I will be replacing all the chips on the mehsa board.
can u verify i am getting the right parts?
also on r25 I am getting a 120 ohm resistor p120act-nd is that right?
why not use thin film resistors instead of thick film?
1 2 IRF3205PBF-ND MOSFET N-CH 55V 110A TO-220AB 2
Immediate 0 2.92000 $5.84
2 4 P47ACT-ND RES 47 OHM 1/8W 5% 0805 SMD 4
Immediate 0 0.10000 $0.40
3 2 P120ACT-ND RES 120 OHM 1/8W 5% 0805 SMD 2
Immediate 0 0.10000 $0.20
4 2 IRF9540PBF-ND MOSFET P-CH 100V 19A TO-220AB 2
Immediate 0 1.72000 $3.44
5 2 IRF540PBF-ND MOSFET N-CH 100V 28A TO-220AB 2
Immediate 0 1.72000 $3.44
6 1 497-1585-5-ND IC REG LDO NEG ADJ TO220 1
Immediate 0 1.07000 $1.07
7 1 LM337TFS-ND IC REG LDO NEG ADJ 1.5A TO-220 1
Immediate 0 0.71000 $0.71
8 2 MURF1620CTGOS-ND DIODE ULT FAST 16A 200V TO-220FP 2
Immediate 0 1.71000 $3.42
Subtotal $18.52
Shipping Estimate
Sales Tax unknown
Total unknown
can u verify i am getting the right parts?
also on r25 I am getting a 120 ohm resistor p120act-nd is that right?
why not use thin film resistors instead of thick film?
1 2 IRF3205PBF-ND MOSFET N-CH 55V 110A TO-220AB 2
Immediate 0 2.92000 $5.84
2 4 P47ACT-ND RES 47 OHM 1/8W 5% 0805 SMD 4
Immediate 0 0.10000 $0.40
3 2 P120ACT-ND RES 120 OHM 1/8W 5% 0805 SMD 2
Immediate 0 0.10000 $0.20
4 2 IRF9540PBF-ND MOSFET P-CH 100V 19A TO-220AB 2
Immediate 0 1.72000 $3.44
5 2 IRF540PBF-ND MOSFET N-CH 100V 28A TO-220AB 2
Immediate 0 1.72000 $3.44
6 1 497-1585-5-ND IC REG LDO NEG ADJ TO220 1
Immediate 0 1.07000 $1.07
7 1 LM337TFS-ND IC REG LDO NEG ADJ 1.5A TO-220 1
Immediate 0 0.71000 $0.71
8 2 MURF1620CTGOS-ND DIODE ULT FAST 16A 200V TO-220FP 2
Immediate 0 1.71000 $3.42
Subtotal $18.52
Shipping Estimate
Sales Tax unknown
Total unknown
Order MANY extra of the SMD resistors. I think they're only about $0.02 each in higher quantities. Order at least 10. Order a few extra FETs also.
You don't want the FP rectifiers if they're soldered to the MEHSA insulator. FP is plastic encapsulated. There's no reason to replace the rectifiers or regulators if they're not shorted.
There are 2 different types of rectifiers. You only have the positive rectifier listed.
You don't want the FP rectifiers if they're soldered to the MEHSA insulator. FP is plastic encapsulated. There's no reason to replace the rectifiers or regulators if they're not shorted.
There are 2 different types of rectifiers. You only have the positive rectifier listed.
rectifiers -
u1620= leg 1-3 = 1.5 ohm's
leg 2-3 = 1.5m and declining
leg 1-2= 1.45m and declining fast
u1620R=
1-3= 2.6 ohm's
1-2= 2k and climbing
2-3= (-)1.8k and dropping
u1620= leg 1-3 = 1.5 ohm's
leg 2-3 = 1.5m and declining
leg 1-2= 1.45m and declining fast
u1620R=
1-3= 2.6 ohm's
1-2= 2k and climbing
2-3= (-)1.8k and dropping
the positive side regulator is short.
and the gate resistor for the regulator, r25 = 1089 ohm,s.
it has 121 on the resistor so I am ordering the 120 ohm resistor.
and the gate resistor for the regulator, r25 = 1089 ohm,s.
it has 121 on the resistor so I am ordering the 120 ohm resistor.
after retest my 9540 and 540 chips seem ok.
i needed 50 to get a discount.
All prices are in US dollars.
Index Quantity Part Number Description Customer Reference Available Quantity Backorder Quantity Unit Price Extended Price
1 4 IRF3205PBF-ND MOSFET N-CH 55V 110A TO-220AB 4
Immediate 0 2.92000 $11.68
2 50 P47ACT-ND RES 47 OHM 1/8W 5% 0805 SMD 50
Immediate 0 0.01620 $0.81
3 50 P120ACT-ND RES 120 OHM 1/8W 5% 0805 SMD 50
Immediate 0 0.01620 $0.81
4 1 497-1585-5-ND IC REG LDO NEG ADJ TO220 1
Immediate 0 1.07000 $1.07
5 1 LM337TFS-ND IC REG LDO NEG ADJ 1.5A TO-220 1
Immediate 0 0.71000 $0.71
i needed 50 to get a discount.
