System Saber Operation Intermittent (Moody!)

[N4UMJ]

My newest System Saber 1 addition appears to have Main board problems I think. Sometimes it will not power up and at other times it will work hours on end. Yesterday it quit in the middle of a conversation! Very frustrating.

When it dies there is no squelch noise or transmit. Totally dead.
Vibration has no effect on it but temperature seems to. Applying heat to the Main board will bring it back to life when it is dead. Too much heat as in extended transmit will kill it. There seems to be voltages on the main processor when the radio shuts down so part of it is alive.

Anyone care to list some common failures? I see the Main PC board construction uses 6 layers. Maybe the feedthroughs get intermittent? I would not think an individual module would shut down the whole radio but I may consider swapping some of them out with a good transceiver. Already tried swapping the ref osc out.

The only schematic I have here is for the regular Saber and suspect there are some major differences.

Wish I had another main board here to swap out and maybe isolate the problem.

When it works it works great...........RX and TX perfectly normal.

Eddie
N4UMJ

[N4UMJ]

Heat and Cooling applied to the area of Y400 (Crystal for Microprocessor IC400) on the main board seems to trigger the problem. Component ID was done with my regular Saber schematic as that is all I have here.

Removed and Replaced Y400 and it looks like it may be fixed.

Luckily it was not a surface mount component but those through holes really take some heat.

I will report back later with the long term results.

By the way the fix came on the same day the parts Systems Saber from ebay arrived so it looks like I may have an extra fixer upper here. It's got a broken bottom plate and the battery latch "c" spring is missing. Funny how those ebay photos don't really show those details. Also it's a 403-433 split ...

Eddie
N4UMJ