To access the shutter assembly, Both lenses need to be removed. The viewing lens comes out completely, while the taking lens detaches its front assembly. The rear part needs of it needs to be removed by accessing it from the back (open the back, remove the light baffle).
Then, by removing the handles of the f-stop, removing the decorative name plate, the whole cover can be removed.
The Ikoflex once both lenses and the front panel are removed looks like this:
The Prontor SVS can be easily opened and separated in its essential components. Be careful with the Sync cable, it is tricky since it is tight and secured on the back with a screw.
At first, I tried flushing the Shutter clean (I use Esane, AvGas), but it would still not reliably run.
The Prontor SVS has two delay mechanisms: one is the actual timer for the shutter speeds, the other one is the delayed action of the self-timer which doubles as minimal delayed action when the the flash sync is set to M. X has no delay instead.
The retarders are ingeniously linked together and are cocked together, one of the inventions of the Prontor.
The Prontor without the two retarders:
This is the actual shutter timer:
The shutter timer is damaged, the small extension that can be seen top-right is bent. Most probably the shutter stuck and somebody forced the action. I suppose that some customer played with it on the shelf too hard.
However, even when I removed both timers, but even then the blades would stuck half open. While being wet it would work, but not when dry. The real problem though was not friction or dirt, but a slightly bent pin. An U-shaped part needs to be in the right position or the pin attached to the blades, which moves during the shutter action, remains stuck. However it also needs to be able to catch it. The amount is really minimal. Once "bent back" the shutter action moved freely.
Repairing the connecting pin on the timer mechanism was impossible: just trying to bend it back pried it apart. Most often repair-men exchange the whole piece, but alas, A. Gauthier is no more and spare parts are rare, I couldn't locate one. However a very similar Prontor SVS part was found as a donor, perhaps a different revision. The lever was compatible, I exchanged it in the timer.
Opening the timer is tricky and the risk of loosing or damaging the spring is high: I do not recommend doing it if not necessary. I would try to clean assembled.
Mounting all tiles back in the reverse order... and the Prontor worked again... and the Ikoflex is a faithful companion again.
So, remember, don't force shutters if they are stuck!