LaSonic Funny Electronics AM Transistor Radio Repair

[@johnfranklin5277]

About 20 years ago I was at a garage sale and saw a bright red plastic radio about the same dimensions as this, maybe a little bit bigger. Its a Westinghouse, and from what I've been able to find out, seen a couple for sale on ebay, it a 1967 or 68. Fortunately it runs on a 9 volt battery which lasts about 4 months! I bought it for 5 bucks. AM ONLY, this radio works, and sounds great. Its in my bedroom and every morning when I wake up I turn it on while getting ready for the day, I listen to the news for about 10 minutes. I mean this thing basically gets used every day!! Always works and sounds good. Definitely got my 5 bucks and more from this old red radio!!

[@_wave64_]

19:33 It was very common in transistor radios to let the driver current (2-3mA) through the speaker, the solution is called "bootstrapping": When the driver transistor closes down, the upper resistor (under the label "TR6") pulls the power amplifier up, which drives the speaker to positive. If the upper resistor was connected to Vcc, it would run out of driving current, as the voltage across it would decrease. But since the voltage on the speaker rises, the voltage on the upper resistor won't change, hence it's able to drive the power stage constantly. The exact same thing is happening in virtually almost all output transformer-less radios (e.g. Sokol 308, yesterday's Hazar 403, etc..).

[@pcno2832]

At first, I thought it might be negative feedback, but on second thought, there is no inversion, so it would almost look like positive feedback, but with no voltage gain. So is the intention to get the swing of the driver to range up to maybe 6.5 V (using the inductance of the speaker and the charge on the cap as sort of a ballast), so the output transistor doesn't cut off .6 V early? Seems like a clever hack, but with only 6V of swing, it probably makes a significant difference.

[@shango066]

I never even took the time to look at or think about the design and im surprised they would put that much thought into the circuit design. thanks for the info on why

[@rfburns5601]

@@pcno2832 That resistor is a leakage sense from output cap to shut down output transistors if output cap goes leaky. With no 8 ohm speaker load, normal leakage thru cap will mis-bias outputs. Advent used a similar circuit in one of their videobeam models.

[@andygozzo72]

@@rfburns5601 no it isnt, its a 'boostrap' as said above, some circuits use 2 resistors but connect the mid point junction of the 2 to speaker via a large value capacitor, it does the same thing but takes more components, but that way they can have the speaker at 'ground level' instead of supply level , many IC output chips use same idea, such as a TBA820/820M.... there 'may' be circuits that sense 'leakage' or abnormal load, this isnt one of them ...

[@randyab9go188]

The comment you made about the Teflon wire exceeding the value of the radio is exactly what I was thinking before you said it. The reason they did not put values on the schematic is that particular genre of set was made out of any surplus components that the low end manufacturer could lay their hands on. How could you provide a value when it may change on a daily basis? Design calls for a 220k resistor but there's a deal on 270k's in the surplus chain use the 270s. Can't get rectifier diodes use surplus switching transistors. Can't get miniaturized capacitors use oversized axial. Hong Kong in the 60 to 70s era was some of the worst build quality electronics that functioned I have ever seen. Even the junkiest Japanese stuff was light years ahead of the Hong Kong products.

[@KameraShy]

Yet it still lives.

[@jsciarri]

That supposed "Hong Kong junk" from the 1960's and 1970's is still many miles ahead of any modern Chinese korona infused garbage made today.

[@watershed44]

@@jsciarri TRUE! While they might have been primitive in design they were STILL built simply and built to be durable! Todays' China junk is built to be cheap, and VERY disposable with little longevity and at times are very complex too.

[@rudolphguarnacci197]

I'm hong kong and i approve this commercial.

[@pcno2832]

3:20 Sometime during this period, the FTC cracked down on marketing that touted a "transistor count" that included transistors that were wired as diodes, or not connected at all. A lot of these imported sets were made with surplus military transistors that didn't make the cut, so it was easy to use them frivolously. They might have built the board this way, then found out they could only call it a "7 transistor" design.

