RCI2950DX CPU-Board-fault

[Joerg]

Radio Make and Model: 2950DX
PCB Number: EPT695014B
PLL Number: sorry, haven't figured out yet
Test gear available: Counter, Scope, Digital V/A/Ohm, ToneGen
Symptoms: Blank Display

What is working: Rattle in Buzzer

Hi,

prior to hanging my iron into those SMD, just one question: is that AM8005 on the CPU-Board able, to produce 3,2V if "blown"?

Story:
I got an 2950DX with a fault, never seen. CPU seems to be OK, the registers also, it reacts on several buttons (display lights comming, sometimes dimming), "rattle" becomes different or stucks while pressing a button etc. It seems, it will not start-up/reset. The regulator becomes HOT after just a few seconds and I measured 3,2V - so a bit low for the CPU. But since now I know of those regulators just three states: working, short-out or blown with no contacts anyway - but none had any lower output (exept total zero). So, prior of soldering (I hate SMD...) maybe for nothing, this above question

Maybe its just another short somewhere on the board I have to search... Any known issues on that model with that CPU-Board? By the way: I can't find THAT specific CPU-PCB in any documentation on Ranger. It has one more connector where a 3-wire-hotmelt-pack is comming out. Don't know what it is or does. Also it has a C619 wich I can't find on the shematic. Maybe export-version?

Thanks for your thoughts!
Regards,
Joe

[Joerg]

Hi again,

I now changed the AN8005 with a descret LM7805 to see, what happens. First was: the supply-voltage of the 7805 drops from 13,8 to 6V, so this may be the reason, why the AN8005 will not work probably. I now wired the input of the 7805 to the mainswitch-out and get 13,8V on input, 5V on output. So far, so good.

The rig still beeps once and the falls in buzzing (rattling with a 1/4-second-pattern) when swithcing on, but NOW it shows following: NB, ANL, R.Beep, SWR, Scan -, the Mhz and khz. Still no frequency-readout. Sometimes I can read a frequency sowhat 24.800.1 Mhz, sometimes it just shows "4 00". But this is for luck about once a hundred times... It seems, that it stucks in reset.?!

Any suggestions? Is the CPU smoked or some circuit shortout?

Another thing: If i pull out that hotmelt-pack, the above readout blinks and the rig beeps and rattles in a 1/4-second-pattern.... So again the question: WHAT is this hotmelt-pack doing?! It is in the CN611 (closest to SK2), wich also I cannot find in my diagram...

Thanks,
Joerg

[euhara]

What you are calling the hotmelt pack plugged into CN611 is the echip which gives you 11 meters. Far as your problem goes I have no idea of the cause.
Regards, Jim