All prices are in US dollars.
Index Quantity Part Number Description Customer Reference Available Quantity Backorder Quantity Unit Price Extended Price
1 4 IRF3205PBF-ND MOSFET N-CH 55V 110A TO-220AB 4
Immediate 0 2.92000 $11.68
2 50 P47ACT-ND RES 47 OHM 1/8W 5% 0805 SMD 50
Immediate 0 0.01620 $0.81
3 50 P120ACT-ND RES 120 OHM 1/8W 5% 0805 SMD 50
Immediate 0 0.01620 $0.81
4 1 497-1585-5-ND IC REG LDO NEG ADJ TO220 1
Immediate 0 1.07000 $1.07
5 1 LM337TFS-ND IC REG LDO NEG ADJ 1.5A TO-220 1
Immediate 0 0.71000 $0.71
i changed the battery on the meter and now i get different readings.
on the 9540 and 540 i get 6k ohm's on leg 1-2, 3k ohm's on leg 2-3
and 630 ohm's on leg 1-3
its the same on all 4 chips.
is 630 ohm's on leg 1-3 to low?
on the 9540 and 540 i get 6k ohm's on leg 1-2, 3k ohm's on leg 2-3
and 630 ohm's on leg 1-3
its the same on all 4 chips.
is 630 ohm's on leg 1-3 to low?
You are reading a 10 ohm and 620 ohm resistor in series. The resistors are connected between those legs.
I replaced 9540 x2,540 x2,lm337tx1 ,3205x2 and put in gate 47 ohm's x2
and 1 120 ohm resistor.
right side no sound.
left side had sound but was distorted and week.
and 1 120 ohm resistor.
right side no sound.
left side had sound but was distorted and week.
With only remote and ground connected, what is the DC voltage on the gate leg of the power supply FETs?
Place the black probe on the ground terminal of the amp.
Place the black probe on the ground terminal of the amp.
the r25 resistor now reads 2340, and the lm337sp seems defective.
i have a new lm337sp chip i can install.
can i stack two 120 ohm resistors to get 240 ohm's?
i have a new lm337sp chip i can install.
can i stack two 120 ohm resistors to get 240 ohm's?
That would parallel the two 120s which would give you 60 ohms. Stack 480 ohms to get 120.
Perry, when you say to hook up B- (grnd) and turn on b+ and check the mosfet gates, what are you looking for?
Last edited:
ok i get 39 vdc on both fet's gate legs.
and now both sides are working 🙂
i am going to test the bridge mode now.
and now both sides are working 🙂
i am going to test the bridge mode now.
#33:
On Rockford amps, the power supply driver IC will operate without B+. This allows you to confirm that you have a good drive signal without any concern for excessive current draw or any other problems.
#34:
The power supply FETs should have only about 5v DC. Are you sure that you were measuring the DC voltage on the gate leg of the power supply FETs? If the amp is working properly, there is no reason to re-check this.
On Rockford amps, the power supply driver IC will operate without B+. This allows you to confirm that you have a good drive signal without any concern for excessive current draw or any other problems.
#34:
The power supply FETs should have only about 5v DC. Are you sure that you were measuring the DC voltage on the gate leg of the power supply FETs? If the amp is working properly, there is no reason to re-check this.
in bridged mode, it worked for a few min. then shut down do to heat.
the speaker on low volume was moving up and down and making a thud thud thud noise.
I am using one rock fosgate p150 10inch sub. 4 ohm's. for this amp.
the speaker on low volume was moving up and down and making a thud thud thud noise.
I am using one rock fosgate p150 10inch sub. 4 ohm's. for this amp.
What are you using for a signal source?
Does the speaker move with no RCAs plugged in?
With no RCAs plugged in, what's the resistance between the RCA shields and the amp ground?
Does the speaker move with no RCAs plugged in?
With no RCAs plugged in, what's the resistance between the RCA shields and the amp ground?
ok i retested the gate leg and got 4.5 with the meter set on dcv 200.
i am waiting for the amp to cool down so i can retest to see if it still works.
as it got really hot.
i am waiting for the amp to cool down so i can retest to see if it still works.
as it got really hot.
ok i retested the gate leg and got 4.5 with the meter set on dcv 200.
i am waiting for the amp to cool down so i can retest to see if it still works.
as it got really hot.
i am waiting for the amp to cool down so i can retest to see if it still works.
as it got really hot.
When it cools down, power it up and let it idle (no speakers and no RCA input). Does it heat up after idling for 10 minutes?
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