Houthitone Transistor Radio Repair Attempt LM386 Mod

[@18WheeledDemon]

For the entire squeal time, you had the full undivided attention of both cats and the dog.

[@HappyDiscoDeath]

One of my cats (curled up on a comfy chair nearby) wondered just what that was.

[@LiquidRadio]

2:35 What did we just learn? “Soldering Iron + Capacitors = Synthesizer”. 😆

[@mrnmrn1]

And if you heat them long enough, a drum machine! Just be sure to wear eye protection.

[@janosnagyj.9540]

I had the same tought: so this is how the pioneers of electronic music started their journey 😅

[@LiquidRadio]

44:23 That’s a hell of a cliff hanger! “It literally sounds like… Tune in next week for the exciting conclusion of this commentary!”.

[@MichiganPeatMoss]

We just lost LA!!

[@bigmotter001]

WOW, 9,000 views and only 797 thumbs up! C'mon people I have been following this man for years and he is producing very entertaining content in a lot of areas. Let's give him a thumbs up for his efforts! It costs you nothing and will help him continue to grow this very entertaining channel! Thanks and take care!

[@gabrielleeliseo6062]

I certainly look forward to his show every week. He's awesome.

[@joefish6091]

People are too involved watching and forget to upvote.

[@ShadowsOnTheScreen]

On a video like this, I am lucky if I really understand 20% of it, but I learn something every time!

[@kd5ozy]

hang in there!!

[@MrCrystalcranium]

This has been a test of the Emergency Broadcast System. Had this been an actual emergency, you would have been instructed where to tune in your area for instructions and information. This concludes this test of the Emergency Broadcast System.

[@RamPravesh-cm5cq]

Beautiful and🌹👍

[@christopherkise]

Beeeeeeeeeeeeeep 🐝 🐝 🐝 beeeeeeeeep

[@chetpomeroy1399]

"This is not a test."

[@billharris6886]

Nice job Mr. Shango, you get an Effort Score of at least 200%. Nice job on the audio amp board install; no signs of a hack job. With these 1950's/1960's Asian pocket transistor radios, they were such a high volume production, it's hard to say how many slipped through with problems. Then there is the problem of absolute cheapest components being used, which can age badly. It's amazing they worked as well as they did. One of the resistor saving tricks you noticed. To save an emitter resistor, they would connect the base bias resistor from Vcc to the collector. This feedback would prevent the collector from going into hard cutoff or saturation. The audio problem you were seeing may have been due to a fine crack in the PC board or wiring error as originally built. This was obviously an upscale radio in its day, with the deluxe exterior and dial cord. This particular radio must also have the CW code practice oscillator option. If you want to go "whole hog" with the upgrades, slip in a subwoofer. 😂

[@angrydove4067]

We don't need no intro or outro, straight into the meat this week.

[@jrocco36]

I've Fixed many Transistor Radios. Sometimes they just defy logic. I did a mod on one of those cheap Department store Hong Kong AM radios. It had stopped working but rather than doing a repair I stripped all the parts off the circuit board and used the board as a template to cut a project board to fit in the radio with the same tuner, Loop, speaker and volume control. I used the same schematic from the Elenco AM780K kit with the 7642 AM IC and a LM386 amp. Plays just as good as the old Hong Kong one. I could send you a picture of it if ya want.

[@andygozzo72]

the 7642 was originally the famous Ferranti ZN414 TRF chip, used in goodness knows how many home made radios , then became MK484, and then the TA7642, plus i think a few other type numbers

[@joefish6091]

@@andygozzo72 Anybody remember the awesome LM3909 !

[@TommyJensen-pl8qz]

it is a beautifully made radio

[@joefish6091]

Radios back then were less disposable, but instead items of status and wonder. A lot of modern tech is mind blowingly amazing, but theres also a lot of dross out there. (also back then herheh) I was reading a loudspeaker history article in Maplin magazine circa 1989, the author mentions a sales tax of 66% circa 1958 OUCH. obviously some form of tariff or luxury goods tax. No wonder British consumer companies failed so regularly.

[@garp32]

Happy to see your video drop. No July 4th EOL video had me worried about ya bud.

[@KameraShy]

The EOL took place in Atlanta on June 27.

[@garp32]

@@KameraShy Isn't that the truth...🤦‍♂️

[@cfd_novotroitsk]

22:44 bias resistor from collector to base gives negative feedback and also increases thermal stability compared to the standard voltage divider, sometimes it can be useful.

