Boston subwoofer help needed

[Original Burnedfingers]

I have a PV700 boston sub with very little output.

It does not make any difference if I feed it spk level or line level source.

I'm not experienced in this kind of amplifier so I am asking for a helping hand here,

I have taken some pictures in the hopes of identifying the different boards it is made up of.

1) a picture of the back of the plate amp.

2) picture of what I believe to be the input and crossover board.

3) power supply board I think.

4 Amplifier board

Now I know that #1 is correct for sure.

Anybody have any ideas?

[nigelwright7557]

You really need circuit diagrams to follow the signal through.

I suppose you could test the output mosfets for shorts.
Check the power supply for volts.
I would also check the speaker for low impedance the voice coil could be partially fried.

[diy didi]

Yep! But where to find schematics?? I also have one!!

[Original Burnedfingers]

Speaker checks fine with my impedance meter.

If mosfets were shorted I wouldn't have any output would I? Also there isn't any excessive current draw.

Signal is good but just low in level.

I generally repair everything I work on without schematics. Generally by the time I get a schematic I have the item repaired. I find companies like this unwilling to share any information that is why I entertained the idea that one of the cult followers here might have access and be willing to share.

[ouimetnick]

I see its an Indigo product (maker of Bash amps) Well.. Boston Acoustics will not under any circumstances release the service manual or schematic. I wanted a schematic for my Micro90pv plate amp (Also Indigo)

Indigo was bought by some Chinese company, and the website is now defunct.. So you might not have luck servicing the amp. Sorry.

[JOHN BALI]

Originally Posted by Original Burnedfingers

Speaker checks fine with my impedance meter.

If mosfets were shorted I wouldn't have any output would I? Also there isn't any excessive current draw.

Signal is good but just low in level.

I generally repair everything I work on without schematics. Generally by the time I get a schematic I have the item repaired. I find companies like this unwilling to share any information that is why I entertained the idea that one of the cult followers here might have access and be willing to share.

This type active subwoofer need Spk level at input to max sounding, have tou try to input from mono source? stereo input has + & - polarity & if wrong connection the sound will be small at the end.
or any possibility you can only test amp board + speakers without input & crossover board so you know which board is bad.

[sreten]

Hi,

3 and 4 are the other way round I would think.

The last time I came across this problem the sub was being fed
out of phase signals, due to some dodgy cable wiring, cancelling
the bass from both channels, giving weak poor output.

Its possible, I guess, the Bass-trac cicuitry is playing up .....

rgds, sreten.

[Nico Ras]

Originally Posted by diy didi

Yep! But where to find schematics?? I also have one!!

Is that the one you are looking to replace?

[Original Burnedfingers]

I have 3 and 4 out of sink in the pictorial lineup.

I believe number 3 to be the power supply and 4 to be the power amp section. Picture 4 has the mosfet output stage on it.

The unit was only fed one signal as is only has one input for full range and one input for sub signal that is already processed thru a crossover.

To answer the question the signal feeding the amplifier was correct.

There should be no difference between feeding spk level into the unit and line level according to the manual.

[Original Burnedfingers]

diy didi I guess its you and me on this one.

Want to share voltages?

Its too nice of a little subwoofer just to junk.