Fuse Blowing Amber Series 70

[Capital]

I picked up an Amber Series 70 with a dead right channel. Both fuses were blown in the right channel and after replacing them I powered up the amp again but they instantly blew. I'm thinking it's the 2N5686 and 2N5684 output devices but before I start throwing parts at it I was curious if anyone had any suggestions.

Any advice would be greatly appreciated.

[jackand08]

I´d start by checking the output devices with either a transistor checker or a multimeter set to continuity test (there are plenty of guides on how to test transistors and what readings you should get between pins available online). It´s probably also a good idea to do a visual inspection and check whether any resistors have scorched or any capacitors or transistors have blown. Also, check the power supply voltages are within a decent range.

A quick google didn´t bring many results for this amp and I checked all of the usual sites I use and could not find a service manual or schematic. If you can find one, it would help out a lot and give something for you to compare with.

[nigelwright7557]

If they are gone I would be asking why and if the original problem is still there.
After all you dont want to fit new components only for them to blow again.
Were you giving the amp some serious stick when it went ?

I would start off by checking speakers and leads for low resistance or a short.

Semiconductors rarely blow for no reason.

I usually fire my faulty amps up without output transistors in the circuit and feedback the VAS output into the LTP to make sure LTP, VAS and bias are working OK.

[Capital]

Thanks for the replies guys. I should have been more clear. The amp would instantly blow fuses in the right channel without speakers or RCA connections. The 2N5686 and 2N5684 output devices pulled out easily and I checked them. The 2N5686 both read the same but the 2N5684 read differently on my multimeter. I decided to swap the 2N5684 to see if powering it up it would then pop the left channel. I was surprised to see that it didn't. Now a logical person would have stopped here and ordered a new part. I being the dufus I am decided, "it's not popping fuses I wonder if I can give it a listen". I plugged everything up and turned it on. It sounded fantastic......for 30 seconds. Bright sparks started flying from the board of the left channel and I quickly unplugged the amp. The LM391N chip was all burned up and the cause of the fireworks.

I'll post pictures later. I know it's beyond my skill level to fix the board, I may run by a shop and see what they think or just keep an eye on the classifieds for another Amber with a bad channel.