Just won a AB International 600LX, what to check first?

[xxllmm4]

Hey everyone,

On the advice given here I just won an AB International Precedent Series 600LX AB International Precedent Series 600LX 2 Channel Amplifier | eBay my question how do I check this amp out before I hook it up? I have a decent multimeter.

Thanks
Jordon

 

[JonSnell Electronic]

Seems straightforward enough.
Power it up with nothing connected. If it shows signs of life, plug in one loudspeaker at a time in. If all OK, switch off and insert a signal input. Power up again and if it works, bonus. that's is about it.
Unless you believe it to be faulty!

 

[xxllmm4]

Thanks, I thought you needed to test these old PA amps first before hooking speakers up. Good news 🙂

 

[ostripper]

You could get the schematic , check offset /bias.

AB 600 series has 3 similar "leach amp" type circuits. Older 600
has no servo (below - the "a").

LX might be a round toroid and a servo - same amp with 3 pair
BJT TO-3 outputs.

OS

 

[djk]

So you're the one that out bid me (by $1)!

Power it up and check there is no DC on the speaker outs (before hooking up speakers).

Use the 1/4" inputs, not the balanced (unless you work on them).

Clean the input jacks and front panel pots.

 

[xxllmm4]

So you're the one that out bid me (by $1)!

Sorry, I was hoping it wasn't someone form here LOL

Thanks for the advice. I'm sure i'll have lots more questions once I get it. I have always been involved in the speaker building side of the hobby, not the amp tinkering.

 

[djk]

"Sorry, I was hoping it wasn't someone form here LOL"

I have so many 400 and 600 now I can't remember the exact numbers.

 

[xxllmm4]

Hey djk, I guess you would be the one to ask then. I'm running a set of Cerwin Vega 6 ohm speakers. The plan is to get another identical set and run them all off the same amp. How would this amp be running a 3 ohm load? I have heard 2 ohm is iffy.

 

[djk]

If you measure those 6Ω Cerwin Vega, I'll wager that the DCR will be under 4Ω, so two will be a problem.

You could buy a different transformer, a 40-0-40V 800VA~1KVA unit would allow the AB 600 to drive 2Ω safely. It might be cheaper to pick up another amp.