Ampeg PF-800 Question...

[rickwebb]

Hey All- My PF-800 shuts down on me if i turn the Gain up past the 2 o'clock position.
Currently running it at rehearsal into an 8 ohm load. Is this normal?

The other night i bypassed the preamp completely and used my Tech21 VT-DI. I experienced no problems whatsoever.

Is it possible i was driving the internal preamp too hard?

Thanx in advance.

 

[Hoochie Coochie Man]

Try it with the -15dB pad switch depressed to test for input overload.

 

[JimmyM]

I've done that a million times with my PF800 and never had it happen. Part of the attractiveness of those heads is being able to crank them past 2:00 and get some cool overdrive. Contact Ampeg on Monday and see what they think. If it's still under warranty, they will likely swap it out. But no, this is not normal.

 

[rickwebb]

I've done that a million times with my PF800 and never had it happen. Part of the attractiveness of those heads is being able to crank them past 2:00 and get some cool overdrive. Contact Ampeg on Monday and see what they think. If it's still under warranty, they will likely swap it out. But no, this is not normal.

No warranty. Local CL sale. Guess i'm on my own on that one.
And the OD past 2 o'Clock sound was what made me buy it in the first place

 

[Hoochie Coochie Man]

You say that signal into the power amp in works. Does this have a pair of effects out and return jacks? There could be a problem with the switching contacts in that circuit, (if the amp uses that design). You could plug an instrument cable between them, and bypass the switching contacts to see what it does.


And you could open it up, (not plugged into 120V power!) and make sure all internal connectors are properly seated.

 

[quickfix]

What was the "Volume" knob set at?
The reason I ask is because mine had been giving me fits and I'm trying to narrow down the problem.

Ampeg specifically said to me (in a private email between me and Ampeg tech services) NOT to run these amps with the "Volume" (master) knob at 100%, in direct contrast to what was suggested by some folks on this forum. The reason specified by Ampeg was that "it's a class D amp."

I'm also not sure that the PF800 is stable at 4 ohms. I had no trouble with mine until I followed TB advice and ran the "Volume" Master knob at a high setting, and the gain knob at a lower gain setting. I had two 8 ohm cabs plugged in at the time. Multiple shut downs.

I shipped mine to the local sanctioned depot. They shipped the same unit back with no repair and the ubiquitous "No Fault Found/Could Not Duplicate Fault" written on the repair warranty tag.

 

[rickwebb]

What was the "Volume" knob set at?
The reason I ask is because mine had been giving me fits and I'm trying to narrow down the problem.

Ampeg specifically said to me (in a private email between me and Ampeg tech services) NOT to run these amps with the "Volume" (master) knob at 100%, in direct contrast to what was suggested by some folks on this forum. The reason specified by Ampeg was that "it's a class D amp."

I'm also not sure that the PF800 is stable at 4 ohms. I had no trouble with mine until I followed TB advice and ran the "Volume" Master knob at a high setting, and the gain knob at a lower gain setting. I had two 8 ohm cabs plugged in at the time. Multiple shut downs.

I shipped mine to the local sanctioned depot. They shipped the same unit back with no repair and the ubiquitous "No Fault Found/Could Not Duplicate Fault" written on the repair warranty tag.

Master Volume was set at 11 o'clock. And i was running it at 8 ohms. Never had this problem running it at 4 ohms.

 

[quickfix]

Master Volume was set at 11 o'clock. And i was running it at 8 ohms. Never had this problem running it at 4 ohms.

Hmmm. I now run mine at 2 o'clock Gain and 9 to 1 o'clock Volume...generally. I've encountered no problems this way.
Haven't had the opportunity to use my two 8 ohm PF115 cabs (so, a 4 ohm load) together again since the last string of failures. I shouldn't really call them failures as the Fault light was not illuminated. The sound would just up and cut out while playing. Semantics...I know.