Nigel's Speed Controller parts list, schematics and instructions

[mrca]

Hi everyone and I hope someone can point me in the right direction.

So, to the funnies.


2. The unit has a display to show output voltage and moving this, you can see the voltage increase/decrease but moving the trim pots, nothing happens to the read out?


Many thanks for your advice and help

G'day Andy

My understanding is that adjusting the Oscillator Board Trim Pots changes the frequency, not the voltage?

The amplitude pot changes the voltage?

Regards
Colin

[nigel]

Sorry Andy, just typed you a long reply and it disappeared ('bad gateway' error or something) 
Will get back to you shortly.

[gninnam]

G'day Andy

My understanding is that adjusting the Oscillator Board Trim Pots changes the frequency, not the voltage?

The amplitude pot changes the voltage?

Regards
Colin

Thanks Colin. I would have thought that the amplitude would then change in the oscilloscope but it does not?

[gninnam]

Sorry Andy, just typed you a long reply and it disappeared ('bad gateway' error or something) 
Will get back to you shortly.

No worries Nigel.
I love technology as I am sure you do!!

[nigel]

Let's try again 

1. There are LED's fitted next to the trim pots but no matter which speed is selected, no light.

Hmm ... well my guess is that either there's a problem with the wiring of the speed selector switch (photo of the back of the switch might help), or else all the LEDs are fitted the wrong way round?

A multimeter across one of the LEDs, when that position is selected, should give you the answer. Any voltage there?

2. The unit has a display to show output voltage and moving this, you can see the voltage increase/decrease but moving the trim pots, nothing happens to the read out?

Yes, as Colin says, the trimpots will only affect the frequency.

I would have thought that the amplitude would then change in the oscilloscope but it does not?

  Not entirely with you there ... what are you measuring, where and whilst adjusting what? 

Whilst we're on the subject of amplitude adjustment, I noticed something a bit odd. There is a trimmer fitted in position R15 (marked 'amplitude') on the oscillator PCB. However, there is also an external pot fitted for amplitude adjustment. You should have one or the other fitted, but not both. The only reason for fitting both, maybe, would be to implement a fine/coarse adjustment, but that would require a modification to the PCB, to be done properly.
What range of voltage can you actually get from the unit, as it is now?

I note the 'symmetry' and 'distortion' trimmers are also fitted. Those need to be adjusted for best sinewave. The trace on your scope doesn't look all that great - a bit too 'spiky' - closer to a triangle than a sine.

Just a couple of other points about the construction of this unit - generally it looks very nicely made indeed, but -

1. I can't see any connection from mains earth to the chassis. Doesn't mean that there isn't one, just that I can't see it. Can you confirm that there is one?

2. It's a bit of a pity that all the high voltage connections have been nicely and carefully insulated, except for that mains filter, which has no insulation whatsover and big sticking-out terminals. Please be very careful making adjustments with the unit powered up.
One of the things I was very careful about, when deciding how to suggest to people how they might build this thing, was that all live mains would be covered, so that the risks of powering up with the case open could be mitigated as far as possible.
That mains filter looks like an accident waiting to happen. Please be careful.

(To clarify : I've got no problem with the way it's been done, when the case is closed up)

[gninnam]

Hmm ... well my guess is that either there's a problem with the wiring of the speed selector switch (photo of the back of the switch might help), or else all the LEDs are fitted the wrong way round?

A multimeter across one of the LEDs, when that position is selected, should give you the answer. Any voltage there?

Putting the multimeter across all three LEDs (moving the speed selector switch to match) they all show 11.55 volts.

A few pictures of the rear of the speed selector switch:

Whilst we're on the subject of amplitude adjustment, I noticed something a bit odd. There is a trimmer fitted in position R15 (marked 'amplitude') on the oscillator PCB. However, there is also an external pot fitted for amplitude adjustment. You should have one or the other fitted, but not both. The only reason for fitting both, maybe, would be to implement a fine/coarse adjustment, but that would require a modification to the PCB, to be done properly.
What range of voltage can you actually get from the unit, as it is now?

Doh - I will look to remove that trim pot in due coarse. The voltage range (with the trim pot in R15 at max) is 146 to 223 volts

I note the 'symmetry' and 'distortion' trimmers are also fitted. Those need to be adjusted for best sinewave. The trace on your scope doesn't look all that great - a bit too 'spiky' - closer to a triangle than a sine.

I will tweak those to see if I can get a better sine wave.

1. I can't see any connection from mains earth to the chassis. Doesn't mean that there isn't one, just that I can't see it. Can you confirm that there is one?

