Novaturn ATC blowing fuse on startup

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MadeForThat
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Novaturn ATC blowing fuse on startup

Post by MadeForThat » Sun 05 Apr , 2020 1:40 am

Hey guys, so my atc control board has started blowing fuses as soon as power gets to it. Not sure what could even cause this, as the motor is always "stalled" right? I am tempted to place a higher burn fuse, but don't want to burn anything sensitive. I have recently readjusted the tool center, and have not been able to rotate it since. Upon looking, I was definitely supposed to adjust that while the turret was indexing. So I have backed off all pressure on the prawls and it still blows fuse on start. I am thinking something jammed in the motor, and I'm terrified that something is broken on that end. Any other recommendations before I tear apart the turret?

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Re: Novaturn ATC blowing fuse on startup

Post by MadeForThat » Sun 05 Apr , 2020 2:10 am

Motor runs fine when disconnected from the turret, and no fuse burns, but as soon as it stalls in the turret it burns the fuse. Why would it be consuming more power to stall?

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Re: Novaturn ATC blowing fuse on startup

Post by MadeForThat » Mon 06 Apr , 2020 17:18 pm

well unfortunately I have had no luck with this, so i have ordered some slow burn fuses, in hopes that it will delay burning just long enough for the current spike to not toast another 12$ worth of fuses. The fuses i have been replacing it with are the same rating as the one that I have used for a long time, but they do not have a zig-zag wire like the "original" had. I dont really know anything about fuses, so I will try slow burn. In the electronics diagrams it is called out as a .5 amp fuse, no additional information. As the machine is using the 3 optical sensors in the turret to meet the input from the controller, is it possible that on start up the controller is telling it to go to a position it is not currently in? Without studying the electronics, is it possible that the turret control board is sending both a forward and reverse polarity to the motor at the same time, and therefore causing a short? How can i test what position the main control board is requesting from the turret controller? I know i can read the 3 relays to identify where it currently sits, i will try to match the two, so on start it certainly only has one direction to turn. Also if an admin could move this thread to the electronics board that would probably be more appropriate.

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Re: Novaturn ATC blowing fuse on startup

Post by TDIPower » Mon 06 Apr , 2020 19:46 pm

It will be marked in the drawings for the machine or maybe marked where the fuse mounts and should say the fuse value eg T500mA 250V or F500mA 250V ?

The T means time delay or slow blow, F would mean Fast blow or Fast acting. M or no letter would indicate a normal speed.

There is always the chance that an incorrect fuse has been fitted at some point in time. Slow blow often look like they have a spring inside them.


Hmmm... I just dloaded the diagram from here http://www.denfordata.com/bb/viewtopic.php?f=42&t=2629

There is no indication if it should be T,M or F. have a look on the Toolpost control board to see if it was printed on the board. page NVT-D3H.pdf shows the values

Pete

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Re: Novaturn ATC blowing fuse on startup

Post by MadeForThat » Mon 06 Apr , 2020 20:57 pm

yeah, I'm not sure my drawings in my machine cabinet are the most up to date, but they didn't have any indication of burn speed either. for your retrofit, did you use the turret driver board? I ordered a couple toroids to wind the turret motor wire on, in the hopes of slowing the current spike, although i suspect this will be largely useless. I gotta figure out how to get the reflective sensor plate rotated 180 on my turret too, I've always been reading tool 5 as 1 and so on. Guess I will just get it all done since it is all apart! That looks like it might need a specific slot nut driver.

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Re: Novaturn ATC blowing fuse on startup

Post by MadeForThat » Mon 06 Apr , 2020 21:42 pm

just looked at the "origional" and it was a fast burn -F so that has worked for a long time with no issue, so i think it isnt quite as easy as fuse speed..... damn

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Re: Novaturn ATC blowing fuse on startup

Post by TDIPower » Mon 06 Apr , 2020 23:16 pm

To be honest my lathe has been on the refit back burner for way to long. By the time i get it done I will have done all the things i wanted to use it for other ways! I only pulled my turret apart once and that must have been 5yrs ago. Mine has the single pawl adjuster and i have a feeling it might be worn as I was having issues with center height before I decided to refit it. I only got as far as getting a control board and looking at the diagrams to see the feasibility so it would be possible to still run in DOS mode if only it hadn't had a flat top on the lid I wouldn't have piled stuff on it!

Been on lock down for a few weeks and I have less time to get in workshop than when i was in work everyday. My workshop is full of a car rebuild that has been plaguing me for 18 months now. Sick to death of ill fitting parts that come with a 2yr warranty, its almost at the point where I need to order 2 of something in the hope one will fit! As this is an every nut and bolt from the ground up rebuild it's not so much the time but the space it takes up.

I've got a couple of other projects I would love to get done, quite quick ones but they are buried under body panels etc. The idea was going to do the lathe and these other bits 1st but my hand got forced and I had to start the rebuild before things got to bad (it was my daily runner for 19yrs and at 26 yrs old with 264,000miles on the clock was needing a new chassis, axles rebuilding, wiring loom, rear body).

