Scooby-Doo Alarm Clock Repair


This is more of a hack than a repair which is a good reason for me to feature my Scooby-Doo alarm clock repair. I started out trying to simply fix some broken hardware mounts that hold the display and button mechanism within the alarm clock that looks like the Scooby-Doo Mystery Van. During testing I noticed the display was very dim suggesting an unusual current load or other malfunction, plus the alarm was not functional.

One of the coolest features of the alarm was that it made a car honking noise when the alarm was activated. Unfortunately, it turned out that the chip-onboard which produced the honking sound was shorted internally causing some transistor overheating and the dim display. It was impossible to restore functionality of the custom chip-onboard, but lucky for me the data sheets for the LM8560 clock chip revealed that it could directly output a standard alarm beeping sound to a speaker. This required the PCB and some circuitry be configured differently.

In the end the clock’s current load came down to normal parameters, the display was once again bright and the alarm functioned using the standard beeping alarm sound that comes from the LM8560 clock chip. It is sad that the coolness factor of the alarm clock cannot be restored with the honking car sound alarm but my son is quite happy to have his favorite Scooby-Doo alarm clock functioning once again.

The circuit modifications may not have been the cleverest or the best solution, so if you have other suggestions please leave them in the comments below. You can watch the video of the circuit evaluation and repair modifications after the break.

60 thoughts on “Scooby-Doo Alarm Clock Repair

  1. It seems like a nice hack, but im slightly annoyed (negatively surprised is perhaps more correct) that you use HAD to post hacks from your own blog. I hope it is not going to become the norm. (I follow HAD for the random interresting things from the corners of the internet, not for the handfull (or two?) of authors here to show their hacks)

    1. IMHO, I personally don’t see a problem with the HAD authors posting their own hacks, as long as their not giving preferential treatment for their own stuff. If there’s a hack worthy of HAD, why should it not be put on HAD? When I refresh the page, I’d rather see a simple project from one of the authors than nothing new at all.

      1. I notice most people that disagree with me says something in the vein of “I do not see a problem… as long as…” And it is that “as long as…” im trying to prevent.

        I fully agree it is not at the problem stage now.

    2. If the time ever comes that HAD will only be a dumping ground for stuff only the main authors make, nobody will be around to complain about that any more. Right now, this is a perfectly decent hack and it suits the site.

      1. Yes, it is that time im trying to pre-emptively avoid. I really tried to write my concern as posivtively as i could (because i agree it is a nice hack) but i am still worried if it starts to become a trend. I would have said nothing had it been someone elses hack. it is only the dangers of “inbreeding” I wanted to address.

    3. I don’t mind at all personally. This is exactly the type of stuff I come to HAD for. Had he not also been a HAD member there would have been no complaint.

      I love seeing people use out of the box thinking type solutions to problems (like re-purposing the onboard chip to make the originally intended sound rather than the honking).

      As long as anyone can submit articles and they all get fair love, I’m ok with it. This seems to follow that just fine.

      1. Yes, I did say the hack itself was not an issue whatsoever. nor was this particular post. It was the possible unfair treatment that i am worried about. and simply tried to nip it in the bud before it might become a problem. (Admittedly I was unaware that Todd was semi-famous here – and of his past history. So as i said elsewhere in this thread, it might be unfair to Todd to pick on his post, but if i waited till it was too late – well, then it would be too late)

        I notice most people do see what my worry is, and realise it can become a problem. Even though it is not so now.

    4. I get the potential conflict of interest but I don’t think this has become a problem yet. For one, this content seems relevant to HAD. And second, many of the author’s previous works have been featured on here in the past, before becoming a contributor. Does that mean that his content is now unable to be posted on HAD? I definitely see how this could become a problem if it got out of hand but at this point it doesn’t really seem like it’s become a problem. This is very much an opinion thing though so we may simply disagree.

      1. And that it _could_ become a problem is exactly why I bring it up. Because when it is a problem it will be too late (I prefer to stop problems for occuring rather than trying to fix it after the fact) If becoming unpopular but still getting the HAD authors to think twice before posting own hacks – I still win ;-)

        I do not think we disagree really, But perhaps I just brought it up a bit earlier than most others would.

