Another transistor validation/condemnation - for a TEAC A2300SD this time

[62vauxhall]

I've had this deck for a while now and lugged it along when I moved. My thought was to part it out after I got here but instead, will give another go at making it work.

There is a 2SD288 transitor at position Q1 that is bad. I thought I could salvage one from a different board but it is bad too so I need to replace it with something. I have some MJE15032G's leftover from the Sony integrated I was helped with. It might be overkill but there do not seem to be specs below 2SD288 except for Transition Frequency - 30MHz comparted to 35MHz.



Does an MJE15032G look viable?




I hope this next bit makes sense.

The 2SD288 originally lay flat against the board, held down with a machine screw passing through the collector plate with nylon spacer washer and a mica sheet - all now long gone. If I am able to use an MJE15032G, any problem if it sticks straight up?

The 2SD288 was flush against PC board material, not a metal heatsink and the machine screw threaded into the deck's metal frame. As mentioned, the necessary mounting hardware is MIA so it woud be much easier if It could be left standing upright. Maybe an MJE15032G won't get as warm, not needing to dissipate as much heat as a 2SD288?

 

[mlucitt]

You can replace the 2SD288 with:
2SC1826, 2SC1985, 2SC1986, 2SC2075, 2SC2334, 2SC3179, 2SC3851, 2SC3851A, 2SC789, 2SD1267, 2SD1267A, 2SD1274, 2SD1274A, 2SD1274B, 2SD1355, 2SD1356, 2SD1407, 2SD1407A, 2SD1408, 2SD2059, 2SD2060, 2SD313, 2SD525, 2SD526, 2SD613, 2SD823, 2SD856, 2SD856A, 2SD857, 2SD857A, BD203, BD241A, BD241B, BD241C, BD243A, BD243B, BD243C, BD303, BD535, BD537, BD539A, BD539B, BD539C, BD797, BD799, BD801, BD807, BD809, BD935, BD935F, BD937, BD937F, BD939, BD939F, BD949, BD951, BD953, BDT81, BDT81F, BDT83, BDT83F, BDT85, BDT85F, BDX77, KSC2334, KSD1408, KSD288, KSD526, KTD2059 or KTD2060.

Do you have any of these?

 

[62vauxhall]

Helluva list, thanks for compiling it.

But I don't have any of them. Just went through what NPN's I do have and nada.

 

[mlucitt]

But I don't have any of them. Just went through what NPN's I do have and nada.

Then open this list up to the gathered masses, I'm sure someone out there has one of these (you just need one, right?).
Come on guys, help a feller out, won't cha?

 

[62vauxhall]

The 2SD288 was in the power supply and to satisfy curiosity I soldered in an MJE15032G in it's place. At this time, there are 24V present at a test point which was my objective. I don't know how it will do in the long run.

Despite that there is 24V coming off the power supply, the reel motors do not operate. I am in the process of trying to figure out how the power gets from the power supply to the "control board" with the relays. I may resort to posting that question on Tapeheads.

To me, this SD version of an A2300's power supply is harder to understand than a standard one. I guess because of all the Dolby encode/decode circuitry, TEAC had to change things around. Instead of being on it's own separate board, this one has the power supply incorporated onto what's called the Bias Oscillator board.

I have a hard enough time comprhending schematic diagrams as it is but it would have been nice if TEAC had some voltages printed on theirs.

 

[BlueCrab]

I would go ahead and try the MJE15032G. I think it should work just fine. This is not a critical circuit - just a standard voltage regulator. It will still dissipate the same heat as the 2SD288. It won't hurt to try. Just ensure you install it correctly and then check the voltage at the emitter and check the temperature over a period of time to see what happens. You could always add a simple heat sink if you feel it's necessary.

BTW - the photo shows those two resistors awfully close. Spread them a bit.

 

[Gepetto]

The 15032 is vast overkill for this lowly application. Correct move. And another POS Japanese transistor removed from the earth

 

[62vauxhall]

The board pictured (bias oscillator) is not the board presently in the deck. It was just handy for a photo-op.

The original board, the one in the photo, was badly wounded, from wire wound resistors burning up damaging traces and my attempts to repair that damage along with more damage caused by me taking direction from some Tapeheads member. That made me imagine I was being advised by someone who knew less than I do.

When I got the deck, the seller disclosed that it smoked. But it was cheap enough, to take a gamble. The smoke was from those wire wound resistors on the Bias Oscillator board. The upshot was me purchasing a used replacement board off e-bay.

So now several years later, the wirewound resistors don't incinerate, the power supply is producing 24 volts but no power is getting to the reel motors.

Ironically, with the original board in place, the reel motors did function in those few brief seconds before smoke began.