MKIV R, S, T Communication Link Inoperative

in our site five machines GE frame6b. three machine Speedtronic drive by MKIV. in two machine suddenly happened <R>, <S>, <T> communication link inoperative in same time. the operation screen hold no action. The turbines not get ready by loss of control <R>, <S>, <T>. in the first check the the power supply for <C> its normal<pre>
<PS.C> P5 To DCOM 4.99 VDC
P15 15.08 VDC
N15 -15.14 VDC
P28 27.69 VDC</pre>
and check the Cable link RS232 normal. All LED red and yellow are done existing means all card active and healthy. The R, S, T, and C are light RED LED happened in main operation board. replacement the two cards HCMC but same result. during reboot <C> to check the RAM, i get HCMC2B Fail and HCMC2D fail. there is no card in slot position 2B !? but suspicion for RAM in 2D replacement the card in position 2D by new card with RAM get same result.

i will be thanks anybody have solution idea to be fix this problem.
 
I have read and re-read this post several times. I'm not clear on exactly what is happening.

It's extremely odd--extremely--that two Mark IVs started exhibiting the same behaviour at approximately the same time. IF both the Mark IVs were powered by the SAME battery, then problems with an electrical (lightning) storm or the battery charger could cause a voltage spike or dip which might have contributed to this problem. And, if both panels were powered by the same battery AND there is a serious battery ground and some electrical storm or battery charger problem then both panels experiencing the same problem at the same time might be possible.

There are basically two versions of the Mark IV--the Mark IV and the Mark IV+. The Mark IV, the early production model, uses battery-backed RAM (BRAM) to store field modifications. It's possible there is some problem with the BRAM battery which might cause this--but on two machines at the same time.?.?.? There have been times when the BRAM battery failed and caused problems with boot-up sequences such as you have described. (The early Mark IV used intel 80186 microprocessors, and did not have Dynamic Rung Display.)

The Mark IV+ used EEPROM to store field changes, and intel 80286 microprocessors (and had Dynamic Rung Display).

Again, I'm not quite clear on what's happening and why it might be happening--to two machines simultaneously. That's why I'm suggesting the cause might be external to the two machines, and in that case it's probably failed hardware in either <C> or <R>, <S> and <T>--though it's hard to imagine that happening simultaneously to two machines.

If the panels use BRAM, how long has it been since the batteries were replaced? (I believe the process is spelled out in the Mark IV Maintenance Manual.) But, if the battery is indeed failed, then any field changes are lost and would have to be input by someone using a dumb terminal connected to <C> through an RS-232 cable with a null modem. (Not an easy thing to do in this day and age with modern laptop computers.)

Wish I could have been of more help. Please write back to let us know what you find and how you resolve the issue!
 
CSA

Thanks for the detail ,you are right about the DC Charger it supplies two machines and the failure happened. This reason for the effect in both turbine in same time. The first GT now normal just one fuse replacement in Card No DS382OPIMB1A1B. this card drive keyboard. when active the keyboard and reboot then rest pass success then all system be normal.

The main problem in GT2 .communication link inoperative for <R>, <S> and <T>. the keyboard not active to pass rest. the card DS3800HCVA1J1H not include battery and Written in the two processors chips PM752 +-5 VDC in +-15 DCV out. card replacement but no change .HCMC two cards replacement no change happened. How to be activate the Keyboard?

Regards
 
The DS382OPIMB1A1B and its associated power supply board could be your problem. There is a switch on the DS3800NPSM card and a fuse to the left of it. The JD plug located to the left of the fuse can be pulled to remove power from the board, and then reinstalled to apply power. I would suggest you try this to see if it resets the board.
 
Thanks for all given suggestion.

The problem solved by replaced the keyboard panel including the keyboard card. Just replaced and power on the monitor response to rest and normalized the MKIV turbine ready to start and start with loaded base load normal.
 
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