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Phono Board SX-737

I appreciate everyone’s help. If anyone has a nice tutorial or video on how to read transistor schematics and install them correctly, feel free to link it. I’m going to go reevaluate and figure out why I was so confidentially wrong.
 
If you like, start with this thread and read everything at post #2 carefully,
P

Post in thread 'Step by Step work and rebuild on a SX-737, done by a newbie'

1. Basics, tools and how to start

Let’s start with the work, but always keep in mind, I had the second SX-737 sitting next, as a kind of master copy if I run into problems and needed a recheck.

Tools used beside the standard soldering stuff:
· DBT
· I use 4 DMM (very helpful when adjusting Offset and bias at the same time), a decent digital meter should have a diode test function
· Smartphone, to take hundreds of pictures, mainly before and during the work, MACRO function is quite handy
· LCR tester mega 328 (my every time saver if I need to...
 
pa_200 said:
If you like, start with this thread and read everything at post #2 carefully,
P

Post in thread 'Step by Step work and rebuild on a SX-737, done by a newbie'

1. Basics, tools and how to start

Let’s start with the work, but always keep in mind, I had the second SX-737 sitting next, as a kind of master copy if I run into problems and needed a recheck.

Tools used beside the standard soldering stuff:
· DBT
· I use 4 DMM (very helpful when adjusting Offset and bias at the same time), a decent digital meter should have a diode test function
· Smartphone, to take hundreds of pictures, mainly before and during the work, MACRO function is quite handy
· LCR tester mega 328 (my every time saver if I need to...
Click to expand...
I appreciate it. I wish I would’ve found this forum 48 hours ago.
 
jmmani2 said:
I appreciate everyone’s help. If anyone has a nice tutorial or video on how to read transistor schematics and install them correctly, feel free to link it. I’m going to go reevaluate and figure out why I was so confidentially wrong.
Click to expand...
you were shown pinouts. i explained the symbol. you were told to look at datasheets.

what else is there?

just apply yourself. it takes time.
 
The base on the circuit board diagram runs straight into the circle and hits a wall, the emitter always has the small arrow and is at an angle.

The collector is just a line at an angle, never an arrow.

Screenshot (1411).png
 
Last edited:
painttoad said:
you were shown pinouts. i explained the symbol. you were told to look at datasheets.

what else is there?

just apply yourself. it takes time.
Click to expand...
Yes sir. I’ve clearly misunderstood something along the way. I even had instructions with a diagram from the seller. Like I said, I grossly misinterpreted something. Just trying to go at it a different way before I remove these misplaced transistors and try again with new ones. I really do appreciate all the help.
 
Between the advice, the step by step guide thread, the diagrams, the photos, and the words of encouragement, I think I’ve got what I need to keep learning and try this again once my new transistors come in. I’ll send pictures before I solder them into place.

Again, thank you everyone for all the help. I’ve never done anything quite like this, so it was awesome to have a community so willing to jump in and give constructive advice. Much appreciated!
 
jmmani2 said:
Is this mark up an accurate label of what you’re describing?
View attachment 3831780
Click to expand...
yes.

these 3 transistors IMG_8783.jpeg
will install in this directionIMG_8797.jpeg

these 3 transistorsIMG_8794.jpeg
will install in this directionIMG_8797.jpeg

can you follow that?

in this situation, i put a little kink in my leads instead of bending the collector like you did. don't feel bad, ALOT of people just flex the leads and cram it in the hole. i've done it. i will probably do it again. it just makes for a nicer job like this.


20260906_222341.jpg20260906_222355.jpg
 
painttoad said:
yes.

these 3 transistors View attachment 3831792
will install in this directionView attachment 3831793

these 3 transistorsView attachment 3831795
will install in this directionView attachment 3831796

can you follow that?

in this situation, i put a little kink in my leads instead of bending the collector like you did. don't feel bad, ALOT of people just flex the leads and cram it in the hole. i've done it. i will probably do it again. it just makes for a nicer job like this.


