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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Minifon P55 wire recorder , pocket size of mid 1950s
Anyone aware of any pitfalls for the unwary renovator? Its been in an
English garden shed for 40 years. But all mechanicals seem to be ok ,despite patchy rust and grime. Spool bearings and sprung tri-ball retainers function, "winch-winding" head up and down mechanism works, motor turns by hand, "capstan" cylinder rotates, and deck slides across on piano key activation. All rubber parts perished. One electrolytic has its aluminium case corroded to dust. I intend getting just the mechanicals in working order , hook the play head up to a modern tape recorder amplifier to hear what is on the wire drums, before looking at the electronics proper. All 3 peanut valves and all the rest of the electronics seem to be present. At least the previous owner removed and discarded the 3 batteries 40 years ago. There is one brand new Protona set of spools with security tape around the outside of its case but also yellow thread with Protona logo stamped lead seal on this thread linking the spools. What is that security aspect about , I cannot find a www reference to that. much prettier looking one http://vintage-technics.ru/Eng-Minifon_P55.htm anyone know of a www higher resolution version of the schematic on the last of the second page? user manual http://www.cryptomuseum.com/covert/m...p55_manual.pdf |
#2
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Minifon P55 wire recorder , pocket size of mid 1950s
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#3
Posted to rec.antiques.radio+phono,de.sci.electronics,sci.electronics.repair
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Minifon P55 wire recorder , pocket size of mid 1950s
N_Cook wrote:
[...] All rubber parts perished. [...] I found the rubber drive belt was unobtainable, but eventually came across a substitute by following the route taken by my local postman. For some reason, red G.P.O. rubber bands seem to outlast the ordinary type you can buy in the shops. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |
#4
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Minifon P55 wire recorder , pocket size of mid 1950s
Adrian Tuddenham wrote in message
alid.invalid... N_Cook wrote: [...] All rubber parts perished. [...] I found the rubber drive belt was unobtainable, but eventually came across a substitute by following the route taken by my local postman. For some reason, red G.P.O. rubber bands seem to outlast the ordinary type you can buy in the shops. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk I can usual fashion-up rubber parts with no problem , rubber tyre, belt and brakes on this all gone west. I was concerned about the plastic from this era. Nothing cracked as far as I can see but I'm aware stress can build up in this sort of plastic and sometimes literally explode to fragments/dust. I was wondering if there was a way of passivating this potential problem or monitoring for it. |
#5
Posted to rec.antiques.radio+phono,de.sci.electronics,sci.electronics.repair
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Minifon P55 wire recorder , pocket size of mid 1950s
N_Cook wrote:
Adrian Tuddenham wrote in message alid.invalid... N_Cook wrote: [...] All rubber parts perished. [...] I found the rubber drive belt was unobtainable, but eventually came across a substitute by following the route taken by my local postman. For some reason, red G.P.O. rubber bands seem to outlast the ordinary type you can buy in the shops. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk I can usual fashion-up rubber parts with no problem , rubber tyre, belt and brakes on this all gone west. I was concerned about the plastic from this era. Nothing cracked as far as I can see but I'm aware stress can build up in this sort of plastic and sometimes literally explode to fragments/dust. I was wondering if there was a way of passivating this potential problem or monitoring for it. I've not heard of any particular problems with these machines, although yours does seem to have had a particularly hard storage life. German plastics were pretty good in that era (self-destructing neoprene came a little later). -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |
#6
Posted to rec.antiques.radio+phono,de.sci.electronics,sci.electronics.repair
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Minifon P55 wire recorder , pocket size of mid 1950s
Adrian Tuddenham wrote in message
