Philip Whiteman
Well-known
A useful thread elsewhere on this forum directs anybody wanting to remove the top plate of an R4 to the Leica Camera Repair Handbook by Thomas Tomosy (published by Amherst Media). This is an indispensable reference book, but in covering many different models the author could not be expected to have covered every last detail.
In my case the shutter speed readout at the bottom of the viewfinder had first started to lag in operation and then simply gone black. Taking the top plate off the camera is a relatively simple operation, provided the black 'button' (actually the broad, smooth head of a fixing screw) above the film advance lever can be undone easily. on my camera, it was easy enough to hold the advance lever in one hand and undo the fitting by thumb pressure.
The speed display takes the form of a tiny roll of tape running on a pair of brass spools mounted on the front of the pentaprism housing. [To be continued...]
In my case the shutter speed readout at the bottom of the viewfinder had first started to lag in operation and then simply gone black. Taking the top plate off the camera is a relatively simple operation, provided the black 'button' (actually the broad, smooth head of a fixing screw) above the film advance lever can be undone easily. on my camera, it was easy enough to hold the advance lever in one hand and undo the fitting by thumb pressure.
The speed display takes the form of a tiny roll of tape running on a pair of brass spools mounted on the front of the pentaprism housing. [To be continued...]
sc_rufctr
Leica nuts
Thanks... And post some photos please.
Boris Stupak
Well-known
Philip Whiteman
Well-known
[Repairing... contd]
I'm glad several of you are out there, listening: the fault and fixing it puzzled me - at one point I nearly gave up and left the camera as it was; working but with no shutter speed readout - but the penny dropped and I succeeded without so much as a single cuss-word.
Back to the story: that funny little tape - more of a length of film, carrying the shutter speeds, and X and B markings - is pulled across a viewing gate, roller-blind fashion by a pull-cord or filament wound round a separate groove in the 'take-up' spool. This filament runs via two miniature brass pulleys to a capstan under the shutter speed dial. (Tomosy makes no mention of this Heath Robinson mechanism, but it is visible in part at least in the cutaway reproduced in the R4 brochure.)
I could see that the filament had come off its pulleys and was trailing loose under the circuit board that is wrapped over the pentaprism. Clearly, when the speed tape had lost its return tension due to the spool axles drying out, the filament had lost tension and come off its guide pulleys - but how to fix it?
This is how you do it: temporarily refit the top plate and wind the shutter dial all the way past the low speeds, X and B to '100'. This fully extends the filament from its capstan, hidden under the speed-dial mechanism. You can gain access - or at least better see - to the two filament guide pulleys by undoing the holding-down screw on the front edge of the circuit board (no need to disconnect or unsolder any electronics, have no fear!)
If it has not broken, the filament should have a knot at its end. Once the filament has been threaded back around guide pulleys, the knotted end goes in a slot cut in the back face of the speed tape take-up spool. My guess - which proved to be correct - was that one needed to pull the speed tape all the way out against spring tension before inserting the end of the filament. Holding the tape in position with one finger tip, the end of the filament is carefully guided in the slot using tweezers (this is the most difficult part of the whole job) and the tape gently allowed to return to the supply spool, making sure as it does so that the filament feeds back into its groove on the take-up spool.
Only now do you apply the smallest spot of lube oil to the pulleys, which restores full spring tension on the speed tape and pull cord. Now all you have to do is refit the top plate...
The only special tool needed is something to undo the securing rings under the wind-on lever and rewind crank. Having the luxury of a bench grinder in the cellar (a £25 el cheapo job from a hobby shop) I was able to grind the points of the jaws of a gash pair of needle-nose pliers to the right square section. They can still be used as pliers, but now I have a handy tool for dismantling other cameras and lenses.
I'm glad several of you are out there, listening: the fault and fixing it puzzled me - at one point I nearly gave up and left the camera as it was; working but with no shutter speed readout - but the penny dropped and I succeeded without so much as a single cuss-word.
Back to the story: that funny little tape - more of a length of film, carrying the shutter speeds, and X and B markings - is pulled across a viewing gate, roller-blind fashion by a pull-cord or filament wound round a separate groove in the 'take-up' spool. This filament runs via two miniature brass pulleys to a capstan under the shutter speed dial. (Tomosy makes no mention of this Heath Robinson mechanism, but it is visible in part at least in the cutaway reproduced in the R4 brochure.)
I could see that the filament had come off its pulleys and was trailing loose under the circuit board that is wrapped over the pentaprism. Clearly, when the speed tape had lost its return tension due to the spool axles drying out, the filament had lost tension and come off its guide pulleys - but how to fix it?
This is how you do it: temporarily refit the top plate and wind the shutter dial all the way past the low speeds, X and B to '100'. This fully extends the filament from its capstan, hidden under the speed-dial mechanism. You can gain access - or at least better see - to the two filament guide pulleys by undoing the holding-down screw on the front edge of the circuit board (no need to disconnect or unsolder any electronics, have no fear!)
If it has not broken, the filament should have a knot at its end. Once the filament has been threaded back around guide pulleys, the knotted end goes in a slot cut in the back face of the speed tape take-up spool. My guess - which proved to be correct - was that one needed to pull the speed tape all the way out against spring tension before inserting the end of the filament. Holding the tape in position with one finger tip, the end of the filament is carefully guided in the slot using tweezers (this is the most difficult part of the whole job) and the tape gently allowed to return to the supply spool, making sure as it does so that the filament feeds back into its groove on the take-up spool.
Only now do you apply the smallest spot of lube oil to the pulleys, which restores full spring tension on the speed tape and pull cord. Now all you have to do is refit the top plate...
The only special tool needed is something to undo the securing rings under the wind-on lever and rewind crank. Having the luxury of a bench grinder in the cellar (a £25 el cheapo job from a hobby shop) I was able to grind the points of the jaws of a gash pair of needle-nose pliers to the right square section. They can still be used as pliers, but now I have a handy tool for dismantling other cameras and lenses.
sc_rufctr
Leica nuts
Well done.