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Old 3rd December 2010, 12:49 PM   #1
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Default Pink Triangle PT TOO power supply

Hi
the separate power supply for my PT TOO is giving out 76v. The motor in the turntable is 110v max.

I thought I had a motor problem as it doesn't seem to have enough torque.

Can someone let me know what the correct output voltage is for this power supply ??

thanks in advance.
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Old 3rd December 2010, 01:12 PM   #2
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Arthur Khoubesserian designed all Pink's turntables. He now runs the funkfirm

Home

If anyone can help, he should be able to.
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Old 3rd December 2010, 01:18 PM   #3
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thanks but already tried. FF push the new dc motor which I'd dearly love but if I can fix this then at the moment that's the best I can hope for.
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Old 3rd December 2010, 08:29 PM   #4
kevinkr is offline kevinkr  United States
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Not unusual to run a synchronous motor on a lower voltage in order to reduce vibration, but 76V on a 110V motor does seem rather low. Can you identify what type of motor this is? (I'm suspecting a Premotec or similar..) I'd figure 90 - 100V would be more reasonable.

I experimented extensively with lower voltages and noisy synchronous motors and found that some motors ran quite well at 70% or so of their rated voltage, but torque was greatly reduced obviously.

Sorry to hear that rather than provide the information to fix yours they just want to sell you one of their upgrades. Frankly I'm not too surprised..

I had a slightly used PT turntable (model now forgotten, and I've tried really hard to forget I ever owned it) in the early 1990s and the ruby in the inverted bearing shattered. Before that I had terrible problems with the dc motor based drive, it had the poorest speed stability of any table I have ever owned. (The motor was widely used in cheap Japanese belt driven tables of the time which had no speed stability issues, I had two controller boards and motors, both just as bad, clearly a design issue.) A shame because it clearly incorporated some interesting design innovations - inverted bearing, fairly heavy acrylic platter, and a honeycomb sub-chassis none of which were very common at the time. Because of a dispute between them and their distributor all American owners were left high and dry with no support from PT. I was not able to get parts to repair it and ended up selling it at a big loss to a fellow in the UK who wanted one and planned to have it upgraded.

I'd inspect your bearing, and also determine whether or not the motor needs some lubrication.

Can you provide any more detail about the supply - is it just a transformer and some resistors and caps or is an actual source that generates the driving voltages required? Could need a recap?

Can you take some pictures of the controller?
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Last edited by kevinkr; 3rd December 2010 at 08:40 PM.
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Old 3rd December 2010, 09:09 PM   #5
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oh dear, sounds like you've had a bad experience with pt !!
I got mine through a friend along with the rest of a setup as a way to get into decent hifi !! the tt comes with a decent arm and cartridge and at the moment getting back up and running is the cheapest option.
the motor has the following on the back:

synchronous motor
990411131813
110v 50hz 250rpm
mb03 ? model number
1588
philips made in belgium

the power supply is a seperate box. I think it's the later of what you mention.

It's with my engineer at the moment but when the snow (yep we're snowed in over here!!) clears I'll see if I can get some photos.

The problems I've had are that sometimes when I switch it on it doesn't power up. Sometimes it gets going with a helping hand, sometimes it spins the wrong way !! . . Although it's not done this at the engineer's place which makes me wonder if I have a supply problem to the turntable power supply unit.

thanks so much for the info. I'll pass it on and see if we can sort something
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Old 3rd December 2010, 09:43 PM   #6
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Mark Kelly has worked on these (see link)-you might try contacting him, or perhaps he'll see this thread. Kevin, pictures of the PS are also on the below link.

FWIW, the VPI SDS starts out at full voltage, then drops down to a user-settable voltage for 'silent running'- I've generally run mine at 80v. Have no idea if this is applicable to your case, but there you are.

Pink Triangle PT Too PSU revival/understanding
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Old 3rd December 2010, 10:04 PM   #7
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Click the image to open in full size.

The two small pots on the right of the phot adjust the output voltage (one for each phase).

Ignore the extra wires attached to the top of the board, they were there so I could graft in a different quadrature generator which allowed adjustment of frequency, phase angle and cogging torque. Before you ask, no it is not available any longer and never will be again.
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Old 3rd December 2010, 10:20 PM   #8
kevinkr is offline kevinkr  United States
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I had hoped I would see something that looked a little more professional, the level of quality IMHO is quite poor - not in keeping with the rest of the turntable design. The PCB looks very amateurish, and the poor execution leaves me questioning the quality of the design as well. The older version DC drive pcbs I had looked somewhat worse, but there were no mains level voltages present on that board. I don't think PT did electronics well at all...

Depending on how old this thing is it should probably be recapped, and I'd certainly see about boosting the voltage a bit. Note that you should try to adjust both phases so their output voltages are pretty close to the same. (90 - 100V depending on vibration)

I'd probably get some more reliable pots from the like of Bourns or similar as I've had some problems with similar pots in other devices - long term they're not that reliable.. IMHO

The fact that it sometimes starts and runs the wrong way could indicate that you are periodically dropping one of the phases or perhaps all the time? This could also explain the lack of torque.

Edit: Apparently the power source generates 100Hz for 33rpm and 135Hz for 45rpm.. So it might be possible to purchase a controller on eBay and modify it to produce the right output frequencies if this one dies.
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Old 3rd December 2010, 10:28 PM   #9
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IIRC the frequencies are 50.0 Hz and 67.5 Hz
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Old 3rd December 2010, 11:03 PM   #10
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by Mark Kelly View Post
IIRC the frequencies are 50.0 Hz and 67.5 Hz
That would make the most sense and is pretty standard these days, in the other thread referred to a poster mentions 100Hz at 33rpm.

There is at least one seller on eBay that offers an electronic controller that is supposedly good.
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