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PT One will not switch on.

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PT One will not switch on.

Postby badboygolf16v » 17 Jun 2018 20:10

Hi

I'd be most grateful if anyone could Help with a problem I'm having with my PT One.

When I set the switch to the 33rpm or 45rpm position nothing happens, the motor doesn't switch on.

How can I get the top panel off to take a look? I've fallen at the first hurdle, as I think the allen bolt holding the selector switch in place is imperial!?

Once the switch is off, any advice as to where to poke around with my multimeter? If I can identify the issue I'm capable of desoldering and resoldering any dodgy components.

I bought the deck in 1989 I think, as an upgrade to my Ariston Q Deck. It has the Alphason HR-100S that I got it with. Unfortunately the Audio Technica AT-37E originally fitted bit the dust.

Later, I bought another TT and put the PT in the loft, then forgot about it. On rediscovering it, I bought a barely used AT-OC9 to put on it for the classic 80's HiFi Choice vibe.

Any ideas how much it would be worth these days? Assuming it can be made to spin again! :lol:

Thanks

Antony

(I did have this repaired by someone a while back, for the same issue, but it broke again the day after I got it home. I'll spare the establishment any blushes, but I was very unhappy with the service I had received up until that point and just put the deck in a cupboard, totally hacked off with the time, money and petrol I had wasted.)
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Re: PT One will not switch on.

Postby abril » 18 Jun 2018 09:07

Welcome to the PT club :?
How can I get the top panel off to take a look? I've fallen at the first hurdle, as I think the allen bolt holding the selector switch in place is imperial!?

Remove the triangular knob with suitable allen key,remove the platter,you will then see a small screw pretty much in the centre - remove,top then lifts off.

Look out for loose connectors first - they do come adrift.
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Re: PT One will not switch on.

Postby P700DEE » 19 Jun 2018 09:26

Hmmm not my route of entry. Assuming you have checked the 9V walwart is giving the correct DC voltage. I would attached the transit bolt to protect the suspension and invert the table to remove the four wood screws that support the base. This usually provides enough vision to find the loose wire that usually is the cause of failure. If you have to remove the top as detailed by the previuos response you should find the top plate is also secured by two sided sticky pads so you need to take care prising the top plate off.
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Re: PT One will not switch on.

Postby tim_bissell » 19 Jun 2018 13:28

The allen key required is 3/32", but I would normally go the same route as P700DEE, from underneath - Although I would wrap the spindle inform/bubble-wrap to protect it as well. You can take the top plate off, but I would be so fearful of clobbering the arm/cartridge with it in the process that I would take the arm off anyway. The issue is most likely to be loose wires; most PT1s had locking connectors on the PCB where you pulled up the connector block a couple of mm, pushed in the wire(s) and pushed the block back down again to secure the wire. sometimes the wires are thin enough to escape. I will post/PM you a pinout, but it won't be today

-- Tim

P.S. The 3.5mm phono jack for power should be +9V on the tip -- although the cheapo unregulated PT wall warts usually put out over 16V if measured without a load.
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Re: PT One will not switch on.

Postby abril » 19 Jun 2018 13:54

I would still remove the top plate,a little care to protect the stylus,all the connectors are on the top surface and avoids messing around from underneath and the wrong side of the board.
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Re: PT One will not switch on.

Postby badboygolf16v » 19 Jun 2018 19:05

Thanks for all the advice! :)

I always used the turntable with a crappy 12V PSU that came with it when I bought it. The repairer advised a 12V psu as well, so I now have a good quality eBay Chinese 12V PSU.

Would you advise 9V? Also would the voltage affect the speed?
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Re: PT One will not switch on.

Postby abril » 19 Jun 2018 22:12

I would suggest a dual voltage one,min 700mA,it it is supposed to be 9V but I run mine on 12V and it might be useful to have two voltages available (I know how awkward the PT1 can be :? ),but make sure it is centre positive on the plug.Absolutely vital.
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Re: PT One will not switch on.

Postby badboygolf16v » 04 Jul 2018 22:08

Finally the imperial allen keys turned up from eBay.

Taking the lid off shows this.

Image

All wires are soldered. I haven't checked the connection to the motor as I CBA this evening.

The LED lights when the switch is turned to 33 or 45 position but is very dim, barely visible.

Any suggestions for diagnosis? Cheers.
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Re: PT One will not switch on.

Postby tim_bissell » 05 Jul 2018 00:06

Mmmm... can't see the picture. I do remember one PT1 I had with an LED attached - that was very dim also. Probably an early one, but I can't tell without a picture!
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Re: PT One will not switch on.

Postby badboygolf16v » 05 Jul 2018 07:42

Second attempt at photo.

Image
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Re: PT One will not switch on.

Postby P700DEE » 05 Jul 2018 09:46

Looks familiar :lol: If the led lights my actual thoughts would turn towards a failed motor rather than a power supply issue. Stick a multitester on the wires that go to the motor and see if you have any (the right) voltage going to the motor.
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Re: PT One will not switch on.

Postby badboygolf16v » 05 Jul 2018 15:46

The input voltage from my 12V supply measures 11V ish at the board input.

There are four wires going to the motor. Anyone know the correct voltages?

Google search got me this:

"Motor is having 4 terminals which contains 2 terminals of field winding and 2 terminals of armature winding."

Is that the case here?
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Re: PT One will not switch on.

Postby badboygolf16v » 05 Jul 2018 20:13

On your suggestion that it might be the motor, I tried rotating the motor spindle and initially it seemed stuck. A gentle twist and it freed up. Powered on at 33 and 45, and the motor spins, but is making a horrible noise.

So looks like that may be the problem?

Any suggestions for replacements?

Thanks
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Re: PT One will not switch on.

Postby abril » 06 Jul 2018 10:51

Initially I would just try running it in with a drop of oil on the top spindle.
See if it frees up.
You would be pushed to find a replacement motor for that board.
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Re: PT One will not switch on.

Postby badboygolf16v » 06 Jul 2018 12:25

Thanks, I'll give that a try.

That would be a temporary fix, I guess, as it looks like the motor's on its last legs.

Would I need to replace the controller board and motor together? Any suggestions?

I'm happy to DIY it, I've got a soldering iron.
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