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  #11  
Old 07-15-2014, 10:42 PM
walkman's Avatar
walkman walkman is offline
 
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Quote:
Originally Posted by Omega232Devils View Post
John,
Glad you solved your problem. I am sure Reggie would have helped if he were not on vacation.

Do you have more information on what you were seeing that made you suspect the IC chips? Are they individual chips for each indicator? I have fluctuating fuel flow indications. I have replaced the fuel flow meter with the newer style that is suppose to be more accurate, but it is not. Generally ranges about 2-3gal per fill up off. Or about 0.8gal/hr more than it actually burns.

Thanks,

Dan
Dan mine is off by that amount at fill up, or roughly 5-8% burn. I think it might be typical. Wish there was a k factor adjustment.
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  #12  
Old 07-15-2014, 10:56 PM
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Omega232Devils Omega232Devils is offline
 
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I would think the same thing, but my old fuel flow meter was accurate to within 0.1gal at fill up regularly.

At least it is inaccurate on the safe side as there is always more fuel than the quantity gauge indicates.

Dan
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  #13  
Old 07-16-2014, 07:53 AM
johnp19 johnp19 is offline
 
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Dan,

I had problems with MAP, fuel flow and oil pressure. The readings would fluctuate or stop working altogether. In the case of the oil pressure it would often read 20 or more pounds low. I plumbed in a mechanical gage and used pneumatic pressure to help work the problem. After trouble shooting the wiring, d-sub connectors, transducers, ground, board solder joints, changing out the onboard battery, etc I decided to swap out the three processor IC's on the analog board. These IC's are in sockets which makes the process fairly easy. I highly recommend the right tools for working with these IC's, especially for removal.

Just prior to swapping the IC's I suddenly lost pretty much every indication except for EGT and CHT. As soon as I swapped the IC's around I regained all indications but now did not have EGT and CHT indications. Based on this I ordered the new IC's from Digi-Key. I replaced the two IC's that appeared to have traces running back to the EGT and CHT inputs and now everything is working.

The point I take from this is that the IC's can apparently fail intermittently, or in the case of my oil pressure only partially fail.

I hope this helps,

John

Last edited by johnp19 : 07-16-2014 at 07:55 AM.
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  #14  
Old 07-18-2014, 01:28 PM
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Quote:
Originally Posted by Omega232Devils View Post
I would think the same thing, but my old fuel flow meter was accurate to within 0.1gal at fill up regularly.

At least it is inaccurate on the safe side as there is always more fuel than the quantity gauge indicates.

Dan
I meant, typical for the VM1000. I've had an EI gauge, which was usually accurate to with .1-.2 gal and a GRT HXr which was almost as accurate.
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  #15  
Old 07-19-2014, 02:05 AM
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Glas467 Glas467 is offline
 
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Default A/D Chips VM1000 & Fuel Flow Accuracy

I am back from vacation, good to see VMS discussion is still going strong!

FYI, bus control (or signal processing or A/D ... all names are synonymous with the same component) chip replacement is the second most common repair I do. In my article "Brains, Batteries, and Busses" http://eaaforums.org/showthread.php?...ies-amp-Busses
part of what I discuss is the analog board and the bus chips. The bus chips are the first processing component in the DPU to encounter the raw analog signal coming from the various sensors and transducers. As such, they are the most suseptable to voltage spike damage (static discharge, starter kickback, intermittant shorts, etc). It is possible for only one or a couple of channels on the bus to be damaged, in this case for example you may have one cylinder where the EGT graph is blank but all others work fine.

When replacing these chips, its important to match the original component as closely as possible. In the case of the bus chips, older (screw terminal type) DPUs use a different chip than the later serial type DPUs. As one poster from above noted, in the case of the serial DPU, exact replacements may not be readily available (I maintain a stock of the correct chips) from the common electronics shops like Digikey or Mouser. For this case it was critically important to get a chip rated for the same or lower amperage draw which the individual did.

The other recommendation I have is to make sure you have the right tools and equipment to do the job. i have lost count of the number of repairs I have done for folks who tried to DITY and damaged their DPU worse either from static discharge (they did not have a static free workstation and/or failed to take static precautions) or from using a hardware store soldering iron on an IC and ruining it and/or burning up the copper etching on the PC board.

Quick note also on the fuel flow accuracy issue ... FYI my EPI-800 totalizer is typically within 0.1 - 0.3 gal of actual fuel at fillup, it has never been more than 0.7 gal off so the EPI-800 and VM1000 systems are fully capable of very accurate fuel computing based on flow. Errors come into play from 3 sources 1) air bubbles or excessive turbulence in the fuel system 2) K factor variations 3) Power or signal interruptions.