[@klafong1]

According to what I learned in college, the "transistors" used as diodes in these radios were floor sweepings that were not usable for amplifying current. The transistors in question were typically alloy junction devices. The base was a small wafer of n-type germanium. A piece of indium was held onto one side of the wafer, and the assembly was baked to cause a heavy concentration of indium to diffuse into the germanium, thereby forming the emitter (indium is a p-type dopant). A second piece of indium was later held on the opposite side of the wafer, and the assembly was run through a second bake cycle that had the goal of releasing a much smaller amount of indium into the germanium, thereby forming the collector. This manufacturing process was not very precise. As the emitter and collector regions came closer and closer together, the result was a transistor with improved beta. However, if the emitter and collector were too close, the result would be a transistor with a low collector-emitter breakdown voltage. If the emitter and collector touched, the result was a diode. Technicians tested each transistor coming out of the production line. A manufacturer might have used several different part numbers, depending on whether the device tested as low beta/high breakdown voltage or high beta/low breakdown voltage. The shorted devices sometimes had one lead snipped off at the factory to identify that they could only be used as diodes.

[@bandersentv]

Ha-ha. That was awesome. I think these bottom end sets can be just as interesting to work on as super high end.

[@annaplojharova1400]

This bias connection is very common with these complementary push-pull amplifiers. It is connected there as the bootstrap, to maintain the bias over the full output voltage swing - during the positive halfwave the resistor is fed from the sum of battery and speaker voltage. Most IC amplifiers intended for such applications are designed to allow this connection as the cost optimized BOM variant (TBA810, TBA820,...), as that way you can save the dedicated bootstrap capacitor and resistor. Most such cheap electronic uses that connection. It disappeared only with the modern low voltage rail-to-rail capable amplifier IC's (do not need bootstrapping to achieve full swing; 90's and later) and most recently the CMOS BTL amplifiers (HXJ8002,...; 2000's and later), which need even less components around (mainly the bulky speaker output coupling capacitor). And judging about the sound quality, it seems some capacitors are still weak there...

[@jeffking4176]

Some of these “bottom-feeder” radios are better than a lot of the junk made today. 📻🙂

[@cipherthedemonlord8057]

Probably superior to those new cassette boomboxes.

[@notthatdigusted7468]

LOL

[@reoman98]

I find this superior because while it is crusty it still can be worked on. Stuff today seems like glued together junk with some surface mount components. The glue is usually stronger than the plastic.

[@attilarivera]

i agree

[@robinsattahip2376]

Yea, at least it's a real radio with IF stages and not a radio on a chip.

[@ocotillo8291]

I cannot get over that they just blobbed solder on the letter "O" in Funny radio MODEL. Classy

[@1marcelfilms]

sloppy O's

[@annaplojharova1400]

The thing was most likely soldered by "partial wave" - soldering iron with big blob of solder was just swiped over a group of joints to solder them at once. When solder masks weren't used, it tends to do cover such "o's" by the solder. Same way as dip or the later wave soldering.

[@jeffreyhickman3871]

I really like this. It looks a little like a waffle. Takes me back to my childhood years. The speaker is permanent magnet. Your friend, Jeff.

[@donsurlylyte]

mmmmmmm waffles

[@williamstevens7090]

Hanging cardboard cutouts on vintage radio = retrochads

[@johnnytacokleinschmidt515]

"Here we have..."

[@poduck2]

Lots of these old transistor radios have transistors as diodes.

[@5roundsrapid263]

I remember seeing Lasonic brand radios in discount stores back in the ‘80s and early ‘90s. They really were bargain basement, but worked.

[@BigDaddy_MRI]

I can’t even tell you how much I enjoy your videos!!! I like them because we think alike. Why did they do it this way? Lazy, Plastic, junk that might work after fixing it, but, what ever. It keeps you busy, and all of us entertained. Keep on keeping on!!

[@Tobinindustrial]

Always nice to see these retro radios. I just love the old school stuff. I have a variety of old school radios. I just display them in my shed. Thanks for posting.

[@robinsattahip2376]

Love the "Funny Electronics" on the board, even they know it.

[@chetpomeroy1399]

Shango needs to head east to the desert and give this quality receiver a good sensitivity test.

[@glenncerny8403]

Some little girl from 1969 is wondering what ever happened to that cute yellow radio she used to have.

[@1964corvan]

no..... she died in a car crash back in '87

[@watershed44]

@Glenn Cerny Marsha Brady wants her radio back...lol

[@Funwithhighnotes]

“The hell with it let’s fix the damn thing. I wanna see this happy times electronic company very nice sunshine radio very good work” 😂😂😂

[@cttv90108]

I wonder if the same people made the large cheap boom boxes in the 80s, branded Lasonic as one word.

[@danieldaniels7571]

I was wondering that myself.

[@dougbrowning82]

LASONiC is an American brand of electronics made by Yung Fu Electronic Appliances of Tainan City, Taiwan. Their American import division, Lasonic Electronics Corporation, is based in Irwindale, CA. I can't find anything on LaSonic, or Funny Electonics Co., based in Hong Kong.