valid.invalid... N_Cook wrote: Adrian Tuddenham wrote in message alid.invalid... N_Cook wrote: [...] All rubber parts perished. [...] I found the rubber drive belt was unobtainable, but eventually came across a substitute by following the route taken by my local postman. For some reason, red G.P.O. rubber bands seem to outlast the ordinary type you can buy in the shops. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk I can usual fashion-up rubber parts with no problem , rubber tyre, belt and brakes on this all gone west. I was concerned about the plastic from this era. Nothing cracked as far as I can see but I'm aware stress can build up in this sort of plastic and sometimes literally explode to fragments/dust. I was wondering if there was a way of passivating this potential problem or monitoring for it. I've not heard of any particular problems with these machines, although yours does seem to have had a particularly hard storage life. German plastics were pretty good in that era (self-destructing neoprene came a little later). -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk I didn't know what sort of plastic. I knew an antiques dealer once and she had a plastic grill on a Dancette or something distintegrate into pieces on moving the cabinet, not touching the grill. I once witnessed an old Thermos vacuum flask cap explode with a surprisingly loud bang when the sun got on it, disintegrated to dust and tiny flakes. I think I can see the original problem area as someone had loosened a screw in that area . The stop slideway works but the rewind slideway is jammed. The piano key pushes a quadrant arm that pushes the spool-swapping slideway for the drive , the quadrant is not turning but not due to 40 years of rust probably. Does T on the schematic translate as nano as in nanoFarad and how does A arrow W of the switch posistions translate to play/record or engaged / disengaged or forward/rearward |
#7
Posted to rec.antiques.radio+phono,de.sci.electronics,sci.electronics.repair
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Minifon P55 wire recorder , pocket size of mid 1950s
I've just noticed that the peanut valves are Mullard make , in a German made
recorder |
#8
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Minifon P55 wire recorder , pocket size of mid 1950s
N_Cook wrote:
I've just noticed that the peanut valves are Mullard make , in a German made recorder I wondr if they were sent over here without valves, so as to avoid an import tax? I believe Grundig were caught many years ago doing something like that and heavily fined. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |
#9
Posted to rec.antiques.radio+phono,sci.electronics.repair
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Minifon P55 wire recorder , pocket size of mid 1950s
N_Cook wrote:
[...] Does T on the schematic translate as nano as in nanoFarad and how does A arrow W of the switch posistions translate to play/record or engaged / disengaged or forward/rearward I don't know, I've never managed to get hold of the circuit. Luckily the machine I borrowed to do some wire transfers had a working amplifier; if it hadn't, I would have done what you propose and brought the head wiring out to a separate amplifier. If you do it that way, you will at least be able to confidently work out the correct time constants from the circuit diagram, rather than guessing at them. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |
#10
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Minifon P55 wire recorder , pocket size of mid 1950s
Adrian Tuddenham wrote in message
valid.invalid... N_Cook wrote: I've just noticed that the peanut valves are Mullard make , in a German made recorder I wondr if they were sent over here without valves, so as to avoid an import tax? I believe Grundig were caught many years ago doing something like that and heavily fined. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk A bit of a mindslip, I was also looking at some miniature 1 inch display diameter Mullard CRTs also today. The Minifon peanuts were England make but HIVAC. As this is rebadged EMI Emidicta then perhaps the sales tax dodge. I removed the steel circlip and steel washer , both now replaced without breaking as surface rust only. Circlip holding that quadrant arm in place and now got that slideway working, latching in both senses. To replace the drive band needs the "capstan" cylinder anchor, near that point, removing. Interesting slip clutch inside the steel cylinder , inferred, not seen. One of those spring clutches , freewheels one way and low take-up of torque the other way. |
#11
Posted to sci.electronics.repair
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Minifon P55 wire recorder , pocket size of mid 1950s
N_Cook wrote:
Adrian Tuddenham wrote in message valid.invalid... N_Cook wrote: I've just noticed that the peanut valves are Mullard make , in a German made recorder I wondr if they were sent over here without valves, so as to avoid an import tax? I believe Grundig were caught many years ago doing something like that and heavily fined. A bit of a mindslip, I was also looking at some miniature 1 inch display diameter Mullard CRTs also today. The Minifon peanuts were England make but HIVAC. As this is rebadged EMI Emidicta then perhaps the sales tax dodge. I think some manufacturers sent stuff into England without the valves, so it wasn't a working piece of equipment. Then, when they put the valves in and tested it, they could claim it was "Made in England"; so they didn't pay luxury import tax (or whatever the tax was at the time). I removed the steel circlip and steel washer , both now replaced without breaking as surface rust only. Circlip holding that quadrant arm in place and now got that slideway working, latching in both senses. To replace the drive band needs the "capstan" cylinder anchor, near that point, removing. Interesting slip clutch inside the steel cylinder , inferred, not seen. One of those spring clutches , freewheels one way and low take-up of torque the other way. My recollection is that only one bearing needs to be removed to put a new drive belt on the capstan drive cylinder - and it was the opposite one from the one I first removed. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |
#12
Posted to rec.antiques.radio+phono,de.sci.electronics,sci.electronics.repair
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Minifon P55 wire recorder , pocket size of mid 1950s
Adrian Tuddenham wrote in message
valid.invalid... N_Cook wrote: Adrian Tuddenham wrote in message valid.invalid... N_Cook wrote: I've just noticed that the peanut valves are Mullard make , in a German made recorder I wondr if they were sent over here without valves, so as to avoid an import tax? I believe Grundig were caught many years ago doing something like that and heavily fined. A bit of a mindslip, I was also looking at some miniature 1 inch display diameter Mullard CRTs also today. The Minifon peanuts were England make but HIVAC. As this is rebadged EMI Emidicta then perhaps the sales tax dodge. I think some manufacturers sent stuff into England without the valves, so it wasn't a working piece of equipment. Then, when they put the valves in and tested it, they could claim it was "Made in England"; so they didn't pay luxury import tax (or whatever the tax was at the time). I removed the steel circlip and steel washer , both now replaced without breaking as surface rust only. Circlip holding that quadrant arm in place and now got that slideway working, latching in both senses. To replace the drive band needs the "capstan" cylinder anchor, near that point, removing. Interesting slip clutch inside the steel cylinder , inferred, not seen. One of those spring clutches , freewheels one way and low take-up of torque the other way. My recollection is that only one bearing needs to be removed to put a new drive belt on the capstan drive cylinder - and it was the opposite one from the one I first removed. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk I'm starting to find differences from this schematic http://vintage-technics.ru/Minifon%2...nned-P55-1.JPG orientation of triple ganged master switch is different I cannot find the fast acting switch parallel to the seriesed end or reel switches |
#13
Posted to sci.electronics.repair
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Minifon P55 wire recorder , pocket size of mid 1950s
N_Cook wrote:
[...] I'm starting to find differences from this schematic http://vintage-technics.ru/Minifon%2...nned-P55-1.JPG orientation of triple ganged master switch is different I cannot find the fast acting switch parallel to the seriesed end or reel switches The first place I would look is around the operating key bank. I assume it momentarily by-passes the end-of-spool switches, so it is probably operated from one end of the slide locking bar on the key bank. Have you tried following the end-of-spool wires back from the deck plate onto the amplifier board (if they haven't fallen off yet) ? They might lead you to it. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |
#14
Posted to rec.antiques.radio+phono,de.sci.electronics,sci.electronics.repair
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Minifon P55 wire recorder , pocket size of mid 1950s
Adrian Tuddenham wrote in message
valid.invalid... N_Cook wrote: [...] I'm starting to find differences from this schematic http://vintage-technics.ru/Minifon%2...nned-P55-1.JPG orientation of triple ganged master switch is different I cannot find the fast acting switch parallel to the seriesed end or reel switches The first place I would look is around the operating key bank. I assume it momentarily by-passes the end-of-spool switches, so it is probably operated from one end of the slide locking bar on the key bank. Have you tried following the end-of-spool wires back from the deck plate onto the amplifier board (if they haven't fallen off yet) ? They might lead you to it. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk I can see why the 2 end of reel switches are in series but not why that "switch" is in parallel with another one , the fast acting one, as it will do nothing unless at the end of reel , which has to act before the fast one , so what is the point? |
#15