It is there. It connects to the mains filter which is in turn connected to the chassis.

2. It's a bit of a pity that all the high voltage connections have been nicely and carefully insulated, except for that mains filter, which has no insulation whatsover and big sticking-out terminals. Please be very careful making adjustments with the unit powered up.
One of the things I was very careful about, when deciding how to suggest to people how they might build this thing, was that all live mains would be covered, so that the risks of powering up with the case open could be mitigated as far as possible.
That mains filter looks like an accident waiting to happen. Please be careful.

I will look to cover those soon.

Many thanks for your help so far - going in the right direction

[nigel]

Putting the multimeter across all three LEDs (moving the speed selector switch to match) they all show 11.55 volts.

Ah ... that being the case, they'll be the wrong way round, then 
(I'm guessing that the idea there, was that they were supposed to illuminate the trimmers. Not sure that will work very well, from the way they are positioned. You might want to experiment with that ...)

Doh - I will look to remove that trim pot in due coarse. The voltage range (with the trim pot in R15 at max) is 146 to 223 volts

Yes, that's a little on the low side. Removing that trimmer should give you a more useful range.

It is there. It connects to the mains filter which is in turn connected to the chassis.

Ah, OK, all good then 

[gninnam]

Ah ... that being the case, they'll be the wrong way round, then 
(I'm guessing that the idea there, was that they were supposed to illuminate the trimmers. Not sure that will work very well, from the way they are positioned. You might want to experiment with that ...)

I did think that so we have a plan - as you say will have to see how it looks once they are working.

Yes, that's a little on the low side. Removing that trimmer should give you a more useful range.

Yep, while the board is out to sort out the LEDs I will also remove the pot and hope I get a better spread of volts.

Many thanks again - will try to sort it this weekend but depends on what plans the other half has in store!!

[gninnam]

So - thanks to Nigel nearly there.

Took the pot out and getting good voltage swing now (140 to 290) but above 260 the output transformer sings....

Moved the LEDs around but still not lighting up but wanted to try the unit on the turntable so played with the trim pots to get the sine wave a bit better (see pic below) then put the lid on and used it on my Lenco - it only bloody works

Many thanks again Nigel, you are a star.
Will look at the LEDs another day, just planning on using it for now.

[nigel]

Took the pot out and getting good voltage swing now (140 to 290) but above 260 the output transformer sings....

OK, that's possibly going the other way a bit (probably the amps are starting to clip, which is what you can hear). Not a problem, so long as you keep the voltage under 240. I would personally go for around 200-220V when fully warmed up (you'll find it will drop a little from cold - which is why I was thinking your original measurement of 220-odd was a bit too low when cold and off-load).

played with the trim pots to get the sine wave a bit better (see pic below)

I'm going to be hyper-critical and say that the symmetry looks a bit off to me. Maybe just the photo, but to me it looks like the bottom of the waveform is a bit spikier than the top. If the trace was centred to start with, then the negative-going peaks are a little greater in amplitude also (compare to the graticule lines). Best to get it perfectly symmetrical  

Glad to hear it's working, in any case 

[gninnam]

OK, that's possibly going the other way a bit (probably the amps are starting to clip, which is what you can hear). Not a problem, so long as you keep the voltage under 240. I would personally go for around 200-220V when fully warmed up (you'll find it will drop a little from cold - which is why I was thinking your original measurement of 220-odd was a bit too low when cold and off-load).

Tested on the TT at around 190 and seemed to have enough torque to start the platter plus keep it stable. I don't think I will ever run it above 240!!

I'm going to be hyper-critical and say that the symmetry looks a bit off to me. Maybe just the photo, but to me it looks like the bottom of the waveform is a bit spikier than the top. If the trace was centred to start with, then the negative-going peaks are a little greater in amplitude also (compare to the graticule lines). Best to get it perfectly symmetrical  

Point taken. I will play around with the trim pots when I have time to get the wave to look better but need to think about the LEDs - will probably drill fresh holes above the holes for the speed control potentiometers and use different LEDS ?

[dimani4]

Dear Nigel,

I have a question to you. Look at the voltage stabilizer with servo.



May I use it with your controller? If I don't have exactly 220V and it changes from time to time (not drastically) may this stabilizer improve the operation of the speed controller or it doesn't matter at all? Or it will blow the speed controller and I shouldn't connect it at all?

Thank you very much. 

[analogadikt]

Dear Nigel,

I have a question to you. Look at the voltage stabilizer with servo.



May I use it with your controller?

It is superfluous when the tt is running on a NSC. You may have some benefits running other gear like the pre and power amps through that.

Regards,

Anwesh