Pioneer RX-570 keeps blowing fuses

[Matt Evans]

Hello! I'm new to the forum. Hope someone can help me.

I am looking at a surround sound stereo receiver for a freind (Pioneer
RX-570). Every time i plug it in it blows a fuse inside the unit. I've
opened it up looking for any obvious signs, but nothing looks out of order
except for the blown fuse. I borrowed a multimeter and probed around a bit
looking for broken circuits or whatnot. The only thing i found that was out
of line to ME (having little experience) was that there was a brown,
cylindrical object about a quarter inch long with two red and one green line
going around it in which when probed, had no needle movement(in ohms) on the
multimeter. I have placed the probes on it different ways on either end but
no dice. I did some reading on the net about it and i believe it to be
resistor. It's my understanding that resistors resist current, but do not
block it, so i figure there should be SOME current coming through, shouldn't
there? I have no training in electronics and know very little about it, but
i'm hoping to learn. If someone replys trying to help me, please keep the
lingo simple for me. Thanks!

 

[[email protected]]

first, dont go poking around with a meter with a needle. Get a digital
meter if possible, or know where you are poking. The reason being that
the needle type meters can cause current to flow where it shouldn't.
That is you might blow things by just looking at the resistance across
them. This is especially true with mosfets, but it sounds like you
don't know what those are.

If you really want to learn electronics, get the service manual to this
thing. It might be available on the net somewhere for free or a small
fee. just google it. Then figure out what the symbols in the schematic
of the service manual mean and what they do. know what a transistor
does. This is a good start.

To directly answer your question, the round thing is a resistor. Get a
resistor color code guide (free on net) and it will show you that red
red green (in that order with a 4th band after green) is 2.2 mega ohm.
thats a lot, and probably wont make the needle move much, but a digital
multimeter should be able to read it ok. Usually resistors are ok
unless they look bad, but not always. I usually asume they are fine
and only test them when i get really stumped.

Hope this helps.

 

[Arfa Daily]

Hello! I'm new to the forum. Hope someone can help me.

I am looking at a surround sound stereo receiver for a freind (Pioneer
RX-570). Every time i plug it in it blows a fuse inside the unit. I've
opened it up looking for any obvious signs, but nothing looks out of order
except for the blown fuse. I borrowed a multimeter and probed around a bit
looking for broken circuits or whatnot. The only thing i found that was
out of line to ME (having little experience) was that there was a brown,
cylindrical object about a quarter inch long with two red and one green
line going around it in which when probed, had no needle movement(in ohms)
on the multimeter. I have placed the probes on it different ways on either
end but no dice. I did some reading on the net about it and i believe it
to be resistor. It's my understanding that resistors resist current, but
do not block it, so i figure there should be SOME current coming through,
shouldn't there? I have no training in electronics and know very little
about it, but i'm hoping to learn. If someone replys trying to help me,
please keep the lingo simple for me. Thanks!

I honestly don't want to put you off learning about the subject some, but
you have picked a mighty tough repair project here, to cut your teeth on.
The reason that the fuse is blowing, is most likely to be as a result of a
bad output stage - although there are other causes, such as a bad bridge
rectifier in the power supply. Pioneer amps are notorious for making the
most experienced of us cry, so I think that the liklihood of you ever
getting to the bottom of this problem, particularly just armed with a
multimeter, is slim to zero. You will probably find that your inexperienced
probing ultimately leads to additional damage, which will do you no favours
with your friend. Believe me when I tell you that you've only got to look
sideways at these DC coupled amps, to make them blow their output stages.
Your best bet would be to bow out of this quickly, and advise your friend to
take the item to a good repair shop, with properly qualified people who
specialise in repairing this type of equipment. Then, get yourself some
beginner's electronics books, and build up some basic understanding of
principles, and above all, personal safety when dealing with line-powered
equipment.

