Shortcircuit DC AMI Conti 2

Hello everyone,

Since a few days i have a shortcircuit problem on my AMI conti 2. One of the two slo blo 1A glass fuses in the DC convertor blows when one of the stop switches touches the selection pin. These stop switches activate one of the two toggle shifter solenoids to determine witch side of the record should be played. If I disconnect both solenoids, the problem dissapears, and everything works fine. You would think that one of these solenoids has a short circuit, but if I reconnect only one of them ( no matter witch one), the problem is back again. The internal resistance of both solenoids is the same: 10 Ohms measured with a digital multimeter. I tried to measure the current trough one of the solenoids during activation, and my multimeter indicates 0.8A just before the fuse blows. Probably this value is to low because the multimeter is slow.
Do I really have a problem on both solenoids at the same time, or am I overlooking something else?
Does somebody knows the normal resistance and the working current of these solenoids, so I can compare?

Answes can be given in German, I can read it, but not correctely write.

Regards,
Michel

Hello again,

Did some further research. I took out both toggle shift solenoids and connected them to the normal 27V DC voltage they are connected to in the circuit. The first solenoid was connected for 3 seconds before the the 1A slo blo glas fuse(6*32) blew. The second solenoid held for about 30seconds, but then the glass fuse blew as well. My basic knowledge of electricity makes me believe that both solenoids are bad, or am I wrong? Is it normal that the fuse blows if the solenoid is under current too long? Does anybody know the normal resistance in ohms for these solenoids (I measured both of them at 9 to 10 ohms, and this seems very low to me.)
Answers can be given in German, reading and speaking is OK for me, writing gets difficult.
Thanks in advance.

Hello Michael,
from what I know those solenoids cause problems once in a while because they are burned. The reason is mostly a bad microswitch which gives current to the coils too long.
30 seconds at 1 Amp. is pretty long, but 3 seconds is too fast.
The little Rock-Ola coils usually have about 25 Ohm, 9 to 10 Ohm seem a little bit to low. Maybe the coils got overheated once and already have a short in the windings.
If no other AMI owner can check a good coil for you I will dig out a coil and measure next week. But right now we are busy preparing the Regensburg show ...
Maybe someone with an AMI can measure for you. I think they are the same on the G, H, I etc. models.

Best regards - Oliver Stamann

Thanks very much Oliver,

Somebody is sending me two new solenoids, and I will have a test with them. I'll let you know about the results.
Regards,

Hello everybody,

Got some spare solenoids (measured them as well as the old one's at about 10 Ohms), put them in , and the short circuit problem stays. Still have some tests to do on the Cam switches, transfer switches, stop switches, and the slipper ring contacts. Does anybody know what kind of fuse there is in the DC-circuit for the Conti 2? My electrical scheme says there are two DC-circuits, both fused with a 6*32 1A slo-blo glass fuse. So I went to the electric shop and got me some standard 6*32 1A standard "slow" fuses. I hope these are the same as the standard ones in the AMI? I am wondering about the 10 Ohms in the solenoid, that will introduce a current of about 3A (according to my calculation?) at 27 V DC for a few seconds, before the cam switches from the transfer motor will disconnect them. Maybe AMI uses special "slow" fuses to cover these few seconds of high current? If my only problem would be that I 'm using wrong fuses, this would be stupid.
If anyone would have some comment or advice on all the above, it would be helpfull to me.

Regards,

No one there to help me out?

I dont know, in which Country you live, but perhaps this link is helping you
[www.action-electronics.com]

Hello Michel

the DC - resistance 10 Ohms is okay for the coils. Instead of both 1A - slo-blo - fuses in the junktion box you can use 2A - standard (medium blow) fuses, they would blow as well as 1A fuses, if a short-crcuit arises.

Now to your problem. First a little theory. If a solenoid is connected to a voltage, a current begins to flow, according to the Ohm's law. At the same time, a magnetic field develops and the plunger begins to move. The change of the magnetic field and this movement inducts a voltage with revese polarity in the coil. This will limit the current as long as the plunger is moving. As soon as the plunger reaches the end position, one of the two microswitches will be operated and will interrupt the current. The whole unit with the two microswitches is designed like a big microswitch. There must be a u-shaped leaf spring, which holds the lever in the (left or right) end position and keeps the microswitch activated. Perhaps this spring is missing. This would cause, that the current isn't durably interrupted and the fuse would blow.

