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JVC RV-B 90 main PCB bypass


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#1 kaboomguy

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Posted 31 October 2010 - 07:42 AM

Hi,

as my RV-B 90 Kaboom doesn't work due to a faulty chip on the main PCB located below the CD drive, I had the idea to bypass it as I don't really need the CD player or tape deck anyway.
So I disassembled the whole thing today to see if there's a simple way to solder a line in jack directly on the amplifier PCB and of course I need to find out how to power the thing up with a separate switch.
I took several pictures and the connectors on the amp PCB (the ones into which the flex cables coming from the main PCB are plugged) are actually labeled. However, I'm not really sure if my plan can be put into practice. Wiring schematics would definitely be helpful, but all I could find on the web was the normal user manual, no service manual whatsoever.

Has anybody ever done this before or knows what to do?
Any help would be highly appreciated! :yes:

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#2 blah blah

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Posted 01 November 2010 - 08:14 PM

i can't advise you on this but I hope someone does because I have the same problem with a bad board on my DVP-100 kaboom. :-D They are pretty complicated boxes to deal with if something goes wrong....

does yours not power up, like it goes on for a second then shuts off due to the board?

#3 kaboomguy

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Posted 02 November 2010 - 03:18 AM

No, it won't power up at all, stays in stand by all the time. The only thing is that the display says "12:00 AM" from time to time, but that's all. :hmmm:

#4 monchito

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Posted 02 November 2010 - 03:56 AM

i belive the kaboom is like most of the newer stuff where the power is turned on electronicly by ic on a cuircuit board so you technicly cannot bypass it ,, the real way was to look at the schematics of the kaboom see which is the powerboard and replace,, see thats why most of the newer stuff were more of a pain it did away with the good ole chance a bad components and all working good on the board... :w00t: :w00t: to a change a complete board or just throw away and get a new one its all about making money :thumbsdown:

#5 kaboomguy

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Posted 02 November 2010 - 04:02 AM

Well, I do know which board to replace (it's located below the CD drive, the LC display is mounted on it, too). I just can't get hold of one... otherwise, I wouldn't bother messing with the amp board.
An easy fix would be just the right thing as I could definitely cope without CDs, radio and tapes :w00t:
I'm not a total noob when it comes to electronics, but without a schematic, I'm kinda helpless :-O

#6 blah blah

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Posted 02 November 2010 - 01:45 PM

i agree with ramon...i looked at the schematics :grim: they are horribly complicated. boat anchor like mine without a new board.

#7 monchito

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Posted 02 November 2010 - 01:57 PM

well the whole thing is compactness you will see a lot of smd on the boards maybe just 2 or 3 ic which controls just about everything so you have to track down powersupply either a small transistor or a ic is controlling the power if the audio amps short out that could well be the problem for it to turning on as some of those ic have thermal stutdown it could be anything ,,you have to take time trace it down and figure out whats causing the problem ...

#8 Superduper

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Posted 02 November 2010 - 02:18 PM

Best I can determine Ramon, these kabooms use about 32 IC's and probably a couple hundred transistors.

When these go bad, it's best to just part it out or sell it and get another one, which is my recommendation. Consider the price difference as basically the cost to repair yours.

As for bypassing to get to the amp -- it's not that simple. The amp itself might be possible to bypass but everything fore of the amp is MCU controlled, including volume, tone, front to sub woofer balance, source switching, etc.

So turning on the amp and connecting it directly -- you will have no way to control the volume. Furthermore, since this is a multi-amp setup, how you gonna control the power distribution to the 4 speakers?

#9 monchito

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Posted 02 November 2010 - 02:51 PM

Best I can determine Ramon, these kabooms use about 32 IC's and probably a couple hundred transistors.

When these go bad, it's best to just part it out or sell it and get another one, which is my recommendation. Consider the price difference as basically the cost to repair yours.

As for bypassing to get to the amp -- it's not that simple. The amp itself might be possible to bypass but everything fore of the amp is MCU controlled, including volume, tone, front to sub woofer balance, source switching, etc.

So turning on the amp and connecting it directly -- you will have no way to control the volume. Furthermore, since this is a multi-amp setup, how you gonna control the power distribution to the 4 speakers?

:lol: :lol: thanks norm for your observation i did not want to scare the man with all those ic and transistors :lol: :lol: :lol: :lol: but it totally true gone are those good ole fix the pc boards :sad: :sad:

#10 kaboomguy

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Posted 02 November 2010 - 03:43 PM

So turning on the amp and connecting it directly -- you will have no way to control the volume. Furthermore, since this is a multi-amp setup, how you gonna control the power distribution to the 4 speakers?


