Alto pa puzzling me

[tonepumpamps]

I have an alto megavox pb-35w battery powered portable pa that's giving me fits.
The problem seems simple but I can't find the solution.
Basically it won't power on. there is a relay that sends power to everything when the coil is activated by a switch (switching 12 volts)
I can't get voltage accross the contacts of the coil. I can hear the relay switching & when I take the relay out & power the coil i get continuity across the contacts.
When the relay is in the circuit & powered up the 12 volts doesn't make it across the contacts unless i jumper 12 volts to the side of the contact needing it. Then i can remove the jumper and it works fine. I have tried replacing the relay with a new one and that didn't work.
Any ideas would be appreciated!!
Thanks!!!!
Scott

[mozwell]

Is this an Anchor product, or Alto ?
I dont have a service manual or schematic for this.

From a quick search i found the operating manual, it says there is an auto shutoff if the battery is very low. the battery LED will flash.
What is the actual battery volts ?
Does the unit work when the mains power adaptor is plugged in ?
It could be a faulty switch in the power input jack.
12VDC may be a little low for a battery and the low battery sense circuit may be active, try charging the internal battery & see if it works then.
http://www.speechtechnology.com/pdf/...Vox_manual.pdf

[tonepumpamps]

i'm sorry it is an anchor product.
It does not work with the power supply plugged in either. I'll try charging it and seeing what happens.
Thanks for the info, it's given me some ideas to look at.

[Jazz P Bass]

I came across a Fixya link where the OP had to remove the fuse & then reinsert it.
Whatever that may indicate.

[tonepumpamps]

Problem solved!
Bad battery. It was a little strange. I always got 12 volts on my meter but yet the relay wouldn't kick in. So I measured the voltage after I jumped around the relay... 9 volts.
So to test my bad battery theory I hooked the unit up to my car battery, works fine.
This must also mean that the charging plug doesn't also power the unit. It's strictly for charging.
As usual it's always the simplest thing that a guy overlooks when repairing stuff.

[Jazz P Bass]

Cool fix.
Rule #1: check the power supply.
Which you did.

[52 Bill]

I don't see a lot of these battery powered amps but the first thing I always check is the battery condition. It seems that very few of these amps will run on the charger power only. They all seem to need the batteries to have some charge beyond a surface charge in order to operate.

I start by charging the batteries for 24 hours and then I stick a load resistor across the batteries and see how low the voltage drops.

[cgoepel]

Sharing and looking for ideas from our bright minds here. I came on the site today looking for an MegaVox Pro model U6000. These units are used for shouting orders to a marching band or a football team. Customer said it will not charge and purchased a battery, a new charger, and a replacement power inlet jack. He came to me to install the new power jack, a 5.5 mm dia jack made by Switchcraft. I noticed the amp did not work with it's new battery, but decided not to start a new science project, I installed the new jack without problem. However, the unit still did not work. I left a message with the customer that his unit needed troubleshooting time that will involve higher cost. I looked over the main board which contains the power amp I.C., the charging circuit and other things. I noticed a SMD power resistor that looked burned, marked as R68 (which means 0.68 ohms). I took a photo of the charred resistor and I am posting it. I need the schematic to help troubleshoot the no power issue. Obviously something caused the resistor to burn. It now reads 135 ohms. If any of you folks have a schematic and or advice of previous work you have done on these units, I would sure appreciate it. Thanks for listening. Charles Goepel Fair Dollar Repair

[Enzo]

Never hurts to start at the source:

https://www.anchoraudio.com/technical-support.html


Try asking for the schematic there.

[cgoepel]

Thanks Enzo