Technics SAGX690 One Channel Cuts Out Intermittently

[@seanjones618]

I have the same receiver I’ve had it since 94. I love it I’ve actually bought other ones since but I always ended up going back to that one

[@tylerlloydboone]

Technics made decent stuff. Newer subscriber here. Digging the channel. Keep it up

[@AstrosElectronicsLab]

Love the technical "let's see if this fixes it", bash the top of it with your hand! 🤣I do that all the time. Lol, I know what you were doing (bad solder joints possibly, maybe a jolt will restore sound).

[@monz7951]

Lol yeah I love his method of no bs repairs, straight to the point and it works. I diagnosed and fixed an expensive bass amp two techs had already given up on the same way, crappy lead free solder joints

[@12voltvids]

Every shop does this. Customers would be freaking out if they knew how their equipment was treated. Why do you think shops would not allow customers in the back and if they were hanging around wouldn't work on their stuff till they left. Even if we weren't busy we never started on something until the customer left. Otherwise they would be strolling into the back to watch.

[@FlingwingNZ]

Hehehehe.... The 'give it the bash' test .... Truly old school. Love it... 👍

[@douglashoff95]

Obviously Panasonic was thinking ahead by anticipating need to access the STK modules for resoldering or replacement. Too bad more manufacturers don't make their products serviceable like that. But that brings us back to cost cutting. Save a few cents and make it more difficult to service.

[@mmichaelnowell1512]

I had the SA-EX320 That was the best little receiver I ever had,it lasted 25 years, not one problem sold it last year for $125.00, guy contacted me! Said that little receiver works excellent!, have all of my panasonic vcrs & dvd player!

[@jeffadams5510]

Been there done that many times. :)

[@stereomann83]

I think that receiver is from the mid 90's i had a Cassette Deck TR 373 that had the same design. i think most of the receivers used a fan for cooling. luckily that was an easy repair that you could get at easily. too bad the whole bottom cover doesn't come off.

[@simplerick3851]

My technics also cuts out on one channel. Flipped it over and sure enough it has a removable panel... Now if I only knew what I was doing.. 😮

[@m9ovich785]

HAHAHAHAHAHA Love "BAM, BAM" testing. Thanks Dave....

[@markmarkofkane8167]

I like to guess before watching. Bad solder joint or transistor. I am fascinated by learning and watching.

[@staszeksowikowski9039]

Hey, is the "class H" just a different name for what Technics used to call "New class A" or is it a different thing entirely? I got a SA-GX550 and that unit runs pretty hot, no wonder the connections go bad on the power amp boards on these.

[@peterlarkin762]

New Class A was different to Class H. Class H is like class AB, but also has two power rails switching to the higher voltage rail when output demands more power. New class A is class AB, plus the bias intermittently turns the outputs on just as they begin to turn off as the wave swings. Same with Class AA, except there the bias varied via the feedback loop. Class AB amps can vary a LOT in terms of biasing and other circuitry, and can sound like Class A in terms of harmonics. P.S. if yours is running worryingly hot, open it up and make sure it's not caked in dust and tighten up any output devices attached to the heatsinks.

[@staszeksowikowski9039]

@@peterlarkin762 Thanks for the explaination. I have serviced my unit and replaced the thermal compound on the main heatsink as well as repaired my faulty fan drive. The inoperable fan was causing it to cut out the sound (protection). I think these units just run hot with the limited vents on top.

[@12voltvids]

New class A is the same as sonys legato linear and Yamaha natural sound. Its a class ab amp that increases the bias at low levels to keep the outputs from going into cut off. So both the npn and pnp are kept biased hot. The bias lowers as the signal level increases. At about 9 watts the amplifier is working as a full class ab. Class h is a dual rail design. Low vilrage high current and higher voltage lower current reserve for quick transients that would cause clipping. By lower current I am referring to the capacitor reserve. Might use 70,000uf for the +- 50 volt rail and 6800uf for the +-80v rail because it is only switched in momentarily as needed and the majority of the current is from the low voltage rail.

[@jiml20]

Why don't people ever remove the old solder and then apply new instead of reflowing sometimes you will get excessive solder and cause Bridges?

[@12voltvids]

Only if you don't know how to solder. Experts don't bridge and if it happens its easy to remove.

[@jiml20]

@@12voltvids thanks for the reply I will assume the mixing of the old and new solder will not have any ill effects. Thanks for these informative videos

[@Mihail_K.]

@@jiml20 Yeah, not any side effects. It's just old cracked (sometimes lead free) solder. A bit of fresh solder and it's good for as long as something else fails. On some 90s TVs I've seen bad factory soldering where they didn't use enough flux and you have to redo joints with lots of flux or even removing the old solder and scraping the component leads, but that's really rare.

[@helpaholic]

So in the end, it looks like you were soldering every other one or everyone, but you never did explain why or what it looks like when there’s something wrong with it in terms of the solder I couldn’t really tell

[@HearTbeat_999]

The “L” is silent in the word solder ( “sodder”) … I’m just saying 😂

[@gower1973]

Only in America its silent the rest of Empire speaks the proper English

[@12voltvids]

Thats an american thing. Thats ok you pronounce many words incorrectly.

[@tharkthax3960]

😂

[@helpaholic]

So he smokes in the garage with the equipment, but not in his house.

[@12voltvids]

Did I say that? No, I said there is evidence of this unit being in a smoky environment. The fella actually bought it for 40.00 for his garage. The previous owner likely smoked.