[@kimkelly3068]

In this application they gave up a bit of gain and saved a penny resistor

[@SpinStar1956]

Well, the motorboating (or whatever quaint-name) is just an oscillation emanating from an errant feedback-path. I didn't really see what the exact topology was, other than 2 XFMRs (interstage and output) and also did not see you check their XFMR-windings or signals sixth a scope. However XFMRs are seldom bad so that is unlikely. I have in the past had to increase the decoupling between stages in the power supply rail. Most times, a small bulk capacitor on the emitter (PNP) supply line is helpful. In others, I had to place and additional resistor in series (along with a bulk-capacitor) to get them to be stable throughout the life of the battery; this is why people relate low or high-impedance batteries as being the problem. The usually complaint, was that a battery that was unusable in one radio, would give additional play in another. Your idea to breadboarding the circuits was a good and instructive one. This allows you to adjust bias, play with coupling/decoupling, and voltage to really learn what causes what. In fact, you can (using capacitors) make your own erant feedback paths, and see which ones cause a similar result. Finally, you won't like this but with the stinkers, a schematic should be drawn from the radio for that section. It really only takes a few minutes, especially when you get the hang of doing it. As an aid, you can photocopy the board (turning the image to lighter) then drawing the devices over the faded-traces with colored pens; obviating the need to keep it in your head!. 73...

[@johnathanasiou9284]

My guess would be dodgy transistor, either in the push/pull amp, dodgy AGC, dodgy detector diode or some dried up sediments on the PCB. The squealing lol i remember from my 1st LM380 circuit how it motorboated likely due to poor decoupling

[@joefish6091]

Any decoupling !!!!!! the LM380 was normally pretty stable.

[@jameswarner3599]

I've had a couple of radios with motorboating that were impossible to track down, did the same and near on rebuilt them with new components. I like the module idea tho, recon that could come in very handy. Thanks for work you put it 👍

[@joefish6091]

cracked circuit boards, dried up caps. cracked resistors.

[@melvinhawkins9208]

That first part reminded me of my first Emerson Lake and Palmer concert, but without the knives.

[@401ksolar]

If there were a crude theveninized circuit analysis then perhaps the soft pwr coupling could account for the low frequency distortion, also the positive to negative feedback ratios could account for other oscillating distortion. Also there are sometimes thermistors used in germanium amps. Phenolic boards can go semicoductive from being sunbaked over time. Just some thoughts, it is a tough one.

[@lauram5905]

I wondered if maybe the board was going rotten... I wonder if that phenolic stuff is (very) slowly hygroscopic, or if something in it offgassed over the years

[@JurassicJenkins]

0:22 Off to the shelter we go.

[@stirlingschmidt6325]

Saturday July 4, 11 am: Hmm, I guess shango is taking a week off, I guess he deserves that. Saturday, July 5, 12 pm: Well shoot - I hope he still has all his fingers intact! Saturday July 6, 11 am: HOORAY! It must be Saturday! Yes, I had 3 Saturdays in a row...

[@davepike6170]

That vintage Hallicrafters E-stat set, turned out to make as nice a picture as they ever did, very good work, Shango066! Thank you for another great and instructional video.

[@joelima201]

Reminds of the Planet Clair B-52's video. Fred is pressing the call button on the Micronta walkie takie , same tone .

[@angrydove4067]

Ah the pink air!

[@thedogbarked123]

The radio straight up cut off at the end. Not sure if it's an error, but this is a good video. The hard troubleshooting videos are the best. Interesting that bias change sort of fixed it, maybe someone was playing. I like the radio videos because of the difficulty. good luck

[@philipbarry9209]

Just did this mod to a 1970 Hy Lite radio. Tried to replace the driver transistor, but it had too much gain on the output section. So I just gutted the original amp off the board. Radio sounds fine, replaced the transistor detector with a diode and added a 1k resistor to dampen the input to the 386 amp. Update. Removed the 1k resistor on input, opened pot fully. Lifted pin 8 on the 386 chip to drop the gain down to 20. Transistor radios don't need a gain of 200 with this amp. Works great.

[@geralderdek282]

Enjoyed this video shango! I too have installed components like resistors and caps where the manufacturer never had them after trying all else to get a tranistor radio to play properly. Like you said,maybe it was a fault from the factory. Succeeding models may of included the modification as the manufacturers were always improving and updating their designs.

[@stevexray6253]

The sound of that voice at 8:58 was extraterrestrial 👽👍

[@cool386vintagetechnology6]

The biassing of the transistor with a resistor from collector to base (22:28) is normal. It provides DC stabilisation; if the transistor starts to draw excess current, the collector voltage falls, and since the base is supplied from this, its current also falls, thus reducing collector current. The AC feedback which occurs with this method also reduces distortion. On that note, removing the emitter bypass capacitor from the driver transistor would have been an interesting experiment - may have reduced the gain to the point where the stage was stable.

