fuse poping questions?

[johncorn]

Hi I need to ask a few question?I have a amp blowning fuses left and right.I opened it up and replaced 3 fuses only 2 are still working the other is gone again.Here is what happens I turn on my amp and turn the volume up slow and as soon as the music starts the fuse turns orange red and blows out.It is a fast acting 1a 250 volts.I do not even have the speaker hooked up to that side or that side turn on?What is happening?Is it worth fixing.The left side works perfect the right side is non working.Is it the power transformer?Everything works perfect on this amp but, that side.Please help me with this problem I have.Thanks jm

[sser2]

> Hi I need to ask a few question?I have a amp
> blowning fuses left and right.I opened it up
> and replaced 3 fuses only 2 are still
> working the other is gone again.Here is what
> happens I turn on my amp and turn the volume
> up slow and as soon as the music starts the
> fuse turns orange red and blows out.It is a
> fast acting 1a 250 volts.I do not even have
> the speaker hooked up to that side or that
> side turn on?What is happening?Is it worth
> fixing.The left side works perfect the right
> side is non working.Is it the power
> transformer?Everything works perfect on this
> amp but, that side.Please help me with this
> problem I have.Thanks jm

You don't provide necessary information. What is the fuse that is blowing? Is it the one that is in series with speaker, or the one in the power supply rail?

Shorted amplifier output will cause exactly the sympthom you are describing. You can test it with a probe made of battery and flashlight bulb. Turn the amp off before testing.

[johncorn]

> You don't provide necessary information.
> What is the fuse that is blowing? Is it the
> one that is in series with speaker, or the
> one in the power supply rail?

> Shorted amplifier output will cause exactly
> the sympthom you are describing. You can
> test it with a probe made of battery and
> flashlight bulb. Turn the amp off before
> testing.

It is the one that powers the speakers.It is next to other fuse for the other speaker.I do not know to much about this amp.It is alot diffrent then the others I have looked or worked on.If it is a shorted amp how do I fix it?

[johncorn]

> You don't provide necessary information.
> What is the fuse that is blowing? Is it the
> one that is in series with speaker, or the
> one in the power supply rail?

> Shorted amplifier output will cause exactly
> the sympthom you are describing. You can
> test it with a probe made of battery and
> flashlight bulb. Turn the amp off before
> testing.

Here is a 2nd fact.I did the light blub test.It was very week and only 2 of three wires lit up.They were bearly giveing light like low watts
or something blocking the power supply.I tried the good fuse channel but no power or watts.The light did not work at all.I think a fuse has to be in at least in one of the fuse holders or it will not work.If I put the fuse in the bad fuse holder it will blow and I will be out of fuses.jm

[jtaylor]

> Hi I need to ask a few question?I have a amp
> blowning fuses left and right.I opened it up
> and replaced 3 fuses only 2 are still
> working the other is gone again.Here is what
> happens I turn on my amp and turn the volume
> up slow and as soon as the music starts the
> fuse turns orange red and blows out.It is a
> fast acting 1a 250 volts.I do not even have
> the speaker hooked up to that side or that
> side turn on?What is happening?Is it worth
> fixing.The left side works perfect the right
> side is non working.Is it the power
> transformer?Everything works perfect on this
> amp but, that side.Please help me with this
> problem I have.Thanks jm

Your description of the problem is your number one problem. You should first identify the amplifier by name and model number, which you don't do. Your statement that it's blowing fuses left and right just adds to the confusion. Are you implying that the left and right channels are both blowing fuses, or that the ampliier is just blowing fuses every time you turn it on?

It sounds like to me that one of the transistors on the bad channel is shorted to ground. It's at this point where you have to decide if you have enough electronic training to dig in and find that bad transistor. If you know how to test transistors with a multimeter to check the junctions between the Base, Emitter, and collector, you shoud be able to do a cold check of each transistor in the bad channel. Knowing if the transistor is either a NPN or PNP junction type at this point would help but is not really needed.

Each channel should have a bank of output driver transistors that will need to be cold checked to find out what transistor is shorted. You will need to unscrew each transistor one at a time and remove it so you can measure the transistor junctions for a short. If the transistor cold checks well, you need to reinstall it with the mica insulator or you will have even bigger problems. If you think you can handle that, go for it. If your Electronics skills are not up to the above skills, you may just want to let a qualiied technician repair it for you. Depending on the brand and quality of the amp will be your decision on whether you want to repair it or at least take a chance of repairing it yourself. Transistors are generally pretty cheap, with a few exceptions. IHTH's

J. Taylor

[sser2]

Transistors
> are generally pretty cheap, with a few
> exceptions. IHTH's

> J. Taylor

They are cheap, yes, but they have to be matched. That is, if only one transistor of the complementary pair is blown, replacement needs to be the same Hfe, or new matched pair should be used. If it is a bank of 4 or 6 transistors, the whole bank is to be replaced. If a tech does the job, the price would be stiff. Fixing is only justified if it is a hi-end or collectible amp. Although I know how to do it, I wouldn't mess and just buy another amp.

[jtaylor]

> Transistors

> They are cheap, yes, but they have to be
> matched. That is, if only one transistor of
> the complementary pair is blown, replacement
> needs to be the same Hfe, or new matched
> pair should be used. If it is a bank of 4 or
> 6 transistors, the whole bank is to be
> replaced. If a tech does the job, the price
> would be stiff. Fixing is only justified if
> it is a hi-end or collectible amp. Although
> I know how to do it, I wouldn't mess and
> just buy another amp.

It all comes down to what kind of amp the dude owns, on whether to repair or toss. Most amps I've owned have been good for twenty to thirty years or more with some repairs. HFE and matched pairs are not as critical as some people will make you think. If you Ohm out a batch of transistors and they all read almost identical between the junctions, HFE and matched pairs shouldn't be a problem, never has been one for me.

I dont have as much ambition of repairing stuff any more, and usually find that after a certain age you are better off buying newer technology at close to the cost of having someone repair it for you. If you repair it yourself and enjoy doing it on your nickle, can make it rewarding at times. I've got two Phase linear 400's that I've been waiting way too long to fix. In the meantime I've bought some really nice amps that are much better sounding.

J. Taylor