I have problem with my PT LPT turntable. The motor is struggling to start and vibrates. If I give it a helping in hand it will spin up but very slowly. I have read many threads about these issues and suspect that resistors are probably ill where the PCB gets hot. My issue is I can't see the bandings on the worst resistors and therefore not sure what to purchase. Therefore looking for a little help if anyone has had similar issues or a PCB to hand or circuit diagram to help identification please?
I looking for the resistor to left hand side of the capacitor towards the pot.
Hopefully you can see the two images I have uploaded 😕
I looking for the resistor to left hand side of the capacitor towards the pot.
Hopefully you can see the two images I have uploaded 😕
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That is a well cooked lump of FR4. Repair is not likely to be the best option at this point, as there is a distinct chance that the tracks won't survive rework. Can't help on the values I am afraid.
If you look at this from here, the resistor appears to be identical to the 2nd resistor on the opposite side of the adjacent electrolytic capacitor. The colour code appears to be ORANGE (3), WHITE (9) AND RED (2) which has a value of 3k9 Ohms. However, judging by the scorch mark on the PCB, I'd say that there is something else duff on that circuit board.
Might look at using a higher power resistor off board, and try to identify what the transistors are and select something similar with a somewhat higher dissipation rating. I owned a PT turntable a couple of decades ago, complete and utter nightmare; I wish you the best of luck!
I have the same issue but ive decided to go a slightly different route.
As the LPT board isnt really fit for purpose Ive thought about going down the simple psu route ala naim armageddon, basically just a transformer and a phasing cap. I know itll only be single speed but i just want a quick fix until I can afford a gyrodec.
I have the airpax 9904 111 31807
50hz, 110v
Both coils measure 2.3k ish
Im unsure as to what phasing cap its supposed to have. I cant find a data sheet for this particular motor although the closest i can find suggests it should be 0.2uF rather than the 0.68uF thats on the board.
I have a fairly weighty tx taken from a mackie stage monitor that has 63-29.5-0-29.5-63 windings on the secondary.
Instead of trying to drop 63v*2 down using some power resistors I was wondering whether using 63v to the 29.5v (92.5vac) on the other side would be sufficient. This is slightly lower than the -15v/+10v voltage spec on a more recent airpax motor but ive heard people run these on 90v to help make them run more smoothly.
I also have a bizarre situation on the primaries.
pri:0-120v(blk-bwn)
0-120v(Blu/Gry-Ora)
Would Blk go to neutral and orange to live?
Brown and Blue or Gry shorted to connect them. Good idea to put a stm cl60 in here to limit inrush?
Any ideas why there are 2 wires on the same end of the secondary coil (blu/grey).
Thoughts?
Cheers
As the LPT board isnt really fit for purpose Ive thought about going down the simple psu route ala naim armageddon, basically just a transformer and a phasing cap. I know itll only be single speed but i just want a quick fix until I can afford a gyrodec.
I have the airpax 9904 111 31807
50hz, 110v
Both coils measure 2.3k ish
Im unsure as to what phasing cap its supposed to have. I cant find a data sheet for this particular motor although the closest i can find suggests it should be 0.2uF rather than the 0.68uF thats on the board.
I have a fairly weighty tx taken from a mackie stage monitor that has 63-29.5-0-29.5-63 windings on the secondary.
Instead of trying to drop 63v*2 down using some power resistors I was wondering whether using 63v to the 29.5v (92.5vac) on the other side would be sufficient. This is slightly lower than the -15v/+10v voltage spec on a more recent airpax motor but ive heard people run these on 90v to help make them run more smoothly.
I also have a bizarre situation on the primaries.
pri:0-120v(blk-bwn)
0-120v(Blu/Gry-Ora)
Would Blk go to neutral and orange to live?
Brown and Blue or Gry shorted to connect them. Good idea to put a stm cl60 in here to limit inrush?
Any ideas why there are 2 wires on the same end of the secondary coil (blu/grey).
Thoughts?
Cheers
been having a play with the phasing caps.
The test setup was a signal generator hooked up to the motor.
The signal generator wasn't enough to get the motor turning but at least there was a load present.
The original cap was 0.68uF but I found that a 0.47uf in parallel with 0.1uf gave the closest to 90 degree shift at 50hz, However at 50hz the phased output was down (they matched at 54hz!) so i tried a few values of resistor to drop the non phased input to the motor and about 1k5 seemed to work best.
It seems each winding on the motor measures differently so when you nudge the motor round the pp of each waveform varies a little. Naff motor i guess, but i think thisll be an improvement.
Having done some back of the envelope calculatons, the resisotor would disipate about 1.2w fed with 110v (its inline with 2k4 coil of the motor) but as im likely supplying only 92v it should be less. However I would use a 2w to be safe. (shame PT didnt do this when they built my psu!)
I may find enough voltage has been dropped and i can put the full 126v across it. Ill know more once ive tried ramping up with the various windings.
The test setup was a signal generator hooked up to the motor.
The signal generator wasn't enough to get the motor turning but at least there was a load present.
The original cap was 0.68uF but I found that a 0.47uf in parallel with 0.1uf gave the closest to 90 degree shift at 50hz, However at 50hz the phased output was down (they matched at 54hz!) so i tried a few values of resistor to drop the non phased input to the motor and about 1k5 seemed to work best.
It seems each winding on the motor measures differently so when you nudge the motor round the pp of each waveform varies a little. Naff motor i guess, but i think thisll be an improvement.
Having done some back of the envelope calculatons, the resisotor would disipate about 1.2w fed with 110v (its inline with 2k4 coil of the motor) but as im likely supplying only 92v it should be less. However I would use a 2w to be safe. (shame PT didnt do this when they built my psu!)
I may find enough voltage has been dropped and i can put the full 126v across it. Ill know more once ive tried ramping up with the various windings.
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