Hey all,
This is one of the SMPS DClass amps. I have seen some entries where R87 & R90 which appear to be 3watt resistors overheat & unsolder themselves from the pcb. I've seen where some techs have just replaced them with 5watt resistors, but guess what, that isn't this issue with this one!
I have had a couple of these amps cut out at high volumes even with proper 4 ohm loads. The only way to get the amp working again is to power it down until the Cylon type power LED goes out, and then power it back up.
Both of the amps were warranty and Ampeg refuses to even let servicing dealers repair these for them, even if it's merely a board replacement. This one is out of warr & of course Ampeg won't share any repair knowledge either.
So, has anyone found or know of a solution other than replacing the main board for this issue?
Visually everything on the board looks fine. Nothing overheating or any bulging caps.
Thanx, g
Ampeg PF-800 going into protection
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Stevem
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Re: Ampeg PF-800 going into protection
I would look at two things .
1)
Watch the positive and negative power supply voltage as the amp is running at close to its maximum rms power.
And report back with what you see.
2)
I have had amps where the output devices have over time become fatigued due to the circuit traces that feed them can not carry the needed current.
You may see this in solder connections starting to go bad and the traces that feed them browning up the fiberglass around these traces, so look close for that possibility.
At times I have added wires to supplement the traces that carry the high current loads.
If the amp uses output pack type devices when these get heat fatigued they will shut themselves down.
1)
Watch the positive and negative power supply voltage as the amp is running at close to its maximum rms power.
And report back with what you see.
2)
I have had amps where the output devices have over time become fatigued due to the circuit traces that feed them can not carry the needed current.
You may see this in solder connections starting to go bad and the traces that feed them browning up the fiberglass around these traces, so look close for that possibility.
At times I have added wires to supplement the traces that carry the high current loads.
If the amp uses output pack type devices when these get heat fatigued they will shut themselves down.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
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Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Ampeg PF-800 going into protection
Sorry to hear this as I have one of those, like it very much & play it regularly.
I know that as a model, the smaller PF-500 had a lot of shut-down issues, but it seemed like the PF-800 wasn't prone to that.
Will be following your progress with interest.
I know that as a model, the smaller PF-500 had a lot of shut-down issues, but it seemed like the PF-800 wasn't prone to that.
Will be following your progress with interest.