View attachment 3831798View attachment 3831799
Click to expand...
Super helpful. Thanks for taking the extra time. I don’t know what had my thinking off, but tonight while reviewing your pic from earlier, something clicked and I realized the issue. Feel like a dummy now, but that’s how it goes sometimes.

Great tip about the kink in the transistors also!
 
painttoad said:
it happens. just gotta shrug it off and move on. i do MUCH dumber stuff than this but i still take time to install a cap or transistor in backwards once or twice a year.

build a dim bulb tester if you plan to keep tinkering.
Click to expand...

About as easy as it gets if you have a Lowe's nearby.
 
painttoad said:
it happens. just gotta shrug it off and move on. i do MUCH dumber stuff than this but i still take time to install a cap or transistor in backwards once or twice a year.

build a dim bulb tester if you plan to keep tinkering.
Click to expand...
Thanks for the encouragement!
 
painttoad said:
it happens. just gotta shrug it off and move on. i do MUCH dumber stuff than this but i still take time to install a cap or transistor in backwards once or twice a year.

build a dim bulb tester if you plan to keep tinkering.
Click to expand...

Warning, kinda long story about my recent screwup!

I'm embarrassed at what I've done this last week. I've been trying to get my old CD Player working again. I'm not sure how it got in such disarray but I believe it started with a replacement belt that was too tight causing too much current through the IC that drives the motors, causing it to go bad. This IC is driven by opamps.

I messed up a couple of opamps by swapping from another location only to fry 1/2 of it. The IC it drove has 6 transistors in it and it checked fine on my meter just as 6 transistors would. I put it away for close to 10 years. Recently, I wanted to see if I could get it going. It fried another opamp. I figured out that if I removed the IC that it drives, the opamp would survive. I replaced the opamps and the IC that they drive. It was up and running, playing CDs perfectly. Then it stopped working.

I lost the 5 V power supply which comes from a 12V power supply. It popped an IC protector (fuse). I replaced it and it was working again. Shortly after, it popped that IC protector again. I decided to clip my meter across the leads in mA mode and see what kind of current draw there was. It came back to life and current draw was around 100mA iirc. Then It stopped working again. So I had 12V going to the open IC protector and I thought I was supplying 12V to section where 12V becomes 5V. I checked those transistors, diodes, resistors and they seem fine. After scratching my head for about a week, I decided to try a different meterto measure current draw. It came back to life! My meter popped a 250mA internal fuse! So at this point I'm thinking something is under the PCB causing a short. I lifted it out and replaced the IC protector but couldn't find anything shorted....until I was reassembling. I knew a ground wire was supposed to be under a screwhead. It was not there when I removed the screw! It was under the PCB causing an imtermittent short!

I really don't understand why the original IC was eating opamps. I think when it had voltage applied, it was breaking down and sending 12V to the output on the opamp, causing it to fail. When the opamp would fail, there was just under 12V output from the opamp causing the spindle motor to run like a bat out of hell when it should have been stopped.

Watchout for rouge wires!!
 
redk9258 said:
Watchout for rouge wires!!
Click to expand...

i can definitely one up you.....

pioneer sa-7100. i was replacing the across the line cap. i made sure my dbt was turned off. i even eyeballed the outlet and made sure the unit was not plugged in to the dbt.

i'm good. get one leg unsoldered. go at the other leg. WHOMP!!!!. my soldering iron touched the pins on the backside of the ac convienience outlets and blew a hole in the shaft of my iron.

my failure was that i did look another 12 inches past my dbt. had i done that, i would have clearly seen the unit plugged into the wall.

MAKE SURE THE UNIT IS UNPLUGGED! make sure you are awake. make sure you are not groggy.

i had tunnel vision. the wall outlet and dbt are in the same view. they are right there. how i did not see that cord plugged escapes me.

things could have ended up very differently if i held my iron like this chick

490324104_8936684426431317_6160856386277254546_n.jpg

note: do not hold your iron like this chick. :no:
 
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