Arfa

 

[b]

Arfa Daily ha escrito:

I honestly don't want to put you off learning about the subject some, but
you have picked a mighty tough repair project here, to cut your teeth on.
The reason that the fuse is blowing, is most likely to be as a result of a
bad output stage - although there are other causes, such as a bad bridge
rectifier in the power supply. Pioneer amps are notorious for making the
most experienced of us cry, so I think that the liklihood of you ever
getting to the bottom of this problem, particularly just armed with a
multimeter, is slim to zero. You will probably find that your inexperienced
probing ultimately leads to additional damage, which will do you no favours
with your friend. Believe me when I tell you that you've only got to look
sideways at these DC coupled amps, to make them blow their output stages.
Your best bet would be to bow out of this quickly, and advise your friend to
take the item to a good repair shop, with properly qualified people who
specialise in repairing this type of equipment. Then, get yourself some
beginner's electronics books, and build up some basic understanding of
principles, and above all, personal safety when dealing with line-powered
equipment.

Arfa

I thoroughly agree with Arfa. Don't keep probing around if you haven't
so much as the basic component knowledge necessary- you will make
things worse, possibly putting the appliance beyond economical repair,
and may do yourself an injury.
IMO there is nothing worse from a tech's point of view, than trying to
sort out the aftermath of someone's inexperienced poking (which often
transforms the original straightforward fix into an expensive component
swapping mess). Some repair shops even refuse to deal with such items.
Do yourself and your mate a favour and put the top back on it!
-b.

 

[[email protected]]

first, dont go poking around with a meter with a needle. Get a digital
meter if possible, or know where you are poking. The reason being that
the needle type meters can cause current to flow where it shouldn't.
That is you might blow things by just looking at the resistance across
them. This is especially true with mosfets, but it sounds like you
don't know what those are.

surely the deals the same with dmms, no?

Believe me when I tell you that you've only got to look
sideways at these DC coupled amps, to make them blow their output stages.

oh, horrors. The only thing you'll learn on dc coupled stuff is how
frustrating tronics can be.


NT

 

[Chuck]

Hello! I'm new to the forum. Hope someone can help me.

I am looking at a surround sound stereo receiver for a freind (Pioneer
RX-570). Every time i plug it in it blows a fuse inside the unit. I've
opened it up looking for any obvious signs, but nothing looks out of order
except for the blown fuse. I borrowed a multimeter and probed around a bit
looking for broken circuits or whatnot. The only thing i found that was out
of line to ME (having little experience) was that there was a brown,
cylindrical object about a quarter inch long with two red and one green line
going around it in which when probed, had no needle movement(in ohms) on the
multimeter. I have placed the probes on it different ways on either end but
no dice. I did some reading on the net about it and i believe it to be
resistor. It's my understanding that resistors resist current, but do not
block it, so i figure there should be SOME current coming through, shouldn't
there? I have no training in electronics and know very little about it, but
i'm hoping to learn. If someone replys trying to help me, please keep the
lingo simple for me. Thanks!

This unit was designed to blow the audio output transistors if a short
is detected on any of the B + lines. If the cassette motor shorts,
for example, the audio amplifier blows. These units can be modified
so this doesn't happen, but I wouldn't recommend repairing one of
these and I spent over 20 years in the consumer audio field. Chuck

 

[Mark D. Zacharias]

Hello! I'm new to the forum. Hope someone can help me.

I am looking at a surround sound stereo receiver for a freind (Pioneer
RX-570). Every time i plug it in it blows a fuse inside the unit. I've
opened it up looking for any obvious signs, but nothing looks out of order
except for the blown fuse. I borrowed a multimeter and probed around a bit
looking for broken circuits or whatnot. The only thing i found that was
out of line to ME (having little experience) was that there was a brown,
cylindrical object about a quarter inch long with two red and one green
line going around it in which when probed, had no needle movement(in ohms)
on the multimeter. I have placed the probes on it different ways on either
end but no dice. I did some reading on the net about it and i believe it
to be resistor. It's my understanding that resistors resist current, but
do not block it, so i figure there should be SOME current coming through,
shouldn't there? I have no training in electronics and know very little
about it, but i'm hoping to learn. If someone replys trying to help me,
please keep the lingo simple for me. Thanks!

