Bass Head = No Output?

[Groove Harder]

Hi, 

 

I have a Harley Benton BA500h with an issue. There is no sound coming from either the speakon nor the 1/4" outputs on the rear of the amp. However, if I plug the cab into the headphone output there is sound. 

 

I have replaced the headphone switching jack thinking it might that but the problem persists. 

 

Everything seems to look alright inside the head although the 7805 voltage regulator seems to be generating a lot of heat. Voltages are fine at the input and output of the regulator though. Does anyone have any experience with working on amps that can maybe give me some pointers on what to look for? I can use a multimeter and soldering iron but my troubleshooting knowledge/skills need some work... 😂

 

Cheers, 

Brian 

[paul_5]

Check the switching jacks on the effects send and return - oftentimes these can become stuck through underemployment, which then cuts the signal to the power amp stage.

Just stick a 1/4” jack lead in and out of the sockets a few times to free everything up and see what that does for you.

 

It sounds like your preamp section is fine otherwise you’d have nothing at the headphone output - this will be using a different amplifier to the main speaker outputs though.

Edited October 28, 2024 by paul_5

[paul_5]

Just looked at the manual and that amp doesn’t have an effects loop, but I’d do the same for the foot switch socket - same principle.

[Groove Harder]

Hi Paul,

 

Yeah, tried that. No dice.

 

Could it possibly be the power transformer?

 

Cheers,

Brian

Edited October 28, 2024 by Groove Harder

[Passinwind]

4 hours ago, Groove Harder said:

Could it possibly be the power transformer?

 

 

Probably about a 1% chance, or less. Do you have a proper schematic, signal generator, dummy load, etc?

[Groove Harder]

Afraid not. Probably struggle to find a schematic online, tbh.

 

I bought it hoping that it was just the switching headphone jack stuck open 😀

 

It would be nice to get it working as the only other amp that I have is a Joyo nano Thunder Bass 😄😄😄

[paul_5]

Can you identify the power amp module and check voltage on the pin outs?

[Groove Harder]

Erm... where would that be in relation to the attached pictures?

 

[Passinwind]

12 hours ago, Groove Harder said:

Afraid not. Probably struggle to find a schematic online, tbh.

 

I bought it hoping that it was just the switching headphone jack stuck open 😀

 

It would be nice to get it working as the only other amp that I have is a Joyo nano Thunder Bass 😄😄😄

I repaired amps professionally for many years and there's no chance I'd try to repair a high power Class D module for component level faults without extensive documentation and access to factory tech support/blessing for advice and parts. The modules are generally "replace, not repair" parts, and with good reason as they are quite complex, dangerous, and rigorously regulated for radio frequency noise emissions, especially here in the US. Does Thomann offer repair service on these? That seems like by far your best chance of getting it working.

 

Please be very careful, 300+ VDC is not uncommon in these things.

[Groove Harder]

Duly noted. I picked it up really cheap just on the off chance that it was an easy enough fix so no big loss. 

[tauzero]

Do you get any output if you put a signal into the AUX socket?

[Groove Harder]

1 hour ago, tauzero said:

Do you get any output if you put a signal into the AUX socket?

 

Yes, if I plug my phone in I get music playing through 👍

[Passinwind]

1 hour ago, Groove Harder said:

 

Yes, if I plug my phone in I get music playing through 👍

Through the power amp output or the headphone one?

[Groove Harder]

5 minutes ago, Passinwind said:

Through the power amp output or the headphone one?

Through the headphone output.

[Passinwind]

22 minutes ago, Groove Harder said:

Through the headphone output.

Dang, hoping for you that it was the other one. 

[John Cribbin]

Looks like the various parts are connected up with plugs/sockets. I'd be tempted to unplug and replug them, if you're lucky it may just be a poor connection or dirt/corrosion on the pins.

 

I doubt if that fuse is for the power amp section, but just in case have you checked it?

 

Obviously do this with the unit disconnected from the mains ....

[Groove Harder]

35 minutes ago, John Cribbin said:

Looks like the various parts are connected up with plugs/sockets. I'd be tempted to unplug and replug them, if you're lucky it may just be a poor connection or dirt/corrosion on the pins.

 

I doubt if that fuse is for the power amp section, but just in case have you checked it?

 

Obviously do this with the unit disconnected from the mains ....

I have tried replacing the fuses to no avail but I'll check the plugs/sockets later on tonight 👍

[PaulThePlug]

Mate has been messin with my SWR Notworking but Nowworking, Workingman's 12...

The IP Jacks, Active and Passive were Lots-of-Pins sealed units, Stereo but something failing on the switching... IP always Grounded... No Tuner Out, No FX R or the FX SR Link...

Replaced with Panel Mount and wires to the board - Sorted.

#NeverUnderEstimateTheDodgeSocket....

[tauzero]

7 hours ago, Groove Harder said:

Through the headphone output.

 

I should have been clearer and said output from the speaker.