[@Seiskid]

I love that they used a whole one screw to attach the tuning cap.

[@Santor-]

Looks like a solder-yourself radio kit my dad gave me in late 70's. Minus the enclosure. Soldering looked similar too. Lol

[@FireandFrostHVAC]

Stupid mistakes are sometimes the best teachers (don’t ask me how I know that...). It’s amazing that you can even get something like that to work. Great video!

[@robertgeary7520]

Video was great. That radio looks like something you would get from grant's in the late 60's

[@volvo09]

Wonder if they had powder blue ones..

[@chetpomeroy1399]

Come to think of it, that cheap radio *does* look like something W.T. Grant & Co. would have had in their electronics department.

[@Steveuk405]

I sent one to my Girlfriend in Ohio. She said she wanted it! They all have basically the same board. Even when it is turned off part of it will be live. Risky by today's standards but they do sound good. Who needs a Zenith when you can use Funny Electronics?

[@reo52]

24:59 Alexander Borodin ... String Quartet No. 2 in D major, 3rd movement This music was used in the musical Kismet for the song, And This Is My Beloved.

[@Torogol85]

Thank you very much for sharing your quest with us Sir. This surprising lesson about audio output transistors is priceless!

[@garp32]

Yay! a triple header weekend! Love the genuine simulated plastic yellow pleather.

[@8080pc]

As a young boy I would have thought of that radio as gold. I'm surprised that I didn't become a radio DJ when I got older.

[@Nick215NY]

This is just amazing. "Funny Electronics". Just awesome. Shango's diagnostic skills are spectacular...

[@pcno2832]

Even when I was a kid, the "Battery or Electric" designation seemed a little silly, as if batteries were not electric.

[@matthiasmartin1975]

Which reminds me of the "metal versus aluminum" thing. Boggles the mind, especially when it comes from otherwise very knowledgeable persons like a certain Mr Carlson.

[@wurlitzergroup]

How about the coin counters in the supermarkets that advertise "Turn Your Change Into Cash", LOL, as if coins are not cash :-)

[@danieldaniels7571]

Right up there with “available as digital and DVD” as of DVDs aren’t digital.

[@joseppuig925]

The video exceeds the value of what's being video'ed. Btw, that resistor biasing through the speaker is a too simple bootstrap connection. It uses the ac signal of the speaker to artificially increase the drive of the power transistor. It ends up delivering a few more milliwatts of power to the speaker, which using such a low voltage supply can be of help. More elaborated desings use a resistor network and an extra capacitor to do the bootstrap and avoid passing dc through the speaker (and avoid the circuit to go unbiased if the speaker is disconnected or the user inserts a crystal earphone).

[@jwl9286]

Darn you're human! Still you're videos are my favotites. The thing is you always figure it out. Wave64 and Michael Robertsons comments gave it even more impact! "Bootstrapping" Hope you never get tired of doing this, cuzz I love em.

[@burntoutelectronics]

G'day from Australia

[@tedbell4416]

Gday mate

[@channelsixtysix066]

Subscribed, Mate. From Adelaide.

[@pyeltd.5457]

Ello govner

[@johnwsimpson3153]

I just about quit watching in the first minute, but each minute thereafter got more fun (and interesting) than the one before. Well done!

[@bobwigg761]

I can swear I remember LaSonic branded Boom Boxes in the early ‘80s. They were huge, but not too sure the build quality was.

[@watershed44]

I remember LaSonic too...early mid 80s

[@danieldaniels7571]

Big with loads of extra LEDs and text that meant nothing. Big, gaudy, and very low quality. They had the look people in the hood wanted, though.

[@kennynvake4hve584]

You 100% blow me away at how you can fix things..........I look at the screen and say WOW...

[@albear972]

Ooooooh! A LA Sonic! I bet that brand is more better than Sorny, Magnetbox or Panaphonics.

[@38911bytefree]

LOL .... here we got in the 90s: Panasoanic (using the Panasonic Font), SQNY, of course using the Sony FONT.

[@genethemachine7169]

I know a genuine Panaphonics when I see it!

[@johnnytacokleinschmidt515]

@@38911bytefree Really?!! What country? That's nuts. My uncle who was a machinist in the heyday USA said that (I think he said Japan) Japan had a region they called Usa... "Ooohsah" That way they could stamp "MADE IN USA"

[@manuelvillanueva3753]

Theres were also names like "PANASONIA" made in HongKong and "PANASANYO" made in Indonesia..