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Re: Novaturn ATC blowing fuse on startup

Post by DavidB » Mon 06 Apr , 2020 23:24 pm

Regarding your question about why more current would flow when the motor is stalled. I'm assuming this is a permanent magnet DC motor like in my Orac tool changer, when the motor rotates as the windings are moving through the magnetic field they generate a voltage which opposes the applied voltage so when it is running no load the true voltage running the motor is the difference between the two and is what is required to overcome internal losses and friction so could be a fraction of a volt and so current flow is low, when the motor is stalled no opposing voltage is generated and so the current will be far higher and governed by Ohm's law and the internal resistance of the motor windings. Between the two when you load the motor it slows down so produces a lower reverse voltage and the true voltage powering the motor increases as does the current and power produced.

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Re: Novaturn ATC blowing fuse on startup

Post by TDIPower » Mon 06 Apr , 2020 23:26 pm

Just re read your post.
The encoder wheel I don't think is an issue.
The motor runs I think 24v forward rotation then 12v reverse to stall. The change over is done IIRC using a relay so no that shouldn't be the issue.
I have had my turret head lock up on me, I can't remember what I did to free it up, for some reason I think I used a 6mm allen key and a 10mm spanner but can't for the life of me remember what it was.

Given the age of these turrets I think a full strip, clean out the old now dried up grease and rebuild wouldn't do any harm. The pawl is just a small metal plate if you only have the one adjuster. I did see a post at some point where someone else had center height issues, they may have posted up all about the strip down, if not I a sure they posted about the pawl being worn and not always sitting right thus giving different center heights.

Pete

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Re: Novaturn ATC blowing fuse on startup

Post by MadeForThat » Wed 08 Apr , 2020 18:09 pm

Pete - I definitely understand how projects sometimes come along demanding all your time, space, and money! It sounds like the worse offending "project" is children, so I am frantically trying to collect all the tools and equipment I can before that! (although I think I've got a few years) What kind of car are you rebuilding? got any pics?

David- It seems so odd that the motor would only now start drawing more than the fuses can handle. It makes me think that the current draw is from some other component of this turret controller. I'm not sure what components are possibly failing, there isn't much to go wrong.

Admin- any possibility of seeing an electrical schematic of the turret control board? Not sure if it is patented or protected, but in this case it would be nice to be able to probe voltages and make sure nothing obvious is failing

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Re: Novaturn ATC blowing fuse on startup

Post by TDIPower » Thu 09 Apr , 2020 15:13 pm

i found this pic of the Turn 270/Novaturn ATC psu. The psu is a simple unit, Transformer, a small bridge rect, voltage reg, a few caps, relay, fuse and what looks to be a 4 diode bridge and a 5th diode possibly to deal with back emf from the coil, the 6th diode im not sure on.
Interesting it states the fuse is a 3.15A T (slow blow)

http://www.denfordata.com/bb/viewtopic.php?f=42&t=2293

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Re: Novaturn ATC blowing fuse on startup

Post by MadeForThat » Fri 10 Apr , 2020 16:51 pm

thanks for that pete! I am really wondering what the fuse is protecting, and if it is before or after the transformer. If it is just before the motor, I will try just a slightly higher rated fuse, but if is before the trans, then I wont experiment with that. Guess I will take it off and make a diagram tonight perhaps. Not sure if I will get into hot water for posting a picture of that...

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Re: Novaturn ATC blowing fuse on startup

Post by TDIPower » Fri 10 Apr , 2020 22:13 pm

I'm in the garage tomorrow and will try to get to my black box, ill pop the fuse and see whats in mine.

Pete

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Re: Novaturn ATC blowing fuse on startup

Post by TDIPower » Mon 13 Apr , 2020 23:00 pm

Hi, I got a look at my black box... the bad news is the fuse in mine IS as 500mA fast blow!
I have just found these specs which i believe to be correct for the 24v motor. (it has the 12v motor too)

I'm trying to remember about how they are wired. I know the cables for the motor run down through the gear box so you need to be careful about them as only really fine wires. This I think was a Denford modification so that the motor/gearbox could be fitted in the external heatsink/case. Now I cant remember what that went to in order for it to then be connected to the cable that on my machine plugged in near the head stock. i do remember having to unsolder the motor so I could strip it to replace the gear box.

So given this information I could check all the cables, I wonder if one has worn through the sleeve possibly in the motor case over time.

Pete
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MadeForThat
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Re: Novaturn ATC blowing fuse on startup

Post by MadeForThat » Mon 13 Apr , 2020 23:31 pm

Well I had hoped the fuse was just a higher value, but I have some good news haha, it is working with a .5amp fuse now. The fuse is glowing a very faint orange, but it has not blown haha! Something still isn't right, and I don't want to have a part fail because I bump my cabinet and jostle the fuse too much haha!

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