If thats the case.. here is a pair of plastic washers that will isolate the jack from the chassis..
http://amprepairparts.com/jacks.htm
Part #ISW-3069
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What happens when you use the wrong cable?
- Thread starter Rusty2867
- Start date
http://amprepairparts.com/jacks.htm
Part #ISW-3069
The old Peavey most likely will not need isolated jacks.
There is always a chance, they have taken more than one big hit so far though.
I have no speaker or jack hooked up at this point,everything is unplugged from pc board still blows fuse!
Oh... rats! Sorry to hear that. To be honest, I wouldnt have thought of that either.. if that's what did it.
It may only be $20 worth of parts that blew, but a tech knows how to handle and the precautions for installing. Miss-handle and they are wasted again. Is the unit worth $80 to $120 for repairs? If not you can fit it to be an extension cab without the amp unit.
To add to what you said, Switchcraft offers insulating shoulder washers and flat washers, part numbers S1028 and S-1029 for isolating jacks from a metal chassis. The chassis hole needs to be enlarged a small amount over what is needed just for the jack. The shoulder flange fits in the hole and prevents the metal jack from coming into contact with the chassis. On a thick chassis, two shoulder washers will fit but on most, you need the flat washer on the other side. This is different from what they show in their image.
These parts are available at places like mouser.com. You see them on a lot of amps. They also tend to get lost when people work on amps. If they are missing, this can create a ground loop.
I took a look at the schematic online (I'm not at home where I have the actual schematics). The output devices are likely two integrated power amplifier devices, not discrete output transistors. One drives the positive side of the output. This signal also is inverted by the second amplifer which produces the negative side of the output. Grounding one side to chassis would probably damage one or both of those devices. Since the schematic isn't clear enough to see the part numbers, I can't look them up to see if there is any output protection.
It's relatively easy to replace those parts, IF you have some tools (a voltmeter, soldering iron of the proper wattage, etc.) and relevant skills. The devices are likely screwed into the chassis for heatsinking, so you have to know how to handle that properly when replacing them. This is a common repair. However, it's possible to do more damage if you don't know what you're doing, so I would recommend due caution.
Also, as mentioned above, a using Speakon connection would be better, because when connecting your speaker, there is much less chance of one of the outputs coming in contact with ground anywhere, ever.
Hope this helps....
It's relatively easy to replace those parts, IF you have some tools (a voltmeter, soldering iron of the proper wattage, etc.) and relevant skills. The devices are likely screwed into the chassis for heatsinking, so you have to know how to handle that properly when replacing them. This is a common repair. However, it's possible to do more damage if you don't know what you're doing, so I would recommend due caution.
Also, as mentioned above, a using Speakon connection would be better, because when connecting your speaker, there is much less chance of one of the outputs coming in contact with ground anywhere, ever.
Hope this helps....
Are you sure using the wrong cable is the problem? That amp is a 4 ohm amp it's very likely that the cab you added in took the load too low and fried the amp.
Not a bad ideal at all if they look alike, or if someone else had to set your rig up for you.
Obviously you don't learn too well!!
May I suggest you rectify the situation before you get yet another "lesson"!
I love it when I see one of the high school kids has "borrowed" the 100' speaker cable from the PA gear to hook up their guitar to the amp. Makes me smile and remember when I was young stupid. I'm not as entertained when I find a guitar chord from the power amp to a PA speaker.
What are they teaching kids these days?
I swear, you could use cables either way when I was a kid.
What are they teaching kids these days?
I swear, you could use cables either way when I was a kid.
For a low powered amp it will work... it worked for me for years. I think it makes a bigger difference with modern high powered amps. For a 50-100watt amp I doubt it would cause a problem. Back when I was a kid... that was a normal powered amp.
Have you read the thread? No, we aren't sure because none of us (other than the OP) has seen it. The prevailing theory now is that when he installed the speaker jack he shorted a conductor to the chassis that he shouldn't have.
Back before I knew better, I played a gig with a studio-grade instrument cable between head & cab.
It was a 140W rig turned up maybe halfway, so I suspect that there just wasn't enough juice running through it to do any damage within the brief 3-song set's time.
Then I learned a thing or two and now use a cable that's rated for anything I'll ever throw at it. The instrument cable still connects (instruments) just fine, as do head & cab work fine still, so I got lucky. But that could've turned bad quickly.
It was a 140W rig turned up maybe halfway, so I suspect that there just wasn't enough juice running through it to do any damage within the brief 3-song set's time.
Then I learned a thing or two and now use a cable that's rated for anything I'll ever throw at it. The instrument cable still connects (instruments) just fine, as do head & cab work fine still, so I got lucky. But that could've turned bad quickly.
The danger is twofold. There is the current that you are pushing through that tiny center conductor, which causes it to heat up, and there is the voltage across the terminals of the connector, which can easily be more than 100V (the voltage between conductors of an instrument/line connection are rarely more than a Volt or two). These factors team up especially badly in a plastic molded connector on an instrument cable. Like I said earlier, I once saw one melted to a dripping lump of plastic. It was a PA cab connected with one of those gray Radio Shack molded plastic cables to a pretty big Crown amp. Blooey. Magic smoke all over the place.
I am going to say the grounding to the chassis is probably what happened,it is only a 100w amp 4ohm the speaker I was hooking up was 4ohm.I mean it blew the fuse as soon as I turned it on,I have the head out and could see the fuse.The amp is pretty much trash at this point because the reason for hooking up a different speaker cab was that my speaker is blown,now the amp is bad so guess i'll go shopping!
