My LPT has died

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abril
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My LPT has died

Post by abril » 14 Aug 2016 14:10

My LPT has suddenly stopped working :?
No voltage at the motor but the LED lights up and the big ceramic resistor is incredibly hot, but nothing else seems unduly hot.
Anyone with any ideas?

PinkTrichard
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Re: My LPT has died

Post by PinkTrichard » 17 Aug 2016 10:01

A hot resistor sounds like a short somewhere. Not that it helps you much, but I am pretty sure Funk don't even attempt repairs on these any more, but recommend a repair by upgrade to a DC motor and control electronics. It IS a real upgrade, but quite an expensive "repair" relative to the 2nd hand cost of the TT itself. Still worthwhile imho - it's a great deck with a DC motor against new TT's available today.

willb
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Re: My LPT has died

Post by willb » 17 Aug 2016 14:40

HI Abril,

Sounds like it's probably got either a dead transistor or a break in the circuit/pcb track. This can lead to overheating. If the LED is on, then the low voltage side should be ok. I'd check the amplifier for continuity as it could just be a dead spot.

Make sure the power resistor is 6k8 - the 10k ones are too big and drop more voltage = more heat. :(

abril
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Re: My LPT has died

Post by abril » 17 Aug 2016 20:36

Hi willb

Did have thoughts of dead transistor and measured the resistor and it is 10k,had thoughts of temporarily making up a passive supply for 33 only for something quick and easy.
Difficult time as getting ready to move :?
Got the PCB out so will check tracks.
Did go very suddenly ,no problems before.

willb
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Re: My LPT has died

Post by willb » 17 Aug 2016 21:04

Aren't leaving Cornwall ar' ee?

I had a similar thing with my mate's GTI psu (split phase = 2 amplifiers).
1st transistor in circuit was gone which caused resistor to burn.

Your old one still runs lovely - using a premotec '813 motor which is not too thirsty for the amp, just those 2w 3k3's that you fitted on the 15v side which do get hot - but all fine :D

abril
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Re: My LPT has died

Post by abril » 17 Aug 2016 22:10

Nah-----not yet :wink:
Might be a couple of years yet
Glad to hear the old mukka is still OK (thought they were 2.5W :!: )

abril
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Re: My LPT has died

Post by abril » 18 Aug 2016 22:02

gamarjoba
Have ordered 12k and 22k 2w resistors (to use in parallel) should give me 11k or 7.8k already have some capacitors for a basic passive supply.

abril
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Re: My LPT has died

Post by abril » 24 Aug 2016 22:18

2 off 22k resistors paralleled are giving me 67 and 74V, got a 0.39mfd cap ,only temp but it runs fine ,but 33rpm only at the mo.

abril
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Re: My LPT has died

Post by abril » 02 Apr 2017 15:09

Now got it running with Technics FG motor system. :D
A little tweaking to get the speed down not checked with a strobe yet but a basic count gets it roughly right :D
37845
Came from an SL-BD22D that had been dropped :wink:

Strobe says speed OK within tiny fraction.
All I have done is set both speed adjust pots to min speed and replaced the 10k fine speed adjust pot with a 22k resistor I had.
Bingo :shock:

backtotheblack
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Re: My LPT has died

Post by backtotheblack » 04 Apr 2017 23:53

often wondered if that would work and how well. i seem to remember that they introduced the quartz locked as the FG stuttered. its a shame that the older plastic technics decks are now fetching silly money. ok if you can find a 'broken' one like abril.

abril
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Re: My LPT has died

Post by abril » 05 Apr 2017 16:00

Have to say the sound quality is stunning,totally stable speed and all the LF grunge from the synchronous motor has gone.
I think £30 for the motor and electronics is a bit of a bargain,going to cost me more than that to get the electronics properly packaged,along with making it switchable on the LPT itself,replacing the original speed and power switches.
If I had a router I would seriously consider routing out the base and housing the electronics in the plinth base.

abril
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Re: My LPT has died

Post by abril » 17 Apr 2017 14:17

Have found that the motor does stutter at certain combinations of resistance but fine with the 22k now in series with the original 10k pot for some easy adjustability.
Have replaced the original slide switch for speed switching and leaf switch for power switching with a rotary 4 pole 3 way switch I had ,so speed and power switch simultaneously,the current draw is only 140mA on the 13V AC supply at start up which drops to about 40mA when the speed is attained.
Have decided I want to house it all in the plinth so I now need to get the base routed out,I think it will look good and almost original when it is all fitted.
37950

abril
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Re: My LPT has died

Post by abril » 16 Jun 2017 19:05

Final tweak to the board is the removal of the original 10k pot and 22k resistor and replacement with a 50k multiturn trimmer.
38564
The motor is glued (temporary?) on the original plate as the original synchronous motor came off easily and the plate cut to fit the magnetic sensor.
The pulley is slightly taller so the mount is set as low as possible.
38565
The original worn belt was too long so bought a new 424 long 0.7mm thick belt which turned out to be marginal so had to go looking for something shorter,found a 408 long 0.6mm thick belt at Thakker,works perfectly :D
Can vouch that the platter runs slower with the thinner belt :wink: ,easy to get the speed back up again though :D
My DC conversion for £50 =D>

abril
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Re: My LPT has died

Post by abril » 03 Dec 2017 15:38

Finished =D> =D> =D> =D>
Had to remove the original transformer to get it in the plinth,so it is now supplied by an external 12V 500mA AC plugtop transformer.
Long old story but finally done,spent so much time listening to it with the board outside before I committed to fitting it internally.
8 months from first trying the FG servo setup #-o
Many trials and tribulations,would have been a lot easier with an open plinth PT,but all worth it in the end. :D
39822

abril
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Re: My LPT has died

Post by abril » 09 Dec 2017 14:23

39841

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