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Trouble shooting a Robyn SB-520D (NOMAD)

T

Thestonerguy

Guest
Apr 3, 2005
338
2
26
Texas
www.cbgazette.com
I got stuck on this deal - "Radio Works", "Shop says it works", it came in today and I noticed the case had been repainted (no biggy), but the power cord looked it's age. Plugged it in, turned it "on" and nada.... no lights, no sound, no channel display. Fuse good. Popped the top and on the left side, near the transformer, I plunked a meter on what I thought was the regulator. Got 12volts.

So, I'd appreciate any trouble shooting tips or hints, with thanks in advance!

Woody
 

Check the on/off swicth and the PA swicth first, it maybe stuck in the PA mode shutting off everything but the pa speaker.

Bub73
 
Check the main board for 12 volts, if you find it try to follow it and look for cracked traces. Some of these would crack very easly even when new.
If the main board is dead its back to the power supply and pass tranistor.

Bub73
 
I've seen a lot of circuit-board damage on this kind of radio when they get shipped. It's a really large board, and will flex enough to crack when it gets drop-kicked, even if you pack it with lots of cushion.

The Realistic TRC-457/458 base radio had a steel strap that braced the (large) circuit board. It would block access to parts in the limiter and clarifier. Tended to get removed.

Look around the mounting screws that retain the main circuit board. That's where the weak points will be found. A crack in the plastic board laminate will propagate and tear a crack in the foil nearby.

Moving parts are always suspect after 28 years. The other similar models that had an alarm clock would have two power switches to check. The one on the front panel, and the one on the alarm clock. At least the two power-switch lugs are easy to find on that one. You'll show juice on one lug but not the other if the power switch has failed.

If it's totally dead and dark, it's gotta be in the main power circuit leading into or out of the power switch somewhere. The internal power supply runs all the time the radio is plugged in. The power switch only cuts the 13.8 Volts DC to the radio. That's why you have 12 Volt power coming out of the internal AC supply, whether the power switch is on or off.

73
 
nomadradio said:
I've seen a lot of circuit-board damage on this kind of radio when they get shipped. It's a really large board, and will flex enough to crack when it gets drop-kicked, even if you pack it with lots of cushion.


Look around the mounting screws that retain the main circuit board. That's where the weak points will be found. A crack in the plastic board laminate will propagate and tear a crack in the foil nearby.


73
Click to expand...

Tnx. Think you nailed it on the PCB. Once of of the board at the mounting screw appears to be cracked. It's cracked at the rear corner on the same side as the PS/Xformer. Picture:
http://www.cbgazette.com/crackedpcb.jpg

I'm guessing this would be my culprit huh?
 
Thestonerguy said:
nomadradio said:
I've seen a lot of circuit-board damage on this kind of radio when they get shipped. It's a really large board, and will flex enough to crack when it gets drop-kicked, even if you pack it with lots of cushion.


Look around the mounting screws that retain the main circuit board. That's where the weak points will be found. A crack in the plastic board laminate will propagate and tear a crack in the foil nearby.


73
Click to expand...

Tnx. Think you nailed it on the PCB. Once of of the board at the mounting screw appears to be cracked. It's cracked at the rear corner on the same side as the PS/Xformer. Picture:
http://www.cbgazette.com/crackedpcb.jpg

I'm guessing this would be my culprit huh?
Click to expand...


Thanks to all and esp. Nomad for the help. I created a bridge from the isolated 12v part of the crack to the rest of the pcb and have lights, and sound. I'll hook it at home later.
-TSG
 
I have a SB-520 here I'm trying to find the alignment info for, but cant find anything.
Where can i find the alignment info for this radio?
 
MonsterAudio said:
I have a SB-520 here I'm trying to find the alignment info for, but cant find anything.
Where can i find the alignment info for this radio?
Click to expand...

the alignment info for the 510/520 is in Sams 170/171. If you can't find a Sams for this, then use the info for the Cobra 138/139 XLR, or the President Washington/Grant (early model). DO Not use the alignment info for the Realistic TRC 449,457,458 because the driver/final circuitry (and the bias settings) is different than in the other 858 ssb rigs. Good Luck & 73s.

- 399
 
Troubleshooting a Robyn SB520D

I had similar problem with my Robyn. No power on 110, only on 12V.The power supply board had a couple smoked parts, R305 , D302 and C304.C304 is the tall blue thing sticking up marked 3300uf 25V, as I read in another forum,that's usually the first thing to go.It's good that the Cobra 139XLR and the Robyn are about the same.
 
I have a Robyn 520D also.I just replaced the capacitor (C304), a resistor (R305).Now, it wont transmit.sounds like it could be the finals. Does anyone out there know the # for the finals and their location on the board ? My eyesight isnt what it once was.Time to check C179 also while I got the cover off. Any help is appreciated. At 56, Im a little old to be doing this, but there are no shops around here close.
 
I got the Robyn to power up finally on 110 house current.But no transmit.When Ikey the mic, the red transmit light comes on, the meter drops to zero.The finals ?Whats the factory final #, 1307 ? Can it be replaced with a 1969 ?
 

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