VaricamLT: P-Tap Fuse

B

BerkeCreative

Member
Was on a shoot this weekend and the P-Tap output stopped working on me. I had one wireless motor and a video transmitter powered at the time. I've used this setup many times before and neither should have been over the amp limit. The only guess I have is that maybe the motor got bogged down, causing a power surge. In any case I'm hoping it's just a fuse.


I'm assuming it should be user serviceable? Do I just remove the plate? I can't find anything in the manual about it.

Anyone know what fuse I should buy?

Also why is the amp limit so low? I thought d-tap could normally handle about 7-8 amps.

Thanks in advance!

EDIT:
It does seem like the fuse has blown. Here's the replacement procedure:
1: Remove battery plate, should look like this:
IMG_0205.jpg

2: Remove fuse compartment by pulling straight up and away from the plate. There are 4 little tabs that hold the fuse compartment in place. It looked like the fuse should slide in and out. IT DOES NOT. Just apply pressure straight up and way from the plate.
IMG_0206.jpg

3. It looks like the fuse is soldered in place. IT IS NOT. There are small endcaps that slip over the fuse.
IMG_0215.jpg

FUSE INFO:
It is a SOC TSC 125v 7A fuse. Can't tell if it's fast or slow blow. I'm looking for the best source for replacements now.

Also can't figure out the 4.5Amp rating and why it blew in the first place. It's obvious they are giving us headroom by saying the amperage out of that port should be 4.5A. But I must have had quite a surge to blow the 7A fuse. Really strange.
 
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I remember reading somwhere that the camera must be sent to Panasonic to have the fuse changed (if it's the one inside the camera). But I'm a bit confused that the P-tap from the battery plate caused this. AFAIK that power doesn't go through the camera. Have you tried changing the battery plate?
 
It's definitely not the main fuse as all other aspects of the camera seem to work fine. It's just the one p-tap connector on the plate that's gone dead. My assumption (hope) is that there's another fuse in the plate itself that covers that p-tap output. I haven't tried removing the plate as I'm still in the middle of production and we're just using the connectors on the batteries for now. I was just wondering if anyone has pulled the plate off and looked. Would love to order the replacement asap.

Thanks!
 
The Powertap fuse(the ONLY fuse in the plate) should be 10-amps, at least they are in all of my A/B plates. I order my fuses directly from A/B, because they can be very hard to find the correct one's 'off the shelf'(i.e: Rado Shack, etc.). I have used "consumer" fuses in a pinch, but they are usually lower amperage or voltage, so likely to blow again much more quickly. You will probably have to call them directly, I don't see them on their site anymore. I usually order 50 at a time and keep about ten spares with each camera. The power tap is too important to lose on my set-ups.

Presuming it's just like every other one, you should just unscrew the four(or so) screws holding the plate on and the fuse should be nested in the back of the plate there in a little black, hard plastic cocoon with two wires running into it. I've lobbied for A/B to make the fuse easily accessible like on some of their stand alone plates, but since they are Vitec, it has fallen on deaf ears.

Just pulled one of mine and it was stamped: SOC 10A 250V

They are pretty tiny. Had to use my camera to read it. Lol
 
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Thanks Run&Gun!

I found these:
https://www.woodencamera.com/f10a-fast-blow-fuse-p/900025.htm

But I was hesitant to buy because the connector says 4.5 amps on it.

I'll prob wait to order until I can open that plate on the camera and see what it says. But I really appreciate the advice to keep spares with the camera. I've never blown a fuse on a plate before so I was really surprised to see it happen yesterday. But now I'll be prepared for it to happen again. Thank goodness for extra taps on the batteries and the hirose power on the camera.
 
Since my recent DC powering issues I did a little bit of digging around to find out what Amp rating the wall outlet DC power supply should have to be suitable for the Varicam LT. According to the manual the maximum power draw from the battery will be 77Watts when all the various output power terminals are being used (DC out at the back panel, View-finder DC supply in the front of the camera, control panel at the back of the camera). Each of these power output supplies are rated max at 1A each (Viewfinder DC output, DC out on the back panel).

When we use the formula P = VI (where P is Power in Watts, V is Voltage in Volts, I is the current supply in Amps)

P = 77Watt, V= 14 V (Average Li-Ion battery output) then I will be 5.5A. So your battery should at the minimum be able to supply 5.5A to power a fully loaded camera. So I am expecting the fuse to be around that much maybe around 6A? Anything lesser will tend to burn out very quickly whenever there is a surge. There is a certain advantage to having 5A, there is lesser risk of damage due to over-voltage, however, that will result in frequent fuse changes based on the current draw needs.

