rick_dykstra Posted October 8, 2008 Author Share #61 Posted October 8, 2008 Advertisement (gone after registration) Mark, I think I'm actually understanding this open drain business now. Thanks for the education. The battery is being sucked down now. I have to keep pressing the test button so I can catch it while LED 1 is flashing. I might be up late with that. Then I'll do another round of measurements. If we see the 6 to 9v, I might have to let the battery chip off the hook. Link to post Share on other sites More sharing options...
Advertisement Posted October 8, 2008 Posted October 8, 2008 Hi rick_dykstra, Take a look here R8/9 Motor Drive - please measure the voltage output. I'm sure you'll find what you were looking for!
rick_dykstra Posted October 9, 2008 Author Share #62 Posted October 9, 2008 Results of voltage measurements with the battery flattened to the final end of discharge state, i.e. the flashing LED no 1 goes out all together (and stays out during measurements), are: red to black: camera off, 7.98v; camera on, 7.93v yellow to black: camera off, 0v; camera on, 0.71v Hmmm ... weird. Summary of observations (with some words to help get my thoughts in order in brackets): a. voltage on yellow (terminal 3) is low when the battery is charged. (Battery chip pin 12 should be 'open' at this battery state and the voltage measurement is consistent with this. The motor does not drive, although the signs are that it should.); b. voltage on yellow is low when the battery is flat. (This is not consistent with pin 12 being 'closed'. The motor does not drive and it is not expected to.) c. the motor does drive when yellow is shorted to ground, with a charged battery. (This emulates pin 12 being 'open'. But as seen in a. above, the motor doesn't drive when pin 12 appears to be open.) d. the battery chip appears to be working correctly in terms of keeping track of charge status and lighting up the LEDs. I need to spend more time trying to get my head around this. Mark, I'd love to see your thoughts. Link to post Share on other sites More sharing options...
rick_dykstra Posted October 9, 2008 Author Share #63 Posted October 9, 2008 Just had a thought. The battery chip is supposed to latch at V(EDVF) or End of Discharge Voltage Final warning, and pin 12 is supposed to go high impedance. This is at less than 0.95V per cell. 8 x 0.95v is 7.6volts. My Leica R8 battery charger/discharger would not take the battery that low. It switched to charging at a little over 8 volts. This was not low enough to make LED1 go out all together. So I used a 9v halogen lamp from a Maglite torch to discharge the battery further. It went rapidly down to below 7.6v. When I started taking measurements I noticed it was higher than 7.6v and that LED1 was flashing again. Is the latch holding? I dragged the voltage down again and took measurements while my son held the battery test button down, so that we could see if it started flashing again. It didn't during the measurements I've reported. But the red to black is still above 7.6v. Curious. Link to post Share on other sites More sharing options...
marknorton Posted October 9, 2008 Share #64 Posted October 9, 2008 I said that 0.71v is suspicious - the voltage drop across a conducting open drain FET is normally much lower than this and the chip spec says it should be no more than 0.5v. I think you need to try connecting a resistor (say, 2k) between the yellow wire and red with the pack discharged and out of the camera. In that state, the FET should be high impedance and you should see the yellow to black voltage pretty much the same as the red to black. If it's still 0.71v, it sounds like the chip is toast - the resistor is not capable of pulling the open drain output high. Incidentally, the 0.7v figure is significant because it's the voltage drop across a forward biased PN junction which would again suggest the chip is damaged. So maybe the chip output is bad after all. If I were you, I'd connect the yellow wire to ground in the battery pack and accept that the camera will not know when the battery pack is flat and will try to carry on - I think you'd get the same message from the sluggish motor. Link to post Share on other sites More sharing options...
rick_dykstra Posted October 10, 2008 Author Share #65 Posted October 10, 2008 Thanks for this analysis Mark. From the start you were pointing to the battery as a suspect for the 'no drive' situation and I believe you were right. I'll perform the tests you've suggested. With the recent voltage measurements completed and with ordering replacement relays in mind I opened up the motor drive yesterday to see how easy it would be to get the circuit completely out, for easier soldering. OMG! It's like a war movie in there! At least two components have blown up - and yet my trusty motor drive kept soldiering on, in a fashion. "It's just a flesh wound!" In the first and second pics, the casualty that's to left of the wind-on/rewind relay was labelled f 924 453 (lucky I took those earlier pics). Any clues what it is/where I can find it on the net? I've not had much luck so far. This one was intact when I first put the motor drive back together, so it's blowing up might have been the reason the full performance resurrection was so short lived. And the other dead'n is to the right of the same relay and I'm pretty sure its label said A4s :3. There's another of these with a legible marking next to the other relay. I think I've found this on the net. BAV70 Silicon Switching Diode, by Infineon. Link below. http://www.infineon.com:80/dgdl/bav70series.pdf?folderId=db3a30431400ef6801141b5844e103ea&fileId=db3a30431400ef6801141c0ba40e041d So my shopping list includes two relays, a bq2010, one or two silicon switching diodes and mystery f 924 453 thingy. What chance of success in soldering a new bq2010 in place? Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/64226-r89-motor-drive-please-measure-the-voltage-output/?do=findComment&comment=680573'>More sharing options...