These models are NOT for newbies or beginners. I have a lots of experience
on these - my old posts on them still come up from time to time. Trust me
and the others here who have advised you to get out of this one. If you're
wanting to learn electronics, don't do it with one of these.


Mark Z.

 

[Matt Evans]

Thanks for the replys guys. I'm wondering though what i would physically
have to do to repair this thing...solder on some transistors? I have a
soldering iron and experience using it, so if that's all that the repair
intails, i think i could do it. If its really that difficult i probably
won't attempt it, but i would still like to know what i would have to do. If
you know of something on the web describing it, please post a link. Thanks
again.

 

[Homer J Simpson]

Thanks for the replys guys. I'm wondering though what i would physically
have to do to repair this thing...solder on some transistors? I have a
soldering iron and experience using it, so if that's all that the repair
intails, i think i could do it. If its really that difficult i probably
won't attempt it, but i would still like to know what i would have to do.
If
you know of something on the web describing it, please post a link. Thanks
again.

ISTM that the general opinion is that you probably have 1940's Ford repair
skills and you are trying to fix a Prius. Probably not looking at a good
result here.

 

[b]

Thanks for the replys guys. I'm wondering though what i would physically
have to do to repair this thing...solder on some transistors? I have a
soldering iron and experience using it, so if that's all that the repair
intails, i think i could do it. If its really that difficult i probably
won't attempt it, but i would still like to know what i would have to do.

....have you paid *any* attention to what people have posted in response
to your original question??

-b.

 

[Matt Evans]

It doesn't hurt to ask. I can can look up anything that i don't know. But if
it's such a big problem, forget it. JEEZ! o_0

 

[Arfa Daily]

It doesn't hurt to ask. I can can look up anything that i don't know. But
if it's such a big problem, forget it. JEEZ! o_0

No, you're right - it doesn't hurt to ask. You did, and we answered you with
what we considered to be honest advice. We really aren't trying to be
obstructive or offensive to you, or to drive you away from the group. You
could learn much by hanging out here. However, although soldering some
transistors will, almost without doubt, be involved in the repair, without
detailed knowledge of how to repair DC coupled amplifiers, you will only
gain lots of skill in replacing and soldering output transistors, because
you will be replacing them again, and again, and again, until your wallet is
empty, or your supplier has run out of them.

Trust me when I tell you, with 35 years experience in fixing these things,
that with the level of skill that you currently possess, you WILL NOT
succeed in repairing this amplifier.

If you are determined to take it a bit further, you could check the bridge
rectifier for shorts, but you will have to remove it to check that you are
not reading across a fault elsewhere ( do you even have desoldering
equipment / skills that will allow you to remove multi-leg items from a
board without damaging the print ? ) If it's not the bridge, then you could
try measuring on ohms across the two main smoothing caps, where you will
almost certainly read a short, from bad output transistors. This will only
be the tip of the iceberg though. As well as bad output transistors, there
will be bad drivers, open resistors, maybe bad diodes, and a trail that can
end you up in the preamps.

If these things can make experienced engineers cry, I hesitate to think what
effect they might have on a beginner. Keep up the interest, but please take
well-intentioned advice from everyone, and walk away from this one.

Arfa

 

[Mark D. Zacharias]

No, you're right - it doesn't hurt to ask. You did, and we answered
you with what we considered to be honest advice. We really aren't
trying to be obstructive or offensive to you, or to drive you away
from the group. You could learn much by hanging out here. However,
although soldering some transistors will, almost without doubt, be
involved in the repair, without detailed knowledge of how to repair
DC coupled amplifiers, you will only gain lots of skill in replacing
and soldering output transistors, because you will be replacing them
again, and again, and again, until your wallet is empty, or your
supplier has run out of them.
Trust me when I tell you, with 35 years experience in fixing these
things, that with the level of skill that you currently possess, you
WILL NOT succeed in repairing this amplifier.

