JVC A-X500VB amplifier

[Skylineview]

Has anyone here had any dealing with repairing the JVC A-X500VB amplifier? Mine has been acting up for some time and just today decided to not work. I can't switch inputs, I get no graphic equalizer, but the speaker protect relay does click in. I can only imagine the issue is with the digital part of the amp.

I'm just wounding if there are any "common" issues with this model that I can check. I'm waiting for the download link for the service manual I just purchased.

Any help is appreciated.

Thanks
Clay

[coromonadalix]

With the service manual, youll be able to check  supply lines,  start with any power supply section(s) you have

If you have  protection kicking in, you may have dc voltages on the speaker output,  check that,  put fixed resistors  like 8 ohm 25 watts 16 ohms  etc ....  measure with dc voltmeter

All your problems maybe related ....   dont change anything, troubleshoot first


I have the service manual from hifiengine, but many oher fakes downloads sites.

[Skylineview]

I also forgot to mention that when it was acting up I could usually give it a few tapson the side of the case and it would usually start working correctly again. I have the service manual, but it doesn't seem to be much help, granted I am new to all of this repair stuff.

I'm trying to get it apart to start looking for bad solder joints, in the boards I've pulled so far, I've been unable to find any thus far. 

[Skylineview]

To clarify the protection doesn't click in, rather the relay clicks as usual, Im unable to select input, adjust the EQ and I don't get any of the spectrum analyzer display.

[PKTKS]

TAPs indicate most likely bad cracked or cold joints.

You definitely will use an optical assist to do that even
some sort of magnifying glass ... all valid

Not easy to spot sometimes and very time consuming job

Some examples attached (they are indeed hires but cropped
and shrink to fit the allow. size)
Paul 

[mzacharias]

Yeah - I would say bad solder at the FL tube on the front panel. Mainly at the filaments on either end but possibly others along the entire row.

[Skylineview]

Okay, I will find my optical loops and check carefully.

I assume that the bad solder joints would also cause a no input select problem as well, correct?

If posting the manual helps, I'll post it.

[mzacharias]

Okay, I will find my optical loops and check carefully.

I assume that the bad solder joints would also cause a no input select problem as well, correct?

If posting the manual helps, I'll post it.

No, but bad tact switches are also very common.

[Skylineview]

I've not had any issues with the tact switches, they have always worked fine for me.   Basically it would drop out of the input I had selected and would then cause a no output situation, I could tap it on the side a few times and then it would miraculously come back up and start working.  The FL display worked flawlessly, unless the input select issue happened.   Maybe I'm over thinking the entire thing and  looking too broadly and need to narrow it down to just around the input selection chip.

[coromonadalix]

on image 7  is this a scratch  or a fissure in the pcb layer ??

[mzacharias]

I've not had any issues with the tact switches, they have always worked fine for me.   Basically it would drop out of the input I had selected and would then cause a no output situation, I could tap it on the side a few times and then it would miraculously come back up and start working.  The FL display worked flawlessly, unless the input select issue happened.   Maybe I'm over thinking the entire thing and  looking too broadly and need to narrow it down to just around the input selection chip.

I would add however, if the display is inoperative, you might press a given tact switch and see no response, even if it worked.

[PKTKS]

on image 7  is this a scratch  or a fissure in the pcb layer ??

On that PCB i posted that thing is CORROSION under the solder mask itself

It took me quite a while to scrap and apply a new UV repair mask on that.
the trace underneath that became a garbage corroded stuff

Other cracks mostly done with new solder blobs

Paul

[shakalnokturn]

Most likely bad solders, start by any large and/or hot component those are the ones that stress solders fastest. (Regulators, power transitors, >1W resitors, VFD filament)
Then there's the interconnect, the wires pull on the PCB side of the connector and weaken the solders there too.

Also look around the 2 large capacitors, this model looks like it may suffer from glue corrosion. The glue used to stick the capacitors can corrode components that have been covered with it, not always obvious and can cause unexpected faults.

Make sure you don't destroy one of those Super-A voltage amplifier IC's, I'm sure they're very hard to find now.