Power-on/off thump issue with A-80

[Timichango]

Hey there

I recently purchased a used Bazooka tube from a guy on craigslist, and based on the wiring diagram, and the illustration of the back panel, I'm pretty certain it's an A-80.

I've read through a variety of threads on the forums about this issue, and I've still been unable to resolve the issue despite re-wiring the tube several different ways.

Here's a bit of information about my setup:

• Aside from thumping issue, unit works and sounds good.
• Tube is installed in a VW Vanagon Westfalia with an auxiliary battery system.
• This aux. battery directly feeds a secondary fuse panel. Aux. battery and fuse panel are chassis-grounded.
• Bazooka is powered directly from fuse panel.
• Bazooka is grounded directly to chassis bolt, tested at 0 ohms
• Stereo head unit (Alpine idaX100) also powered from aux. fuse panel on separate circuit. Grounded to dash via stock ground location.
• Both the stereo head unit remote turn on and the bazooka's orange 'remote' wire are toggled by a single switch installed in the dash.
• Bazooka's Auto Turn-On jumper is set to the 'off' position.
• Bazooka connected via low-level RCA inputs.
• Bazooka thumps on power on/off regardless of whether inputs connected or not.
• Also tested set-up with 'auto turn-on' configuration (moved jumper, disconnected orange wire) instead of the switch toggle, and that thumped as well, so it's likely not the switch.

All-up, the connections seem very straighforward, and even when all other connections aside from +12v and GND are disconnected, and the unit is switched on via the orange remote wire, the unit thumps on power up/down.

Any insight into how to resolve this thumping would be hugely appreciated!! I'm properly baffled.

Thanks!

-T

[heavyduty]

Originally Posted by Timichango

Hey there

I recently purchased a used Bazooka tube from a guy on craigslist, and based on the wiring diagram, and the illustration of the back panel, I'm pretty certain it's an A-80.

I've read through a variety of threads on the forums about this issue, and I've still been unable to resolve the issue despite re-wiring the tube several different ways.

Here's a bit of information about my setup:

• Aside from thumping issue, unit works and sounds good.
• Tube is installed in a VW Vanagon Westfalia with an auxiliary battery system.
• This aux. battery directly feeds a secondary fuse panel. Aux. battery and fuse panel are chassis-grounded.
• Bazooka is powered directly from fuse panel.
• Bazooka is grounded directly to chassis bolt, tested at 0 ohms
• Stereo head unit (Alpine idaX100) also powered from aux. fuse panel on separate circuit. Grounded to dash via stock ground location.
• Both the stereo head unit remote turn on and the bazooka's orange 'remote' wire are toggled by a single switch installed in the dash.
• Bazooka's Auto Turn-On jumper is set to the 'off' position.
• Bazooka connected via low-level RCA inputs.
• Bazooka thumps on power on/off regardless of whether inputs connected or not.
• Also tested set-up with 'auto turn-on' configuration (moved jumper, disconnected orange wire) instead of the switch toggle, and that thumped as well, so it's likely not the switch.

All-up, the connections seem very straighforward, and even when all other connections aside from +12v and GND are disconnected, and the unit is switched on via the orange remote wire, the unit thumps on power up/down.

Any insight into how to resolve this thumping would be hugely appreciated!! I'm properly baffled.

Thanks!

-T

With having all of your bases covered with regards to voltage, resistance at ground, etc., you will most likely need to install a filter to prevent this turn-on thump. The A-80 is over twenty years old. What used to be considered a "soft turn-on" is now thought of as noise. Not to mention, anytime you buy a used component you can never be sure how the original, or any number of owners since treated the product.

[Timichango]

Thanks Heavyduty!

Can you clarify what you mean by a filter? What kind of filter, and where in the the installation?

I've also read about wiring a resistor in-line with the turn-on wire: any thoughts on this?

Thanks for any further help you can provide,
Tim

[heavyduty]

Originally Posted by Timichango

Thanks Heavyduty!

Can you clarify what you mean by a filter? What kind of filter, and where in the the installation?

I've also read about wiring a resistor in-line with the turn-on wire: any thoughts on this?

Thanks for any further help you can provide,
Tim

Look to purchase the PAC-TR4, this is will eliminate the turn-on thump you have. Another option is to install a toggle or rocker switch into the turn-on circuit. With this method you will have to flip the switch after you power up the headunit. One other option would be installing a 25 volts 330 uF capacitor in-line on the remote turn-on wire, you may want to try this cost effective method first. The local Radio Shack should have that capacitor in stock.

If you are a DIY type, you could always build a turn-on delay circuit. However comparing cost with the PAC unit, you may save $5 and you don't have a nice box that everything sits inside of.