Fender PD-250 Passport has low audio output Right Side

[tfs2015]

Dear forum members,

I bought a Fender Passport PD-250 at a rummage sale for $20.00. The owner said that it a bad speaker. Tested the speakers they were fine. Found that the right side output has to turned up higher then the left side to get the same amount of sound from the Right speaker then the Left speaker. Also the Right speaker's sound seems to be distorted and does not seem as clear as the left side.

I have attached the complete service manual to this post in hopes that someone here can help me troubleshoot this problem.

Thanks
Tom

[ben7]

Re: Fender PD-250 Passport has low audio output Right Side

Check to make sure the power amp is getting + and - 52V.
Also, check for the DC offset on the amplifier outputs, in reference to the 0V supply connection.
The power amplifiers are on page 25, just for a quick reference.

Also, to me, the amplifiers appear to be the same design for each channel. So you can compare voltages from each channel, and that can help track down where the issue is.

Oh, and, does the heatsink for the right side amplifier get hotter than the left? That would definitely indicate a problem in the amplifier.

-Ben

[tfs2015]

Re: Fender PD-250 Passport has low audio output Right Side

How can I do that with it running a fard of getting shocked.

[Compgeke]

Re: Fender PD-250 Passport has low audio output Right Side

You shouldn't get shocked with a multimeter unless you're touching the tip of the probes.

If you're getting shocked off the chassis you have far bigger issues.

[budm]

Re: Fender PD-250 Passport has low audio output Right Side

At least plug the unit into GFCI outlet, just do not touch anything in the PRIMARY side.
So do you have proper tools and experience in soldering and troubleshooting down to component level? If not, then take it to pro repair shop.

[tfs2015]

Re: Fender PD-250 Passport has low audio output Right Side

OK, I cannot get to the +52, -52 volt connector unless I take the whole unit apart and take all of the circuit boards out. Any advice on doing that?

[tfs2015]

Re: Fender PD-250 Passport has low audio output Right Side

What I really need is a take apart video that shows me how to take this apart so I can check the various connections and things on the circuit boards if someone knows where I can find one, would you please share with me.

Thanks
Tom S.

[budm]

Re: Fender PD-250 Passport has low audio output Right Side

1) Did you try cleaning the send-return jacks using 1/4 plug sticking it in and out a couple times to clean the switch contacts inside?
2) Use the send output of one channel to feed the return input of the other channel to see if the same speaker still has low output.
3) Use the send out jacks to feed another external amplifiers to see if one channel is still low, if it is, then the problem will not be in the power amp section.
We just need to find out first if you have pre-amp problems or power-amps problems.

[tfs2015]

Re: Fender PD-250 Passport has low audio output Right Side

I will check and report back. Thank you for the help.

Tom S.

[ben7]

Re: Fender PD-250 Passport has low audio output Right Side

We just need to find out first if you have pre-amp problems or power-amps problems.

Hmmm, good idea, I didn't think of that.

[tfs2015]

Re: Fender PD-250 Passport has low audio output Right Side

1. If I SEND from the LEFT and RETURN to RIGHT that is when I have a problem. If I SEND from RIGHT and RETURN to LEFT I don't have a problem and the sound is nice and clear. Also the fan power supply cooling fan speed up when I have the problem of distorted sound.

[budm]

Re: Fender PD-250 Passport has low audio output Right Side

"1. If I SEND from the LEFT and RETURN to RIGHT that is when I have a problem" So the left pre amp out fed into the Righ channel power amp, it sounds bad.
And without using the sends/ returns cables, the right channel is also bad, so the right power amp is the problem then since the Right Line out (R send) fed into Left POWER AMP sounds OK.
Then you need to get to the right channel power amp section some how.

[tfs2015]

Re: Fender PD-250 Passport has low audio output Right Side

Ok, I can do that what am I looking for?

[budm]

Re: Fender PD-250 Passport has low audio output Right Side

I thought you cannot figure out how to take the unit apart to test the Voltages.

[tfs2015]

Re: Fender PD-250 Passport has low audio output Right Side

I figured out how to get to the power amp board. I just had to cut the plastic tie wraps to move the wires out of the way.

[budm]

Re: Fender PD-250 Passport has low audio output Right Side

We are going to need good clear pictures next.

[tfs2015]

Re: Fender PD-250 Passport has low audio output Right Side

What are you going to need pictures of on the Amp board?

[budm]

Re: Fender PD-250 Passport has low audio output Right Side

I want to see what it has inside the unit and how all the boards are connected, and to see if there are any labels or test points on the boards, etc.
What tools do yo have?

[tfs2015]

Re: Fender PD-250 Passport has low audio output Right Side

Thought I would post this picture. This is the solder connection that someone did when they replaced Q217 on the Power Amp Board.

[budm]

Re: Fender PD-250 Passport has low audio output Right Side

So some one worked on this unit before you? Did it work before after the repair was done? or you do not have the past history of this unit.
You should at least verify if the correct type of the device was replaced, or look to see what else was done to it also.
The power amplifier circuit is direct couple, so if one device failed it can have chain reaction and can wipe out lots of parts.