[@johngalt7382]

A Kelrcotwinqulated Sonyo, oh sorry Malulated in this case

[@brianfletcher9774]

Thank You Shango for making these videos. You should be on TV. I watch (and-rewatch) your videos, so my TV gets less mileage than my iPad.

[@stirlingschmidt6325]

'The Sounds of Love' - is this K-TEL? Gotta LOVE IT!

[@watershed44]

MSFB T.S.O.P.

[@tommyb.6064]

I have to setup a bench one day and start fixing those basic electronics. Thanks for letting us learn with you!

[@gabevee3]

Those two transistors in front of the audio output transistors are bias "diodes" for the output transistors.

[@chrisa2735-h3z]

I do love the cheesy woodgrain and yellow with chrome combination That is such a 60s look!I’m kind of sad because On ebay I could not find any radios like this radio!

[@gerardcarriera7052]

Sometimes the junkiest radios will surprise you with superb sound and DXING.

[@jeffscomp]

Lasonic was famous for their giant boomboxes in 80’s

[@Oldbmwr100rs]

I saw them sold out of white vans at flea markets! They were big, lots of plastic and colors, and probably little more than a simple radio and cheap walkman knock off tape transport. You don't see those around any more, not that you saw anyone actually buy them in the first place.

[@watershed44]

*I swear this radio was a prop sitting in the bedroom of the Brady Bunch girls!*

[@clemstevenson]

Historically speaking, selling a radio with a needlessly large number of transistors in it made sense to purchasers in the late sixties. Transistors were much more expensive items at the time, whilst being an unknown technological factor to much of the general public.

[@helioshaul3924]

State of the Art Quality Radio you lucky thing.

[@wrnchhead76]

I have watched hundreds of hours of Shango, and this circuit board has to be the most dogs**t POS I have ever seen!

[@tedbell4416]

Great video as always Mr Shingo

[@pyeltd.5457]

Tango

[@mrbyamile6973]

Shanghai

[@randyab9go188]

Thinking about the bias circuit I wonder if the engineer was actually more clever than initially thought. Since the speaker is in series with the bias Network, when you would plug in an earphone (which is usually a higher DC resistance than the speaker) could the change be a primitive power saving function? It would definitely reduce the bias and the output stage would draw less quiescent and active current when using the earphone. If this is truly what the engineer was thinking he's pretty damn clever.

[@Lifeless11111]

hmm yea ... i didnt see the headphone jack on it... is that the "Z" symbol below the speaker on schematic?

[@westelaudio943]

For Class AB it should be biased at the bottom of the transistors' linear region, no matter the load. So this doesn't really explain it, and it probably only works with low impedance headphones because of this. Maybe it's really just for NFB.

[@RobertLeyland]

I was thinking it was for negative feedback.

[@cool386vintagetechnology6]

It’s a bootstrap circuit, standard with complementary symmetry output stages. It effectively increases the voltage to the driver stage by adding the speaker voltage in series with the supply. This allows the driver transistor to swing over a greater amplitude.

[@charlesstauffer6806]

A gem in the rough! Actually a nice radio!

[@M0XFXUK]

Shango cardboard covered in pvc boxed radio's were all the rage in the 70's. they were cheap and they worked reasonably well hence why they were popular. Crappy yes I certainly do admit, but the price point put them in reach of low income families. You really cant knock them that much. Competition is a good thing, well i think so anyway. Love the channel keep up the good work.

[@tgheretford]

Love Sounds is the sort of music I expect to hear from Pages from Ceefax when the BBC broadcast that for decades.

[@craignehring]

Nice going shango066 Yeah, what a strange circuit. Funny Electronics is right Looks oh so pretty in sunshine yellow

[@swrzesinski]

20:08 funny electronics at full glance 🙂 What a funny way to get power to the transistors 😆

[@michaelrobertson575]

As far as I know there are two ways of arranging a Bootstrap Circuit for an Audio Power Amplifier and this is the cheaper one which involves passing a little bit of direct current through the Loudspeaker and it's quite conventional. I have never seen Transistors used as Rectifier Diodes for the Mains P.S.U. before though.

