DB750 Help Please

[bassboysam]

My amp suddenly started making this buzzing noise (not heard through the speaker) that fades in and out every few seconds. i've tried multiple outlets and it didn't make a difference. I removed the cover, made sure the tubes were not loose but it sounds like it is coming from the area of the transformer.

Yes, I will take it to get checked out, but just wondering if its a known issue or a simple fix perhaps? seems like some sort of filtering issue maybe?

 

[agedhorse]

Contact an experienced, QUALIFIED service tech. This isn’t a a DIY project.

 

[bassboysam]

Contact an experienced, QUALIFIED service tech. This isn’t a a DIY project.

already dropped it off. was not planning to DIY this, thanks

 

[lele_sakko]

Hi, i had a similar issue with an Ampeg svt2pro many years ago..
When the head starts to hum, the bias lights goes crazy..
I’ve discovered that I had a toner printer in the same room, when the printer was off there was no hum and no bias problem, when the printer was on there was problems..
Maybe try the head with all the electronics in the house turned off, hopefully it will be enough to solve the problem..

 

[bassboysam]

Hi, i had a similar issue with an Ampeg svt2pro many years ago..
When the head starts to hum, the bias lights goes crazy..
I’ve discovered that I had a toner printer in the same room, when the printer was off there was no hum and no bias problem, when the printer was on there was problems..
Maybe try the head with all the electronics in the house turned off, hopefully it will be enough to solve the problem..

i unplugged everything that was on the same circuit as the amp, but that did not help. hopefully its just the filter caps and not the transformer itself.

 

[MechaSparky]

Hi, i had a similar issue with an Ampeg svt2pro many years ago..
When the head starts to hum, the bias lights goes crazy..
I’ve discovered that I had a toner printer in the same room, when the printer was off there was no hum and no bias problem, when the printer was on there was problems..
Maybe try the head with all the electronics in the house turned off, hopefully it will be enough to solve the problem..

Interesting, I was thinking rfi too. You could try wrapping the power cord around a torroidal ferrite ring or use one of the snap-on types to stop common mode current from making its way up the cord and into the rig.

Ferrite Core Products - Palomar Engineers®

Shop premium ferrite cores in Mix 31, 43, 61, and 75 for RFI/EMI suppression. Reduce noise in cables, power lines, and audio systems with Palomar Engineers’ proven ferrite solutions.

palomar-engineers.com

 

[JamesGrant]

Is there a fan? Try poking a wooden chopstick through the fan grill to stop the fan. Apart from that

 

[bassboysam]

Is there a fan? Try poking a wooden chopstick through the fan grill to stop the fan. Apart from that

the fans did not turn on in the few minutes that I played through it, so not, not the fans

 

[agedhorse]

Hi, i had a similar issue with an Ampeg svt2pro many years ago..
When the head starts to hum, the bias lights goes crazy..
I’ve discovered that I had a toner printer in the same room, when the printer was off there was no hum and no bias problem, when the printer was on there was problems..
Maybe try the head with all the electronics in the house turned off, hopefully it will be enough to solve the problem..

Nope, not the cause because it makes the noise with nothing else plugged into the circuit. What you describe is a one in a million cause.

i unplugged everything that was on the same circuit as the amp, but that did not help. hopefully its just the filter caps and not the transformer itself.

Almost 100% certain not to be the power transformer. It’s possible that it’s a defective filter cap, but even that is unlikely. There are many much more common causes that a qualified tech will test for. They should NOT shotgun the repair by replacing parts that have not been verified as defective.

Interesting, I was thinking rfi too. You could try wrapping the power cord around a torroidal ferrite ring or use one of the snap-on types to stop common mode current from making its way up the cord and into the rig.

Ferrite Core Products - Palomar Engineers®

Shop premium ferrite cores in Mix 31, 43, 61, and 75 for RFI/EMI suppression. Reduce noise in cables, power lines, and audio systems with Palomar Engineers’ proven ferrite solutions.

palomar-engineers.com

 

[JMarkD]

The fans did not turn on? The DB750 fans should run all the time when the amp is on.