rockford fosgate t15002 amp troubles

[Perry Babin]

There should be 317s and 337s. These are the positive and negative regulators. They only VERY rarely fail.

I would only replace parts that need to be replaced.

 

[grandam88]

i know this may seem like a stupid question, but what should my meter be set to value wise(obviously ohms but which), my meter is a bluepoint eedm503a, and i have a centech(junk). my values on the blue-point are i guess diode check(|<-), a dot with what looks like sound waves, 200,2k,20k,200k,2m,20m.

i seem to get different readings from the same components, i guess from a shorted component in the line. on one i will get like .700, then the other .160.

thanks

 

[Perry Babin]

Which components?

Which legs were the red and black probes on?

 

[grandam88]

alright here is all my measurements. measured on outside legs while still on board. going right to left

75344g measured @ 200 input side
1---0
2---0
3---0
4---0
5---0
6---0
7---0
8---0
9---0
10---0
11---0
12---0
lm317t measured @200k input side
1--7.1
2--3.7
lm337t measured @200k input side
1--.2
2--.2
28n15 measured @2k output side
1--.001
2--.113
3--.113
4--.112
5--.111
6--.111
7--0
8--0
9--0
10--0
11--0
12--0
36p15 measured @ 200 output side
1--158
2--21.6
3--148
4--146
5--146
6--146
7---0
8---0
9---0
10---0
11---0
12---0

thats all my measurements minus the components i have already removed and ordered replacements.

i kept having to switch the measuring value to get a reading.

thanks

 

[Perry Babin]

What were you trying to determine here?

What was the meter set to?

Where was the black probe?

 

[grandam88]

well from what i have been reading, i can test to see if the mosfets and transistors r any good using a dmm on ohms. thats what i was doing, i didnt put the black probe and red probe on any certain foot besides outside feet.

if i am doing something wrong here please let me know.

 

[Perry Babin]

You need to check them with the black on one leg and the red on another leg.
On the following page, go to the bipolar transistor section and open the link indicated in the attached image. This section is for bipolar transistors but the lead placement is the same when checking either type of transistor initially.

Basic Amplifier Repair - Transistor Test Applet Link

Post the values (or screencaps of the form with the values) for one power supply FET, the first 28n you listed and the second 36p you listed.

Which FETs have you removed from the MEHSA insulators?

 

[grandam88]

i have already remove the (4) u1620's from not only the mesha boards but the from the amp its self, and tested them outside amp, and still they appear bad. and basically from what your article says all my readings that are 0 are bad, and some of the items reading an actual resistance may still be bad?

 

[Perry Babin]

OK. Don't remove anything else.

 

[mike49504]

Listen to perry hes the man here.

The quickest way to test the output transistors (FQA28N15-FQA36P15) is to place black meter probe on leg 1 (right leg) and red probe on middle leg. Then black probe on leg1 and red probe on leg 3 then finally black probe on middle leg and red probe on the 3rd leg. You should read nothing near 0 ohms.


If you arent sure if its defective or not pot your results as followed


Leg1-2:
Leg1-3:
Leg2-3:

Do this with all outputs and all power supply fets.

 

[grandam88]

thanks for all your patience perry, i am new to this though i have done some soldering, i am glad i have someone who knows whats up to walk me through this. i will go test the fets and see what happens. thanks

 

[grandam88]

alright, did all the testing.

on the output side i set my meter to the 200 ohm range. went from right to left on amp testing the 28n15's and 36p15's.
doing it in order described i got.
first the 28n15's
1--.2-1.3-1.3 !!!!
2--40/115/76
3--40/115/76
4--40/115/76
5--40/115/76
6--40/115/76
on seven through 12 got a no reading meter on any of the legs
now the 36p15's
1--53-148-96
2--53-148-96
3--53-149/95
4--53-149-96
5--53-149-96
6--53-149-96
also on these on the last six got a no reading on meter on ANY of the legs
this was the output side

now for the input/power side i got a no reading on everything on any legs.

 

[Perry Babin]

The first 28n15 appears to be shorted. Cut its legs free from the board and recheck them again.

 

[grandam88]

also as previously stated i ordered the fairchild u1620 from ebay, should i order some from another site, if so all i can find is a cross reference to a nte chip from mouser?

and what are your thoughts on the fets on the power side of the board?

 

[mike49504]

Never use NTE parts they are usually very expensive and they tend do do more harm then good in amps.

I think this is what your looking for:


MUR1620CTG ON Semiconductor Rectifiers

 

[Perry Babin]

There are MUR1620CTRGs and MUR1620CTGs. Probably 2 of each.

 

[grandam88]

alright retested...after cutting legs off shorted one
first are the 28n15 measured @ 200k
1--155/0/82
2--140/0/84
3--130/0/96
4--117/0/105
5--111/0/10
6--163/0/95
7--153/0/96
8--153/0/101
9--136/0/105
10--129/0/111
11--124/0/116
second are the 36p15 measured @ 200 range on meter
1--53/115/95
2--.4/21/21
3--54/149/96
4--54/149/96
5--54/149/96
6--54/149/96
7--0
8--0
9--0
10--0
11--0
12--0
no readings on any legs on last six

next are from the power side of the amp
the lm317t's measured @ 20k
1--7.2/7/.1
2--5/5/.1
now the lm337t @20k
1--17/.2/4
2--13/.2/13


thanks

 

[grandam88]

There are MUR1620CTRGs and MUR1620CTGs. Probably 2 of each.

so there is a difference between the two of them? lol i had no idea.

 

[mike49504]

There is both positive and negative rails in your amps.

The MUR1620CTG controls your positive rail

The MUR1620CTRG controls the negative rail in the amp.

 

[grandam88]

yeah parts are labeled as u1620 and u1620r. 2 of each. unfortunatley i have already removed them so i have no idea which one goes where.