Hopefully this is helpful in making your decision on the fuse rating.

As for the specific fuse for the P-Tap, I am not sure how that is wired. Is it wired serial to the main power supply to the camera or is it wired in parallel to it? It appears it is wired in parallel to it? If it were wired in serial once a source draws too much current from it, the fuse will be triggered and the camera as a whole will not be able to power up after that. Given the camera is working independently of the P-tap working or not, chances are high that it is fused separately from the main camera circuity?

Best to confirm with Yusuke Ota on the facebook group. He is an engineer at Panasonic, NJ who will give accurate information.
 
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BerkeCreative said:
Thanks Run&Gun!

I found these:
https://www.woodencamera.com/f10a-fast-blow-fuse-p/900025.htm

But I was hesitant to buy because the connector says 4.5 amps on it.

I'll prob wait to order until I can open that plate on the camera and see what it says. But I really appreciate the advice to keep spares with the camera. I've never blown a fuse on a plate before so I was really surprised to see it happen yesterday. But now I'll be prepared for it to happen again. Thank goodness for extra taps on the batteries and the hirose power on the camera.
Click to expand...

You're absolutely right. I actually have an LT demo unit sitting in my dinning room right now and I saw that after I had posted. I had never seen that on an A/B plate before that.

I went through a period several years ago where I was popping fuses left and right, because unknown to me at the time, I had a partially broken wire in one of my top lights and it was shorting out. Something else to watch out for that has bitten me: If you have a power cable for something like a Lectro wireless, make sure you plug the cable into the wireless before you plug into the power tap. I've popped the fuse many times having it plugged into the tap first and then I accidentally hit something metal with the 'plug' end of the cable.
 
I'd really like an official response from Panasonic. Is the fuse in the battery plate supposed to be user serviceable??? I have removed the battery plate. It looks like the fuse should be in that plastic cylinder on the lower left of the plate. But I cannot figure out how to remove it without breaking something.

Why is this not in the manual? Why is it limited to 4.5amps for a p-tap connector? What's up with the 7A stamp? What is the reorder information for replacements? I can't believe this is something that should have to be sent back for service?

IMG_0205.jpg
 
OK figured it out. Frustrated rant over. Patient sanity has returned. I'm going to edit the front post to show the replacement procedure.
 
Appreciate the detailed breakdown. Glad to hear you were able to figure out how to replace it (though knowing you I doubt it was something too hard for you :) )

When I first bought the Varicam LT I was wondering why they did not offer their own version of a V-Lock plate replacement? I am sure many people would buy one. Looks like my calculations about the amp draw was as expected, however, 1A above the listed draw (approx 6A) for the fuse seems a bit high, considering electronic circuits are easily damaged with sudden current draws, compared to electrical circuits (which have lesser fail rates due to over current in the ranges of 1-2A) As I suspected it seems to be wired in parallel to the main power circuit, hence it did not affect functioning of the camera when it blew.

I guess manufacturers would prefer for it to be sent back for replacement since not that many people are comfortable/competent in small repairs? Though this seems simple enough. Curious to hear what Panasonic has to respond.

Did you notice another fuse for the main camera power circuit Stephen?
 
Yeah you pretty much had it right with your numbers. I just wonder was the 77Watts max an arbitrary number?

It is definitely wired in Parallel with the main battery. The fuse definitely doesn't effect any other aspect of the camera. So that's a big plus.

I'm including another picture, this is of the back of the camera. There is no access to the main fuse that I can see. Not without starting to remove things that I'd be uncomfortable with. It does look like mounting a different plate (native v-mount) would be doable. There seems to be extra holes that look to be the right pattern. Interestingly, there is also an unused cable sitting back there right now too. The small black 2-pin connector at the top of the bundle is not connected to the battery plate from the factory. Service cable? Support for an alternate power option? It's certainly interesting.

IMG_0228.jpg
 
The supplied battery plate is a standard part from Anton Bauer. At least in the US (It might be worldwide), Panasonic has supplied cameras with these plates for decades. The cameras are manufactured to include the proper hole pattern for standard V-mount plates in case that is what clients prefer. The spare cable is a data cable used in some mount design systems. I believe it is vestigial on the VariCam LT - the camera uses the standard connectivity harness and circuit even if not utilized on this model.

Again the battery plate and it's in-line fuse is a product of Anton Bauer, unmodified by Panasonic. I've seen variations of that same plate on dozens of cameras, monitors and other devices.
 
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