Bringing a dormant Discolite back to life!

flufftronix

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Sep 30, 2010
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Looking to get this dang Skitronic Discolite back up and running, but I'm short a resistor, and have scoured the internet for pics of other people's boards but haven't found pics clear enough to figure out what color stripes are on this thing.

The biggest pic in the bunch is mine, though the resistor looked burnt when I opened it up a few years back (looking at it now, it looks like it may have been put on there backwards by the previous owner).

Since then this thing has been passed to a few different people for repairs, and no one's interested in taking this on, so I'm going to try and fix it myself, if I can figure out what's missing. Thanks!
 

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flufftronix

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Sep 30, 2010
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Thanks! These are all the same component, so that last one should have another stripe behind the filter cap. Would brown-black-gold-gold make sense? I wasn't looking for gold on anything but the last band, but I guess this resistor is probably from the late 80s or early 90s..
 

caution

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Mar 25, 2014
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Yes. It's a low-resistance, high-wattage resistor acting as some sort of current limiter. Looks like 1/2W or 1W
Don't care about the last band, it just notes the tolerance, which is probably 5% (gold band)
 

flufftronix

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Sep 30, 2010
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Brown-black-silver-gold would be 1 gigaohm so it's probably not that, BUT brown-black-grey-gold would be 0.1 ohm.. hmm.
 

flufftronix

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Sep 30, 2010
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Superduper said:
Maybe it doesn't work because the power socket is already overheated, melted and the internal connections already fubar'd.
That's possible, though I hope not! Worst case, I'll try to retrofit a new power supply in there, run the speakers off bluetooth, and try to get the lights going off an arduino.

JVC Floyd said:
Looked like the fuse was missing till I saw it in last pic.
The one with the missing fuse is my unit (in troubleshooting this, pulling the fuse and trying a new one was my first stop). The other pics are the same or pretty similar units posted elsewhere.
 

caution

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Mar 25, 2014
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flufftronix said:
Brown-black-silver-gold would be 1 gigaohm so it's probably not that, BUT brown-black-grey-gold would be 0.1 ohm.. hmm.
You have it backwards - a gigaohm is brown-black-gray (10x10^8) and 0.1 ohm is brown-black-silver (10 x .01)
 

flufftronix

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Sep 30, 2010
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caution said:
Brown-black-silver-gold would be 1 gigaohm so it's probably not that, BUT brown-black-grey-gold would be 0.1 ohm.. hmm.
You have it backwards - a gigaohm is brown-black-gray (10x10^8) and 0.1 ohm is brown-black-silver (10 x .01)
Gotcha, thanks.

I just cleaned up the power board, resoldered some of the wires that had disconnected (over the course of me, a friend and a few technicians all having no idea how to fix this thing), put in some batteries and have audio and the VU meter working again. Line audio is crystal clear (what I mostly will be using this for anyway), the radio has a slight hiss to it, switching to tape mode makes the right speaker whine like a rave siren.. but hey! Everything's not fried.

Seems like that missing resistor is either for the tape decks or the lights!

EDIT: DC power is now working too.. still no lights, but the bulbs come on when I feed them some current. And the tape deck is this problem (which went away after monkeying with the record buttons)
 

flufftronix

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Sep 30, 2010
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Got a replacement resistor (1 ohm, 1 watt, 5% 500v max) and now almost everything’s working—including power from either AC or DC which is a first for this radio since I bought it!—but no magic from the bulbs or LEDs.

I can feed a 5v current into either of the small boards on the inside back of the unit and all the lights turn on, so my bulbs are fine. And instead of changing with volume the LEDs do a chase pattern when the disco mode is turned on. Any ideas on what to look into next? I’ll post some pictures of the current wiring later this afternoon.

Here’s how the innards of this thing look right now. The two boards on the back are mounted 180° from the other ones I’ve seen in other threads on here (on mine, the writing isn’t upside down and the soldered contacts are on the bottom instead of the top). But taking that into account I think I have everything where it should be. Still no woofer lights or volume-tied chase for the LEDs.
 

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flufftronix

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Sep 30, 2010
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I think there were some incorrect wirings in those last pics, but I’ve since triple and quadruple checked everything, and all seems correct.

Seems like my TDA2822M chip is fried (at this point I’ve literally seen the thing puff up some smoke a couple times!). I ordered some new ones and am going to solder in a chip inlet along with the next chip so that if any more of them blow, it’ll be easier to replace them.

I could certainly imagine some other defective component on that board sending too much power into that chip, and might just fry another when I add it. And actually.. is there anything I can measure as far as voltage or amperage on the chip that’s in there now on it’s input pin which would tell me if it’s being overpowered?

Oh and, also just to clarify: it seems like this chip on the power supply board is what’s powering the lights, even though it’s an audio amplifier. Is that right? Because all of the audio functions on this radio *are* working. Just not the lights at this point. Thanks!

And also thanks ahead of time for patience watching me do some potentially numbskull (but hopefully not dangerous) stuff trying to fix this thing. I am very much learning as I go, and am trying my best not to hurt this box or myself lol (testing primarily off battery power seems a lot safer than a power plug at least, and I’m not a beginner with fixing electronics, just haven’t done much at the component level)
 

flufftronix

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Sep 30, 2010
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Thanks! At this point I'm committed to replacing every part on that board if it's what it takes. Hopefully it doesn't :lol:
 

flufftronix

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Sep 30, 2010
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Removed this lil guy while I wait for the mail carrier. Thank you for your service.

Do these things usually have botch wires on the board behind the EQ like this? The tape on top certainly looks like it could be 30 years old 😜

Board from behind the tuner.. are there usually botch wires like this? The tape on top certainly looks old enough to be from the factory 🤷🏻‍♂️
 

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flufftronix

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Sep 30, 2010
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It’s alive! New chip is sitting in a socket soldered onto the board instead of the chip itself, so in case it dies again it’ll be super quick to replace.

Also swapped out the sand grain bulbs for some LEDs which came with pre-installed resistors that I put directly onto the boards behind the speakers, which will be easy to remove if I ever want to go back to the original setup.

Also swapped out one of the original LEDs surrounding the woofers. I tried first to sub old to new LEDs 1:1 without that preinstalled resistor, but wasn’t getting any light. But it did work with the preinstalled resistor on there! Not the prettiest inside the thing, but it’s working so hey.

I saw someone else on here swapped out the potentiometers on the VU meters for some newer, more accurate ones.. does anyone know anything about this? I see the ones on the board, AN6884, are still in use today. Would a newer one just work better, or would anything else need to change?

And.. soon as I figure out how to situate these new LEDs inside the woofers I’ll post a video. Have a few more small changes I’d like to make, but couldn’t be happier to finally have this thing operational again and I really appreciate the posters on here who chimed in! And the ones who documented similar teardowns and restores previously.. I’m guessing you all put this stuff up in case someone might need it later and it sure helped me out a ton!
 

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