I am working on the newer model of this amp. I'm trying to find some repair info on it but the only links that I can find are dead. Any help would be appreciated. Thank you.
I am missing CE1A and RE1A they are right by the relay. What are the values and what do they do? This amp had shorted power supplys and shorted outputs. I pulled all the outputs and replaced the power supply transistors (sfp 70n06) upon powering the relay clicks, power light flashes, then blows my 5a inline fuse. Also what does the pot on the board do? It is turned all the way counter clockwise.
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Can I try 47R gate resistors and Irf3205s for the power supplys? All I had was 51.1R so i tried those. Would that cause a problem? I also moved the pot to about half way.
Here are the requested photos:
Here are the requested photos:
Did you check the drive circuit for the power supply FETs. The driver circuit could be damaged causing the fuse to blow.
Contact US Amps to see if they can give you the value of those parts.
Contact US Amps to see if they can give you the value of those parts.
The missing parts appear to be for the bass knob. On the bottom of the board I can see that the leads are still there. I'm wondering what would have caused the cap and resistor to melt off?
As you can tell from this and all of my other threads I am new to this. I'm sure I should have known to check the drive circuit but I get a little confused sometimes and I guess instead of thinking about it I just get on here and ask.
I am learning a lot from your (Perry's) Repair manual and when I am at work on nights like tonight I read through the free one on my phone over and over again. I am learning though! I need to get the full version on my phone so I can do the same with it.
Thanks for putting up with my noobness.... lol
As you can tell from this and all of my other threads I am new to this. I'm sure I should have known to check the drive circuit but I get a little confused sometimes and I guess instead of thinking about it I just get on here and ask.
I am learning a lot from your (Perry's) Repair manual and when I am at work on nights like tonight I read through the free one on my phone over and over again. I am learning though! I need to get the full version on my phone so I can do the same with it.
Thanks for putting up with my noobness.... lol
That's likely the DC offset potentiometer. This amp appears to be very similar to amps like the Hifonics BXI1606D and that's what the pot is for in those amps.
I fired this thing up with the outputs out of the circuit. Will that fry the HIP4080? I'm sure it was already bad because there were multiple shorted outputs but I would just like to know for future reference. Also, do I need all of the outputs in circuit to test it or will that hurt the HIP4080? Thanks
It won't damage the 4080. If you have a scope, you can check the drive signals for the output transistors.
I got this thing to turn on but it smoked 1 bank of power transistors. I clipped them out and it turns on fine. I measure the op amp that's right by the 494 ic, it's a 4558 with the readings as follows:
Pin1 11.0v
Pin2 1.25v
Pin2 1.32v
Pin4 0v ground
Pin5 1.43v
Pin6 5.14v
Pin7 1.43v
Pin8 11.69v
Do these look ok? I'm still waiting for funds for a scope.
Pin1 11.0v
Pin2 1.25v
Pin2 1.32v
Pin4 0v ground
Pin5 1.43v
Pin6 5.14v
Pin7 1.43v
Pin8 11.69v
Do these look ok? I'm still waiting for funds for a scope.
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The op-amp appears to be OK but that doesn't mean that the voltages are right for the amp to function normally.
I'm assuming that you meant power supply transistors. All of the TO-220 cased transistors clamped to the heatsink (both audio and power supply) are power transistors.
Does the amp produce clean audio (audio output transistors and 4080 installed)?
I'm assuming that you meant power supply transistors. All of the TO-220 cased transistors clamped to the heatsink (both audio and power supply) are power transistors.
Does the amp produce clean audio (audio output transistors and 4080 installed)?
Yes I did mean power supply transistors. I don't have the output transistor in place as I am waiting for them to be delivered, also ordered HIP4080s. I got this amp with shorted power supply transistors and shorted outputs. I am just trying to troubleshoot the power supply until the parts get here.
So far I found a shorted driver transistor on top of the original problems. How far back have you seen damage go? Does it make it past the driver transistors? I am getting ~4v on pin 9 and 10 of the 494 so it seems ok. I just don't understand why it smoked that bank of power supply transistors. I guess I need to check the transformer for shorts.
So far I found a shorted driver transistor on top of the original problems. How far back have you seen damage go? Does it make it past the driver transistors? I am getting ~4v on pin 9 and 10 of the 494 so it seems ok. I just don't understand why it smoked that bank of power supply transistors. I guess I need to check the transformer for shorts.
Before. I figured it out, now the power supply is running smooth.
I took another look at it and found a bad driver. Wasn't reading shorted on resistance but on diode was not showing voltage.
I took another look at it and found a bad driver. Wasn't reading shorted on resistance but on diode was not showing voltage.
I have a few old outputs from this amp that aren't shorted. If I put 1 in each bank is it safe to power it up?
How do you define safe?
There's no guarantee that there won't be a problem that could cause the failure of other components if measures aren't taken to protect the rest of the components. The information in the yellow box on the basic repair page tells you what to do to protect the amp's components.
If the 4080 was in the circuit when the output transistors failed, the IC is almost certainly damaged. The output transistors could have been damaged and may fail even if the drive circuit is OK. This sometimes happens with transistors that were in the circuit when the amp failed even if they check OK out of the circuit.
If you drive a strong signal into the amp (~100Hz) with no output transistors installed, you may be able to determine of there is a good drive signal on the gate pads for the output transistors. You should read ~5v DC (black probe on pad 3 and red probe on pad 1). If you do not, you'll need to solder a bridge between legs 1 and 2 of the LM833 (IC4C in hifonics amps, I don't know what it will be labeled in this amp). Pin 1 of the LM833 will drive pin 7 of the 4080 through a 10k ohm resistor.
There's no guarantee that there won't be a problem that could cause the failure of other components if measures aren't taken to protect the rest of the components. The information in the yellow box on the basic repair page tells you what to do to protect the amp's components.
If the 4080 was in the circuit when the output transistors failed, the IC is almost certainly damaged. The output transistors could have been damaged and may fail even if the drive circuit is OK. This sometimes happens with transistors that were in the circuit when the amp failed even if they check OK out of the circuit.
If you drive a strong signal into the amp (~100Hz) with no output transistors installed, you may be able to determine of there is a good drive signal on the gate pads for the output transistors. You should read ~5v DC (black probe on pad 3 and red probe on pad 1). If you do not, you'll need to solder a bridge between legs 1 and 2 of the LM833 (IC4C in hifonics amps, I don't know what it will be labeled in this amp). Pin 1 of the LM833 will drive pin 7 of the 4080 through a 10k ohm resistor.
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