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Minifon P55 wire recorder , pocket size of mid 1950s
N_Cook wrote:
Adrian Tuddenham wrote in message valid.invalid... N_Cook wrote: [...] I'm starting to find differences from this schematic http://vintage-technics.ru/Minifon%2...nned-P55-1.JPG orientation of triple ganged master switch is different I cannot find the fast acting switch parallel to the seriesed end or reel switches The first place I would look is around the operating key bank. I assume it momentarily by-passes the end-of-spool switches, so it is probably operated from one end of the slide locking bar on the key bank. Have you tried following the end-of-spool wires back from the deck plate onto the amplifier board (if they haven't fallen off yet) ? They might lead you to it. I can see why the 2 end of reel switches are in series but not why that "switch" is in parallel with another one , the fast acting one, as it will do nothing unless at the end of reel , which has to act before the fast one , so what is the point? I haven't got the machine in front of me, but my guess is: At end of reel, the motor is disconnected and then cannot run either way. Pressing a button will operate the slide bar and momentarily re-connect the motor for long enough to get the wire moving and re-close the limit switch circuit. It could have been done much more elaborately, so that each direction button operated in association with the appropriate limit switch; but that would have involved more wires from the deck to the chassis and extra switches on the button bank. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |
#16
Posted to rec.antiques.radio+phono,de.sci.electronics,sci.electronics.repair
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Minifon P55 wire recorder , pocket size of mid 1950s
Adrian Tuddenham wrote in message
nvalid.invalid... N_Cook wrote: Adrian Tuddenham wrote in message valid.invalid... N_Cook wrote: [...] I'm starting to find differences from this schematic http://vintage-technics.ru/Minifon%2...nned-P55-1.JPG orientation of triple ganged master switch is different I cannot find the fast acting switch parallel to the seriesed end or reel switches The first place I would look is around the operating key bank. I assume it momentarily by-passes the end-of-spool switches, so it is probably operated from one end of the slide locking bar on the key bank. Have you tried following the end-of-spool wires back from the deck plate onto the amplifier board (if they haven't fallen off yet) ? They might lead you to it. I can see why the 2 end of reel switches are in series but not why that "switch" is in parallel with another one , the fast acting one, as it will do nothing unless at the end of reel , which has to act before the fast one , so what is the point? I haven't got the machine in front of me, but my guess is: At end of reel, the motor is disconnected and then cannot run either way. Pressing a button will operate the slide bar and momentarily re-connect the motor for long enough to get the wire moving and re-close the limit switch circuit. It could have been done much more elaborately, so that each direction button operated in association with the appropriate limit switch; but that would have involved more wires from the deck to the chassis and extra switches on the button bank. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk So a mistranslation, for "fast acting" read short duration momentary on. There is some sort of leaf switch under the master sw bank although I cannot see any wire to it without removing the master sw. This is activated by the stop slideway. Indeed, should a reel stop, with the end of wire spring-out lever touching an end sensing switch then the motor would be locked out without such a fudge or manually turning the spool. Presumably p19 of the user manual about the red light coming on at end of spool |
#17
Posted to sci.electronics.repair
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Minifon P55 wire recorder , pocket size of mid 1950s
N_Cook wrote:
Adrian Tuddenham wrote in message nvalid.invalid... N_Cook wrote: Adrian Tuddenham wrote in message valid.invalid... N_Cook wrote: [...] I'm starting to find differences from this schematic http://vintage-technics.ru/Minifon%2...nned-P55-1.JPG orientation of triple ganged master switch is different I cannot find the fast acting switch parallel to the seriesed end or reel switches The first place I would look is around the operating key bank. I assume it momentarily by-passes the end-of-spool switches, so it is probably operated from one end of the slide locking bar on the key bank. Have you tried following the end-of-spool wires back from the deck plate onto the amplifier board (if they haven't fallen off yet) ? They might lead you to it. I can see why the 2 end of reel switches are in series but not why that "switch" is in parallel with another one , the fast acting one, as it will do nothing