Sony PS-X7 direct drive, slipping at 33 RPM

After a recent move, I set up my vinage bedroom system and fired up a Pavoratti LP on the PS-X7 (circa late '70s). After about 4 songs I was immediately surprised to hear the platter start to drag. It followed a slight pattern; drag a noticable step down in pitch, then back to nomral, step down, then back to normal. You could see the strobe lose its steadiness. I immediately switched it to 45 RPM's and it held rock solid. Then switched it back to 33 RPM's only to have it once again slip. I powered down the unit and fired it back up, then let the platter spin for about a half hour. I then put on another LP and it ran fine. The Pavoratti LP was clean and had only been played about twice.

Am I in for trouble in trying to service this table? It's built like a tank.

Footnote: the house has 200 amp service, and the room (and power lines) were renovated and upgraded in the late 90's.

I look forward to your remarks.
Best Regards,
There are a few possibilities:

(1) That some components on the circuit board have failed or gone out of spec. This may be fixable provided you can find a service manual and equivalents.

(2) That the platter system is damaged. The Sony X7 had a series of magnetized markings on platter's outer edge which are "read" by a tape head. The tape head feeds that info to the speed circuitry. If the markings are obscured or damaged, or the tape head is gunked up, it may not be sending proper readings. CAREFULLY examine and perhaps clean both.

(3) Like any motor, the Sony's needs some lubrication. Find a service manual and see if you can clean out the old stuff, what to replace it with and where the lubrication needs to go. Bearings can get damaged too.

The X7 was a very good (if butt ugly) table. It's worth fixing if you can do it for under, say, $200.

I think -- but can't guarantee -- that the only real difference between the X6 and X7 was the tonearm. You can probably pick up an X6 as a parts unit fairly cheaply and use it as an organ donor if necessary.
Ekobesky. Wow, what a fast and thorough response. I do have the old manual, and I even think I have the shematics. I'll take a look to address your suggestions. Thank you much!!!
One more thing. All the electrolytic caps in your turntable electronics are likely to be as old as the table itself. Thirty plus years is ancient for an electrolytic capacitor. It is quite possible that one or more of these caps is leaky, which could cause weird malfunction, such as what you are experiencing, or could result in the destruction of an irreplaceable IC or transistor. I suggest you consider replacing all the electrolytics. New ones of much higher quality than those available in the 70s are cheap. If you don't know how to solder, get someone to do it for you. It does not require a lot of deep thought.
Lewm is correct. replacing the caps may be an option.

May not hurt to make sure the spindle is lube'd and the platter spins freely by hand too.

This series was really built well. No reason it should not outlast the average person.
Lewm and Johnss, thanks very much for your input. I really appreciate it. I'll start looking into finding an electronics shop that can do this sort of stuff.

best regards