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Pink Triangle LPT psu

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Postby willb » 03 Apr 2009 18:34

Phil Y wrote:Hello Chris,
Please tell me if I have this right. With my 'square' PSU (parallel connected?) running an 807 motor the phase cap should be 0.39u not 0.242(0.22+0.022) as fitted to mine? Could this be due to the replacement motor I fitted when my deck was a few years old?

Thanks for the info, Phil.


Hi Phil,

By square, read rectangular! The older type at the back of the deck. If yours runs ok - leave it as it is. According to Philips, 807/818 are exactly the same, save for the fixing lugs. Mine seemed to be better with a higher value. You could try connecting a 0.15 across the screw terminals and see if it's better or worse - only way to tell!

Cheers.
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Postby willb » 03 Apr 2009 18:41

abril wrote:Hi Chris

and how does it sound after all that?
So that was the reason for 0.68mfd - series coils!!!!!!!!!


Hi Abril,

Sounds very good considering its running on a makeshift bearing!

Most later LPT's were connected this way. My mate had one in early 90's (long psu), and it didn't use the middle terminal. Red to capacitor and 2 twisted together to ground. I think the export PSU that he later got was the same. The old motor on yours has a diagram on the label showing the two different connection methods! Parallel - 110v; Series - 220.

As to why - :?:

Cheers.
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Postby Phil Y » 03 Apr 2009 18:49

I have been reading through the "converting to export spec" bit. All 3 of the big electrolytics on my PCB are 33uF 250v !!!

Ho Hum. Are any 2 PT decks the same?

I got my deck in march 1990 (Sn. 0233)

Does this make it especially early or late anyone know?

Cheers, Phil.
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Postby willb » 03 Apr 2009 19:22

Phil Y wrote:I have been reading through the "converting to export spec" bit. All 3 of the big electrolytics on my PCB are 33uF 250v !!!

Ho Hum. Are any 2 PT decks the same?

I got my deck in march 1990 (Sn. 0233)

Does this make it especially early or late anyone know?

Cheers, Phil.


Par for the bloody (Pink Triangle) course!

If you're running an Airpax 31807, then use 2x47uf and 1 x22uf, 350/400v.

If yours are all 250v, then you've probably got a big 10 or 15k resisitor in there. This was for the old 043** motors which are lower current. If so, put a 6k8 in which will run the 807 much better. But don't forget the cap on the end has to be at least 160v when you do this!

Cheers.
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Postby Phil Y » 07 Apr 2009 18:18

Replaced the 0.22u phase cap with 0.39, this seems to be an improvement.
Tried 0.68u but the motor seemed like it was going to shake loose from its mountings with that!

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Postby Phil Y » 08 Apr 2009 17:53

On checking the voltages on the 2 phases, they are now a bit closer 33rpm but a bit wider at 45rpm. Looking at the data sheet this is to be expected as the phase cap value is different at 50 and 60 Hz. I suppose the "correct" way to do it would be for the speed change switch to switch a second parallel cap in and out of circuit as required for the different speeds.

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Postby Phil Y » 10 Apr 2009 19:43

Hello again Chris,
I have been looking at your notes and my PSU. A picture paints a thousand words as they say, could you please have a look at my drawing and say weather I have the "export" changes correct.

Thanks again, Phil.

9139
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Postby willb » 14 Apr 2009 14:46

Hi Phil,

I think this is what you need. (I just edited it and added a couple of text boxes). I presume the "1.8k" on resistor was a typo? Are you sure all 3 caps are 250v, as the first one will see 330 odd (rectified mains), even if there is a big resistor!? :?

Basically, the resistor sits between the 47's and the 22, instead of between the two 33's.


9175
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Postby Phil Y » 14 Apr 2009 17:43

Thanks Chris,
Yes 1.8K is a typo. I presume the only reason for putting 2X47u in series is to raise the working voltage. I plan to fit a single 450V 22u cap for simplicity as that is near enough to 23.5uF to make no odds.
As to my board, yes they are all 250V caps. This is not a problem. If you look at the "original" sketch on my drawing, the first cap is not across the full supply voltage, the bottom end is connect to the downstream end of the (originally 15K) power resistor so raised well above the -ve rail. The full supply voltage only appears across the 2 caps in series which is therefore 500V working.

Cheers, Phil.
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Postby willb » 14 Apr 2009 19:14

Hmm....