    5. mh, I share your concern. When I had free time for hacking, my projects were regularly picked up by Hackaday because the content was good I guess. I did this alarm repair and video before I was hired by Hackaday as a contributor back in August of 2013 and only now had enough free time to post it to ToddFun. When I get fee time I use it to get a Hackaday article or two done instead of personal projects. Knowing how the past 4 months have gone I won’t be getting much time for ToddFun hacks but when I do and if the editors like the hack I would love to share with the Hackaday community. If this community isn’t interested in my hacks anymore I will abstain from posting my personal projects but it would make me sad.

      1. I don’t think that getting hired by HAD as a contributor is a evident signal that what you do isn’t interesting to the community. I may be a odd fellow, but I’d say that this would more likely signal that your work is more often then not appreciated.

        I’m sure most of the people here can differentiate between a proper hack and a veiled info-mercial for a litigious 3D printer company.

      2. It entirely depends on frequency. But I have just seen too many sites become so selfabsorbed that it dies vecause nothing external is ever allowed. We are very very far from that – but as i said, i tried to voice my concern about the possible future, not the present.

      3. And I did not mean to put down your effort, or say your hacks do not deserved to get posted. It was mostly a comment on the concept of authors posting their own stuff in general and what that may look like from the outside (I do not know the names of all the hackers posted on this site. I mostly read the hacks without giving any thought to who actually made it, judging them on a case-by-case) – not directed at this particular post as such (but this happened to be the post that made me stand up and say something)

        On the positive side, at least we got a discussion about it. and so far I think we managed without namecalling too :-)

    6. If this was nothing but a SupplyFrame ad in four acts, you would be right. But. This is a nice post and video, perfectly in line with what had made Todd a HaD author in the first place.

      Now it just reaches you sooner.

      Keep ’em coming, Todd.

      1. It seems im rather alone in my concern. I have tried answering those directly commenting on my point – but im sure i missed some, and likely repeat myself too.

        The problem is that when (or rather if) this is nothing but a supplyframe ad (or a Todd ad – to stay with my original issue) it will be too late to say anything and all we can do is leave. – I am sure most of us who have been online for some time will have lost a few good sites to this kind of change. Why wait till it is too late to say something? We need to keep the site on its toes both for our sake but also for theirs (and I am willing to accept I might be wrong, but that is not going to stop me from bringing it up – even if it might be a bit prematurely and unfair to Todd)

        1. When that happens, we will collectively move along to a new site that will, by necessity, have sprung up — see supply-demand model. Or it will not spring up, in which case also see the supply-demand model and draw the conclusion.

          I am sure most of us have lost a few good sites to this kind of change. I am also sure relatively few of us lost sleep over any such occasion. I am also pretty freaking sure none of us could ever have done squat about any of them.

          Overlords fsck up, herd moves. Has happened, will happen. Case closed. Your bid as to make it not happen should be sent to With plenty of zeroes in it. That the herd does not care you surely must remember as it’s only been what, half a year?

          And yes, it *is* utterly unfair to Todd. Maybe he should balance it by posting a few dozen Arduino hacks in rapid succession.

          1. I still prefer not having to move along, i generally like HAD. And you never know if you could have changed it early on if you didnt try. Ofcourse “things take their course” but that is not to say we cant try to nudge them in our prefered direction.

            So far it also seems that sending money to sales@ is not required, and HAD listens (also under supplyframe).

            I think “utterly unfair” is a stretch, at what point does a bad direction need to be changed. in the beginning or when it is too late?

            (and btw, regarding arduino, since you brought it up. Id prefer not, especially if its out-of-the-box boards with code copy-pasted from the web. but if it goes beyond that, sure – but maybe not several right after eachother)

            That you do not care if HAD dies and are willing to just move on without even giving it a try is kinda sad. but your choice ofcourse.

          2. g, I will not make it a habit and you actually made me laugh out loud near the end with your string of zeroes comment and retaliatory Arduino follow-ups. :) HA.

    7. Good hack. Regarding how it was posted, on the surface it may seem questionable, but it doesn’t make sense to say that it should have been posted by someone else or even not at all, so posting it himself is completely logical.

