DJ Tech strange issue.....

blu_fuz

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So I have a new BIG battery in my DJ Tech.

Right off the charger, all charged lights are on for full power. I can turn it on and default on the display says "HI" and first mode it turns on bluetooth to open the receiving end of the bluetooth signal.

I can connect to BT but then for only about 1 minute the bluetooth signal stays connected and then the boombox clicks like it turned off and "HI" is displayed for a second and then the "bluetooth" receiving is displayed. Then it repeats this click noise, HI, bluetooth, click, HI, bluetooth, etc...... Almost as if it doesn't have enough power to keep the bluetooth module on and it turns itself off and on again. If I push the mode button before it clicks and says "HI" again, I can switch it to radio and it plays the radio just fine without turning on and off.

Mind you, all of the battery "full charge" lights are on.

If I plug the boombox back into it's power/charge brick, the bluetooth signal stays connected and all functions work as they should.



Thoughts? Bluetooth module malfunction, maybe not getting the volts it should? Voltage regulator for the BT module?
 

JVC Floyd

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Joe check the voltage at the battery terminal and then check the voltage at the wires feeding the BT to see if there is a voltage drop.
 

Transistorized

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Does this behavior change when you plug the charger into the wall? If so it sounds like you may have gotten a bad battery. It has voltage but no amperage. If it does this even when plugged in you may have other issues.
 

blu_fuz

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Well, looking for obvious problems, I am certain the R12 and R14 (resistors?) are burned up. Can anyone pop open their DJ Tech and give me some values or pictures of these?

I checked continuity across each and got no continuity. Not sure if I am correct that these are resistors or not and if I can even due a continuity test on these burned up parts.... 73.2 ohm across the burned up parts but no continuity beep from my meter.

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Superduper

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No continuity means infinity so if you are getting 73 ohms, there is definitely continuity. Whether or not your meter beeps depends on your meter & how much resistance it allows before it determines that there is a continuity issue. For the most part, continuity tests are for locating breaks in wires and traces, therefore this setting is usually expecting close to 0 ohms. Obviously a resistor (unless it is a very low ohm resistor) will appear as excessive resistance in a wired circuit path.

If you want to confirm what I’m saying, you can test any other resistor on that board & I’ll bet none, except low ohms resistors will cause your meter to beep.

Resistors should be tested with an ohms test and not a continuity test (meter function). Whether or not those resistors are toast depends upon whether they are out of spec so you are right to determine what the proper value is. I suspect they might be 68R resistors because that is the closest standard value to your reading and the extra 5 ohms might well be in your leads & oxidation on the probe tips. I’ve often cleaned probe tips with steel wool or scrub pads and found measurable differences in readings.

Still even if the orig value is 68 ohms and within specs, given their appearance, if you have the ability, I would advise to replace them anyhow because they might be opening or drifting out of range with a high current draw which could cause the reset you speak of. Keep in mind due to their size, they definitely are higher wattage resistors than their smaller counterparts.
 

blu_fuz

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Amen to that. I figured I would post all of the dumb **** I tested even if it was irrelevant or wrong :-D . Hopefully this was just a one time failure and if I can replace them, that this doesn't happen again.
 

Reli

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Maybe the volume on your phone is too low, so it thinks the signal is too low?
Btw which board is that? The amp board, BT board, power regulator board, or....?
 

blu_fuz

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Yeah, I don't know what would cause that kind of failure..... My ipod/phone usually is at 3/4 volume, then I set the volume on the radio when I'm sober. As I drink, I can add a few +++ clicks to the volume and rock out.

That is the main board attached to the rear cover that the battery mounts to.
 

Superduper

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By their very nature, power resistors handle a lot of current which is converted to heat. Unfortunately, SMT, by their very nature, is mounted flat on the pcb and often ends up scorching or discoloring the PCB with the heat. If this were a normal through hole installation, those resistors will probably be mounted higher off from the board which (1) allows convection to function more efficiently and (2) prevent the board from scorching if the resistors fail. Either way, it's not a given that they have failed, we don't know this yet. It's possible that many of these DJT have those 2 resistors discolored -- only you DJT owners will know (I don't own one). Since I doubt a schematic is available for this, low hour owners might want to take this opportunity to verify the value of those 2 resistors so we can document this for future reference. Once they are scorched to where you can't read the value, then it's anybody's guess what the OG value should be. I also can't tell but I am wondering if those resistors are run in parallel to increase the current carrying capacity. Perhaps a single resistor is unable to carry enough current. If I were redoing those, I would want to know this. The reason is that if they were run in parallel, I might be tempted to mount a larger discrete power transistor off the board and attached onto a heatsink which will help with heat dissipation.
 

blu_fuz

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You make my heart happy!

Also, I'm a dummy - I have another DJ Tech in the kitchen that my wife uses I could check it for the values I need if they aren't burned up too!
 

blu_fuz

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Ok, what am I looking at here ? Resistors? Values? Now what?

R12 and R14 both read 330

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Superduper

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Also check & see if any of those leads are tied together, I’m curious. And what is the ohms measurement here?

Oh and measure the resistor size (L x W) in either mm or in (decimal inches). You need to order the correct package size because they all look the same in pictures but there are numerous sizes.
 

blu_fuz

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16.6 ohm across a single resistor.

And I get a beep from my meter across a single resistor and a beep if I probe opposite corners using both resistors.
 

blu_fuz

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Correct, adjacent legs (probe both left or both right side) reads 0 ohm.

Do I measure the printed white box on the pcb or the black area of the resistor or the whole body of the resistor including the legs?
 

Superduper

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I don’t understand your question. The two metal edges at the ends of resistors are the legs. Yes looks like they are run in parallel because one resistor is unable to carry the design load by itself. They are a bit hard to remove without the proper equipment but if you have 2 soldering irons, you can do it. Melt solder in both end simultaneously & push resistor off the pads, then clean up the pads with flux & braid. When choosing replacements, I suggest getting high tolerance resistors (1% or less) as you can get lower tolerance components. 5% or even 10% are available. I’ve even seen 20%. It is critical that the resistors are as closely matched as possible in resistance. You might want to buy a bunch and individually test & inventory to find the closest pair.