2245 in protection

[bluescat]

nope, transistor is connected to DCA-55 leads are identified correctly. And then soldered to corresponding positions on the board which are clearly marked. And yes I think 2SC496 is ECB and board is marked EBC so the legs were crossed to be correct.

After reading the above I checked the wire locations against the left channel which has not been disturbed.
Rt board:
E= green
B= blue
c= yellow

Left board:
E= yellow
B= blue
c= green

 

[patfont]

I did not solder the 3 wires on by color when I did it, you will see the transistor has a white dot on the "E" side of the transistor, (it is ECB) and that if you will follow each lead you will see it goes to the proper location on the board and is installed correctly. I have some pics I can post later.

-all semiconductors on the board were tested, any resistor connected to a shorted/toasted component had one leg lifted and tested. I am fairly confident the board is repaired but without being able to power up could not be 100% sure.

It did come out of protection when 1st installed so?

Please check all of the JXXX pins and compare left to right to make sure board is installed correctly?

After reading the above I checked the wire locations against the left channel which has not been disturbed.
Rt board:
E= green
B= blue
c= yellow

Left board:
E= yellow
B= blue
c= green

 

[bluescat]

I did not solder the 3 wires on by color when I did it, you will see the transistor has a white dot on the "E" side of the transistor, and that if you will follow each lead you will see it goes to the proper location on the board and is installed correctly. I have some pics I can post later.

-all semiconductors on the board were tested, any resistor connected to a shorted/toasted component had one leg lifted and tested. I am fairly confident the board is repaired but without being able to power up could not be 100% sure.

Yes, you are correct the white dot Is on the E side. That was the one that had broken off in shipment and I soldered it back.

 

[bktheking]

Well, despite doing h760 in the 2270 it just blew my two original replacement outputs- the thing was running for 8 hrs prior.


I need a sj2518 if anyone has one.



Back to the drawing board.

 

[bktheking]

Replaced the 2sc945 now it's behaving. Gonna dbt it for days.

 

[patfont]

H753?

Like I mentioned before in the Pioneer world 2SC945's are replaced as we do
2SC458's.

Replaced the 2sc945 now it's behaving. Gonna dbt it for days.

 

[bktheking]

Ah I didn't realize they are troublesome as well.

 

[patfont]

Here are a couple pics:

4 parts on the left are shorted/smoked. You can see a black ring around the resistor.

On the right 3 new caps, trimmer pulled and tested, diode pulled and tested, along with checking everything else





all legs shorted on this guy!

 

[patfont]

ok round 2, heading your way Monday.

 

[bluescat]

ok round 2, heading your way Monday.

Hey old friends!!! I figure anyone who is/was following this thread will be interested in the outcome of the parts install. Sad to report that the same resistor(R786) smoked again, immediately upon turn on. DBT said to plug in direct so I did and then it started to smoke. Didn't leave it on long enough to see if it came out of protect. Yes I moved the ground lead from j756 to j758 where it was supposed to be.

 

[bktheking]

DBT is a difficult thing to read- i'm better dollars to donuts that the filament was glowing enough to show something was wrong , if all is well on a 2245 a 100w-150w bulb should have been OUT completely. Was it glowing?

 

[bluescat]

DBT is a difficult thing to read- i'm better dollars to donuts that the filament was glowing enough to show something was wrong , if all is well on a 2245 a 100w-150w bulb should have been OUT completely. Was it glowing?

Yes, went very dim, but not out, and it's a 75 watt bulb. This is true of the other times I tested and then got smoke. OOP's

 

[bluescat]

DBT is a difficult thing to read- i'm better dollars to donuts that the filament was glowing enough to show something was wrong , if all is well on a 2245 a 100w-150w bulb should have been OUT completely. Was it glowing?

Ahh, I thought that I needed a bulb 50% higher than the wattage rating of the amp (45 watt amp) not 50 % of the power draw of the unit (as printed on the back). Thats what happens when a "dim bulb" uses a DBT!!

 

[bktheking]

Nope- it's the draw not the wattage output. If you left it on the 75 watt for a while the resistor would start to smoke but you could shut it down quick enough not to cause damage- full power will smoke it instantly. I usually use a clear 150w bulb to do my DBT.

This theory doesn't work well on large amps, just too much draw to tell, my citation 16 looks like a short on a 150 cause it draws so much through the 20 outputs on the back at idle.

 

[bluescat]

Nope- it's the draw not the wattage output. If you left it on the 75 watt for a while the resistor would start to smoke but you could shut it down quick enough not to cause damage- full power will smoke it instantly. I usually use a clear 150w bulb to do my DBT.

This theory doesn't work well on large amps, just too much draw to tell, my citation 16 looks like a short on a 150 cause it draws so much through the 20 outputs on the back at idle.

Thanks Brad, "another lesson learned"!!!!
OK, "again" I might have found the problem. It almost has to be something as simple as this, because between you (Brad) Pat, and Pete, it appears that everyone is running out of ideas on this #&^*@! thing.

Under bright sunlight and magnification it appears that the solder joints under R795 are run together. Don't know how or when it happened, not even going to speculate. The buck stops here. Below are pics.

 

[bktheking]

Test it with a meter to see if it's bridged. 2 pins should be common and the other not common.

 

[bluescat]

Test it with a meter to see if it's bridged. 2 pins should be common and the other not common.

Yeah, that's the 1st thing I did. Continuity, no matter what combo of pin's I touch>

 

[bktheking]

The that may be the source of the issue.

 

[patfont]

take a q-tip with Iso alch. and swab around all that area that way you can see the traces better. If bridged heat up suction away and redo, yes that is right next to H753.

 

[bluescat]

take a q-tip with Iso alch. and swab around all that area that way you can see the traces better. If bridged heat up suction away and redo, yes that is right next to H753.

Yeah, Swabbed, joints are bridged. After desoldering, do you want me to re-solder?