Author Topic: Help: Trying to fix remote  (Read 316 times)

Online Wim

Help: Trying to fix remote
« on: October 13, 2018, 05:48:33 PM »
Have an unresponsive remote (Marantz RC-63CD). IR LED does not light up checking with phone camera (tried other remote, phone sees it). New batteries. Opened and trying to figure it out but I have been out this game for some years! See picture:



Carbon pads seems like new. Remote looks just about unused. Was apparently in storage for 15 years!

Track at bottom is V+ and track right at top is V- and both end up at the tin cap (47/6v). Continuities seems ok from the batteries.

Measure LED and get 0.9v forward bias (meter on diode), no power connected, reverse bias nothing.

Top and bottom transistor measures ok.

Resistors measure ok, tin on top seems to be cap (47micro / 6v) I assume. Ohm measurement shows it "charging". Not shorted or open.

What is the white thing?

Please help! Any ideas appreciated.

Offline Steerpike

Re: Help: Trying to fix remote
« Reply #1 on: October 14, 2018, 01:33:52 AM »
The white thing is a ceramic resonator - cheap substitute for a crystal. The capacitor may be leaky - SMD electrolytic caps are notoriously short lived. Try bridging one of the button contact foils with a ball of aluminium foil, the conductive rubber is usually the first and only thing to fail in remote controls, but I have seen hairline cracks in the PCB when people press the buttons ever harder to compensate for reduced conductivity in the rubber.
« Last Edit: October 14, 2018, 01:37:07 AM by Steerpike »

Offline CAD

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Re: Help: Trying to fix remote
« Reply #2 on: October 14, 2018, 05:49:27 AM »
Thanks Steerpike as I have a similar problem and had no idea that the conductive rubber could fail.

Is there any way to "revive" it say with contact cleaner ?

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Online Wim

Re: Help: Trying to fix remote
« Reply #3 on: October 14, 2018, 06:57:52 AM »
Thanks Steerpike. I cannot let this thing beat me! Man, I need a oscilloscope so bad. Must buy one. This remote is so clean with no wear and tear that I even suspect it did not work out the box and the previous owner made another plan or got another remote. It has also never been dropped as there are no impact marks of any kind on the shell.

I measured the rubber pads of the buttons putting the probes on opposite ends of the pad and they all measure 1.5k - 2.5k. So there is something there.
The tracks look perfect but it is possible to have some underlying cracks or even a manufacturing fault


I thought it was a crystal as it was connected to the OSC-In and OSC-Out. (Scope!!!!  :headbanger: :headbanger:)
Description/Picture of IC. They also mention this Ceramic Resonator. I did not know of its existence.

Thanks for your inputs. Much appreciated! Any more tips will be greatly appreciated. Or even if someone knows of an alternate remote that will work on this. Andile said Phillips, Wadia or Arcam will also work. Anything will do. This is for the Marantz CD-53, which by the way is fantastic!
 




Offline Hi-Phibian

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Re: Help: Trying to fix remote
« Reply #4 on: October 14, 2018, 07:35:45 AM »
Any rc5 protocol  remote will work.  Early Arcam. Most Philips. Early Rotel. Say pre 95.

That marantz remote is expensive but there is another one thatís not as expensive to buy as a replacement which looks different but works 100s.  The one for the cd4000/5000/6000 I think. 

Have you checked for voltage over the emitter diode while pressing a button.  Try volume as it repeats continuously so easier to check. 
According to a tech  friend, the diodes  do fail from time to time.
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Online Wim

Re: Help: Trying to fix remote
« Reply #5 on: October 14, 2018, 08:20:43 AM »
If I measure the led:
DC: 0.02v (not pressed) to 0.179v (volume button pressed). Don't think it is enough to get it going. But there is a definitive change.
AC: Around 0v to 0.2v button pressed. But I get the same if I touch the battery terminal so I think it is just me injecting a .2vac with my finger.
I will definately look at getting another remote, it just seems such a waste taking into account the cosmetic condition of this one. Thanks Mr G. 

Offline Hi-Phibian

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Re: Help: Trying to fix remote
« Reply #6 on: October 14, 2018, 08:44:08 AM »
Seeing as itís open and all that I would slap another led in there and try. Even from a donor old remote for eg. 

If the led is poked / shorted it could pull power down. Perhaps Lift one leg off the pcb and measure voltage. 
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Online Wim

Re: Help: Trying to fix remote
« Reply #7 on: October 14, 2018, 08:58:04 AM »
Good idea, I have some old remotes around here somewhere and it is pretty easy to change. I'll give it a measure first when it is out.  :thumbs:

Online chrisc

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Re: Help: Trying to fix remote
« Reply #8 on: October 14, 2018, 09:55:32 AM »
Got a friends old Philips TV working by using a cheapie Chinese learning remote.  After figuring out the terrible instructions, I found it could be switched to Philips/Marantz mode.  Thing cost R35,00
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Offline Steerpike

Re: Help: Trying to fix remote
« Reply #9 on: October 14, 2018, 10:13:15 AM »
The conductive rubber ages, even without use. The first step is to clean it and the contact traces with acetone.  If that does not work, they can be revitalized by putting graphite powder on them and "working" the powder into the rubber with a hot clean soldering iron (no solder!) .

Online chrisc

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Re: Help: Trying to fix remote
« Reply #10 on: October 14, 2018, 11:17:49 AM »
Does the graphite conduct then?
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Online Wolla

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Re: Help: Trying to fix remote
« Reply #11 on: October 14, 2018, 12:24:42 PM »
Does the graphite conduct then?
I bought a pure graphite Ďpencilí from an art supply shop some years back and have revived many a rubber conductive pad with it. Yes Chris, it works.
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Offline Coenoes

Re: Help: Trying to fix remote
« Reply #12 on: October 14, 2018, 01:00:49 PM »
I have fixed 2 of my marantz remotes with aluminium foil.

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Online Wim

Re: Help: Trying to fix remote
« Reply #13 on: October 14, 2018, 06:51:20 PM »
FIXED!!! the SOB!!!

I thought let me first retouch the solder and check continuities. Found the resistance from a transistor base to the resistor reading 40k?  :thinking: :thinking:

Clean and resolder, now better but still no continuity. Then I just bridged it with a couple of strands of solder wick, measure continuity as expected. Put batteries in and voila! Works!

Hahaha, like riding a bike. I love troubleshooting stuff. Think it was a manufacture fault, hence the remote in pristine condition after many years. Don't think it ever worked.

See picture (blurry) of offending track.



Online chrisc

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Re: Help: Trying to fix remote
« Reply #14 on: October 14, 2018, 06:55:07 PM »
It looks like that device was hand-soldered to begin with.   That is almost a guaranteed source of dry joints.   The old style CRT TVs were full of them
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