Testing a power amplifier

_brian_

_brian_

Member
I have a knackered HH V800 power amplifier to try and repair. However, I've never dealt with power amplifiers before, and don't know much about it.

I've looked at the unit, and I see no ohm rating of speakers that have to be connected, will i be ok just connecting one or two 4 or 6 Ohm speakers, and connecting a sm58 directly into the input?

I'm prob being stupid, cheers!
 
If its a power amp i would have thought its inputs will be expecting line level not mic level.
Can you find any info on the net about its speaker ohm setting? I'd be more tempted to use 8 Ohms
it's rated at 250watts per channel with 8 ohm speakers.
Get something thats more than 1.5x the max wattage (600 watt speakers)

plug your mic into a mic pre and from the mic pre to the amps input should be fine for testing purposes i'd have thought


more info here


V800 | Classic | HH Electronics

i hope this helps
 
kip4 said:
If its a power amp i would have thought its inputs will be expecting line level not mic level.
Can you find any info on the net about its speaker ohm setting? I'd be more tempted to use 8 Ohms
it's rated at 250watts per channel with 8 ohm speakers.
Get something thats more than 1.5x the max wattage (600 watt speakers)

plug your mic into a mic pre and from the mic pre to the amps input should be fine for testing purposes i'd have thought


more info here


V800 | Classic | HH Electronics

i hope this helps
Click to expand...

That's great, looking at the unit in it's present condition i wouldn't have thought HH would have retained that information.

I have limited equipment, I don't have a mic preamp at work. There is a mixing desk, but I cannot find the power supply for it - it's a dual 18V XLR supply I'm needing to get that up and running.

I might be able to use an old rack multieffect unit just to get the signal up to line level.

Unless that's going to be a problem.

I'm just worried something blows up, when turning the unit on there's a big jolting sound - and that's without anything connected! When something sounds powerful just by the flick of an on switch, it makes me want to run for cover and hide. :o
 
Most amps make a noise switching on dont they?
What makes you think it's knackered?
what do you think is wrong with it?
 
_brian_ said:
I'm just worried something blows up, when turning the unit on there's a big jolting sound - and that's without anything connected! When something sounds powerful just by the flick of an on switch, it makes me want to run for cover and hide. :o
Click to expand...

its an 800watt amp. even if its not true RMS 800 watts its going to be loud.
 
Yeah, i suppose lol.

It was given to me by someone who said it was... broken (not the word he used), and he left it to me to fix. I want to power it up to see what the problem is first before I open it up as I wasn't given any other information.

I've not much experience with this type of thing, I've more experience in small signal electronics. Although I'm mains power savvy I'm apprehensive about dealing with this type of thing. Perhaps because I've no experience of it.

Cheers for all your help :)
 
I dont have any mains experience at all. Only small signal and voltage circuits so far.
I'd be tempted to power it up too if thats all the info i had.
beyond that i'm stumped. The most i could do is look inside and see if i can spot anything obviously blown or burnt. Then i'd have to take it to the EE (electrical engineer)
Sorry i cant help more. Id be cautious with 240volts.
I hope you get it sorted.
 
I think that this will be a job for a tech. Particularly if you can't get a schematic diagram.

With the amp completely unplugged from mains power, visually inspect the inside of the amp. Look for things like:

obviously loose wires or connections.
anything that looks or smells burned out - even the power transformer.
bulging or leaking capacitors
blown fuses (there might be fuses on the circuit boards as well as the mains fuse on the back panel).
check that the power transformer is secure, nothing is shorting.
check that no loose metal items are floating about.

If you are experienced with electrical testing, then you could carefully verify the power supply.

Otherwise, without a schematic and oscilloscope, you will have great difficulty tracing the audio signal to find problems.

With a start-up clunk as you mention (assuming it is not just a relay click), I might be tempted to suspect a power supply issue.

Paul
 
You could plug just about anything into it and see what it does. If it is an 800 watt amp, you should be able to hear a 57 plugged into it. It might be kind of quiet, but it should still work. You might be better off plugging a CD player or something into it.
 
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