[@highpath4776]

I would probably take the mains out completely and just keep it as a battery one

[@NY411Info]

Yeah , I had 2 of them. Cassette player boom box. They worked fine and had better sound then all of the name brand boom boxes of the 80's and were less money. 1 of mine was the 6.5" speakers and the other 1 had 8" speakers. Both had 2 " tweeters. The specs. said 50watt per channel, all lies. The bigger one I tested, actual power without distortion was 7-9 watts per channel. 15 watts per channel maximum with full distortion. It still sounded good and was loud. Makes sense, big speakers. I believe Yung Fu Electronics made them at point in time. I still have the bigger one and it works. The smaller one was louder and had better sound quality with better Bass and better Highs. Never tested power output on that. Specs in the book were the same 50w X 2. I have a feeling it put out more power than the bigger LaSonic.

[@macgvrs]

Shango, you got upset about your mistake but many would have made that same mistake, and, probably wouldn't have figured out what they did wrong. One thing you can say about that radio. It may be cheap but it is still working after all this time. That is not bad.

[@johnnytacokleinschmidt515]

That works fairly well! Good lessons for me. I'm guessing someone who bought that at the check-out line at the grocery or pharmacy might have been satisfied if they all worked like yours.

[@frostedlc1082]

I want to learn where to find love sounds!

[@johnnytacokleinschmidt515]

I have to make my own...

[@wurlitzergroup]

1-900-YOU-LOVE

[@dayleedwards3521]

These cheap radios were a masterpiece of brilliant design , using every fudge and method to cut costs. The circuitry was fluid enough to use any and all components that were available at that time. These output stages were very common, the bias from the speaker also applied NFB to the driver and used no extra parts. The cost cutting was just an extension of the same economy with the earlier valved sets, thats why they all tend to be very similar in design.

[@Zickcermacity]

Nice to still see the 'S' in Sonic capitalized, as it should be! On later boomboxes, from the 1980s onward, it was "Lasonic". Assuming that was the same company

[@inventorkr1]

Like☝️

[@1blisslife]

Funny made circuits from a Funny company out of HK. Thanks for sharing your experience with this radio. Cheers 🙂

[@melockavich9596]

I like it no bad solder connections works good your to hard on the little thing

[@CLUBNEON-m6i]

Lasonic was around at least till early to mid 90s, but manufacturing in Korea as oposed to Hong Kong. I had a Lasonic HD2000 black and white portable from 1991 and it worked quite decent (for what it was).

[@raymondleggs5508]

"We'll never know if that one was shorted, because it fell apart when I took it out" 😂

[@MsCori76]

Cheesy crusty radio. LOL 😂 Laughed my arse off when I actually read "Funny Electronics" on the circuit board..........Priceless!

[@h7qvi]

R1 feedback bootstrap makes its ac impedance much higher. Check that the voltage at the output emitters is mid supply, and adjust that lower dc feedback resistor if needed.

[@bluepen61]

My Realtone AM-FM has a similar schematic I think. Thank you for explaining this.

[@radiofm7694]

I literally laughed down to earth when you say 'happy electronic' instead of funny!!

[@td3993]

The stuff on the right of the schematic is push-pull audio. Prob has a pnp and npn transistor working in the output.

[@barryfairwood2174]

Great Job. BUT Tecsun, may not sell too many new radios after you show how to give life to old junker radios. Keep up the good work!

[@RestorationAustralia]

Very cool vintage well done.

[@angryshoebox]

1968 or '69 sounds about right for that radio, given how it looks. It's an el cheapo portable radio of its era, I could see it costing like $7.99 at TG & Y, or someplace like that.

[@grege6287]

The yellow carry handle and vinyl case look to be the same as on the black "Vintage Ross Transistor Radio Repair" done two months ago.

[@qrplife]

Did you say “hanging chads” ?

[@JUANKERR2000]

What some of my fellow electronics hobbyists referred to as 'Hong Kong Horrors' back in the 1960s, they looked as though the assembly method was to fire a blunderbuss filled with components as a bare PCB and just solder up the result.

[@KC4RAE]

Where are you getting this music? I love it!

[@paulp2089]

Looks like two dry joints on the PCB between the speaker terminals and the tuning cap. The wire are through the holes and bent over, maybe soldered, but appear the be very poorly done.

[@studioA.G.T.]

Indeed, Nothing But the Best

[@a587g]

I think Funny Electronics is still around, I believe they made some stuff for NAD in the 80's or 90's. They're one of many contract manufacturers where essentially a marketing company will ask them to build a radio to go in the cabinet they've designed. Bright yellow seemed to be popular for radios in the late 60's, I've got a vertical FM/AM portable marked "Douglas" also in bright yellow, laying around here somewhere. Made in Japan though.

