mep-831a suspected K8 relay fault

[Mtour]

Hey Guys I have purchased a mep-831a with a tier two reset with 7hrs showing on it, the circuit interrupter will only work in battle short. The governor control module is shot, I have one of Kurts boards on route to solve that. I was able to get a stable 240vac measured at the inverter with no warning lights from the unit at no load by disconnecting the governor control module and using a elastic band on the governor linkage to achieve 178vac at a-b terminals.

I traced the ground circuit to the inverter to connector p17-11, but I do not get continuity between terminal p17-11 and p17-12. My understanding is that P17-11 goes to relay k8 which is normally closed and continues to p17-12 and then on to the battle run switch.

This is leading me to think that the K8 relay inside the inverter is faulty.. I am I on the right track here, and if so has anyone done a relay swap on the K8 relay..

Thanks
Dave

 

[Mtour]

Hey Guys I have purchased a mep-831a with a tier two reset with 7hrs showing on it, the circuit interrupter will only work in battle short. The governor control module is shot, I have one of Kurts boards on route to solve that. I was able to get a stable 240vac measured at the inverter with no warning lights from the unit at no load by disconnecting the governor control module and using a elastic band on the governor linkage to achieve 178vac at a-b terminals.

I traced the ground circuit to the inverter to connector p17-11, but I do not get continuity between terminal p17-11 and p17-12. My understanding is that P17-11 goes to relay k8 which is normally closed and continues to p17-12 and then on to the battle run switch.

This is leading me to think that the K8 relay inside the inverter is faulty.. I am I on the right track here, and if so has anyone done a relay swap on the K8 relay..

Thanks
Dave

Hi all.. was able to get the inverter out, what a royal pain..the bottom bracket bolts were threaded into inserts that all snapped at the shoulder..had cut the vent holes out and get to them through the bottom of the unit..

Went looking for k8 relay, there was a relay on the top circuit board marked k1. Both p17-11 and p17-12 leads went into a rom chip..so that was the end of looking for k8..

While I was in there I covered the pots with nail polish..

So still have the same only problem of the circuit interrupter working in battle short..

 

[kloppk]

The black relay cube on the top circuit board is the one that changes the inverter from 120 to 120/240 operation. In 120 mode it puts the two inverters inside it in parallel.
I've had the inverters apart but didn't attempt to locate the K6 & K8 relay.
Having those two signals from P/J 17 go to a ROM doesn't seem right.

I ought to be able to get my hands on an inverter in a wee or so to tear into and see if I can locate the K8 function.

 

[Mtour]

The black relay cube on the top circuit board is the one that changes the inverter from 120 to 120/240 operation. In 120 mode it puts the two inverters inside it in parallel.
I've had the inverters apart but didn't attempt to locate the K6 & K8 relay.
Having those two signals from P/J 17 go to a ROM doesn't seem right.

I ought to be able to get my hands on an inverter in a wee or so to tear into and see if I can locate the K8 function.

That would be a big help if you could find the K8 relay, I tried to remove the back panel of the inverter, removed the screws but it wouldn't budge, even tapped it with a hammer..

I guess I could install a smart gen auto start unit and it could be the brain and let it manage all the fault functions if need be..

Thanks for the reply..

 

[kloppk]

Will post up what I find regarding the relay once i get an inverter to tear into. A friend has 3 dead ones I can dig into. He should be stopping by as soon as this weekend.

 

[kloppk]

I got my hands on an inverter to tear into to locate where the TM K3, K6 & K8 are inside the inverter.
My preliminary findings are..
K8 in the TM is K3 and Q7 on the main control board in inside the inverter
K3 in the TM is K2 on the main control board in inside the inverter
K6 in the TM is K5 on the main control board in inside the inverter
The relays inside the inverter are SPST solid state relays part number AQV251. They look like 6 pin integrated circuits.
I haven't been able to identify Q7 yet. I suspect they use it to create the second TM K8 relay function that's in the contactor close and open circuit.

K3 in the inverter is located behind the small circuit board with J17.
K6 is located just to the right of the ribbon cable from the J17 circuit board to where the ribbon cable attach's to the main board.
K2 is located on the main board just below the ribbon cable.
Q7 is located just above J17 on the main board.

 

[NATCAD]

Hi Kurt,
since these inverters are generally so sensitive, what about instead of trying to improve or fix the current design, a low frequency transformer design was utilized instead and the current inverter ditched? I guess looking at the space there isn't enough room. It would also be expensive.

 

[kloppk]

At first glance there are a few issues that come to mind.
1) Inadequate space for transformer based LF inverters
2) It would need to be compatible to accept the dual ~200V 3 phase power generated by the PMA.
3) The engine would probably need to run at full speed since there would be no feedback from the inverter to modulate the engine speed based on the inverters load.

 

[kloppk]

Solid State Relay Locations...

 

[NATCAD]

Got it.