rockford fosgate t15002 amp troubles

[grandam88]

i have a t15002 rockford power series amplifier, as soon as power is applied @ remote wire, amp pulls every ounce of power out of my car.

i have already been inside and tested all mosfets/transistors, some are bad.

i have some in my amp that look "out of place" like they were substitute parts. this amp has definitely been worked on before. and i am sure some are sub parts and i wanna replace with correct parts. heres a list of all mosfets and output transistors. p.s. i am a super noob to amp repair, have only worked on one amp before.

36p15--12
28n15--12
75344g--12
lm317t--2 (suspicious ones)
u1620--4(i have a feeling there are supposed to be 6 of them and 2 of these have have a r after part number)
what i beleive is a lm337t or a 337t(maybe a replaced part also.)

Amp was made in 2004, i have managed to remove mosfets from mesha boards already, with a torch.

if anyone has a schematic, that would help.

thanks

 

[Perry Babin]

Did you have a question?

 

[grandam88]

yes the question is based on the list i provided(of components) does anything look out of place, or a substitute part.

thanks

 

[Perry Babin]

No.

 

[spooney]

Glad to see you made it over here from caraudio.com. Do you know how to identify the output fets versus the power supply fets ? If you don't do yourself a favor and check out Perry's basic amp repair tutorial in his sig. If you don't know what you are looking for when you are testing you are going to lead yourself in a lot of wrong directions. It's going to be very difficult to help you out if you don't know the basic parts and their locations inside the amplifier.

 

[grandam88]

lol yes i did come from caraudio.com. over the past few days i have learned alot about testing the components and have found alot of bad ones based on testing with dmm.

i have been to perrys sight numerous times, even before i bought my rockford thats now blown. but i will go again to assure i am doing things correctly.

 

[grandam88]

does it matter if i replace a 28n15 case:t0-39 with a 28n15 with case t0-220?

 

[spooney]

Which components did you find to be bad? What readings are you getting that lead you to believe you have defective components ? Depending on the part you are probing the orientation of your leads may lead you to believe a part is measuring as defective when it is reading normally. It may also be necessary to pull parts from the board to test them. Other components in parallel with the ones you are testing may skew your results.

 

[grandam88]

well the components reading bad are 36p15(7), 28n15(7), 75344g(12), lm317t(2), readings are of no continuity on dmm. i know i may be replacing stuff that may be bad, especially on power side, but i figured i would do more good than harm.

but it would be great to know that some may not need be replaced, especially 28n15 which i cannot find with out a 5 month lead time from mouser.

i found the 75344g's bad, all 12 of them. which leads me two believe i am getting bad numbers from my meter due to the parallel components.

anything i can figure out to avoid replacing some of the harder to find components would make my life easier. and any tips are very appreciated thanks

 

[Perry Babin]

Generally, if the amp doesn't draw excessive current until the remote voltage is applied, the power supply FETs are OK.

 

[grandam88]

cool, so i am guessing my bad readings are due to the parallel components?

also, this would mean the ones i tested as bad on the output side of the amp are bad?
if so thats great, less stuff to replace.

thanks

 

[grandam88]

also still curious if i can mix the package/case types? thanks

 

[Perry Babin]

As was previously stated, parallel components can cause it to appear that more components are defective than really are defective. If you've already removed the parts, you can check them individually. You can't re-use the old parts if one of the parallel group is defective but you can reinstall the ones that are not defective to allow you to continue troubleshooting.

How would you mix case styles?

 

[grandam88]

i found some fairchild 28n15 case style to-220, but my current ones arent that case style. would it make a difference?

 

[Perry Babin]

Can you post a link?

 

[grandam88]

alright, heres a link.
15 Fairchild FQP28N15 150V N-Channel MOSFETs TO-220 - eBay (item 200541893676 end time Jan-09-11 08:01:31 PST)

and i have pulled some mosfets i felt are bad from the power side of the amp, and they did indeed test bad with DMM.

 

[Perry Babin]

Search result for: 8971947 - Future Electronics

With only a few exceptions, you should not buy semiconductors from eBay.

 

[grandam88]

thanks very much, no i cannot find my 36p15's, i have found my 75344g's @ future electronics, but only issue is its labeled to be a HUF75344G3, does this make a difference? heres a link
FAIRCHILD | HUF75344G3 | HUF75344G3 Series N-Channel 55 V 0.008 Ohms UltraFET Power Mosfet - TO-247 - Future Electronics

 

[Perry Babin]

FAIRCHILD FQA36P15 is in stock|BuyFQA36P15|FQA36P15|Onlinecomponents.com

The '3' suffix isn't significant on the power supply FETs.

 

[grandam88]

thanks again, i have found all parts, i still am thinking the lm317t or lm337t was a substitute for one of the two. so there should be either four lm317t or 4 lm337t. what do u think?

do u think that i should just replace all mosfets/transistors instead of just replacing the ones that r bad?

also i really appreciate your help, it has made my quest easier. thanks