rick_dykstra Posted October 10, 2008 Author Share #66 Posted October 10, 2008 I had another look at the R8 motor drive gear system, which was easier in this more advanced state of disassembly. Pics below. Of particular interest to me is the group of gears in the grey metal casting, which houses the clutch that engages with the camera. I believe this is the mechanism that reacts to the film being pulled tight after the last frame. The casting (and the clutch) pivot against a strong spring, turning opposite to the motion of the clutch. Pivoting also causes a pair of spring contacts to ride over a cam surface on the casting and then separate. These contacts are wired to the circuit and their separation probably stops the motor. This is interesting to me because my motor drive has a nasty but intermittent habit of ripping up the sprocket holes at the end of the film. The spring tension is adjustable, via the screw in the curved slot on the top plate. When I get this thing working again I'll be looking to see if adjustment of the spring tension is the solution, or if the motor was not getting the "Stop!" signal. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/64226-r89-motor-drive-please-measure-the-voltage-output/?do=findComment&comment=680583'>More sharing options...
rick_dykstra Posted October 10, 2008 Author Share #67 Posted October 10, 2008 Advertisement (gone after registration) <snip> ... connect the yellow wire to ground in the battery pack and accept that the camera will not know when the battery pack is flat and will try to carry on - I think you'd get the same message from the sluggish motor. Yes, on the two occasions I've done this the motor drive works as you suggest, though I've not run it with the battery flat to see if it keeps going past the End of Discharge Voltage Final flag. If one was to make this adjustment to the battery, it'd be an idea to keep an eye on its charge status manually, to avoid over draining the cells. I'm also wondering what blew up the f 924 453 component. That happened after I first made this wiring adjustment to the battery. Can you see a cause and effect here? Link to post Share on other sites More sharing options...
marknorton Posted October 10, 2008 Share #68 Posted October 10, 2008 Oh dear, it doesn't get any better. I might have lost something in the sequence, but at some point, didn't you connect an external power source to the motor to see if it would run without disconnecting the motor wires? It did run and you got smoke. It's fatal to connect power to an electronic circuit where it's not expecting it. I agree it looks like the small burned out component is a diode - two of the three pins are connected together on the board and that matches the specification. That MAX3483 is a serial communications chip, slightly surprises me, maybe connects to some sort of remote control or timer? As for the bigger component, it's a power mosfet - the "G" is for "Gate", the "S" is for "Source" and the third connection is the drain. Basically, a voltage applied to the gate allows current to flow between source and drain. To be honest, this thing has so many problems - battery, electronic, mechanical - who knows where it will end? Leica might sell you a replacement circuit board but at huge cost and you'd still have the issue of the battery and the mechanics. If it's any indication, without a circuit diagram and the way I price my time, I wouldn't touch it. I think you need to face up to the fact it's beyond economic repair. I noticed that ffordes (ffordes photographic : Main Index) are showing a secondhand motor drive set for £269, E+ which for them means it's pretty good. Besides, isn't your wife tired of this new line of pillow talk? "Honey, it's definitely a BAV70 from Infineon!" "Go to sleep, Rick, it's 3 in the morning..." Link to post Share on other sites More sharing options...
rick_dykstra Posted October 10, 2008 Author Share #69 Posted October 10, 2008 Finding the BAV70 was easy. The other one is definitely giving me nightmares. Which manufacturer uses that F symbol? A power MOSFET. Hmmm.. One thing I've found is it's relatively easy to find components by spec - but component manufacturers don't list their wares by the markings. They expect the people who bought them know what they are. I'm treating this repair job like getting a vintage car going. My film cameras are vintage now I guess. p.s. My wife knows what an open drain is too now. Link to post Share on other sites More sharing options...
SJP Posted October 10, 2008 Share #70 Posted October 10, 2008 The 924 45G thingy indeed looks like a power MOSFET, this was as close as I could find: http://www.datasheetcatalog.org/datasheet/on_semiconductor/MTW45N10E-D.PDF My advice would be is to go to your local (or not so local) electronics parts store & ask their advice on finding equivalent parts. Considering the type of circuitry in a motor drive you are looking at power/switching electronics, which narrows it down somewhat. Plus such parts are not really critical, so long as the power/current ratings are similar. There are all sorts of online electronics databases for finding parts but I expect you have tried that already. See Datasheet catalog for integrated circuits, diodes, triacs, and other semiconductors, view for example. Link to post Share on other sites More sharing options...
marknorton Posted October 10, 2008 Share #71 Posted October 10, 2008 p.s. My wife knows what an open drain is too now. Yes, open drain, closely related to bottomless pit... Link to post Share on other sites More sharing options...
