Pioneer PL-71 refurbishment (Stu Version)

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karatestu
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Re: Pioneer PL-71 refurbishment (Stu Version)

Unread post by karatestu »

Lindsayt wrote: Thu Apr 01, 2021 11:51 am Apart from the 33 and 45 rpm micro switches, does this turntable have any other micro switches? And if so what do they do?
There aren't any other micro switches. Just a mains on / off.
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Lindsayt (Thu Apr 01, 2021 1:36 pm)
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Re: Pioneer PL-71 refurbishment (Stu Version)

Unread post by Stemcor1990 »

I’m following this with great interest.

I managed to buy RD’s PL71 when he wanted to investigate an alternative tt. I liked the 71 so much that I bought another one at a very low price. It was on ebay with a US plug and voltage. Two minutes with a soldering iron and it was running at the UK voltage. Result !

Richard’s 71 had been refurbished; caps replaced etc. My cheapo has a bit of speed drift but that stops after about 30 minutes. I’m interested to see where Stu can take the 71 as I might be tempted to try to do the same with the cheapo.

Stu - please keep posting on this subject !
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karatestu (Thu Apr 01, 2021 1:16 pm)

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Re: Pioneer PL-71 refurbishment (Stu Version)

Unread post by karatestu »

Stemcor1990 wrote: Thu Apr 01, 2021 1:01 pm I’m following this with great interest.

I managed to buy RD’s PL71 when he wanted to investigate an alternative tt. I liked the 71 so much that I bought another one at a very low price. It was on ebay with a US plug and voltage. Two minutes with a soldering iron and it was running at the UK voltage. Result !

Richard’s 71 had been refurbished; caps replaced etc. My cheapo has a bit of speed drift but that stops after about 30 minutes. I’m interested to see where Stu can take the 71 as I might be tempted to try to do the same with the cheapo.

Stu - please keep posting on this subject !
Well, I'm not one for keeping things to myself. Most of this has been done before by others. Not sure anybody has offboarded the psu or used a super regulator though. The raw psu has enough headroom for the dropout (approx 6V) when using a super regulator which has very low noise and output impedance and there might be enough for a gyrator (capacitance multiplier) before that which will mop up ALOT of noise making the super regs job easier.

Other things I have seen mentioned is pouring something on the underside of the platter (bison kit might work there - I've got loads of it) and putting it in a slate plinth. Not sure about those two things.

Do DD's really benefit from a heavy dense plinth like slate ?
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Re: Pioneer PL-71 refurbishment (Stu Version)

Unread post by karatestu »

Unfortunately this PL-71 suffers from the usual speed stability issues. Set the speed by strobe and go back 20 mins later and it's moving. Also switching between 33 & 45 they are never where you left them.

So it looks like I will have to get on change the micro switches and pots. Also recap the electrolytics. I need to do this before I take it to Ant for tonearm bearing attention and a rewire. Nothing goes to plan eh :roll:

Unfortunately there is going to be a bit of guess work here as the much mentioned maplins micro switches are not available anymore. They have to fit ofc and then there is the pushing force required.

The speed pots are 1K I believe. So I will have to try and find a bourns model that is the correct size and fits.

The electro caps are easier to source and should improve things as they are nearly 50 years old :shock: :shock:
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Re: Pioneer PL-71 refurbishment (Stu Version)

Unread post by Vinyl-ant »

Spray some servisol into the pots and give them a load of turns to work the stuff in
You might be surprised, no point just arbitrarily replacing them if a good clean sorts them
The pots on my akai r2r were the main reason it didnt work, copious amounts of servisol as the first step brought it back to life
The caps arent too much of a bother to replace but there are a heck of a lot of them. Concentration and making sure that the caps go in the right way around are required.

You might get away with servisol in the switches too rather than searching out replacements
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karatestu (Thu Nov 11, 2021 6:21 am)
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Re: Pioneer PL-71 refurbishment (Stu Version)

Unread post by Geoff.R.G »

Vinyl-ant wrote: Wed Nov 10, 2021 7:48 pm Spray some servisol into the pots and give them a load of turns to work the stuff in
You might be surprised, no point just arbitrarily replacing them if a good clean sorts them
The pots on my akai r2r were the main reason it didnt work, copious amounts of servisol as the first step brought it back to life
The caps arent too much of a bother to replace but there are a heck of a lot of them. Concentration and making sure that the caps go in the right way around are required.

You might get away with servisol in the switches too rather than searching out replacements
Not forgetting that Servisol needs to be applied to the inside of pots and switches. I have seen it sprayed all over the casing to, obviously, no effect.
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karatestu (Thu Nov 11, 2021 6:21 am)

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Re: Pioneer PL-71 refurbishment (Stu Version)

Unread post by r3xj0hn570n »

After trying the above

clean the pots below making sure they are back in the original position...
motor.jpg
motor.jpg (111.25 KiB) Viewed 1620 times
Then try replacing the 3 circled caps. Those are associated with the motor drive, 3 phase i presume from the drive circuitry.
Anyway, electrolytics don't like being sandwiched next to heatsinks.
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karatestu (Thu Nov 11, 2021 6:21 am)

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Re: Pioneer PL-71 refurbishment (Stu Version)

Unread post by karatestu »

Thanks all.

I will give the pot and switch cleaning a go I suppose. I have read that most of the time it doesn't work or works for a short time then starts misbehaving again. Is servisol thd best product for this ? Despite gers mentioned a lot.

Rex, I will be replacing all the electro's in due course, might as well whilst I am in there. In everything I have read nobody has mentioned cleaning those two pots on the motor board but I might as well do them whilst I'm at it.
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