rockford fosgate t15002 amp troubles

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#45
alright went outside and tested amp. got alot of no reading or rising to 200 then drops off to no reading. heres my reading

28n15 @ 20m range
1--1/16/15
2--1-16-15
3--1/19/15
4--.8/19/15
5--.8/19/15
6--.8/19.15
7--.8/19/14
8--.9/19/14
9--.9/19/14
10--.8/19/14
11--.8/19/14

now the 36p15 measured @ 20m range (RL) means rising to 20 then dropping off....L means no reading at all
1--.13/RL/L
2--.13/RL/L
3--.11/RL/L
4--.11/RL/L
5--.10/RL/L
6--.09/RL/L
7--.02/RL/L
8--.02/RL/L
9--.02/RL/L
10--.02/RL/L
11--.01/RL/L

NOW THE 75344G on power side of board measured @ 200k (L) means no reading

1--76/L/184
2--74/L/186
3--71/L/190
4--70/L/190
5--69/L/194
6--67/L/198
7--66/L/196 RISING TO A NO READING
8--63/L/L
9--61/L/L
10--58/L/L
11--57/L/L
12--56/L/L

now the lm337t measured @200k
1--13.7/.02/13.5
2--6.7/.02/11.8

now the lm317t
1--7.3/7.2/.1
2--4.4/4.4/.1


does anything else look shorted?? thanks
 
#56
yeah waiting for diagram to be emailed if they give it to me. but like i said i am kind of stuck @ a dead end as of right now. my meter doesnt pick up anything on the 36p15 but in the left leg center leg test. and on the input side on the 75344g's i dont get a reading anywhere but left right leg center leg, and left leg center leg. and i only get readings on 20m ohm range, which is odd.

should i get another meter? or should i proceed to ordering my components?

and again thanks for helping me, i really appreciate it.
thanks
 
#57
I'd suggest that you reinstall the rectifiers and power it up (via a 15 amp fuse and with all FETs clamped down). If it doesn't blow the fuse, see if it produces audio. If it does, you'll need to order the replacement outputs and maybe a few resistors or SMD transistors. If it doesn't produce clean audio, we'll have to determine why.

I don't think you need another meter at this time. It doesn't seem to read like a more expensive meter but it worked well enough to find the shorted FETs.

Are the emitter resistors for the two shorted FETs within tolerance?
 
#58
resistors are rated @ .1ohm, i am testing the the resistors @ the shorted outputs at 41 ohms and 53 ohms, the other resistors not on shorted outputs are reading .4 ohms. so i would say they are not within tolerance.

all i know about the resistors are they are .1 ohm, when i order them what should i look for?

thanks
 
#59
Desolder those resistors and look for a couple of small SMD resistors directly connected to the ends of those source resistors (I called them emitter resistors but they're actually source resistors since this amp uses FETs - bad habit). The resistors are likely to be 33 and 10 ohms. Confirm that the ones for the open source resistors are within tolerance.

I'd suggest that you use the following source resistors but others will work as well. I'd suggest that you replace all for one half of the outputs (28N or 36P) in the blown channel. You don't have to replace the other half with new resistors, you can use one of the good ones that you pulled.
Search result for: *LVR03R1000FB12* - Future Electronics
 
#60
okay removed resistors on blown fets, measured resistance on the 2 surface mounted mounted resistors for each blown fet, both resistors on each blown fet measured between 35-40 ohms.

i got a magnifying glass and looked at part number, ones a 20r0 the other is a 37r4. the 20r0 supposed to be 20 ohms, and 37r0 is supposed to be 37 ohms. i don't know what the tolerance is on the 20r0 but its off by about 17 ohms if my meter is reading correctly.

and do i need to desolder ALL source resistors and test ALL surface mount resistors, or just the ones for the blown fets?

and to be on the safe side, i will replace all .01 source resistors. there easy to solder and desolder anyway. but i would hate to work on the smd, i can barely read the number on them ,lol.
 
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