having a problem with r-x500 model not working. dim display

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PaulR2007
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having a problem with r-x500 model not working. dim display

Post by PaulR2007 » Tue Oct 02, 2007 4:45 pm

ok my friend bought himself a new receiver and placed his jvc r-x500 one in his garage for storage for about a year so he wrapped the receiver in a plastic bag. last week he takes the receiver out and plugs it in because he was going to use it again and it dont work. it turns on with a relay clicking and very dim backlight on the display but nothing shows on it. so we took the cover off and noticed some capacitors look like they leaked or mayby that is how it was from original purchase so we dont know. anyway here is a couple pictures i took of the capacitors. the big capacitors next to the heatsink also leaked but i couldnt get a good pic but they basicly looked like this. so my question is does this look like some problem common to other old jvc recievers?
Image
Image

Victory
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Post by Victory » Tue Oct 02, 2007 9:14 pm

Hi Paul,

Good pics, thanks for posting.

Most Electrolytic capacitors die from use, these have died from lack of it !
The circuit boards look in very good condition, especially for an old unit that`s been stored for a while. If you can get all the capacitors replaced with equivelents, you should have a very nice, working receiver.

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Andy Cippico
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Post by Andy Cippico » Wed Oct 03, 2007 2:17 am

Hi Paul,

Hate to say it, but that looks like the glue they use to secure the capacitor to the board. I've had an electolytic capacitor blow up on me and it didn't have any goo inside like your example.

What's the texture of the goo? If it's fairly solid then I'm willing to bet it's securing glue. I could be entirely wrong of course...

Andy.

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Post by PaulR2007 » Wed Oct 03, 2007 2:30 am

thanks for reply to you both. ok so if its hard to the touch then its glue. ill have to check next time i go to his house. i really hope that receiver can be saved some how and cheaply. it worked nice a few years ago. so if its not the capacitors what can make it not work just by storing it?

PaulR2007
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Post by PaulR2007 » Thu Oct 04, 2007 9:16 pm

It looks like the spilled stuff on the bottom of the capacitor is glue because when i screped it with my pocket knife it turned into powder so that tells me its hard and not gooey like some chemical in the capacitor. Which brings me back to a dead receiver with dim display. this receiver is computer controlled do you think something died in it just because it was sitting in a bag on a shelf in my friends garage for a little over a year? i printed out a list of JVC service shops in my area and i gave it to my friend so he will call them but to me it seems like it will cost more to repair it than a new compareable reciever.

Victory
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Post by Victory » Thu Oct 04, 2007 9:47 pm

HI Paul,

Can you post a pic of the Power Supply ?

Capacitors, being `wet` devices are the first to go if stored for a long time. The batteries in your remote control dont leak, but if you leave it in a drawer for a long time, they will. Capacitors and batteries are electrically similar.

I think if you replace the Electrolytics in the Power Supply, you`ll be much closer to a fully working receiver.

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Post by PaulR2007 » Thu Oct 04, 2007 9:51 pm

I will have to go there again and take more pics. but the unit does turn on and relay clicks. its just the display doesnt show any writing but it glows red. I think this receiver has inverse lcd but im not sure as its been a while since i seen it working.

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andywilks
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Post by andywilks » Fri Oct 05, 2007 4:05 pm

The glue in the pictures is just well glue and generally has no ill effects (corrosive etc) that I'm aware of on these old receivers. On some models where this glue is around a diode which is part of the protection circuit the slight conductivity or an other effect causes the prot cct to remain out. The RX500 I don't think have this... certainly I've never seen that fault on one caused by that.
However I have seen that fault on a couple of RX500 now. Capacitors have never been a problem. The small 4"x3" stand up board near the main power output Trs is the most likely place to start looking for problems. You'll need to desolder it and may find an odd Tr failed and the board riddled with dry Joints. Just don't try to work on the board in the unit as the resevoir caps + & 60v rails are supplied to this board and thus 120v is left present until voltages have decayed!! watch for this when desoldering the board too.
Before you desolder the board it is worth checking the emmitters of the main OP trs (best done on the white 0.22r resistors) Look for a DC voltage relative to the cabinet of + or - 60v indicating that 1 or other channel has a major problem.
Beyond that I do have the paper manual, but they are rather a beast to work on so unless you have experience on amps I wouldn't get too involved.

