Technics SH8025 Equalizer Troubleshooting part 1

Troubleshooting a Technics Equalizer with heavy distortion

[@RandallDibble]

I have one of these units. IT's great to see on the inside. My unit works great !

[@12voltvids]

The fun part will be the wait for the part. I found a bunch of them, but they all appear to be on the other side of the planet, in the UK of all places.

[@zx8401ztv]

Now that does look empty, and how cute does that tiny transformer look. I first thought the input/output coupling caps were bad, causes hell with bias. Hopefully the chip isn't "Unobtainium", never heard of that chip before. it's really nice when they lay the parts out in a symetrical way, like the riaa eq pre amplifiers.

[@pitsnake]

Hi Dave, You can replace those opamps TA75559 with UPC4570C which are much quieter and if you dont find it in SIP9, just try to build a mod circuit that uses sip-8 to dip-8, they sell pcbs on ebay for that purpose and dont worry about VEE, it should be moved from pin 5 (old) to pin 4.

[@mochs3869]

Yeah, what he said, lol (what'd he say??)

[@glenngoodale1709]

Your videos inspire me, thankyou for sharing

[@jhunc2776]

Is svd1s2076at still available in the market? What is the replacement for this diode? Can I use IN4148 diode as a replacement? Thanks for replying....

[@vibra64]

I love the smell of solder!!! You are right. None of this fancy solder crap.

[@12voltvids]

Then there is the small of burning skin when you slip with the iron. Oh yes, it hurts too!

[@MrHBSoftware]

i clean the tip of the iron on my jeans now thats badass :) . have you tried to blow solder out of the pins by heating and blowing into it with a straw?it works amazingly well..just have to clean the mess afterwards

[@12voltvids]

I used to clean the soldering iron using either my bare fingers. Now THAT is bad ass. I will do it on a future one to watch people cringe. Why use a straw to blow solder out, Get get close enough to kiss the board and let fly. I am sure I have some shots of me doing just that, but they got edited out.

[@abc-ni9uw]

Sg-9800 hard to find like sa9800 stereo amplifier

[@johnohara54]

Haven’t watched the end of video yet but with those dc reference voltages you got, I would bet some pin-to-pin resistance readings will show some shorts in this IC. Real quickly, pin1 and 2 referenced to 7 and 8, 3 and4 , 5 and 6 ,, then 2 and 3 simultaneously to 2 pins will find a hard short real quick. Back to video to see if I am right.

[@victorcoss2600]

Awesome stuff, curious what do you think caused that IC to go bad?

[@12voltvids]

Could be anything. Overloaded input possibly, or it just failed.

[@jp040759]

What brand of solder wick did you use here? It sure does work well and fast. I need to get some good stuff. Thanx in advance.

[@finscreenname]

Did you ever finish this? If anyone has parts to this I need a face plate. Everything is fading on the front of mine.

[@quasarhi]

got one of those ! thanks for posting !

[@JIMO415]

Hello, that EQ looks similar to mine but without the VFD spectrum analyzer. Also, I appreciate your teaching format. You have a great talent. Just curious, can you share with me how you get your schematics for your various repairs. Is it just a google search or do you have a source? Thank you.

[@victorcoss2600]

Google or something like HiFi Engine for audio equipment.

[@12voltvids]

That one came from hi fi engine. I just do a google.

[@crashbandicoot4everr]

JIMO415 freeservicemanuals.info is a nice website too.

[@Luke-san]

I love those displays ... seems when I was younger I would buy devices for those things.

[@JIMO415]

thank you!

[@God-CDXX]

I built 2 small mod boards to use TL072CP much quieter and the chips are only $2 for 10 pcs on EBay

[@stphinkle]

It appears that that IC was originally made by Toshiba and is a discontinued part and appears to be quite rare. Maybe you could find a current production one with similar specs that would work.

[@12voltvids]

Stephen Hinkle Lots available out of the UK. Under 10 bucks.

[@stphinkle]

12voltvids that is good news.

[@Luke-san]

Why not use like a TL072 or so. Plenty of those types in my drawer and cost next to nothing. Bet you won't hear the difference and if you hear the difference use for both channels. Some small wires and a bit of hot glue and ready to go.

[@chris7662]

I'm a carpenter...what the heck is an IC?

[@ronwaasdorp4581]

Where do you get the schematics?

[@12voltvids]

Usually hifi engine.

[@Synthematix]

Holy shit, look at that bare live wiring about 5mm away from the frame, now thats fucking bad. id have to heatshrink that at least

[@12voltvids]

What bare live wire? The one on the switch or the one on the convenience outlet? They are mounted to the cabinet, and 120 v is not going to jump that space. That is how they built them.

[@Synthematix]

Really? wow suppose this was built before all the health and safety we have today

[@12voltvids]

Synthematix We used to have hot chassis remember. That would never fly today.

[@God-CDXX]

I like hot chassis amps much liter I am building one as we speak 4 25BQ6 1 12at7 the 12at7 heater is the mane cathode resistor for the 25BQ6 output tubes

[@God-CDXX]

when I first opened mine I exited half this much

[@God-CDXX]

( 10PCS IC TL072CP ) search this on EBay

[@craigstaggs8597]

FFs Technics not tequniques !! , do you say Panasonic or Panasonique ?.....

[@oldguy8177able]

refloat it

[@markanderson350]

Kinda boring, not much else can fail. You don't see EQs much anymore.

[@12voltvids]

Mark Anderson There is lots that can fail. Regulators can go capacitors can go bad and the front board with all the pots has a hand full of parts that can go bad. In this case it was a op amp that died.

[@markanderson350]

yes well I guess you are right. Just in general, these are easy to troubleshoot.