Axel Falcon 35 FM Digital Audio Processor (SOLVED)

[razvanm]

Hey guys,

This device served as a DSP processor for the radio station where I work and a few years back something happened with it and it was tossed in the "dark room" because some guy said it can't be repaired. Since it's a relatively expensive piece of hardware I took it out for inspection and powered it on.

Behavior :
Powers on, some blue leds illuminate and the display (two rows of <didn't count> the characters) is dim I can barely see that the upper row has all the characters filled.
After a few minutes, the display starts to flicker each second or so. If I turn it off for a few minutes and start it again, the flicker starts with the same delay.

What I know so far :
The device had something placed over (a SONY receiver) when it was still alive and functional favoring excessive heat. You can see this in the picture below. The 4700uF cap is bulged.


I took it apart and started to verify the voltages and noticed that one of the 5V rail measured 4.2V when the unit powers on then 5.00V when the flicker started happening. The chip responsible with this rail is the LM2940T-5.0
Took out all the caps (1 x 4700uF and 6 x 1000uF) and I'll replace them on Monday.

My questions :
Does any of you have the service manual for this?
Should I also replace the chip?

Thanks for the help and feedback.

[mariush]

All chips installed on the heatsink are linear regulators, so they don't require ultra low esr capacitors or some speciality capacitors, any 105c quality capacitors would do.

You have LM2940-5.0 (fixed 5v max 1A)  , a 7815 ( fixed 15v) , a 7905  ( fixed -5v ) , a 7805 (fixed 5v) and a 7915  (fixed  -15v)  ... so basically you have +/- 5v and +/- 15v and a separate +5v. 

All those ICs have  input, ground, output ... one pin will be ground, one will be the voltage specified on the regulator (as i wrote above) give or take 0.1v and the other pin will then be input (above the output voltage by at least a 1v).  If you measure them with a multimeter and they show fine, no need to replace them.

If you want to use this device, you should use decent capacitors and you should replace even the ones that aren't swollen or showing signs of failure, my guess is the insides overheated and that 4700uF cap is more swollen because it was closer to bridge rectifiers and heatsink...

If you want, I can mail you some quality Panasonic or Nichicon for store price plus a bit for postage, considering i'm in the same country .. should have everything except 4700uF in my personal stock.  PM with a list of capacitors you want and I can tell what i have and a price if interested.

[razvanm]

Thanks Marius,

I sent you a PM.

[razvanm]

Today I changed all caps on the board and held my breath.


Powered the unit up and measured the 5V rail. It is now reading 5.1V. All other rails were within specs so I plugged the connectors to the other boards.

Everything looks good.

Easy fix for a 2500 EUR device, tossed away due to lazy people.

[razvanm]

@barrakutz, check your email.