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Pioneer PL-400 Strobe Issue

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Pioneer PL-400 Strobe Issue

Postby faintaxis » 19 Apr 2017 15:10

Hi all,

Apologies for the crossposting - I wasn't sure which forum I should post in! :D

I've picked up a cheap Pioneer PL-400 turntable. It had a few issues - some of which I think I've fixed - mostly with the control panel and the speed select switch.
I doused the speed select switch in contact cleaner and WD40 to loosen it up and now it latches properly. However, the turntable seems to have issues with 33rpm - the strobe lights seem to go steady at far too slow a speed for 33rpm. I can of course adjust the speed using the fine tuning controls underneath (which I also cleaned) but then the strobe is out (showing the record as spinning too fast).

Any ideas what could be going wrong?
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Re: Pioneer PL-400 Strobe Issue

Postby Coffee Phil » 20 Apr 2017 17:51

Hi Faintaxis,

Welcome to the forum.

The drive for your strobe is derived from the same quartz clock which controls turntable speed. What you describe should not be possible in quartz lock. Do you have a variable speed mode which you are using?

The manual is here: https://www.vinylengine.com/library/pio ... -400.shtml

Sorting this will take at least an oscilloscope and very high level electronics troubleshooting skill.

Do make the effort or find someone who can as this seems too nice a machine to dump.

Phil

faintaxis wrote:Hi all,

Apologies for the crossposting - I wasn't sure which forum I should post in! :D

I've picked up a cheap Pioneer PL-400 turntable. It had a few issues - some of which I think I've fixed - mostly with the control panel and the speed select switch.
I doused the speed select switch in contact cleaner and WD40 to loosen it up and now it latches properly. However, the turntable seems to have issues with 33rpm - the strobe lights seem to go steady at far too slow a speed for 33rpm. I can of course adjust the speed using the fine tuning controls underneath (which I also cleaned) but then the strobe is out (showing the record as spinning too fast).

Any ideas what could be going wrong?
Coffee Phil
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Re: Pioneer PL-400 Strobe Issue

Postby faintaxis » 21 Apr 2017 10:53

Hi Phil,

Thank you :)

The TT doesn't appear to have a pitch control on the control panel, just a speed switch (which I have replaced - it doesn't appear to make a difference).

I've read through the manual and service manuals but can't seem to find anything useful unfortunately. I've ordered a new power board as I've noticed this TT has a voltage selector which has had its wires cut, and the power transformer appears to be the wrong type (less output cables, and completely different model number to the manual)
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Re: Pioneer PL-400 Strobe Issue

Postby faintaxis » 06 May 2017 18:31

Okay, so, the replacement power supply didn't fix the issue. It appears despite not being listed anywhere in Pioneer's paperwork, the strange power supply set up it originally had was correct.

I've recapped the powersupply and all of the electrolytic capacitors on the drive board but no dice still.

I've bought a turntable speed calibration app for my phone ("rpm") where I've managed to find out the following:

- When the strobe steadies at the turntables' setting of 33rpm, the phone is reading 29.9rpm
- When the strobe steadies at the turntable's setting of 45rpm, the phone is reading 41rpm.

Interestingly, the speed control pots on the underside can be used to get it almost perfect, but of course in doing this, the strobe is no longer steady!

I'm really not sure what to do next.
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Re: Pioneer PL-400 Strobe Issue

Postby faintaxis » 06 May 2017 22:18

can't find the edit button...

Anyway, I've found a resistor on the drive board that is way out of spec. I'm wondering if that has a bearing - it is in part of the circuit dealing with the speed control. I've ordered a replacement.
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Re: Pioneer PL-400 Strobe Issue

Postby Todd141 » 12 May 2017 22:52

I don't think those phone apps are accurate. I remember seeing a video where someone proved they weren't accurate. I would trust the strobe.
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Re: Pioneer PL-400 Strobe Issue

Postby faintaxis » 12 May 2017 23:01

The strobe is definitely off, I.e the turntable spins visibly slowly and the music plays far too slowly when the strobe says the turntable is spinning at the correct speed.
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