Fender Passport PD500 - Sounds dirty

[Steve Ambrose]

Hi Everyone

I have been using a Passport PD 500 for over seven years. Its been great. Last night setting up for a party I was playing some music through it from my laptop and to be frank cranked it up to loud. No Red-Line though and not full chat. After a few minutes I noticed the sound deteriorate and become dirty, distorted. It did not cut off and I did not see a protection light.

From posting going way back on this Forum I know they are a pig to work on. Unfortunately I have no choice. I am here in Liberia West Africa and no local Fender shop or decent electronics shop close by. I have a friend who is an electronics guy but works with boards from slot machines. He will help. Fender said they would send a schematic.

I know some of the senior members worked on these units. Can they give any tips what we should be looking for. I'm pretty sure its an electronics issue and not blown speakers (both cabs same time?). However I know someone with a PD250 here so will try the speakers on that (if possible) to check. But think I am looking at a component issue somewhere that effects both channels.

Glad of any help you can give.

Many thanks.

Steve Ambrose
Monrovia, Liberia

[Enzo]

The key is to isolate the problem.

First the speakers. Just because it seems unlikely both died at once in the same manner doesn't mean it din't happen. So play the amp through some other speakers, and also play your speakers from some other amp. Just to check.

I don't have my schematics with me, but if there are power amp input jacks on that amp, play something into those to see if the power amps are OK or if they have the issue.

Beyond that, inside we would want to make sure all the power supplies are right. This unit has an SMPS, so is not simple.

Liberia isn't very specific. Are you in an urban environment with proper mains voltage? Or are you in rural or isolated surroundings running on generator power or batteries?

[Steve Ambrose]

Thanks Enzo

I will do all that first and get back to the Forum.

By the way I am in Monrovia, Liberia. Although we do suffer from power issues I have a rather large stabilizer. When this happened all was fine and power clean.

I believe it happened as a direct result of me turning up the volume. I was using Laptop connected through a Allen Heath small mixer to the XLR inputs set at Line. Mixer was clean signal not overloaded on that side and the inputs set with only the occasional Red peak. Main volume I was running at 4 then six but I did raise it to 7. It was clean. I then tried another track and it sounded dirty. I tried various tracks that I know are well recorded using FLAC and there was no question something had happened.

KR
Steve Ambrose

[Jazz P Bass]

The coastal atmosphere may have gotten to the speakers & they failed when you pushed them a tad hard.

[km6xz]

I have all the PD series schematics except the PD500......
If both channels are distorted the same way the odds are favoring a power supply problem or an opamp IC in the preamp/mixer section because almost all the IC amplifiers are dual section with one section for each channel. The power amp has almost no common components between the channels.. The mixer has no PA In jack to send a signal directly into the power amp to verify whether the fault is in the PA section or preamp/mixer section. It is very unlikely the power amp is faulty since most of the time if a PA section was down, the power supply would shut down in protect mode. My wild but educated guess is one of the dual opamp ICs failed due to the high input level.