Hi pjaneiro,
I think lighter packaging will do just fine. The packing would weigh more than the amp easily.
To make sure you actually have a problem. The AC supply is good? Go over the exact problem again when you return my PM (you have mail). I want to make sure that you don't ship it for no reason.
-Chris
I think lighter packaging will do just fine. The packing would weigh more than the amp easily.
To make sure you actually have a problem. The AC supply is good? Go over the exact problem again when you return my PM (you have mail). I want to make sure that you don't ship it for no reason.
You got me there. I've never heard of those, but then again. . . . I was in service. We are just like mushrooms - don't ask me to explain that if you've never heard it!
-Chris
Well yesterday i checked all my rails, and they were all in normal operational values, except for the fan voltage wich was at 8 volts, i thought it should be at around 12-13v ? Anyways, i got mad and decided to take the whole fan assembly and resolder the fan board, guess what !!! They work fine now, i guess i had a cold solder joint somewhere, BTW at the same time i replaced the fans by two 1.5 ac fans they work great and are quiet, , at high volume they follow the beat just fine...I am still looking for a way to remove the xlr board and just replacing it with a std rca,
Anyone here owns a 1.5T and could give me their board number for the input board ? I beleive they are the same amp, but without the fans and xlr jacks...
Thanks...
Anyone here owns a 1.5T and could give me their board number for the input board ? I beleive they are the same amp, but without the fans and xlr jacks...
Thanks...
Hi pjaneiro,
I'm very happy you found the fault. No packing and shipping. No hacking by a tech that doesn't understand these either. The very best outcome. I was worried about the supply regulation misbehaving.
The fans should be barely turning when the amp is idling, so you measured what I would have expected.
Do you have the make and model of what you used?
Hi Kanwar,
There are other techs on this forum who understand these amps as well as I do, or better.
-Chris
I'm very happy you found the fault. No packing and shipping. No hacking by a tech that doesn't understand these either. The very best outcome. I was worried about the supply regulation misbehaving.
The fans should be barely turning when the amp is idling, so you measured what I would have expected.
I lost the meaning of that, but as long as they work - GREAT!
Do you have the make and model of what you used?
Hi Kanwar,
No one can live up to that, but thanks. Now I have to hide somewhere.
There are other techs on this forum who understand these amps as well as I do, or better.
-Chris
Concerning my PM 1.5, i've double checked my rails and they all are in their normal values, so i'm still wondering why would my right channel still play a little louder and the clipping light turn on, on the right channel when i drive it hard, the only thing i have yet to check would be the pot on the right channel board, it's a bit off compared to the other one,
Help oh great one !!!
Help oh great one !!!
Hi pjaneiro,
Check the connections between the amplifier boards and the power supply board. The solder connections may be cracked. There is also a coupling capacitor on each amp board near the top about 1/4 away from the power supply board. Check for bad solder joints. There should be some glue between it and the board.
The pot on the board is for bias. Don't touch it unless you are setting the bias. It would not cause this to happen.
-Chris
Check the connections between the amplifier boards and the power supply board. The solder connections may be cracked. There is also a coupling capacitor on each amp board near the top about 1/4 away from the power supply board. Check for bad solder joints. There should be some glue between it and the board.
The pot on the board is for bias. Don't touch it unless you are setting the bias. It would not cause this to happen.
-Chris
pjaneiro said:
Back to the beginning of this topic, did you ever wash/clean the PCB so you could inspect it thoroughly? A board was replaced, what board? Caps were replaced, what caps? Check it to see that the work is good. Give us some pics?
In general, I always seemed to find resistors near the output that got fried but did not smoke or completely open making it visually hard to see, especially if the amp is not clean inside. Sometimes it is hard to measure resistors while they are in the board. Lifting one end allows proper measurement. It goes without saying; do you have a schematic and an oscilloscope? (These things are your eyes and ears) Look for hot components (be careful with your fingers). Are there bias adjustments and procedures to set this amp? Sorry, just a few points of thought.
Cheers,
Shawn.
I cleaned the boards as best as i could, The pcb that was replaced was the one for the failing Capacitors, the fans work great now, i have a stable power supply, and for the bias, no it has not been tempered with as to my knowledge, but i did notice that on my right channel board the pot for bias is not quite at the same plce than the left, but on my pm 1.5 they are identical, for the scope, nope i do not own one, just my trusty metex voltmeter, i do own the service manuals for both model and i am oin the process of checking all transistor, long lengthy process i must say...
Hi pj, The bias pots not being at the same position doesn't mean anything. Leave it alone unless you have confirmed there is a bias problem. Let the amp run for 20 minutes with no signal. Feel both channel heatsinks with your hands. Your hands are very good at feeling a similarity or difference in heatsink temperature. If they are very similar, they both sound good, and there's no reason to think the bias is misadjusted, let it be.
The pot is there and allows for different settings because the output transistors (and drivers) have different Vbe characteristics. Even transistors packaged from the same wafer cannot have matched characteristics. The bias control needs to be there to account for variability in manufacture.
The pot is there and allows for different settings because the output transistors (and drivers) have different Vbe characteristics. Even transistors packaged from the same wafer cannot have matched characteristics. The bias control needs to be there to account for variability in manufacture.
Hi pjaneiro,
There is only one thing on this amp that I can think of if the sound is clean with full bass.
First, check C4 (470 uF 16 V), then check the values of R3 (910 ohms) and R59 (20 K ohms). Those components set your channel gain. Some models had variable damping and that did affect the circuit gain.
The other thing to check is that there is no voltage on OC1, pins 1 & 2. OC1 is part of the protection and attenuates the input signal. Also, check to make sure your display is not the thing that is unequal.
-Chris
There is only one thing on this amp that I can think of if the sound is clean with full bass.
First, check C4 (470 uF 16 V), then check the values of R3 (910 ohms) and R59 (20 K ohms). Those components set your channel gain. Some models had variable damping and that did affect the circuit gain.
The other thing to check is that there is no voltage on OC1, pins 1 & 2. OC1 is part of the protection and attenuates the input signal. Also, check to make sure your display is not the thing that is unequal.
-Chris
Hi mrshow4u,
Both channels use the bottom of the chassis for a common heatsink. They are generally going to be at the same temperature. Since some of these transistors can have up to 130 VDC (higher with some faults) on the collectors, I never recommend people stick their hands in those areas.
Also, pjaneiro does have the service manual and is able to set the bias to factory recommended spec. Do not deviate from the specified settings pjaneiro.
Pjaneiro,
Please consider getting a 'scope. A new inexpensive model is more than enough for your work. New is good because they work and the trace is sharp.
-Chris
Both channels use the bottom of the chassis for a common heatsink. They are generally going to be at the same temperature. Since some of these transistors can have up to 130 VDC (higher with some faults) on the collectors, I never recommend people stick their hands in those areas.
Also, pjaneiro does have the service manual and is able to set the bias to factory recommended spec. Do not deviate from the specified settings pjaneiro.
Pjaneiro,
Please consider getting a 'scope. A new inexpensive model is more than enough for your work. New is good because they work and the trace is sharp.
-Chris
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