      1. It is very hard to voice a concern on the internet about something that might happen without it turning into a flamewar (especially when it is directed at a popular regular). I tried hard to write it in a positive criticism way and did not mean to put down the hack itself, but just make the HAD authors consider this when posting. (it is ofcourse their site to do with as they please, but i hope they still dont mind some input :-)

    8. I don’t recall anyone complaining when Caleb posted his own hacks and he did it quite often. Fact is, the site was better for it and I even looked forward to his hacks.

      Besides that, what good would an author be on HAD if he never showed the community his or her hacking skills. From reading the new hire posts, those skills are part of the criteria that determines an authors qualifications.

      It is not hard to insure that the site does not come to what you fear. All HAD needs to do is implement a ratio of non-author hacks to author hacks such as 10:1 or 20:1. Doing so prevents any potential problem in the future.

      1. SATovey, I think 20:1 would be just right. That would let me post a personal project every month or two. I will bring your idea up with the editors. It would also solve my personal concern about over doing personal posts and give contributors as well as the community firm limits. Thanks.

        1. Your quite welcome.
          I do come up with a good idea now and then; unfortunately, people choose to take offense at them rather than have a problem solved.
          Makes me wonder if it’s me that’s insane, or everyone else?

    1. Mark, I have the Adafruit wav shield and was thinking maybe using a custom spin of that with one of my older custom arduino compatible constructions. The Sprakfun board looks promising as well; however, their sample audio in that link was horrible! If it can do better than that they really should change that sample. I was also thinking of just a super cheap key fob voice recorder that you can for under $10 on eBay.

  2. I am annoyed to see more dialog on disrespect than recognition of Hacking at it’s basic levels. The employment address of the Hacker does NOT diminish the merit of a Hack!

    Being contemplative- there’s now more than a few “recordable greeting card” modules out there that might be whacked in to a new horn for the Mystery Van. I suspect more than one Vanner has one of these.clocks and maybe they need repairs:>

    1. I am sorry it annoys you that I care about the future of the site. I never meant to start this (long) discussion and have it overshadow discussing the hack itself. I wanted to bring up a concern that I have about a behavior – that if continues -have been known to ruin sites before (and i simply do not know these people well enough to judge what they will do in the future). And I hope it did not come across as diminishing the hack itself – that was very far from what i wanted to do. And I do apologise to Todd (and the rest of you too) if that is actually how my posts have been understood.

      1. mh, no need to apologize. As I said, I share your concern. I was quite conflicted how it would come across. I’m sure I will not have time to do much work in my lab but if I share any more hacks I too want them to be relevant to community interests and doesn’t drag HAD down any content black holes; I do agree it could happen. I have enjoyed HAD for years and wouldn’t want the content or great variety of hacks to change. PS: even my own content has to be approved by HAD editors and I can tell they wouldn’t hesitate to turn down my content if it wasn’t up to a level of quality…. unless it used an Arduino ;)

        1. I agree its a very fine line, one you havent crossed yet. I am glad to see you did have this debate with yourself first and that the editors will not blindly accept your (or other authors’) posts. that is really all I am asking. I would never have bothered to bring it up if I didnt think you would take it as the constructive citicism it was meant as.

    1. tekkieneet, THANKS! I really like that option. I would learn a lot from lashing that circuit up and I’m thinking I have most parts in my bins already. If I make any such alteration I will post it to my YouTube channel.

    2. Then, not just a car honking but include a bunch of sound bytes from Scooby Doo…
      “Zoiks!” or the running music, “and I would’ve got away with it, if it hadn’t been for…
      how did that go now?

  3. I deconstructed a horn sound a while ago. A US police style horn from a PA300 (very grating)was a square wave wavering between 1667Hz and 893Hz. Some cleverness with an LM556 should get you there. I used a microcontroller with PWM outputs though.

    1. If you go back a generation to the Federal Signal PA-20 ( the sound generation circuit is actually very simple, just a couple of transistors, capacitors and resistors. Somewhere I have an eagle file of a clone I made from the original schematic, omitting the amplification and PA (Public Address) circuitry. The cool thing about looking at the manuals for those old sirens is that they even have a section that describes how the circuit works. I also saw this when I was doing some work cloning the Minimoog analog synth, which also had a theory of operation in its service manual. Someday I guess I should do a writeup for both projects and submit it to HaD.

