Hi,
I'd check the tantalum caps C5, C6, C7 in the first place - did you check the voltage over C4?
Cheers Roland
Hi !
As far as I can tell this is a fairly common misbehaviour.
The 701 is in constant "cold start" mode and the operational amplifier does not (or: cannot) turn the motor down.
Usually this is a fault with the tantalium capacitors C5, C6 and C7 as Roland pointed it out already. These are known to produce internal shorts over the years and - in rare occasions - the LM709 is damaged already.
You should replace all tantalium capacitors - either with "modern" tantaliums or normal electrolytics. It does not matter too much in the end. The error with using standard types sums up to a few promilles only for the motor flutter in the end. The LM709 today is available in an 8-pin package in most cases. But as far as I can tell there is a printing on the board how to solder the 8- and 14-pin variants.
My own 701 has these capacitors replaced already as well as the "main" caps for the power supply (C3 + C4) as well as the LM709. It wasn't as bad as on yours, but it had occasional "hick-ups" already, so I decided to renovate the most obvious points beforehand.
.
Hi !
I found a condensator in short circuit between the connector n°20 and the resistor R31 !
Capacitors C6 and C7 are responsible to initiate the startup process.
On normal operation the relay rests on the R contact and only C6 is used.
On "cold start" the relay switches to the A contact and C7 is pulled additionally, which causes the OpAmp to shift to "Full Power Ahead" to get the heavy platter startet. After C6 + C7 are charged the relay drops and the OpAmp regulates to the normal speed set and controlled from the generator.
When C6 / C7 are shorted the unit runs permanently in startup mode.
This causes T8 to fully conduct and give full power to the motor drivers.
So is T10 & T11 and the relay never shuts off.
The usual regulation via T9 and the OpAmp is then bypassed.
.
Hi
This is a thermistor , on short-circuit .
I change T8 and now it's good 
Tanks
Hi !
I change T8 and now it's good
Okay - so while you have changed the most prominent parts that *could* go wrong sooner or later, you *might* have fixed the 701 for a looong time as well. 
Good luck & lots of fun with it !
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