Acquired a Pioneer PL-400 turntable - Some questions

[eightyeight]

Hi, I recently bought a PL-400 cheaply with the speed running slow. I fixed the speed by replacing the trimpots on the motor control circuit board. It seems to be working fine now.

I had some questions about the behavior though. When the turntable stops, is the platter supposed to freespin until it eventually stops or is there some kind of braking mechanism to stop the platter quickly?

The other question is, should the dots on the strobe be perfectly stationary or is some amount of wobble expected? The music sounds fine to me but the dots wobble back and forth slightly. Video here to demonstrate what I mean.

Thanks in advance!

 

[redk9258]

I have a PL-200 and it does not have a brake, so I assume the PL-400 does not either. I don't think the wobble is normal.

 

[eightyeight]

I have a PL-200 and it does not have a brake, so I assume the PL-400 does not either. I don't think the wobble is normal.

Good to know about the brake. Does your PL-200 have a minor strobe wobble or is it dead on?

 

[Donal64]

Hi, I recently bought a PL-400 cheaply with the speed running slow. I fixed the speed by replacing the trimpots on the motor control circuit board. It seems to be working fine now.

I had some questions about the behavior though. When the turntable stops, is the platter supposed to freespin until it eventually stops or is there some kind of braking mechanism to stop the platter quickly?

The other question is, should the dots on the strobe be perfectly stationary or is some amount of wobble expected? The music sounds fine to me but the dots wobble back and forth slightly. Video here to demonstrate what I mean.

Thanks in advance!

I have a PL-400. The platter does not have a brake. The platter will turn freely till it stops, after the arm returns to the rest and the table shuts off. I think its pretty normal, what I saw of your strobe. Just my opinion.

 

[redk9258]

I just played my PL-200. It does do that little wobble too. Yours may look a little more pronounced becaus you have one row of dots. Mine has 4 rows of 'dashes', 50 /60 Hz , 33/45RPM.

I recently took this out of the closet where I have had it stashed in it's original box for probably over 20 years. I had the original transport screws holding the platter, so that part is fine. Unfortunately the rubber mat had it's edge resting against the dust cover and now it has a curl to it. I have heated it up with a hair dryer to make it pliable. It seemed to help but still wants to curl up. I heated it up again and put it between a bunch of LPs. I need to check it out again. If it doesn't flatten out soon, I might have to wait another 20 years for the rubber to flatten out! Next Time I put it away, I will put the mat in a cardboard LP jacket.

 

[larryderouin]

That amount of wobble is probably normal. If you look at it it's NOT advancing or retarding in speed, and actually keeping it pretty good. It probably needs tweaking. there is a Service manual addendum for PL-200-300-400 turntables on vinylengine. Need to register (free). Download the Service manual and the 1st additional Service manual. It will detail adjustments to dial in the speed correctly on these models. You will need a 2 probe O-Scope.
https://www.vinylengine.com/library/pioneer/pl-400.shtml
redk9258. Put it on the turntable upside down and use it. The weight of the LP's should hold it down and get it to flatten out.

 

[redk9258]

I pulled the mat out last night and it was flat within about 1/8". Today it's up about 1/4". I guess it really has a memory! I read somewhere where someone recommended putting a warped mat in boiling water, then putting it between something flat with weight on it. I might try that if we have a pan bigger than 12" and my wife doesn't catch me! LOL. I don't think 212 degree water would melt rubber. I also thought about taking the platter off and wrapping the platter / mat tightly with saran wrap and putting it in the sun for a few hours.

BTW, sorry for hijacking the thread on your PL-400.

 

[Donal64]

Or , you could just get another mat. That would give you several options. You could buy a new, aftermarket mat, you could probably find an original on ebay. Or you could just find a junk turntable and pull the mat. I think these have an adjustment on the back of the tone arm , somewhere, that you can adjust the verticlal tracking angle, should you use a different thickness mat.

 

[redk9258]

Or, I could just put some thin double sided tape or a dab of rubber cement under it.

 

[eightyeight]

It will detail adjustments to dial in the speed correctly on these models. You will need a 2 probe O-Scope.

Thanks very much. I do have a old analog dual trace scope packed away. I'll dig it out and see if I can dial the speed in some more.