RF T30001BD warm problem!

[MarioRestucci]

Hello to all boys.
I'm worried for my rockford t30001bd.
I recently repaired this amplifier that had some problems at the preamp section.
The amplifier works perfectly now, but after 10 minutes of operation, the heat sink of the amplifier, warm enough.
the heat sink of the power supply part is always fresh.
I also have a rockford t20001bd, and this has always been very warm.
I wondered if it was a normal thing, or should I be concerned.
Feeder I installed instead of the original mosfets, 12 x IRFP064N.
The amplifier I installed the original IRFP260, in addition, I had to replace Q402 and Q409 (mpsa56 & mpsa06) which are part of the driver stage of the output stages.
I replaced all the TL072 because there was a problem on the supply line +/- 15v.
Looking at the circuit diagram of the t3000 and t2000, I realized that 2 banks of 4 output MOSFET bank, reach the battery ground, through some of SMD power resistors of 0,3ohm 3w.
Below, I have attached a diagram I drew a hand of person, just to let you know what I mean.

 

[Perry Babin]

The heating of the amp may be difficult to determine unless you measure the exact temperature and someone else has done the same under the same conditions.

Did you have a question about the shunt resistors or the FETs connected to them?

 

[MarioRestucci]

The heating of the amp may be difficult to determine unless you measure the exact temperature and someone else has done the same under the same conditions.

Did you have a question about the shunt resistors or the FETs connected to them?

The main reason for my question was directed to strange heating after only 10 minutes of operation of a load of 2ohm.
The amplifier works really well, it is a beast, but I've never seen a class D that heats after just 10 minutes.
I had the same problem (if indeed it can be considered a problem) with my old T20001BD, but I have to admit that in spite of this, I never had problems.

 

[Perry Babin]

If it doesn't heat significantly at idle and there isn't one bank of outputs that heats significantly quicker than the others, it's likely Ok (the heating is normal).

 

[RockfordFIx]

What is the rail voltage? Voltmeter on red and Blue wire with it connected to the audio board.
These amps typically get warm because they draw about 2 -6 amps at idle. Another thing to check is the fan coming on at all?

 

[MarioRestucci]

Hello,
I apologize if I was not present at the discussion for a long time.
I wanted to inform everyone that in the meantime, my t30001bd has been put aside because I have not had time to fit it in my car.
This afternoon I opened the amplifier because it seems really too strange that the heat even also without load output.
Placing my fingers on the mosfet, it seems to me that the more heat is developed by a group of MOSFET, compared to the other groups.
Unfortunately I do not have a scope, for this reason, I could only measure the voltage with a multimeter.
I put the positive probe on the gates and the negative probe on the sources of mosfets groups; in this way I was able to collect these data:
GROUP 1:
Q418-Q419-Q420-Q432: 3,30V

GROUP 2:
Q427-Q428-Q429-Q433: 2V

GROUP 3:
Q411-Q412-Q413-Q431: 2V

GROUP 4:
Q404-Q405-Q410-Q430: 3,30V

THE VOLTAGE BETWEEN RED AND BLUE CABLES is EQUAL TO 116VOLTS.
Group 3 seems to me that heat up more than the other (to the touch).
This happens without any speaker connected.
I wanted to point out, however, that despite this, the amplifier works well.

ONLY AFTER TWO MINUTES, THE SINK NOT HOT, OF COURSE, BUT SEEMS TO ME THAT WORRYING BECOME WARM AFTER VERY LITTLE TIME.
P.S. SINCE THE UNIT COMES FROM AN OLD LABORATORY, ALL MOSFET, NOW ARE WITHOUT THE MEHSA SUPPORTS.

 

[Perry Babin]

Can you borrow a scope?

 

[seankane]

Almost every t30001bd and t20001bd I have had on the bench heats up very warm even at idle with minimal load. I think it is normal, have you taken a measurement with an infrared heat gun to see what the temp actually is?

If the amp isn't going into thermal protect, your likely fine.

As RockfordFix stated are the fans working on both boards?

 

[Perry Babin]

I think he was concerned because one of the 4 banks was heating more than the others.

I think a better test would be to see how the heating compares when all of the FETs are tightly clamped to the heatsink and the amp was driven into a load.

