Hello everybody!

I have 4 players with same issue. Models SONY EX5, FX5, EX650(652), EX660(652)

All of them have same mechanism with "closed" capstain and variable tension of the belt.

Issue: play starts but switch forward-revers direction every 2-3 sec. FF and REW starts but stops after 2-3 sec.  I replaced belt from working one but it did not help. I think that it is common issue for this mechanism. Does anybody khows how to repair it?

I had similar issues with most of my EX-1 based series. Not a belt issue. Mine seem to be caused by dried/smooth pinch rollers. Otherwise a seemingly solid mechanism.

FF and REW issue I have not encountered. Maybe wrong belt size/tension or photo sensor related issue?

This models have photosensor? Probably you have electronic diagramm for model like this?

Yep. Seems like 2 in the EX5 mech, under the board. PH701/702.  You may have to desolder the board to access it. I think photo sensor issue is unlikely, maybe the paint on the wheels have faded/corroded off?

Oh yes, you sure. But today I bought pack of thin belts and ex652 repaired! It looks like this mechanism required specific belts, very elastic. I will test player 2-3 days. Then will buy and replace belts for other three playrs. I will write results and belt leight.

During september-october i replaced belts for 6 sony.

All of them works well with belts from DocP. I tried to use cheap belts (3$ for pack of 20 belts) but they are not suitable for Sony with variable tension mechanism.

It was a question on the forum about leight of belts required.

Models Sony ex-65x, ex-66x, ex-2, ex-1, ex-5, ex-9, ex-910 required high-quality belts o,7mm 105-108 half-leight. Both dimensions suitable. 

Sony 63x required same size but works well with cheap belts. because of no variable tension on this model.

! if you test new belt with open cover be careful with light. Extra bright light disturb the work of fotosensors and looks like failing of logic control. ff and rew modes switched chaotically. Just turn off your lamp

Old belts from these models very good for Sony ex-50, wm-701, wm-702, ex-707 and etc. These models required more long belts (i think 110-112 half-leight) so old belts from Sony 65x are exactly what we need.

Yep these units require the exact belt size and then they come alive, had the same issue with mine.  Got them from DocP and works like a charm. 

what or Who is DocP ??

I need few belts myself...

Thanks