[@jonbos2876]

Thanks for the video and giving us your time it is appreciated

[@chetpomeroy1399]

That LM386 module hopefully won't interfere with being able to hear those critical CONELRAD frequencies. Those war frequencies might come in handy right now.

[@cbsolo5628]

From all of us who listen to you on headphones, thanks for the volume jumps!

[@markseymour5558]

Thank you, you've cured my tinnitus

[@anthonydenn4345]

🤣

[@agoogleuser704]

Screetchtastic 🔊 thanks for the video

[@ArlenMoulton2]

I've had several of this style of radio that just never worked properly from the factory, I fixed one last night where the ground connection on the volume control had never been soldered to the board from the day it was made, there was still solder resist under the connection, so for the last 60 years it's been running at full volume!

[@gustavoangelero4068]

Never like now, there's a lot of China radios that are completely deaf.

[@wklorenz]

I've worked on a lot of these small radios. Distortion many times is caused by a poor connection with the on/off switch. Jumping it sometimes makes the distortion go away. You should automatically replace every electrolytic capacitors.

[@_-_Michael_-_]

That EDM intro killed me 😂 nice noise core set, European tour when? 😂

[@X5Industries]

31:37 that’s Gaité Parisienne by Offenbach! The fact that I recognized it instantly baffles me 😵‍💫

[@marksimendinger3462]

Thank you for introducing me to the LM386 module.

[@drsysop]

Shango, Have you ever came across some old Realistic radios from Radio Shack like the portable AM Flavorradio (catalog #12-166) that came in different colors back in the 1970's though the early 1980's for example? Awesome job as always. -73's

[@johnathanasiou9284]

From my college experience using LM380 & the LM386 chip is similar, you need to be careful & keep adequate decoupling cap & don't forget the zobel network. I made the mistake in college of forgetting to prototype these first on veroboard & checking the output is clean on a scope, and had to do stacks of mods & bodge wires to stop motorboating & squealing. Love the LM380/386 amp but man can it be unforgiving of layout especially PCB tracks which were too long. The scope output showing lower half clipping reminded me of small signal push pull amps where either one of the push-pull transitors were off, different hFe or bias resistor was messed up

[@deanagoes2791]

It is possible that the audio amplifier PCB has become slightly resistive due to moisture and aging, resulting in unwanted feedback. Just a guess.

[@kd6tas]

Seemed to me like it had one too many audio amp stages. The classic/standard/bedrock design is 6-transistor with two transformer-coupled audio stages. This radio follows that yet there is an added troublesome pre-driver stage. The audio was verified good at the output of the volume control. Disabling the pre-driver and coupling the audio from the volume control to the base of the driver transistor through a 10uF cap might have been worth a try. That would be signal injection in an effort to verify the driver stage, the output stage, and the speaker with something more definitive than a single tone from an external source. My thinking is the motorboating and distortion was due to too much gain/overdrive.

[@basspig]

Oscillation suggests bad DC bypass capacitors. Open capacitors create unwanted feedback loops in the amplifier.

[@russellhltn1396]

I'm going to take two guesses: insufficient filtering of the power supply (a dim bulb is going to make things worse), or you may have a hidden short - a microscopic bit of copper left from the etching that shorting things out. As small as a tin whisker, but different cause.

[@MrHBSoftware]

It runs on batteries...what filtering?

[@russellhltn1396]

@@MrHBSoftware Batteries have internal resistance. That results in the power rail fluctuating with the output signal. If that fluctuation gets into the sensitive low signal stages, it can cause motorboating. Most battery powered radios will have a cap somewhere on the power line to prevent that.

[@MrHBSoftware]

@@russellhltn1396 There is no ripple on the output of a battery...sure the voltage can drop if you crank the volume up but the radio will work fine...maybe you need some decoupling but i dont understand the need for any filtering..i understand the internal resistance of the battery and it will cause a voltage drop and also cause battery drain when idle but i dont understand the need for a filter, and by filter i mean a "large" cap between - and +...not saying youre wrong but its not clicking on my head..... oscillations of that type are usually cause by feedback problems between stages

[@caulktel]

I had one that did this once, found that the internal resistance of the battery was causing it, change to a different type battery and it played perfect. I don’t understand why.