Here I will address K factor variations ... for carb engines, FloScan manufactured the model 264 with an integral pulse damper in the unit with a K factor approx 47k (I dont have the tech specs in front of me so I am typing from feeble memory) ... Production ceased on this unit and the replacement is the 201B-9 with an external pulse damper and K factor approx 44.7k ... So you do the math and see that from the get go you have a 4.9% error when you replace a 264 with a new 201B-9. The newer serial type DPUs with software rev 2.0 and higher have a K factor adjustment feature, older DPUs do not and cannot be upgraded.

All the best,
Reggie
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  #16  
Old 10-21-2021, 06:25 PM
johnp19 johnp19 is offline
 
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Just an update. My VM-1000 is still going strong after replacing the signal processing chips seven years ago.

Another VM-1000 on the field went bad after an apparent voltage spike from a failed alternator. Three new chips, along with a new battery for good measure, and it appears to be working well.

Some notes on the chips.

The ones for mine, which is a later unit with the sub-D connector uses
DG407DJ, DJZ, or DJ-E3 chips. It appears that all of these chips are obsolete with no good replacement. I did find, and order, some DG407DJ's today so that I have some spares. I found them at the following:

https://rcfreelance.com/p/ic/218094/dg407dj/

No minimum quantity required, good pricing, low shipping cost. Other places have these or newer versions such as the DJ-E3 but you have to order 50 or 100 of them.

My friends VM-1000 that went bad recently was the older style with the wire terminals. Fortunately it is the type with the pin and socket board connectors so it was easy to separate the boards. The chips for this version are also obsolete but seem to be much easier to find. We found some Harris CD4097BE chips (the same as what was in the board) for $1.80 a piece plus tax and shipping. Watch out for used chips, I see some adds for them. Especially shipping from China.

One note on this particular unit. We found many of the wire terminal solder connections fractured when we inspected the board. They were easy to re-solder but this likely would have caused problems. This box was out a about 7 years ago for chip and battery replacement. it was working fine until the alternator problem. 7 years ago there were only three cracked solder connections. Now most of them showed signed of stress. He is going to see about supporting the wiring bundles better to reduce stress on the terminals. It takes a high power magnifying glass, or better yet, a loupe or stereo microscope to see most of the cracks.

The batteries, M48T02-150PC1 or M48T02-70PC1, seem to be readily available from suppliers such as DigiKey, etc. As Reggie suggests I would replace them every 10 years. If I had my box out and open at 7 or 8 years for some reason I would replace the battery. Remember to write down the engine time before replacing the battery as you will have to reprogram the time in the VM-1000. There is a thread on how to do this somewhere on VAF.

Remember to use proper static control measures when working on these boxes/boards. Having the correct tools for removing, and especially for inserting, the chips is very important.

I hope this helps,

John

P.S. I believe Reggie is still working to get his new shop set up so he can once again support these units.
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  #17  
Old 11-29-2021, 05:02 PM
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Dan 57 Dan 57 is offline
 
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First of all, a big thanks to all the guys providing information about maintaining and fixing the VM1000, above all Reggie

Since I bought my present ride 3 years ago, my FF keeps flashing at about 1Hz. Useable but annoying... the VM was installed in 2005, and all the other indications work fine.
The clock/battery chip had been replaced 7 years ago, so I thought it could well be the culprit. Ordered a M48T02-150PC1 from DigiKey (great service and super quick affordable delivery to EU), and then dived under my panel to dig the CPU out. Removing the back cover and replacing the chip was very easy in comparison
Reinstalled the lot, but unfortunately no joy, the on-off-on ain't fixed

Anyone else around with the same issue? Solution?
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  #18  
Old 11-21-2022, 07:54 PM
KelvinRempel KelvinRempel is offline
 
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I have a question regarding the battery in the VMS1000 units. I have a complete VMS 1000 system that was new in box with a kit I bought. It's probably around 20 years old. Should I change the battery out before I install the unit?
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  #19  
Old 11-21-2022, 10:25 PM
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RV8JD RV8JD is offline
 
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Quote:
Originally Posted by KelvinRempel View Post
I have a question regarding the battery in the VMS1000 units. I have a complete VMS 1000 system that was new in box with a kit I bought. It's probably around 20 years old. Should I change the battery out before I install the unit?
I would. The VM 1000 battery is for Tach Time and Fuel Remaining, and the recommendation is to replace every 10 years. See Reggie's post:
https://vansairforce.net/community/s...44&postcount=1
My previous RV-8 (first flight in 2001) has an early VM 1000 system and it's still going strong after 2300 hours.
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Last edited by RV8JD : 11-21-2022 at 10:34 PM.
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  #20  
Old 11-22-2022, 04:59 AM
KelvinRempel KelvinRempel is offline
 
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Thanks Carl.
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