[@missyd0g2]

Looks like one cheesie gizmo from Hong Kong or beyond. Still enjoyed your video.

[@crbielert]

Much Funny, Lot Quality!

[@leonardgoldberg2879]

This radio would have looked great on the set of 'Trailer Park Boys'.

[@sonsofthunder915]

Funny Electronics, duh. I laughed my arse off as soon as you opened that huge case and I saw that tiny board in there with the cheap components sloppily soldered onto it.

[@randyab9go188]

You obviously never opened a late model console color television set with a CRT. At the very end of production the printed circuit boards were so small some were little larger than a paperback book.

[@randyab9go188]

You obviously never opened a late model console color television set with a CRT. At the very end of production the printed circuit boards were so small some were little larger than a oversize paperback book.

[@sonsofthunder915]

@@randyab9go188 Yes I have opened "late model" television console sets that contained CTR's. So, I have no idea how you're finding a thing "obvious". You're merely assuming I haven't. And. you've made a huge mistake by doing so. The difference is those television sets didn't carry the brand name of "Funny Electronics".

[@Rev22-21]

Ya know they could have just as easily called it "Funny ha ha electronics"........and who would have known any difference?

[@jonathaneastwood2927]

Funny electronics incorporated 1970 Disolved 1997

[@Graham-ce2yk]

I'd love to see a cleaned up version of that schematic with the component values added. Any chance? And did you find out what (if anything) was wrong with the mains transformer, after all there was a reason that power cord was cut?

[@hotpuppy1]

Probably nothing wrong with it. The cutoff cord is worth more as scrap copper than the entire radio.

[@Antony_Jenner]

I just love that Gruen Amp meter, It's got soul...

[@horizonr639]

Are you a electronic engineer? How have you learned all of these?

[@youtubetv7000]

SUPER

[@vitajazz]

My first solid state shortwave radio was a massive multiband thing with FM, shortwave, and aircraft, I forget the brand, I believe it was indeed Sonic-something, but what will always stick in my memory is that it was made by "Funny Electronics." And yes, it was very sloppily built, but after alignment worked quite well. I believe, by some convoluted path, its manufacturing facilities became part of Samsung. There were a LOT of radios made by Funny in the 1970s, they could be bought very cheaply in bargain stores. And yes, I've seen transistors used as diodes or rectifiers before in consumer electronics.

[@tntreviews3602]

I HAVE A FISHER MO MC 4050 STEREO THE POWERSUPLLY WENT OUT DO U HAVE ANY IDEAL THE STEPS ON IT?

[@RonaldDaub-g7z]

It's what grandmother bought a teenager for birthday when they didn't know what else to get

[@GoldSrc_]

That's some old flux crust. Reminds me of when I started to learn how to solder lol.

[@johnnytacokleinschmidt515]

I am. Just now. At a half century. Cleaning up my flux after soldering. Sweating a plumbing or HVAC joint you wipe it good because it will corrode over years.... But the electronics? Nah! I'm a little slow. But I'm picking up speed on the downhill.

[@ryanpascual9598]

Can someone tell me the title of the music at 18:36?

[@mikemcmanus3918]

Hello, enjoy the Lasonic radio surgery. How do the Russian "Sokol" radios compare ? I had a Nordmende portable "Globe Traveler" portable that finally died.

[@ajl9491]

Luscious solder excess!

[@danytoob]

Yo Shango ... Just a FYI ... you got a nice shout-out from Mr. Carlson's Lab. Paul speaks quite highly of you.

[@rfburns5601]

Yep its Funny Electronics - jokes on you yankee! - hahahahaha! I ran into this problem once on an old Advent Videobeam that was in the student union building. They told me the speaker was blown. I knew it was blown - measured open. That speaker had a humungus magnet on the back of it, and was certain there had to be an amp failure. So I troubleshot the amp all day to no avail - couldn't find any bad parts, but bias voltages were all wrong. Finally I connect a speaker and walah - damn thing works - bias voltages correct. Disconnected speaker - bias went bad. Then I realized the large speaker output cap has leakage current thru it that is ordinarily pulled to ground by an 8 ohm speaker. The no load voltage thru the feedback resistor mis-biased the outputs. I couldn't possibly fathom the idea that the students wuz rockin out to MTV. Its not Neg FB or bootstrapping - it protects speaker and outputs if speaker cap goes leaky. I think you'll find that if you cut that resistor ( listed under TR6) open, there would be little or no change in performance.

[@cipherthedemonlord8057]

Funny Electronics what an appropriate name.