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Post by PaulR2007 » Sat Oct 06, 2007 7:59 am

Thank you Andy for your detailed reply. I don't think me and my friend will try to do the work ourselves to fix unless its simple but we would like to have an idea of whats wrong with it before it goes to a repair place. I took some more pictures and if possible can you or anyone else look at them to see if anything is visibly wrong?
I made a slide show here-> http://s68.photobucket.com/albums/i20/y ... eshow=true

and the gallery is here->
http://s68.photobucket.com/albums/i20/y ... %20R-X500/?

I compressed the pics to the smallest file size without sacrificing detail so they can load faster and you can see them at 300 dpi (6 megapixel) when fully zoomed in.
Thank you for your time once again.

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andywilks
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Post by andywilks » Sat Oct 06, 2007 1:11 pm

All looks ok from the pics. Many components are 'flame proof' so wont look any different even when blown!

Just to correct my earlier info, the amp board on the 500 doesn't have the stand up preamp board (Iwas thinking of the similar/later RX9)

Note the glue on the cap is round the diode. scrape the glue off as best possible and check the diode on a meter for its junction etc.

As mentioned before check for a dc voltage on the single pin end of the white resistors when its running. any voltage means that channel has failed usually with 1 or more Tr failing.

worth taking the bottom cover off to inspect for bad joints.

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Post by PaulR2007 » Sat Oct 06, 2007 4:07 pm

Ya we took the bottom covers off and everything looks perfect like new. When I go to my friend's house I will read everything you wrote and it should make sense to him as I dont know much about electronics. Thanks again!

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andywilks
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Post by andywilks » Thu Oct 11, 2007 12:25 pm

Just read the original leading post again...

you've got no display info on any screen! but the backlights are lit (one of your photos appears to show that yes?)

It comes on with a click.... is there a click after 5-10 secs from switch on? If so the amp may be ok and its just that you can't see what the display is doing to get the amp running! If there's no click then the protection cct is detecting a problem- 2 very different possibilities exist here.

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Post by PaulR2007 » Tue Nov 20, 2007 10:31 pm

ok sorry for the long time since i posted here. my friend was on business trips and couldnt deal with this receiver in the meantime. Anyway we opened it today again and we counted 4 seconds from power on until the relay clicks.

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andywilks
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Post by andywilks » Wed Nov 21, 2007 10:45 am

Sounds like the amp main board is working ok then.

. The backlight bulbs are lit yes? dimly you say? but no display? there may be a power supply rail down (fuse resistor gone) feeding the control stage.

Power rails to the ENB-015-1 board (display/logic section) are +13v & -13v on pins 5&6 of FW/FC 404 and a 5v on pin 2 FW/FC 403. check these with a meter- earth probe of which will be on the metal chassis

If the -13v is missing check FR873 180 ohm for open circuit
if the +13v is missing check FR874 68ohm for OC
for +5v R868 may be OC (it should have 12v on both sides of it)

Worth also checking for bulb supply problems as we have had problems here in the past.

R847 848 & 849 (paralleled) should have -36v on 1 side and -32v on the other (with respect to chassis) Its not uncommon when a bulb fails, since all 3 are in series, for one of the zener diodes to go short circuit (across/ behind the bulbs) thus pulling that supply rail down with a heavy load. The zener is there to ensure the other bulbs stay on... but the circuit design is poor and imbalances usually mean the diode sees too high a voltage and cooks.



I've tried to make it as clear as I can, but if none of the above makes sense then you will have to enlist the help of a service guy to do the checks for you.
I can scan/email the psu schematic if you need it.

Andrew

PaulR2007
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Post by PaulR2007 » Wed Nov 28, 2007 4:16 am

hi again. my friend checked the big psu capacitors and they are ok. he cross jumped and the spark was strong. if you have any service manuals or schematics please email them to me at sonicmixmaster at gmail dot com. Thank you

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