RS PRO-93 won't work on batteries

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mjw357

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As title states, my scanner works fine with batteries in place and connected to the 9V adapter. I've tested the batteries they seem fine. I've also substituted batteries with a known good set of NiCD batteries and same results.

I'm currently (trying) to run it off the rechargeables with the yellow battery holder. I have the black holder for alkalines laying around somewhere but haven't looked yet. It seems to me the issue is for some reason the battery power isn't making it very far.

Is the coaxial power plug the type that has a 'switch' of sorts that only allows the battery power to pass with the plug removed? I haven't done any component level check or voltage measurements yet.

Ideas?
 

blangell

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Mike not being completely familiar with the 93 (from an exploded view I saw of it) it looks the radio has those spring loaded type of connectors in the battery compartment. I had the same problem with my PSR-500, I gently pulled out on the three connectors and problem solved.
 

RickS31

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But, Brian's suggestion aside (and it's worth checking that), there is indeed a disconnect switch built in to the external power jack that removes the battery connection and receives power from the jack via the external adapter. They can go bad, though not often. A quick test to insure your batteries are indeed good is to put regular alkaline batteries in your yellow battery holder (AC adapter unplugged of course) and see if that works. If so, your rechargeable batteries are bad. If not, then the external power jack or, as suggested, your battery connections in the radio may not be making connection. Insure that you never put alkalines in the yellow battery holder when you have the adapter on the radio.
 
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gmclam

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PRO-93 power

There is also a diode to protect against reversed polarity power. If you're able to power from the jack, and it was "reverse powered" at one time, then it likely took out a coil or PCB trace.
 

mjw357

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Checked the spring terminals, they are OK. Tried using alkaline batteries, still nothing. Poking around in that area of the board there is voltage present, but with all the pass-thrus etc makes it hard to follow the path.

Anyone have a schematic for this radio?
 

N1GJB

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Not to hijack the thread, but I have the same issue with my Pro-89 portable. At some point along the way, I lost my black battery holder and only have the yellow one. But anyway, the radio will not power up at all with alkaline batteries in the yellow holder (AC power disconnected, of course). Don't really want to spend the cash for the black battery holder for a (nearly) obsolete basic analog scanner. I will be following this thread as well for a possible solution...
 

W2PMX

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The only difference between the black and yellow holders is that the yellow one has the charging contact. If you don't plug in the charger/wall-wart, there's no difference.
 

mjw357

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Poking around in this thing again tonight, looking at the power jack there seems to be a set of contacts that aren't quite closing with the DC plug removed. Hard to see it due to the big square sheilded can in the way.

Anyone got a schematic or service manual. Even a partial section of the battery terminal/power jack section.

Anyone?
 

W2PMX

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There's a switch (those contacts) in the jack that disconnects the batteries when you plug in a plug. (That prevents the power from the wall-wart from going directly to the batteries - which will damage them.) Either bend the contacts enough that they make good contact with the plug removed or replace the jack. (Either one is fairly simple if you know what you're doing - if you don't, find someone who does, or you'll be paying the Shack to repair the scanner.)
 

gmclam

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Pro-93

External power comes in on J3. If you are able to power the scanner from J3, that means L29 & L30 must be good. Those are the coils I spoke of earlier. The only thing that can break the path from the batteries to power the scanner is the switch built into J3. It has to either be the batteries, battery contacts or J3.
 

kruser

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External power comes in on J3. If you are able to power the scanner from J3, that means L29 & L30 must be good. Those are the coils I spoke of earlier. The only thing that can break the path from the batteries to power the scanner is the switch built into J3. It has to either be the batteries, battery contacts or J3.
I looked at this as well and agree fully.
It's a pretty straight forward circuit and typical jack.
I suppose he could always short the switch if he cannot find a jack that will fit but he will need to be careful with using batteries of any kind when using an external power source as that looks like it would also bypass the charging circuit from what I saw with my quick glance.

I'd try to find a replacement jack that fits first. I think the same jack can still be found but maybe not as a part from Radio Shack under that model and part number at least.
If no suitable jack is found, I'd try and see if I could get a dental pick in there and attempt to get the switch working again if it is not physically broken.
If he chooses to short the switch, I'd insert a dummy plug in the jack as a reminder for when he tries to plug an external supply in a year later!
I did that with something once. I had to bypass something internal and I knew I'd forget about it so I super glued a broken plug in the jack so I could never plug an external power source in again. Of course he could also unsolder the jack from the board so it cannot be used again without taking the radio apart first.
Sticking a broken plug in would still allow the jack to be used and when the broken plug obstruction is hit with the good plug, that will hopefully remind him to remove the battery holder!
 

mjw357

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Well I've found the issue, surgery complete.




Turns out a part of the plastic insulator from the DC adapter decided to break off. It was lodged all the way in the bottom of the power jack, just enough to hold the contacts open. I removed the jack from the PC board, pushed the plastic disc out with a paper clip and reassembled. Everything now works as it should.

Thanks to everyone who replied.
 

kruser

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That's a first, a broken plug instead of a broken jack.
I've never seen one break like that before.

Glad it's back working!
 
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