The function of this part is similar to your AMI H. The H has "normal" contacts instead of microswitches and the spring is inside the gripper-housing. The coils are the same.

By the way, have you alredy repaired your automix?

Best regards

charly49

Hello,

Charlybrown, thanks for the site. I live in Belgium, but nevertheless it's interesting!

Charly49, thanks very much for your reply. Your theory about the current in the solenoid freshens everything a bit up for me (I'm an industrial engineer, and saw these theories during my studies, more then 20years ago), and it's good to hear that the resistance for the solenoid should be 10 Ohms. The thing with the Continental is that the solenoid current isn't interrupted by the transfer switches, but by the camswitches that are commanded when the transfer motor starts. Between energizing and de-energizing the solenoid there is about 1 to 2 seconds time. Can you tell me how long these solenoids can be energized before the current get's too high?
At the moment I changed both solenoids, the 2 cam-microswitches, and checked the slipperring contacts. This took some hours, and still the problem stays. After 1 or 2 selections the 1A slo blo glass fuse blows at the moment that one of the stop switches is activated and transfer motor starts to run. If I disconnect both solenoids (just unplug one of the solenoid connections, this way the solenoid and his camswitch are disconnected ), the problem is gone. This should mean the rest of the circuit is OK (the box is playing both even and odd record sides, shifting is done by hand). If I reconnect only one or both solenoid connections (even or odd, doesn't matter), the problem is there again. Do I have an overcurrent in the system at that moment( activated items are: one solenoid, dynamic bracking of the magazine motor, transfer motor relay), or do I really have a shortcircuit at that moment? Still searching....

Thanks anyway for your replies,
Regards,
Michel

Hello Michel

I have found a Conti, which I have sold many years ago. In the next days I will visit the owner and measure the resistance of the coils, the voltage and the current. As soon as I have the values I will tell it.

Best regards

charly49

Hey Charly,

you are a great help to me, I don't know how to thank you! If you can check on a Conti, can you find out what slo blo fuses are in there for the DC-circuit, please? My electrical plan says both circuits 1A, but I'm starting to doubt that this is high enough.
If I compare it to my AMI H100, the plan says2 times 8/10A (is this 8 to 10A?), while I find a 6.3A fuse in it.
Thanks very much again,
Regards,
Michel

8/10 A means 0,8 Ampere, i will think

Hey charlybrown,

What you tell me seems logical, but if I check (for the H100) the 3 fuses in the fuseholders on DC-unit, I find 2 times 8A and one time 6.3A. Is there somebody who knows what fuses should be in the DC-circuits of the AMI H100 and the Continental 2??

Regards,

Dear friends,

I did some more tests on my AMI Conti 2 tonight. As explained before I allready changed my 2 toggle shifter solenoids, the cam switches 4 and 5, and I checked the connections of the slipper rings. No result the 1A slo blo DC glass fuse keeps blowing 1 to 2 seconds after one of the 2 toggle shifter solenoids is activated by one of the 2 stop switches. I tested the 2 "new" toggle shifter solenoids( resistance measured at about 10 Ohms for both) connected directly to the 27V DC circuit, measuring the DC current running trough them. Both of them do the same: After one second the solenoids pull a current of about 2 to 2.5 Amps, and about one second later the slo blo 1A glass DC fuse blows (seems even logical to me). I also checked both solenoid connections for short circuits to the mass, but no problems found. If I tink back where this story started: one evening my DC glass fuse blows, and when I took it out there was no indcication on this fuse, so I went checking the electrical plan. The plan indicates 2 glass slo blo DC fuses of 1A, so I went to an electrical shop bying me some standard 1A glass slow fuses. From that point on the box starts blowing that fuse every time one of both solenoids is activated. Looking back on this story and the last tests on current through the solenoids, makes me decide that I have the wrong fuse????? Am I right, or am I making some supid mistake here?? Can anybody tell me exactly what fuse should be in both of the DC circuits for the AMI Conti2? Nobody else had similar problems before?

