ampeg ba-115 bass amp.

[Jose8a]

Hello.. i need some help.
i have a problem with an ampeg ba-115 bass amp.
i don't have any noise in the speaker ( i checked the speaker with a battery 9 v, and the speaker sounds)
i checked with the schematics
and i have sound in the headphones plug.. but the speaker doesn't sound..
i checked all the transistors, and i don't know how to check the mosfets, the are not in short, no one element is in short, but at the exit, to the speaker, with all the controls at 10 (volume, master) and the treble middle and bass at 5... i have max 16 v, i think it is not enough to make the speaker sound...
what can i do to check if the mosfets are bad... or what can i do
sorry for mi english and thank you for your help
as always

[Jazz P Bass]

Amp output voltage

[QUOTE=but at the exit, to the speaker, with all the controls at 10 (volume, master) and the treble middle and bass at 5... i have max 16 v, i think it is not enough to make the speaker sound...
[/QUOTE]

Are you measuring the output voltage as AC or DC.
AC 16 volts into 8 ohms is 32 watts.

Any DC voltage indicates an output section failure.
If it is a Vdc, what polarity is it? + or - .

If the MosFets do not indicate a short, look elsewhere.

Measure the plus & minus Vdc power rails. They should be the same except fot the polarity.

[Enzo]

I'll bet my lunch money it is far simpler than all that. The headphones work, so the amp is working. The headphones jack cuts out the speaker. I'd be checking the phones jack itself.

Look down on the top of the headphones jack. See the three contact strips crossing it? The one closest to the front panel is the ground contact. WHile playing something through the amp, press down on that contact with something - a toothpick, a ball point pen, most anything. SOUnd come back? If so, you might be able to clean the jack, or the jack might be sprung, in which case you replace it.

[Jose8a]

hello, thanks for your help
the voltaje i measured was 16vAC. at the output pins with a 1 khz sine signal 170mv measured with a multimeter
i'll check the headphones jack tomorrow morning
so the watts i think is like 60 watts because the speaker is 4 ohms @ 16 vac
thanks for your help again...

tomorrow i'll tell you what o found

[Jose8a]

ok... i just want to thank you for your help.
without your help it had been very dificult.
i solved my problem. it was the headphones jack earth,
it was not make contact.

thanks again
and sorry for my english