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RCBS ammoMaster Chrono repair.
Discussion regarding the reloading of ammunition and tuning of loads for accuracy
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gelandangan
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Joined: May 07, 2006
Posts: 5757
Location: Sydney Australia

PostPosted: Sun Feb 23, 2014 7:38 pm    Post subject: RCBS ammoMaster Chrono repair. Reply with quote

Got a mate in real distress.
His RCBS chrono died out of a sudden, when he need to check his load for an IPSC comp.
The unit he brought the unit to me it is dead as door post.
A quick test on the power input show that there is a short circuit in the unit somewhere.
So, I opened the damned thing.



Opening the unit, my first impression is that it is definitely very cheaply made.
Absolutely do not worth the price tag.
It is a PCboard within cheap plastic enclosure shaped in fancy bullet style .
The buttons are membrane type which are good only for a short amount of push, and the membrane switch is GLUED on to the cheap plastic, thus made it not repair friendly.

First scanning for the obvious problem such as corrosion, dirt accumulated between pins or other usual problems.
Nope, beside some oxidized lacquer near the PCB, the whole board looks Ok.

Here are the pictures of the board front and back




And here are pictures of the Piece of S membrane switch.

[


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Last edited by gelandangan on Sun Feb 23, 2014 7:54 pm; edited 1 time in total
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gelandangan
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Joined: May 07, 2006
Posts: 5757
Location: Sydney Australia

PostPosted: Sun Feb 23, 2014 7:53 pm    Post subject: Re: RCBS ammoMaster Chrono repair. Reply with quote

Using my lab power supply I try to power up the unit and it swallowed up a whooping 6 Amps 9 volt (almost 60 WATTS !!) onto the board Shocked
My hands bangs on to the table trying as fast as possible to remove the power. Ouch!

Next touching each of the power device with temperature probe to find where the 60 watts is sinking to, I found that the large MOSFET (AMP3095P) near the power input is heated up.
This mosfet is rated 30V/6A, I wonder why in the world you would need such a large MOSFET in a small battery operated device?
I digress..

So hooking up my scope, I isolate and test trigger the mosfet, and it works Ok. Hmmm..
Lets test the ESR of the accompanying capacitor.. and AHA!!
The goddam capacitor shorted down to 2 ohm.



So I replaced the capacitor and now the unit works again.

All in all it is a simple repair, but for the price you paid for the piece of crap chrono, you would expect the company uses better rated parts.

My suggestion if you want to buy one of these, you will be much better off buying a Chrony instead.

_________________
A straight line is the shortest distance between two points.
A smile is the shortest distance between two people.

The government I trust .. is my .45-70 Government.

Do - Not try!


gelandangan.weebly.com/
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Pumpkinslinger
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Joined: Sep 22, 2007
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Location: NC foothills

PostPosted: Sun Feb 23, 2014 11:05 pm    Post subject: Re: RCBS ammoMaster Chrono repair. Reply with quote

Good info Gelan, thanks!

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"I ain't no better than anyone else, and there ain't no one better than me!" Ma Kettle

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Vince
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Joined: May 25, 2005
Posts: 13204
Location: Brisbane AUSTRALIA

PostPosted: Mon Feb 24, 2014 5:53 am    Post subject: Re: RCBS ammoMaster Chrono repair. Reply with quote

That's good to know Gelan...thanks for that mate. I have looked at these units in the past and thought they looked a little too "gimmicky" for me...now it seems that they are cheap and nasty inside as well.

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dhc4ever
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Joined: May 26, 2011
Posts: 2275
Location: Ipswich, Queensland Australia

PostPosted: Mon Feb 24, 2014 12:43 pm    Post subject: Re: RCBS ammoMaster Chrono repair. Reply with quote

My club has a dead one of these sitting in the corner, didnt last long at all.
My first question was why didnt we just buy another chrony, cost less and seem to last quite well until you shoot them.

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Dont do anything you wont like explaining to the paramedics..............
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gelandangan
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Joined: May 07, 2006
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Location: Sydney Australia

PostPosted: Mon Feb 24, 2014 4:38 pm    Post subject: Re: RCBS ammoMaster Chrono repair. Reply with quote

I read on the web that there are a lot of these units gone dead within a few weeks off the warranty.
I guess most of them are having similar issues.

_________________
A straight line is the shortest distance between two points.
A smile is the shortest distance between two people.

The government I trust .. is my .45-70 Government.

Do - Not try!


gelandangan.weebly.com/
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