      1. Just like there was a time when TVs came with schematics.

        There is a lot to learn from how things were done in the past. And older electronics tend to be easier for basic hobbyists like me to mess with (mostly through-hole or larger parts compared to what you find inside todays electronics)

      2. blanham, Wouldn’t that be a shockingly wakeup if I changed the circuit in my son’s alarm with this Federal PA20 Interceptor! That would bring him out of bed in a hurry. HA!

      3. For the PA300, they got fancy with some VCO ICs, a 556 or two IIRC, analog switches, and plenty of R-C combos. The analog curves are so smooth, it was deceptively difficult to match the siren sweep with the micro. I took a guess at a step size and ended up halving that along with a by-four interpolation between points to get close enough.

  4. Great information… both general (in terms of troubleshooting and electronic theory) and specific (in terms of this toy). I don’t understand all the hooplah about this post…solid material is solid material, and it doesn’t matter to me who the author is. Let’s have more.

    If I have one piece of constructive criticism it is to this and every other maker of project videos (I love Fran’s stuff, for example, though she’s among the most guilty…)

    Please be conizant of lip smacks when you speak. For some people it’s a nervous tick, others seem to use it in lieu of “…uh” between sentences. I suppose some think it makes them sound authorative. Whatever the reason, when it gets excessive, it’s grating to listen to and I will hit leave the page.

    This speaker seems pretty comfortable in front of a recorder and the smacks are few and far between, but it is common enough a fault in videos of this type that I thought I’d mention it.

    1. Fee D’back,I have also noticed Fran’s lip smacking and found it quite distracting too. I had no idea I too had such a nervous twitch. I know I stutter, use wrong words and pause often, I will have to keep a lookout in my editing for such twitches and cut them out or change my delivery. Thanks for the tip.

  5. I for one don’t care a whit about the source of the contribution, as long as the content fits the HAD criteria. Kudos for sharing! It’s good to see a svelte solution that doesn’t involve rebuilding the circuit from the ground up. (Though I have to admit I’d probably have to revisit the horn coolness). With unlimited time and money, If I had a cool van like that I’d probably look a putting some fancy LCD screens in to animate the characters and maybe add a rotating soundtrack like other toys employ. Maybe even wifi it so it could pick up the animation data from a server…

    1. W Lowry, Those are some interesting alterations. I could never be that ambitious mostly because I lose interest in projects if I don’t finish them over a weekend. Thanks for the ideas.

  6. Good god, half the discussion spent on one persons concerns over staff projects, spend the time on the project instead.

    To complete the hack, there must be a small audio chip like those annoying cards that can be programmed with the correct sound once sourced :)

  7. ******, you guys complaining…

    he did, after all, “stick it to the man” by repairing, without buying anything.
    isnt that a win?
    isnt that what we are here to hopefully read?

    i mean the only thing better he could have done is find out
    what exactly went wrong inside the mystery blob.
    but that, to most people, is WAY not worth it,
    and outside most of our skillsets.

    the acetone and all it has to offer, ahh … the smell …
    or should i say your stomac will offer it’s contents to
    the floor-gods if you dont use proper ventilation! lol

      1. Justice099, I see you found the same on budgetronics source too. I will try for a free sample first and if that fails I will drop the $9 to have a chip sent. Thanks again.

    1. Justice099, WOW!!! The HK637- 5 has a trigger-able sound event that is 100% the same as the original Scooby-Doo alarm sound.

      I will bet you the chip-onboard is just the same as what is in the HK637- 5 IC, just ordered up as a cheap chip-onboard.

      Looking at the datasheet ( this would be super easy to slap in and trigger from the clock chip just as it was wired originally to trigger the chip-onboard.

      Ordering the chip is complicated with bank fees for orders under $100 and shipping charges over $10. It would cost ~$30 just to get the chip. However, I did find it on ( and I could get a chip for under $9 with shipping, not too bad. If I can’t get a free sample I will order from budget.

      If I use this chip to fix the honking sound I will post a follow-up on my YouTube channel.

      Thank you very much!

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