rick_dykstra Posted October 10, 2008 Author Share #72 Posted October 10, 2008 <big snip of helpful thoughts>There are all sorts of online electronics databases for finding parts but I expect you have tried that already. My eyes are bulging out of my head from looking! Thanks for the tips. I will be certain to follow them up. Link to post Share on other sites More sharing options...
marknorton Posted October 10, 2008 Share #73 Posted October 10, 2008 The 924 45G thingy indeed looks like a power MOSFET, this was as close as I could find:http://www.datasheetcatalog.org/datasheet/on_semiconductor/MTW45N10E-D.PDF You'd get a shock if you bought one of those. The TO-247 package is huge by comparison, 15mm wide. The 4 main parameters you need to think about are maximum voltage (VdS), maximum current (Id), polarity (P or N, depends on where it connects to in the circuit) and physical package (size and pinouts) Link to post Share on other sites More sharing options...
rick_dykstra Posted October 10, 2008 Author Share #74 Posted October 10, 2008 ah, Stephen was probably thinking I'd need a bigger stronger one, knowing how clumsy I am with connecting up live wires. He must have seen the war movie pictures of inside the drive and selected one with kevlar packaging. My wife and I were looking out the family room window a few weekends ago when we saw the neighbour and his 19 year old son, running around the boy's hotted up V8 Holden (the one with the very noisy exhaust) trying to deal with a rapidly growing electrical fire. I was heard to say, with forced gravity, "Oh dear, look at that. I don't think we're going to be hearing that exhaust note for a while." Or ever again in fact. As a replacement he bought a four cylinder Japanese thing, just as noisy but without the tolerable rumble of a V8 as consolation. Perhaps the smoking of my motor drive is some deity's idea of payback. Link to post Share on other sites More sharing options...
rick_dykstra Posted October 11, 2008 Author Share #75 Posted October 11, 2008 Do you think this is a reasonable choice for a power MOSFET? Link below. My vernier calipers say it's a SOT-223 case. The S pin is connected to ground, D is connected to the red wire that goes to the motor. I believe I need an N channel MOSFET, enhancement mode (normally off). Fairchild FDT439N http://www.fairchildsemi.com/ds/FD%2FFDT439N.pdf I found this at Mouser (they have all the bits I need) at this page. If it's not a good choice, choose me another. MOSFETs There are two power MOSFETs in this part of the circuit. The one that isn't blown up takes power through the lower relay's normally closed pins and feeds it through the upper relay's normally open and closed pins in a cross-over network. Depending on the activation state of the upper relay's coil, the motor will advance or rewind the film. The MOSFET that is blown up serves to connect together the red and black wires going to the motor. It's purpose could be to stop the motor at the end of an advance stroke. My motor drive makes a sound like it is over-running after an advance stroke at the moment. The MOSFET looked OK when I reassembled the motor drive the first time and it worked properly for a while (no over-running). This was when I had the yellow lead connected to black in the battery. But soon the motor started over-running upon each advance - possibly when this MOSFET blew. *** This morning on an early walk I noticed the kid next door has his V8 Holden back. A few minutes ago I heard it fire up. Louder but better than the Jap thing. This has to be a good sign for my motor drive! :-D Link to post Share on other sites More sharing options...
marknorton Posted October 11, 2008 Share #76 Posted October 11, 2008 As I explained to you, a DC motor can be braked by removing the power and dumping the back EMF it generates and it looks like they are using the mosfet to do this. When you connected the motor to an external power source, it was trying to short circuit your power supply instead so no wonder it went.... pooooff... That mosfet looks fine... Link to post Share on other sites More sharing options...
rick_dykstra Posted October 11, 2008 Author Share #77 Posted October 11, 2008 That mosfet looks fine... Thank you. Link to post Share on other sites More sharing options...
SJP Posted October 11, 2008 Share #78 Posted October 11, 2008 Buy a couple as backup Are we sure that it is a N-channel MOSFET? EDIT: stupid question, there are no P-channel SOT-223 MOSFETs according to mr. Mouser, useful site!! Link to post Share on other sites More sharing options...
rick_dykstra Posted October 11, 2008 Author Share #79 Posted October 11, 2008 Yes, I've added two to my cart at Mouser. Great website. I scoured the web for a clear definition of N vs P channel for MOSFETs and concluded that I needed N channel. The source pin is connected directly to the battery's negative. The drain is connected to the positive track, having worked its way through the first relay, the other MOSFET, the second relay and the motor. I'll see if I can post a marked up pic showing where it sits. Wait a sec. Link to post Share on other sites More sharing options...
SJP Posted October 11, 2008 Share #80 Posted October 11, 2008 Rechecking Mouser I did find P-channel MOSFETs in SOT223 but I think you did the homework right to identify it as N-channel. Link to post Share on other sites More sharing options...
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