unless at the end of reel , which has to act before the fast one , so what is the point? I haven't got the machine in front of me, but my guess is: At end of reel, the motor is disconnected and then cannot run either way. Pressing a button will operate the slide bar and momentarily re-connect the motor for long enough to get the wire moving and re-close the limit switch circuit. It could have been done much more elaborately, so that each direction button operated in association with the appropriate limit switch; but that would have involved more wires from the deck to the chassis and extra switches on the button bank. So a mistranslation, for "fast acting" read short duration momentary on. That would be my assumption. There is some sort of leaf switch under the master sw bank although I cannot see any wire to it without removing the master sw. This is activated by the stop slideway. It sounds as though you have found it. Indeed, should a reel stop, with the end of wire spring-out lever touching an end sensing switch then the motor would be locked out without such a fudge or manually turning the spool. Presumably p19 of the user manual about the red light coming on at end of spool I haven't got the manual, but I do remember a light coming on at the end of the wire when the motor stopped. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |
#18
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Minifon P55 wire recorder , pocket size of mid 1950s
user manual
http://www.cryptomuseum.com/covert/m...p55_manual.pdf it says , for wire breaks, just knot the ends together, I may try stretched PTFE spaghetti tube for butt joints of the wire breaks, if interesting contents. technical details and pics of a museum grade one http://vintage-technics.ru/Eng-Minifon_P55.htm schematic http://vintage-technics.ru/Minifon%2...nned-P55-1.JPG |
#19
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Minifon P55 wire recorder , pocket size of mid 1950s
N_Cook wrote:
user manual http://www.cryptomuseum.com/covert/m...p55_manual.pdf Thanks, that could come in useful. it says , for wire breaks, just knot the ends together, That is the standard way with all wire recordings. Most of the standard systems run around 20 ips, so the duration of signal dropout due to the amount of wire in the knot and the loss of head contact is not terribly significant. I have had to recover the sound from wire recordings of gaelic, which become tangled and then the bits edited back in the wrong order (some backwards). Now THAT was fun! -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |
#20
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Minifon P55 wire recorder , pocket size of mid 1950s
Adrian Tuddenham wrote in message
valid.invalid... N_Cook wrote: user manual http://www.cryptomuseum.com/covert/m...p55_manual.pdf Thanks, that could come in useful. it says , for wire breaks, just knot the ends together, That is the standard way with all wire recordings. Most of the standard systems run around 20 ips, so the duration of signal dropout due to the amount of wire in the knot and the loss of head contact is not terribly significant. I have had to recover the sound from wire recordings of gaelic, which become tangled and then the bits edited back in the wrong order (some backwards). Now THAT was fun! -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk Low heat and stretching reduced 1mm outside diameter ptfe tubing down to ..5mm diameter. Easily passes alonwire-sense through the eyes of the tape-head. Hopefully superglue would have enough binding with the ptfe and recording wire to make a joint. |
#21
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Minifon P55 wire recorder , pocket size of mid 1950s
N_Cook wrote:
Adrian Tuddenham wrote in message valid.invalid... N_Cook wrote: user manual http://www.cryptomuseum.com/covert/m...p55_manual.pdf Thanks, that could come in useful. it says , for wire breaks, just knot the ends together, That is the standard way with all wire recordings. Most of the standard systems run around 20 ips, so the duration of signal dropout due to the amount of wire in the knot and the loss of head contact is not terribly significant. I have had to recover the sound from wire recordings of gaelic, which become tangled and then the bits edited back in the wrong order (some backwards). Now THAT was fun! Low heat and stretching reduced 1mm outside diameter ptfe tubing down to .5mm diameter. That's gigantic compared with the wire diameter. You run the risk of it hitching in adjacent turns and causing a snarl-up. Don't risk it, knots are quite good enough. ..Hopefully superglue would have enough binding with the ptfe and recording wire to make a joint. I doubt if any glue would successfully bond to PTFE. (If PTFE is non-stick, how do they get the PTFE coating to stick to saucepans?) -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |
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