Not sure that's the same thing at all. If you put 2 in series, then tie them to ground, you've effectively charged up nearly 100uf, although it is "seen" as 23.5! You'd be lowering yours in doing so as they're 33 anyway!

Surely caps adjust power, not voltage - that's the resistors job? I ran old motor with 15k resistor and "export" caps for extra power and smoother running, but the working voltage into amplifying stage stayed exactly the same - cos the 15k was still in there! Single 22 is as per standard LPT layout, (although later "long" boards for 807's used 47u's with 10k).

I'm sorry but the original diagram shows first cap connected to rectifier - (as all mine were), only 2nd cap is at lower voltage end of resistor. :? Mine is 0137, (about 100 older than yours), so the board will be the same layout.

9176

Sorry if I'm missing something, but I just don't get what you're saying.
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Postby Phil Y » 14 Apr 2009 20:39

Hi again Chris,
Really, the most important thing for me to know is what to do with my deck. Could you confirm that the right hand circuit below is what PT did with the 807 motor.
The one on the left is how mine is connected.
If you look at the top capacitor it is indeed connected to 330V but look at the bottom end, it is not connected to 0V. It is connected to the 'output' which is at approx (I have not measured it) 200V. This means the capacitor sees 330volts minus 200volts ie about 130volts. Well within its 250 volt rating. The bottom cap is connected between 200v and 0v, again well within its rating.

I hope this explains what I mean.

9179

Sorry, my mistake, late units 10K standard, 6.8K export ?
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Postby willb » 16 Apr 2009 12:09

Hi Phil,

You were almost there that time! Except: Resistor= 6k8 and 2nd (or 3rd if you like), cap is 22uf. (the single one at lower voltage end).

Yes, later LPT's used 10k with 807 motor, but Exports used 6k8, (as per Philips datasheet).

But don't forget the 100uf dc blocker on the output changes to 47uf, and needs to be 160v, not 100v. Yours probably measures about 50-60v at the moment, but with a 6k8 it will be more like 125v - hence the higher rating.


[img]9197

Cheers

Chris.
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Postby avinunca1 » 19 Apr 2009 20:19

Phil Y wrote:Hello avinunca1,
I have not got a DC motor yet though I am still considering it. I have only recently got my RB250 back from having the full Origin Live treatment so I am still enjoying the improvements produced by that at the moment.
I was also thinking of getting an Achromat. Does anyone know, if I get the 3mm version, would I still be able to to use my Mitchell record clamp? I would like to preserve that option if possible.

Regards, Phil.


Recently bought s/h OL Silver. Sounds amazing on my LPT with the Denon DL160. Everything so tight on bass and drums. Hard to fault it really though it doesn't really look much. Will look into the psu mods next.
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Postby Phil Y » 20 Apr 2009 00:23

I should think the silver sounds great. It is their next arm up from what I have and I am very pleased with that. Mine sounds way ahead of the standard RB250. I have converted my LPT to Export Spec. as described by Chris and that has improved things as well. The deck sounds more solid and focused now although as it turned out my motor and PSU were not matched as the phase cap and current limiting resistor were the wrong value. I think this was due to my having to change the motor when the deck was a few years old and the spec. having changed in between times. As a result I can't really say how much difference it would make to a standard but correct deck. I have not tried the DL160 although it seems to be very popular at the moment. Many years ago I used a DL110 but moved to a Sumiko Blue Point, then onto my current Goldring 1042 which I think is the best cartridge I have owned. I think I will be ordering an Achromat in the near future as they are not too expensive and just a further development of the acrylic platter idea.

Cheers, Phil.
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Postby willb » 05 May 2009 20:53

Hi
Phil Y has asked if I could post this information for anyone else who may be interested. It shows the changes needed to convert older LPT psu's from dual (TL072), to single (TL071) op-amps.

This generally results in more output for less current drain on the psu - especially useful with older Airpax 31807/31818 motors, which were slightly more current hungry anyway.

[img]9386[/img]

The 2 components which need replacing are 1 off 220k resisitor and 1 off 10nf (0.01uf film cap). There should be a double pad next to pin 6 on the pcb -but do check yours first before attempting the conversion!!

The capacitor has to straddle the chip between pins 2 and 6 instead of 1 and 2 with dual op-amp.

The resistor has to have longer leads so that it will reach to Pin 6 instead of pin 1 previously. This is on the opposite side of the chip - hence the need for longer leads.

If anyone needs any clarification, (or have any variations which we haven't yet encountered!), post your findings and we will try to sort them out.

Chris
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