Do not confuse rectifier with transistor on the TO-220 package

 

Do not confuse rectifier with transistor on the TO-220 package

its Q907, says right on the front D2395. looked up datasheet. it tests bad. will TIP31a work as substitute?

 

Well, most of the specs look the same except for Ft; the 2SD2395 is 100MHz where the TIP31 is 3MHz - that's a heck of a big difference.

MCM electronics claims that the 2SD2396 is a replacement for the D2395;
http://www.mcmelectronics.com/product/2SD2396
$2.09/ea. I have not dealt with them before.
I have no idea if they have a minimum order amount.

The ROHM 2SD2396 has an Ft of 40MHz; but the gain is much higher than the 2396. I don't know if the potentially lower Vsat will make up for the lower Ft or not.
http://media.digikey.com/pdf/Data Sheets/Rohm PDFs/2sd2396.pdf

 

Looks like it left a little scar on the board, blow out the back instead of the front?

 

Looks like it left a little scar on the board, blow out the back instead of the front?

it looks that way, but its just dust. im not goona be able to afford a replacement this month, money is pretty tight. anyone have one or equivalent their willing to put in the mail? also, any other tests i can do to rule anything else out while i wait for a replacement?

 

The TIP 31 needs a lot of drive, it's built to be an output transistor for an amplifier, rather than a switch, so I don't think the circuit will switch it fully on as intended.

A TIP31 might work enough to see if the power supply issue was fixed, but not well enough for the amp to put out any amount of power. That's up to MrChips or RIFAA if they want to continue or wait until it is properly replaced.

 

I'm still waiting to hear back on my last tests. I have lost track of where you are now.

 

well i tried the tip31a just too see. didnt make any difference. so i guess i have to wait till i can find a direct replacement. anything i can do in the meantime?

 

Did you...

1. Cut that jumper?
2. Remove C908 and C925?
3. Replace Q905 and Q911?
4. Tested the signal at the right side of the cut jumper?

 

Did you...

1. Cut that jumper?
2. Remove C908 and C925?
3. Replace Q905 and Q911?
4. Tested the signal at the right side of the cut jumper?

yep, left side of jumper is on 10v per division 10uS. right side is .2v/div 10uS.

 

I'm still waiting to hear back on my last tests. I have lost track of where you are now.

q907 is the last transistor on the + output of the dc/dc converter. its emitter should have +15v. tested bad

 

yep, left side of jumper is on 10v per division 10uS. right side is .2v/div 10uS.

You are confusing me here.

With the jumper cut, Q907, C908 and C925 all removed, what is the DC voltage reading (using DVM) on the RIGHT side of the jumper and the scope picture (no need to post photo, just describe it and height)?

 

You are confusing me here.

With the jumper cut, Q907, C908 and C925 all removed, what is the DC voltage reading (using DVM) on the RIGHT side of the jumper and the scope picture (no need to post photo, just describe it and height)?

this is what im doing. q907 is on the heatsink removed. didnt get the reading on camera on the one pic. the waveform is on post #110. i forgot to turn off power after several minutes c927 exploded.

 

i forgot to turn off power after several minutes c927 exploded.

It probably needed replacing anyway.

 

Sorry. The waveform on post #110 does not help me.

1. There are two waveforms posted there.
2. I do not know which is which.
3. I do not know where the 0V reference is on the scope. You have to tell me.

Do not post any more photographs for now. I cannot see clearly the data on the voltmeter. I will ask you to describe in words what I am looking for in future.

C927 should not blow if the jumper was cut. There should be 0V on C927, unless it was subjected to -12V as reported on post #78. (Note that on Post #66 this was reported as 12.7V - which I assume was in error.)

I need to know the DC voltage at the RIGHT side of the jumper. I am expecting about +45V. I also need to know if this is DC or pulsed and the amplitude and frequency of the pulse. I am expecting the frequency to be about 35KHz.

Edit:
Sorry, I went back and looked at the voltmeter reading on post #113. I'm thinking this through...

If there is 0V at the jumper, then there is no signal getting to the secondary side of the transformer.
We have to go back to the primary side of the transformer and probe with the scope.

 

Are you able to get at the right-hand side of R918 with the probe - the side connected to the transformer and two hexfets?
Or do you need me to post a picture of the solder side?

I am expecting to see 12V high pulses with 35kHz frequency.

 

can i do this with C927 out of the circuit? i went through my collection and scrap boards and couldnt find a replacement.

 

Yes. It should be OK. There is some leakage coming back from the -ve side but let's ignore that for now. Learn to focus on one thing at a time.

 

Are you able to get at the right-hand side of R918 with the probe - the side connected to the transformer and two hexfets?
Or do you need me to post a picture of the solder side?

I am expecting to see 12V high pulses with 35kHz frequency.

12.8v 36.7khz

 

12.8v 36.7khz

Cool! Best news I've heard all week long.

Let's assume that the transformer is good.
So must mean that diode D907 is open or something on the secondary side is killing the voltage.