 

[seankane]

I agree Perry, but the only thing that is strange, almost every T30001bd I have had on the bench one bank or should I say section of the heatsink gets much warmer or warmer quicker.

To add to this theory I have a T30001bd brand new in box I bought years ago and never used. When I hooked it up for this test, same thing. One section heated much quicker than the rest. It may be coincidence, I don't want to mislead anyone as there may be a problem with the amp.

Answer me this MarioRestucci, forgive me if it's already mentioned.....Is the bank that heats the quickest Q413 Q412 Q411 Q431?

 

[Perry Babin]

Yes. That's the 'group 3' that he referred to above.

 

[seankane]

That's strange because on all 3 T30001 bd's that I have here those are the exact same FET's that heat the quickest in the new amp and the 2 used repaired ones. I don't know but it seems normal from my experience with these amps.

I also noticed this on the T20001bd as. That being said when I install these amplifiers into a vehicle and run them hard on the way to work I noticed less heat than on the bench hooked to a power supply. I'm not sure if any of this is useful, just thought I would share my experiences with this amp.

 

[Perry Babin]

It may be normal. Have you noticed if they run hotter than the other 3 banks when they are clamped down and driven hard into a load?

 

[MarioRestucci]

Answer me this MarioRestucci, forgive me if it's already mentioned.....Is the bank that heats the quickest Q413 Q412 Q411 Q431?

yes sir! exactly!
The amplifier is already mounted in the sink.
to measure the temperature, i use only my fingers.
It is something that I'm assuming.
I really hope that I am worrying needlessly.

 

[MarioRestucci]

I would like to recreate this thread to explain some things.
I re-opened my t30001bd after so long that it was unused because now I would like to finally mount it in the car.

I'm really curious about this abnormal heating, so I decided to see what happens on the mosfet gate with my oscilloscope.

I would like to share these with you.

The first photo shows the signal on Q432-420-419-418 with a voltage of 3.4 volts.

The second photo shows the signal on Q433-429-428-427 with a voltage of 1.98volt.

The third picture shows the signal on Q431-413-412-411 with a voltage of 2.02 volts.[group that heat more quikly and strange]

The last photo shows the signal on Q430-410-405-404 with a 3.5 volt voltage.

All the signals were observed with the connected reference on the source of each group, even the voltages were detected by a multimeter with the black probe on the sources.

What do you think? Are these signals normal?

 

[Perry Babin]

I don't have the waveforms for a 3000. The attached waveforms are from a 1000. Use the diagram to find the corresponding transistors. The file names of the photos indicate the output FET designation.

 

[MarioRestucci]

I don't have the waveforms for a 3000. The attached waveforms are from a 1000. Use the diagram to find the corresponding transistors. The file names of the photos indicate the output FET designation.

We admit that t10001bd is identical to t30001bd (with the only difference of having a higher number of power devices), it seems to me that the signals in Figure 2 and 3 are somewhat strange.
I put a red circle in the underlying images to highlight the strange fact in the signals that concern group 2 and 3.
I'm thinking of C415-C417-C419-C447 + C449-C435-C437-C439.
In both groups, these capacitors are uninsured to a 10ohm resistor, if only one of these condensers is in loss or damage, it can alter the signal of the whole group because they are all in parallel with each other.
Or, it's strange that the signal is altered on groups 2 and 3, both generate low side signal but at this point the problem (if it really is a problem) may depend on the driver (UC3706) but it would be really impossible for both of them to give the same problem, for this reason, the only thing that they share is the TOGGLE A and TOGGLE B signals.
What do you think?
i've attached also T30001BD OUTPUT BOARD schematic

 

[Perry Babin]

Have you checked the drive signals with no rail voltage?

If you disconnect the red and blue wires, make sure that the voltage across the rail caps doesn't exceed their rated voltage.

 

[MarioRestucci]

Have you checked the drive signals with no rail voltage?

If you disconnect the red and blue wires, make sure that the voltage across the rail caps doesn't exceed their rated voltage.

I don't have checked signal whit no rail voltage, but today i do it.
My rail voltage il 116volt between Red and blue cables.

 

[MarioRestucci]

Sorry for double post.
116volts are intended CONNECTED to OUTPUT board.