post. Welcome to AK!
It has been a while since I had this philips apart and I don't remember exactly what it looks like on the inside. HOWEVER, I actually have another one (my 3rd) to work on in the next few weeks. Next time I have a chance, I can put it on the bench and see what's up. Can you upload a picture of what you are talking about?

My recollection is that for some reason the cantilever holding the film doesn't traverse the proper path and do it's thing as far as stopping the motor and lifting the tonearm unless the table is right-side-up. Is that how the film got knocked out? For me, it didn't matter TOO much how precisely the film was located with respect to the sensor.

 

[KristerSv]

@KristerSv I see this is your first post. Welcome to AK!
It has been a while since I had this philips apart and I don't remember exactly what it looks like on the inside. HOWEVER, I actually have another one (my 3rd) to work on in the next few weeks. Next time I have a chance, I can put it on the bench and see what's up. Can you upload a picture of what you are talking about?

My recollection is that for some reason the cantilever holding the film doesn't traverse the proper path and do it's thing as far as stopping the motor and lifting the tonearm unless the table is right-side-up. Is that how the film got knocked out? For me, it didn't matter TOO much how precisely the film was located with respect to the sensor.

Thank you, I do get a lot of help from this site.
The film was gone when I got the tt, so I need to replace it and is looking for some advice what to use instead. Testing it up side down also makes the scanner traverse the LDR with more than the recommended distance of 0,5-2,0 mm. I guess I must test everything with the tt on its feet before doing any changes. But first, some new film.

 

[klamsoss]

I'll open it up this weekend and see what I think would work. It's all about transmitting the right amount and wavelength of light. There's sure to be a suitable substitute.

Maybe others will chime in. This was a popular model and there must have been other folks who ran into the same issue.

 

[KristerSv]

I'll open it up this weekend and see what I think would work. It's all about transmitting the right amount and wavelength of light. There's sure to be a suitable substitute.

Maybe others will chime in. This was a popular model and there must have been other folks who ran into the same issue.

Again thank you for early replies and your help.
Greetings from Sweden

 

[tballinger]

Folks
I’m getting started with the Electrical Adjustments from the 212 Service Manual and Im hoping you can point me to where I should measure the supply voltage to adjust it to 9V. I tried placing my multimeter leads on the bottom of the rectifier where the red and grey wires are (attached photo) - but I’m only getting 6.5V there, so I suspect I’m not in the right spot.

 

[tballinger]

Through pure dumb luck, I got the table sorted out. I didn't figure out how to measure what I needed to measure, so I just set all 5 dials to halfway. I figured that chances are, that would at least get the table operational — and it did! After that I just had to tinker with R469 and R471 to get the speed to where it needed to be.