Thanks for all the answers you gave me already up thill now!!

Regards,
Michel

Heute Morgen bin ich noch nicht fit für englisch, dehalb schreib ichs mal in German
Hast du denn schon mal mit nem Ampere-Meter den Strom gemessen, der durch die Sicherung geht, auch die Spannung wäre in dem Moment interessant, da nicht alle Sicherungen alle Spannungen vertragen.Ausserdem könnte man daraus ersehen,ob die RICHTIGE Betriebsspannung überhaupt gegeben ist.
Gruß aus dem sehr sonnigen Hamburg
Dieter

Hello Dieter/Charlybrown,
No problem for reading German (even speaking is possible), only writing isn't that easy (never learned German on school). Thanks very much for your advice. In the meantime I did some more tests. As explained above I measured more than 2,5A through the solenoids, while the circuit is fused with 1A. This is not logic to me, so I followed Charly49's advice and tried to change the 1A slow fuse with a 2A fast fuse, and guess what happens??? The box plays for hours now without any problem!!!! The only explaination I have is the following. The first day the glass fuse blows, for whatever reason. I don't find any indication on this fuse, so I check the manual, which says the fuse should be a slo blo 1A glass fuse. I get myself some fuses in an electrical shop and start testing. Each time the fuse blows again, untill I change to 2A fuses, and everything works, without any overcurrent or short circuit. This makes me conclude that, or the electrical plan of the Conti is wrong on the fuse indication(??), or the old fuses had a longer reaction time (resisting the first seconds of higher current ) than the ones I use now. I would go for the second conclusion. Someone to give me some advise?? Charly49, thank you very much for your tips. If, as you explain above, can get your hands on a Conti, it would be very helpful for me to know the following parameters: solenoid resistance, current when activated, which glass fuse in the DC-circuit to cover the current.
Again, thanks very much to all of you guys for helping me.
Regards,

The correct fuses for Continentals are
Junction Box Assembly Left to right side. 5 amp Fast Blow 1 amp Slow Blow 1 amp slow blow, In the Selector (button Bank) 6/10 (.6) Slow Blow,
Credit Unit 8/10 Slow Blow (.8.).
The trouble you are having sounds like the micro swithes are not set correctly as per manuel these settings can be very fine.

Hello Michel

I have found my Continental2 - servicemanual. In this the fuse is descripted as "Fusetron (1A)". The expression "Fusetron" is used in the Bussmann - Catalog for "Time Delay Fuses". I have found the datasheet of another "time delay fuse", the MDA, which is used in pinball games. The datasheet contains a current / time diagram. This 1 A - fuse blows, according to this datasheet, after 1 second at 4.5 A, after 10 seconds at 2.5 A and after 100 seconds at 1 A. It may be that the slo-blo fuses in Europe have another characteristic. We have, like I wrote in my first answer, the fuses changed to 2 A, because the original fuses was very expensive. After the exchange there was no more problem.

I presumably come on tuesday to the owner of the Conti and will then report the measured values.

@ Graeme

I'm sorry, but I must refer you to a small error. The main fuse has not 5 A, but 8 A (fast blow). There is a further fuse inside the junktion box with 2 A for the transformer and, of course, one in the amplifier, with 3 A. On the 26VAC - transformer (for the selector motor and eventually connected wallboxes) is a big round fuse ("FUSTAT") with 3.2 A.

Best regards

charly49



1 mal bearbeitet. Zuletzt am 29.04.07 12:08.

Yes you are right on the 8 amp fuse for US. on 117 volts. I am in Australia and 240 Volt Continentals were made in Australia and have 5 amp fuses with 2 amp fast blow. in side the amp. Sorry for any confusion. Graeme

Hey guys,

Great thanks to all of you for helping me out, especially to Charly49. I did exactly what you told me, change the 1A slo to a 2A fast fuse, and everything works fine!!!!

Regards,
Michel