[@russellhltn1396]

The output stage sucks power, resulting in the audio signal appearing on the power rail. If that fluctuation gets into the low signal part of the radio, you're going to have problems. Most radios would have a cap on the power rail to take care of that. But it's either missing, bad or undersized. As a result, it's sensitive to the internal resistance of the battery. Using a dim bulb source is going to increase the power supply impedance.

[@gabrielleeliseo6062]

That was a pretty cool find. If it was me, it’d be my luck that it was the last thing I tried before tossing it. xD

[@jdmccorful]

Much to learn from the "blue" gloved devil. Always fun!

[@frankowalker4662]

That's one way of fixing it. 👍

[@michaelrobertson575]

It seems that you've been beaten by a simple Discrete Component Audio Amplifier with a high frequency instability problem Shango. I'm very surprised at that but to be fair you didn't have a schematic for the Honeytone.

[@Synthematix]

Well done shango, you just made a synthesizer, put some reverb on that sucker will be perfect for todays pop music

[@mikefinn2101]

Only you could do such amazing work. I learn so much because of you I used a TA7205AP chip to fix my Drake R4B replacing the bad audio xfrmer. worked I attribute this to my Shango determination mentor. Just got done. But I have learned so much from you over the years. Love Sango Saturday learning. Thanks for all you do. Mike

[@palipixel]

Sorry in advance Dan if you covered this possible problem, or maybe you did but it got cut from the video: I suspect the driver transformer of having either a shorted primary turn, or possibly a soft primary to secondary short of some sort. The near-zero volts on the driver collector and that 'latching' behavior when the volume of the test tone is turned up just shouts amp + inductor interaction, forming a floppy saturation kind of behavior. Along with the frequency dependent shift in distortion, with the test signal growing cleaner as the test tone freq rises. But the fact that the new amp board didn't help much is very curious - maybe bad speaker as you mentioned. Still a good show, regardless of how it ended. Would like to know what the actual trouble really was, when the time is right. Thanks and Carry On!

[@gustavoangelero4068]

When I have a problem and I can't solve it, I put it aside for a few days and then start from scratch again.

[@foozball2012]

No 4th of July EOL this year? This would’ve made a good candidate and a good plot twist at the end 🧨

[@ricardogiampieri1408]

Excelente adaptación!! el lm386 es espectacular y en equipos como radiograbadores utilizaba el TDA 2002/3. cuando no se conseguían los chips originales!! Saludos desde Arg.

[@mxslick50]

Seems like a shorted mylar or ceramic cap in the audio chain.

[@cfd_novotroitsk]

19:14 this weird signal shape looks like both phase inverter and output transformers have shorted windings.

[@brianmoore5498]

love the mid sentence cut off for the endin...

[@imranahmad2733]

You could sample the feedback squeels at 0:43 and use it in a Prodigy song.

[@gabrielleeliseo6062]

lol I love this channel.

[@pzftw]

Even when he "gives up", he doesn't! The LM386 cyborg attachment was entertaining, I am not sure what I was expecting the outcome to be; perhaps the Honeytone magically transformed into a Roberts?

[@TheRogey1]

You can get an LM386 module much smaller than the one shown,useful if you don't have much space.

[@jonathaneastwood2927]

Robert's are no better than Honeytone these days 😂

[@Christopher-re2hl]

Did someone work on it before and switch the phase on the push pull transformers?? If so it will promote oscillating instead of preventing it. Maybe someone before you changed a transformer with the wrong type

[@consuelovalderas1645]

43:18 lol, point is that back in the first days of America, everything was in Spanish

[@47K-ohm]

You probably have not noticed it yet, but there is a cat stuck inside the speaker

[@50shadesofbeige88]

I'm awake. I'm awake!

[@scottbrady7499]

very early Sixties look to case, tacky chrometone handle too

[@tomtke7351]

Always interesting... this time my cats were especially alerted.... Then about 1/2 way and another cat favorite happens

[@tennesseered586]

Back in the day, some of those cheap transistor radios were really bad. This might be one of them.

[@Chems7308]

24:03 a very genuine true sometimes

[@briang.7206]

Well we have to assume when it came off the assembly line someone then aligned it and it worked ok before leaving the factory.

[@joefish6091]

Someone swapped a finished good one for a reject bin one, took the good one home.

[@tarcisiomendes2658]

Que radinho lindo, parabéns irmão

[@Tony770jr]

If you had the schematic you could verify the values of the bias resistors. Maybe the wrong value was put in by mistake.

[@gustavoangelero4068]

Always I have seen that problem, was a low battery.