Damn, I hate being confronted with reality. :sad:
So I'll just have to check eBay day by day... even run-down units (CD player defective, remote & battery cover missing) go for over €100 ($140) :no:
JVC just shouldn't have discontinued the RV-NB10, then we wouldn't have all those greedy people making considerable cash by selling their old Kabooms...

#11 Superduper

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Posted 02 November 2010 - 06:44 PM

All those greedy people selling their kabooms for $140+ probably bought them for more than double that.

Going back to the preamp, volume control, etc......

Keep in mind that MPU controlled DACs do not use potentiometers for their controls. Sure the volume control is round and looks like a normal potentiometer but it is actually something called a digital encoder that generates digital pulses interpreted by the controller chip as a single depression of a button. So in other words instead of an up/down button for the volume, a knob that performs the same fuction is used instead and rotating the knob will generate the momentary pulse signals the MPU uses to adjust volume and/or other functions using the same knob. Unless you devise your own preamp using standard tonal and volume controls (which costs big $$'s), reviving and firing up the amp separately is of no value. By the time you invest money to do all that, might as well just part out yours and buy another one. Analog circuits are hard enough to work on but insert digital / logic circuitry and now, additional technical expertise and skills is required. In general, the labor alone makes the item not economical to repair. Some parts are still available including some of the IC's such as the controller but the prices I saw on partstorecom makes the cost prohibitive. I've seen some IC's sell for over $60 per chip. At that price, and without guarantee that replacement of the item will resolve the problem, it's not money well spent.

#12 kaboomguy

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Posted 02 November 2010 - 08:20 PM

Obviously, those people selling merely junk didn't handle their Kabooms with care, though.
People who don't appreciate their gear don't deserve big $$$ when selling it either.
Making good money with units in mint condition is fine by me, maybe that came out wrong...
Anyway, thanks for your help. I'm actually familiar with encoders, I've got a bunch of them sitting in my parts box. (However, I haven't had the time to get into programming µCs yet in order to use them).
As I said, it was just an idea to use the rest of those parts in the Kaboom that are still likely to work (i.e. a 'quick and dirty' solution). But as the whole thing turned out to be way more complicated than it seemed at the beginning, I'll just leave it at that and continue trying to find some spares.
At least, I still have my nearly-mint mini Kaboom, which makes it a bit easier to be patient. ;-)

#13 blah blah

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Posted 03 November 2010 - 04:29 PM

i looked into the pc board i needed...over $65 + shipping and i am not positive that's the issue so it's a gamble. Booo. The worst part is it seems this is the only real issue with these which means no spares around... :grim:

#14 Superduper

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Posted 03 November 2010 - 07:11 PM

Hey Tim. Are you talking new? Is that board populated or just the bare board?

#15 monchito

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Posted 03 November 2010 - 07:22 PM

well if mine ever dies i am going to install a car stereo so i can use the case and rig some speakers and powersupply :w00t: :w00t: :w00t: :w00t: :w00t:

#16 Superduper

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Posted 03 November 2010 - 07:27 PM

:hmmm: :hmmm:

#17 monchito

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Posted 03 November 2010 - 08:15 PM

dont think norm lets do it.. :lol: :lol: :lol: :lol: a nice high power jvc stereo with color display and some speakers whatya think :w00t: :w00t: :drool: :drool: :drool:

#18 Superduper

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Posted 03 November 2010 - 08:55 PM

:hmmm: :hmmm:

The hard part is how to break one of my kaboom so I have a shell to do it. Can't in good conscience do that to a good, fully working one. But so far, they seem bulletproof.

#19 blah blah

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Posted 04 November 2010 - 07:54 PM

Hey Tim. Are you talking new? Is that board populated or just the bare board?


Norm I am pretty sure it was populated and complete but it was quite a while ago when I looked and could be wrong. It was on the JVC site I believe. At the time I was under the delusion I might find a used one.

Somebody poured something like coke down across my board and it basically ate away at it...probably the only damn way to hurt one :-D

#20 Superduper

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Posted 04 November 2010 - 07:57 PM

Well Tim. If JVC is willing to sell you an entire PCB module, complete and populated for $60, you should buy it like NOW. :yes: You have the RV-DP200, right?

#21 blah blah

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Posted 04 November 2010 - 08:26 PM

I have to check it's been so long, I believe it is the DP-200. So now you have me thinking I should jump on it Norm! But what if something else was fried cause the board got fried? This box scares me now :grim: but I am gonna see if I can find where I saw it and if it was for real or I imagined it.

Which is entirely possible considering I am a boombox addict :lol: And wishful thinking is a symptom!