Bass Amp cuts out, please help

achtung jackass · 15th March 2005, 10:36 AM

hi, i'm new so excuse me if this is posted in the wrong place.
i've got a 100w Session Sessionette Bass Amp (puts out 90w through speakers in cab). the problem is the amp cuts out sometimes, the power stays on(red light on switch is still lit) but all of the sound goes. it 'fizzles' out and then there is a small pop. sometimes the amp turns on but there is no sound, it powers up. the amp still works but generally cuts out after approx 20/30 minutes of playing, if not sooner. there are no problems with the speakers which are celestions.

Can anyone help me find out whats wrong and how i can fix it.

thank you

oh, the amp is about the same age as me, its from 1986 as far as i know.

anatech · 16th March 2005, 02:15 AM

Hi achtung jackass,

Is it possible that a thermal cut out is doing it's job? What happens if you play at low level?

-Chris

Enzo · 16th March 2005, 10:29 AM

If the amp has an effects loop, connect a spare guitar cord from the send to the return. Yes, connect the jacks together. If this restores the sound, the return jack needs service or replacement. Also if there is a power amp in jack and a preamp out jack, treat them as an effects loop and connect them together for test.

This will not harm the amp, the jacks have internal contacts that carry the signal past them when they are NOT in use. If those contacts get dirty or fail, then the signal doesn't get past them.

A very common problem in instrument amps.

Frank Berry · 16th March 2005, 10:30 AM

Check that the output transistors have not loosened from the heat sink(s) and that the thermal grease hasn't dried out.
Sometimes the screws which hold the transistors to the heatsink work themselves loose with age.

achtung jackass · 16th March 2005, 11:13 AM

i've tried playing at low level, or plugging into the low input jack it has no effect, the sound still isn't there. i thought at first it cut out to prevent itself from overloading (as i have an active bass w/ 18v power.) but the previous owner, a friend of mine, had the same problems and he uses passive basses.

yes the amp does have an effects loop, maybe this could be the problem i'll try connecting the send and return together. i'll also open it up and see is there anything loose.

thanks.

achtung jackass · 18th March 2005, 09:55 AM

Quote:

Originally posted by Enzo
If the amp has an effects loop, connect a spare guitar cord from the send to the return. Yes, connect the jacks together. If this restores the sound, the return jack needs service or replacement. Also if there is a power amp in jack and a preamp out jack, treat them as an effects loop and connect them together for test.

This will not harm the amp, the jacks have internal contacts that carry the signal past them when they are NOT in use. If those contacts get dirty or fail, then the signal doesn't get past them.

A very common problem in instrument amps.

thanks a lot Enzo, it worked. i can't be bothered/ don't have enough time to replace them at the moment so i'm just gonna leave my patch lead connecting them. the sound has improved a lot, and it doesn't cut out anymore.

thanks.

Diode · 23rd March 2005, 03:52 AM

The jacks are the first place you should look but what about good old BAD SOLDER connections. This is consumer electronics, you know.

Chris

15th March 2005, 10:36 AM	#1
achtung jackass diyAudio Member Join Date: Mar 2005 Location: Dublin	Bass Amp cuts out, please help hi, i'm new so excuse me if this is posted in the wrong place. i've got a 100w Session Sessionette Bass Amp (puts out 90w through speakers in cab). the problem is the amp cuts out sometimes, the power stays on(red light on switch is still lit) but all of the sound goes. it 'fizzles' out and then there is a small pop. sometimes the amp turns on but there is no sound, it powers up. the amp still works but generally cuts out after approx 20/30 minutes of playing, if not sooner. there are no problems with the speakers which are celestions. Can anyone help me find out whats wrong and how i can fix it. thank you oh, the amp is about the same age as me, its from 1986 as far as i know.

16th March 2005, 10:30 AM	#4
Frank Berry diyAudio Member Join Date: Sep 2003 Location: Midland, Michigan	Check that the output transistors have not loosened from the heat sink(s) and that the thermal grease hasn't dried out. Sometimes the screws which hold the transistors to the heatsink work themselves loose with age. __________________ Frank

23rd March 2005, 03:52 AM	#7
Diode diyAudio Member Join Date: Feb 2003 Location: Oklahoma USA	The jacks are the first place you should look but what about good old BAD SOLDER connections. This is consumer electronics, you know. Chris __________________ The best audio is clean audio!

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16th March 2005, 02:15 AM	#2
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi achtung jackass, Is it possible that a thermal cut out is doing it's job? What happens if you play at low level? -Chris

16th March 2005, 10:29 AM	#3
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	If the amp has an effects loop, connect a spare guitar cord from the send to the return. Yes, connect the jacks together. If this restores the sound, the return jack needs service or replacement. Also if there is a power amp in jack and a preamp out jack, treat them as an effects loop and connect them together for test. This will not harm the amp, the jacks have internal contacts that carry the signal past them when they are NOT in use. If those contacts get dirty or fail, then the signal doesn't get past them. A very common problem in instrument amps.

16th March 2005, 11:13 AM	#5
achtung jackass diyAudio Member Join Date: Mar 2005 Location: Dublin	i've tried playing at low level, or plugging into the low input jack it has no effect, the sound still isn't there. i thought at first it cut out to prevent itself from overloading (as i have an active bass w/ 18v power.) but the previous owner, a friend of mine, had the same problems and he uses passive basses. yes the amp does have an effects loop, maybe this could be the problem i'll try connecting the send and return together. i'll also open it up and see is there anything loose. thanks.

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