the home of the turntable

PT LPT motor issue

light fantastic

PT LPT motor issue

Postby art1cj1m » 05 Sep 2016 23:59

My beloved LPT has suddenly decided to stop rotating at 45rpm. The 33rpm works fine, and even though the green '45' light comes on, the motor won't rotate. When it's engaged I can feel the spindle vibrate - like there's some power getting to it. I tried giving it a helping hand by rotating the turntable to no avail.

I'm not at all technically minded, so would appreciate some advice. Is it still safe to use at 33rpm?

I live in the Yukon in northern Canada so getting access to parts can be tricky.

Thanks, Jim
art1cj1m
 
Posts: 4
Joined: 05 Sep 2016 23:41

Canada

Re: PT LPT motor issue

Postby abril » 06 Sep 2016 19:48

hi and welcome

will it start on 45 if you give it a helping push or if you start it through 33 first and then to 45?
User avatar
abril
long player
long player
contributor
 
Posts: 2130
Images: 192
Joined: 13 Oct 2002 20:48
Location: Cornwall/Republic of Georgia

Georgia

Re: PT LPT motor issue

Postby art1cj1m » 06 Sep 2016 20:52

Thanks for getting back to me.

Nope, I tried various methods to get it to rotate, but it only kind of vibrates.

Any other suggestions would be greatly appreciated.

Cheers!
art1cj1m
 
Posts: 4
Joined: 05 Sep 2016 23:41

Canada

Re: PT LPT motor issue

Postby Seaharrier » 07 Sep 2016 12:38

Hi - mine has just gone the same way though the power supply is connected though a Heed turntable power supply with speed change which I believe replaces the on board speed control - am just about to start trouble-shooting to see if the issue is with the deck or the PSU. I have noted a low level rumble (bearing checked out ok and lubed fine) that only appears when the motor is under load driving the platter. It also looks like the motor can't drive the platter without a bit of assistance at start-up. 33 is pretty steady but no change in speed when 45 selected on the PSU. Initially thought there was a voltage control issue on the PSU or the onboard circuit but now leaning towards the motor slowly dying.
Seaharrier
junior member
junior member
 
Posts: 8
Joined: 10 May 2014 16:11
Location: South West Scotland

United Kingdom

Re: PT LPT motor issue

Postby willb » 08 Sep 2016 15:49

Hi,
Sounds very much like you've both got a failed film capacitor across the output (usually an orange philips 0.68uf). Replace this with a 0.22uf (250v or 400v) and it should sort the problem.

Although the motor is actually 0.39uf at 50hz/33rpm, it's better with 0.22uf as the cap needs to be half the value at 45rpm (67hz!). Therefore you'll be ok on 45, but 'a bit out' on 33, but no major problem so it will start on either speed. :)

These decks are all 20-25 years old now, but the fact that it runs on one speed means the amplifier and generator are WORKING - just not properly on 45. As the original cap is much too high for either speed (+ aged as well), it will just stall on 67hz which is not surprising really. :(
Cheers

Chris.
willb
senior member
senior member
 
Posts: 331
Images: 14
Joined: 10 Jun 2004 17:32
Location: Devon, UK

Re: PT LPT motor issue

Postby art1cj1m » 09 Sep 2016 18:20

Hi willb,

Thanks so much for the information and advice.

It'll likely take a while for a replacement cap to find its way to me up here, but I'll keep you posted on the progress. Fingers crossed.

Cheers, Jim.
art1cj1m
 
Posts: 4
Joined: 05 Sep 2016 23:41

Canada

Re: PT LPT motor issue

Postby geoffallan » 07 Oct 2016 17:48

willb wrote:Hi,
Sounds very much like you've both got a failed film capacitor across the output (usually an orange philips 0.68uf). Replace this with a 0.22uf (250v or 400v) and it should sort the problem.

Although the motor is actually 0.39uf at 50hz/33rpm, it's better with 0.22uf as the cap needs to be half the value at 45rpm (67hz!). Therefore you'll be ok on 45, but 'a bit out' on 33, but no major problem so it will start on either speed. :)

These decks are all 20-25 years old now, but the fact that it runs on one speed means the amplifier and generator are WORKING - just not properly on 45. As the original cap is much too high for either speed (+ aged as well), it will just stall on 67hz which is not surprising really. :(
Cheers

Chris.


Hi Chris, would you know if there's a full refurb procedure for the psu? I have an LPT and the motor has always needed a little helping hand and I've always thought it was running slightly slow.

Is it possible the motor is ok and it's just the psu that's tired?

I'll continue to research.

All the best,

Geoff
geoffallan
junior member
junior member
 
Posts: 10
Joined: 21 Nov 2014 23:29

United Kingdom

Re: PT LPT motor issue

Postby willb » 26 Oct 2016 20:20

HI Geoff - sorry I haven't been on for a while.

Yes - generally new electrolytic capacitors and possibly replacing the power resistors as they get heat damaged. I personally do a few other things which get them working a bit better, and fit a mains switch in the power lead so it can be switched off completely when not in use. This makes a big difference over months/years as it's not hot all the time!

Let me know if you need any Help.

Cheers

Chris.
willb
senior member
senior member
 
Posts: 331
Images: 14
Joined: 10 Jun 2004 17:32
Location: Devon, UK

Re: PT LPT motor issue

Postby art1cj1m » 25 Jun 2017 18:40

So......sent the turntable off to a reputable repair/dealer in Vancouver to solve the issue. Six (yes, six) months later and checking by 5 experts including Master Electricians there's still no solution. The company is totally exasperated - and gone to huge expense. What to do?

Find a replacement board, although it could develop the same problems? Have an off-board DC motor fitted? Look for another table to fit the arm? I'm heading towards a DC motor although any advice would be appreciated.

Thanks, Jim.
art1cj1m
 
Posts: 4
Joined: 05 Sep 2016 23:41

Canada

Return to Pink Triangle / Funk Firm