[@38911bytefree]

I would let it as it was and repurpose it as the telemarket companion 2000. You cant polish a turd .... Circuits are simple but as they were stripped down to their minimun and use all kind of tricks to get things done. Plus on the audio amp, since there is feedback the failure all around and is hard to tell the one to blame. Worked a little on audio repairs and when an amp want to oscillate (speciall the early 70s ones with poor PCB designs), it is really hard to point the failure. You end doing thing like base stopers and miller caps on the predriver. And as you play with the tone control, you can see the oscillation starting to creep again. Happened me 2 or 3 times. For me sometimes is PCB layout ... bad grounds with shared currents that create unwanted feedback

[@benrose7534]

At first it sounded that interference coming from outside... You know from all the aluminum powder still lingering in the air from all those fireworks..that can really screw up radio

[@davidhollfelder9940]

That motorboat is speedboating .. Houthi(tone) air raid siren

[@Christopher-re2hl]

LM386 with positive ground???

[@pyeltd.5457]

Give it to Bethesda for a new Fallout prop like they did to the Philco Predictor in Fallout 3.

[@HughTVDX]

Is it the circuit board itself leaking across?

[@kpc5]

Your Videos have lost the 480 option from viewing your videos, i can not watch videos in 1080, the video is motionless, i really enjoy watching your videos and i am a ham like you, i have a G7 UK callsighn and have been a licensed ham since 1991.

[@xsc1000]

Its YT problem, but 360p or 720p are still avaiable.

[@livinlifetothefullest2750]

Here in Oz and i have 480 option to watch

[@xsc1000]

@@livinlifetothefullest2750 Now I have it too. So it seems it took YT longer time than usually to convert video to all resolutions.

[@RPike-bq3xm]

I think the distortion is coming from the RF. I may of missed that part of the TS'ing. You did use the tracer after the diode but? Run the 455 through the front, checking w/ that cool Chinese scope?

[@ko2fjb]

Hi, love your videos especially the resurrection videos. Is there a cross reference for US germanium transistor to Russian numbers. I would like to get a Heathkit XR2P running, it belonged to a fellow ham. If you watch my latest video you'll see my dilemma.

[@wheatenclient3623]

You konw, that waveform looks awful lot hotter than the ones from my FM synthesizer.

[@markmarkofkane8167]

An organ transplant! Awesome. It was cut off at the end?

[@hoosiernick]

Houthitone??? What does it do, sink ships?

[@jamesmdeluca]

Greetings: I noticed that your scope is AC coupled. how does the scpe signal appear when DC coupled going between good and bad sounding outputs?

[@TheEdneck]

Ooohhhhh, High Sensitivity! Hyyyyungggg zzzzzzzssssstttt

[@ekj24uk]

Ahh, Rebel radio 😂

[@gavincurtis]

0:44 the inner DJ comes out.

[@ToneHobart]

You may have been on to something when you said that maybe the radio never worked right out of the factory. Poor quality control? could have had multiple issues right out of the gate.

[@monkeyboy4746]

It's an old radio, it has performed well over the years and will still do gooder going forward, it's just going through a little rough spot right now. Even though it's a little deaf and sounds like crap, it will still perform well after 8pm, you just have to wake it up.

[@Roland_Tr909_Swing]

Houthitone shephard tone

[@kevinb158]

RIP head phone user that was loud

[@Antony_Jenner]

Stylophone plus! As long as Shango had fun, You did have fun didn't you Shango?

[@f.k.b.16]

If you play the first 4 minutes of this video in 5x fast forward, it plays the American Anthem!

[@danmyers7827]

Some wonderings: what's the actual input impedance of the dubious AF amp module? What level of input signal can it handle? It might turn out to be easier to build an amp on some Veroboard or PCB, using discrete PNP transistors.🙂

[@Seiskid]

Input impedance of a chip amplifier will be way higher than anything you can build with discretes.

[@pride293]

Thanks Shango. You're almost as cool as Shingo

[@fernandoscrenci4874]

Cap!!!!Clap!!!😮

[@LutzSchafer]

Looks like it needs a lot of negative feedback. Why more than factory is the question.

[@gretalaube91]

Is the detector diode reverse breakdown-ing? I have seen some that PRV with as little as 2 volts. Eh, yeah. Life's too short to futz around with a crappy AM radio. God Bless, 73 DE W3IHM

[@dirk013adfa]

This video is a visual metaphor of America right now.

[@joaopedroalbernaz]

Reminds me of the meme the guy is hitting the broken car horn, every time he hits it changes the tone and the third time he hits it, they added a George Michael song.

[@TheXGamer969]

The one video where “stable volume” would help… and it’s not available!

[@pyeltd.5457]

He turned the microphone gain down.