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Hitachi TRK-5450 weird problem, Superduper ?


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#1 T-STER

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Posted 01 December 2016 - 12:23 PM

So i have this tiny little TRK-5450 i bought, i only got it as it is a teeny feature packed mono and i had to save it.

 

It has no power at all, i plug in a 9v supply and nothing works. However, when i touch the small lead that comes off the side of the adaptor, specifically the tip of it, the radio fires into life. What does this mean? I was working it through in my head and assume it would be an earth issue?

 

 



#2 Superduper

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Posted 01 December 2016 - 01:57 PM

Yeah, so there are several possibilities:

 

1:  There is very common problem in that the adapter plug heads actually come in dozens of sizes.  They have the same overall "look" but the exterior dimensions, depth of plug, inside hold diameter, etc varies.  You need to get the proper one or else there will either be a poor connection, or no connection.  Or worse.... some jacks are positive (+) in the inside hole and grounded (-) on the outside edge, but not always.  In these cases, if you plug in the wrong polarity plug, well you know what happens then.

 

2:  The jack connector might have the spring contact bent and not making good contact. 

 

3.  The plug end of the power adapter might have a broken internal connection.  You'll have to test with a meter to verify.

 

4.  The jack might have a broken solder (-) joint or other broken connection. 

 

=====================================

To figure this out:

 

1. Test the jack head to verify that it is indeed getting power and doesn't have an internal (-) break.

2. Visually verify that there is no physical defect in the jack that would prevent the outside spring contact to plug sheath when inserted.

3. Test for continuity of jack contacts with internal circuit board.  If no continuity using meter, correct the cause which could be as easy as reflowing the solder joints to the jack, or bridging broken PCB traces, or replacing jacks.



#3 T-STER

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Posted 01 December 2016 - 02:42 PM

Dude thanks, really appreciate your input, I was hoping you would see my cry for help!!

 

Ok i'll try all of the above and report back, many thanks.



#4 T-STER

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Posted 10 December 2016 - 11:27 AM

Hey Norm,

 

1. Test the jack head to verify that it is indeed getting power and doesn't have an internal (-) break

 

Do you mean the head of the jack on the radio, how so i test it? I have a multimeter but im not sure which setting to use.

 

 

2. Visually verify that there is no physical defect in the jack that would prevent the outside spring contact to plug sheath when inserted.

 

Spring looks good and seems to touch the inserted jack ok.

 

3. Test for continuity of jack contacts with internal circuit board.  If no continuity using meter, correct the cause which could be as easy as reflowing the solder joints to the jack, or bridging broken PCB traces, or replacing jacks.

 

I have resoldered the jack so contacts are good tho they seemed ok before i did it just in case.

 

No change to radio function tho.  I know its a tiny model but i just want to get it working!



#5 Superduper

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Posted 10 December 2016 - 12:31 PM

Sorry, in #1, I meant the plug. Verify with meter that you are getting proper voltage.

In #3, set meter to ohms function and test both contacts at the jack where plug inserts, one probe at either the pin or spring ground and the other probe at the corresponding internal contact at pcb.