... There is a heat-sinked transistor labeled IC 701 ... or something like that.
That transistor seems to have an unusual appearance, maybe due to heat stress.
That one would be a good one to check.
... It is next to the one labeled IC 306.

Yeah I noticed this the first day I looked inside the unit. But I didn't have enough research knowledge to start removing stuff I did t know anything about. I better test the other one too. And just replace it.

 

Where is the best place to get these parts online? Suggestions on brands or aftermarket or OEM or what? I've never even touched a circuit board before this.

 

... I can't recommend a place to make any purchases, but the use of Solder-Wick desoldering tape
is very useful for removing melted solder ... capillary action draws the solder into the woven tape copper mesh. A product called liquid solder flux comes in a small bottle usually and seems to make desoldering and soldering go more smoothly ... better heat distribution maybe.
And usually a compound called heat sink grease or paste is applied in a small amount to the back of the component, actually on the heat sink surface, so that there is improved heat flow between the component and the heat sink. ... Don't forget a soldering iron of some sort, and maybe a roll of solder.

 

DigiKey or Tayda are good US suppliers. You can't test regulators the same as transistors.

 

Farnells, Digikey, Mouser..RS. are good suppliers, if the regulator has gone check the other one too, it might be a 7912..

 

... SamR is correct. That burned looking part isn't necessarily a transistor. See if it is located near the AC/DC rectifier section. ... Try to follow the traces to nearby parts. Any markings have likely disappeared. See if there is a KLH interest group or forum some place.
... I owned a KLH portable record player at one time. ... Very high quality sound for the 1960's.

 

... SamR is correct. That burned looking part isn't necessarily a transistor. See if it is located near the AC/DC rectifier section. ... Try to follow the traces to nearby parts. Any markings have likely disappeared. See if there is a KLH interest group or forum some place.
... I owned a KLH portable record player at one time. ... Very high quality sound for the 1960's.

I have a soldering iron and stuff. I do wish I had some of that mesh tape to remove solder. I made a solder sucker out of a baby nasal sucker bulb and a brass fitting. It didntbwork all that well tho...lol. I have some MX thermal paste already from when I tried to fix my nintendo switch lite. That part says it is a voltage regulator. If it doesn't get tested the same as a transistor, then what is the procedure? It def looks like it's burnt up. And the solder connection s were loose. I have some resin core solder. Can I use flux that I have here already? It's called stay clean. It's paste soldering flux.

 

I found how to test it. I also have a voltage regulator on another board I have laying around that is the same part number! Guess I'll rig up a power supply and do some testing.

 

Well I put 19VDC to it and it drops it down to 11.6 volts. Is that what it is supposed to be?

 

Don't know without a circuit diagram... Sounds like a weak 12V regulator.

 

The other regulator tests the same. 11.6 volt output. Dammit. Going to put the new one in anyways. And the transistors that are fine. And try something else I guess

 

Home made solder sucker.... Hey man. It works great!

 

Just a thought but low voltage means higher current which can burn things up. Really just pulling ideas out of thin air without a circuit diagram...

 

Just a thought but low voltage means higher current which can burn things up. Really just pulling ideas out of thin air without a circuit diagram...
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Yeah I know. It sucks. I'm going to remove and test the main transistor drivers. The one with the smoked resistor is connected to the opposite one that has that slightly toasty resistor. I guess I'll just start going through stuff.

 

I pulled out Q301. Which is the transistor right by the blown resistor. And it is dead shorted across all terminals no matter how you configure the test leads. It goes to . 0000 on diode test. And. 4 ohm on normal resistance. Test. So now did I figure it out? I pulled out Q302 also. And it reads normally. It is a pnp. Toshiba # 2SA1943

 

I ordered all 4 new transistors, resistors to replace the burnt up ones, solder flux, a sucker gun and wick tape, and more solder. Be here next week. Thank you guys for the help. I'll post up the results after I change the parts out.

 

OK, seems you found the bad parts. Now, what caused them to fail and will it happen with the new parts? You might want to consider some fuse protection.

 

OK, seems you found the bad parts. Now, what caused them to fail and will it happen with the new parts? You might want to consider some fuse protection.

Well if I play by that logic then I have to replace every part in the stupid thing. I've checked every damn thing in there that I can think of. The parts were all of 10 dollars. There are fuses in it. All I can do is start with this stuff and see what happens. With no schematic I'm kinda stuck. What would you suggest I check to see what caused the transistor to fail? Do they not just go bad from use or blasting the speakers? This thing is 20 years old. I found it in my mom's attic. It's had probably been up there for 5. I'll check whatever y'all can suggest me to check. It seems to me that the burnt resistor acts as a fuse for each transistor and protects the board.

 

Short of soldering in the good transistor and resistor where the failed one was and see if it smokes it, I'm out of ideas.

 

Take a close look at each electrolytic capacitor. Those are the large, black, cylindrical ones. ... not the small, ceramic ones. They are prone to failure when they age. It is difficult to tell visually if one of them is bad. The only sure way is desolder each one and test it. ... Any sign of leakage, maybe a discoloration next to the capacitor would be a clue, but the only sure way is to desolder and check.
Checking usually requires a capacitance measuring meter.
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