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Problem with my ampeg portaflex pf-350

L

leosep

Guest
Sep 12, 2012
71
0
#1
Hi how are you all?

I'm having this problem with my amp. I connect it to the power, i connect the cab's cable, the bass cable to the input and turn it on. The purple light is on, the fault yellow light is off and i think that the signal form the bass is ok because the clip/peak light is blinking when i play. The thing is that i tested more than one cab and there is no sound coming out of the speakers. I tested the cabs with another amplifier and worked, so the problem is with the portaflex. I can hear my bass with the headhones out so i think the preamp is working, something is happening to the amplifier circuit or the speaker output. I opened the case and cleaned all the inputs with a contact cleaner, the fx send return, headphones out, bass input, speakers outputs, everything. I cant see any blown caps or something like that. What could be happening?
 
#2
Another sad case of S.A.D.S. or Sudden ampeg Death Syndrome. :dead: It's a planet wide pandemic, and thousands upon thousands have died. So S.A.D.S. :bawl: Yet ampeg's parent company, LOUD Tech, laughs all the way to the bank with your money and you're left holding their dead product. :(
 
#4
It sounds like you've done a pretty good job of doing what you can and debugging.

Since the sound is coming out the headphone output, this indicates that the signal is passing from the pre-amp, through the effect send and return jacks then splits to the headphone amp and the input to the power amp. So either the problem is in the output jack connection or the power amp.

Try what Jon said above with the instrument cable connected between the effect send and return jacks.

If you took the amp to a tech, they would reseat the connector inside the amp. Carefully pull them out, one at a time, and reinsert them. If something came loose, you could loose your signal. Next, inspect the connections from the speaker output jacks back to ensure that those connections are sound.

If the issue still isn't resolved, the next step would be to check out the voltages in the power amp and perhaps use a scope to examine the signal at each stage in the power amp. A schematic for the amp is available on Loud's web site, there are reference voltages on it that the tech would use and compare them with readings taken in the power amp.
 
#5
Hi,thank you for your responses.

I did the connection between the fx send<--->return and got the same results, the headphones jack works but no sound from the speaker. :(

I'm not very sure of what to test with the multimeter.
 
#10
leosep said:
Well, it didn't work. I don't know what else to do, i'm not the original owner.
Click to expand...

I think that you've done everything that you can.

The next step is to take it to a tech and get an estimate for the cost of repairing it. They have test equipment that can be used to get to the bottom of the issue. You might need to pay for a half hour to an hour of bench time. Provide a sheet detailing what tests you performed. Based on what you found, I suspect that the issue is in the power amp. Also, based on their bench rate, you might want to tell them how much you are will to pay to have the amp repaired. You don't want to pay more than the amp is worth. The schematic is available from Loud's web site. Print a copy and take it with you to the tech if you decide on this option.
 
#12
leosep said:
Hi how are you all?

I'm having this problem with my amp. I connect it to the power, i connect the cab's cable, the bass cable to the input and turn it on. The purple light is on, the fault yellow light is off and i think that the signal form the bass is ok because the clip/peak light is blinking when i play. The thing is that i tested more than one cab and there is no sound coming out of the speakers. I tested the cabs with another amplifier and worked, so the problem is with the portaflex. I can hear my bass with the headhones out so i think the preamp is working, something is happening to the amplifier circuit or the speaker output. I opened the case and cleaned all the inputs with a contact cleaner, the fx send return, headphones out, bass input, speakers outputs, everything. I cant see any blown caps or something like that. What could be happening?
Click to expand...
So I had the same issue( apparently a lot of people do with this same prob), my tech guy sent schematic of where the issue was. A tiny chip resistor in the power supply that stayed "open" preventing the oscillator from starting. He replaced with a heavy duty / higher quality part. I dont know if this is from overdriving input, eg: active electronics or high end hot output pick ups but if you go on $Ampegs F.B./Youtube page check out Dino's info on how to set limiter on this amp !! Cheers , good luck
 

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#14
Bob Blore said:
So I had the same issue( apparently a lot of people do with this same prob), my tech guy sent schematic of where the issue was. A tiny chip resistor in the power supply that stayed "open" preventing the oscillator from starting. He replaced with a heavy duty / higher quality part. I dont know if this is from overdriving input, eg: active electronics or high end hot output pick ups but if you go on $Ampegs F.B./Youtube page check out Dino's info on how to set limiter on this amp !! Cheers , good luck
Click to expand...

Is the amp working again?
 
#18
Bob Blore said:
Possibly!! I ve seen this issue quite a lot, but thats why I have a great tech guy !! He's done some amaaazing mods /upgrades to a number of my amps !!!!!
Click to expand...
You've seen this issue a lot? Are you a tech, or are you going from hearsay? If you have a great tech guy, then I'm assuming you aren't a tech and just passing on a lucky tidbit (as Beans also suggested).
 
#20
So hearsay then, just your opinion based on something you experienced or heard but do not understand. If you understood how this controller works, you would realize why it's not a vulnerable or even remotely sensitive, failure prone part.

I have actually used this IC, and since there is virtually no current flowing or power dissipated in either of those resistors, there's nothing fundamentally wrong or vulnerable with those parts. I have also not seen this fault either, and I have a fundamental mistrust of the information passed around as fact on forums (this forum included), and when such inaccuracies are perpetuated this does not do any good at all.

While you may have had an issue related to this, (damaged part, solder joint) that doesn't mean that all failures can be traced to these two parts (and in fact there are other much more common failures associated with this family of flyback controllers). This is based on experience with the part at the engineering and manufacturing level.
 
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