If you are determined to take it a bit further, you could check the
bridge rectifier for shorts, but you will have to remove it to check
that you are not reading across a fault elsewhere ( do you even have
desoldering equipment / skills that will allow you to remove
multi-leg items from a board without damaging the print ? ) If it's
not the bridge, then you could try measuring on ohms across the two
main smoothing caps, where you will almost certainly read a short,
from bad output transistors. This will only be the tip of the iceberg
though. As well as bad output transistors, there will be bad drivers,
open resistors, maybe bad diodes, and a trail that can end you up in
the preamps.
If these things can make experienced engineers cry, I hesitate to
think what effect they might have on a beginner. Keep up the
interest, but please take well-intentioned advice from everyone, and
walk away from this one.
Arfa

I'm fond of saying that Pioneer's engineers should go to jail for this one.
(even though it was really Mitsumi who made those amp modules)

There is a so-called "protection" circuit which operates to INTENTIONALLY
destroy the output transistors if any fault is detected. A power supply
voltage down, a bad cassette motor, bad op-amp IC, etc can cause the output
transistors to fail. All this to make the fuse blow, so the unit cannot
continue under the fault condition.

Sort of like designing a car engine to throw a rod if a brake light goes
out, so that you cannot continue to operate the unsafe vehicle.


Mark Z.

 

[[email protected]]

It doesn't hurt to ask. I can can look up anything that i don't know. But if
it's such a big problem, forget it. JEEZ! o_0

That looks like a no to me. OK then, look up design of dc coupled amps.
Get back to us in 2 years time.

NT

 

[Matt Evans]

Ok, i guess it really is something that is way over my head. I appreciate
that you guys took the time to explain it to me in more detail. My dad is a
retired electician. He gave me some books to read as well as an old
multimeter, so i've got a start learning about this stuff. I'm going to try
googling some of the terms you guys were talking about in your replys to see
if i can make heads or tails of it. I'm more than likely NOT going to try to
fix it though, although my friend to whom it belongs to is way in debt and
won't be able to take it to a repair shop. It will go back to its duty of
filling a hole in his entertainment center for aesthetic value only. Cheers.

 

[[email protected]]

Ok, i guess it really is something that is way over my head. I appreciate
that you guys took the time to explain it to me in more detail. My dad is a
retired electician. He gave me some books to read as well as an old
multimeter, so i've got a start learning about this stuff. I'm going to try
googling some of the terms you guys were talking about in your replys to see
if i can make heads or tails of it. I'm more than likely NOT going to try to
fix it though, although my friend to whom it belongs to is way in debt and
won't be able to take it to a repair shop. It will go back to its duty of
filling a hole in his entertainment center for aesthetic value only. Cheers.

If you seriously want to understand this one, google for the schematic
of a dc coupled amp and try and follow it thru, see how it works. Just
make sure youre not in any way suicidal beforehand.


NT

 

[Homer J Simpson]

Ok, i guess it really is something that is way over my head. I appreciate
that you guys took the time to explain it to me in more detail. My dad is
a retired electician. He gave me some books to read as well as an old
multimeter, so i've got a start learning about this stuff. I'm going to
try googling some of the terms you guys were talking about in your replys
to see if i can make heads or tails of it. I'm more than likely NOT going
to try to fix it though, although my friend to whom it belongs to is way
in debt and won't be able to take it to a repair shop. It will go back to
its duty of filling a hole in his entertainment center for aesthetic value
only. Cheers.

Try learning to repair simpler things - small appliances or basic radios.
Work your way up to nasty stuff like this.

 

[Jonesy82]

hi Homer,
check your audio output power Transiters Q7511, Q7512 A1264 or Nte37,
Q7513,Q7514- C3181 or Nte36 fuse FU1101 6.3a 125v this use come from full
volum without speakers attached hope this help.

 

[Homer J Simpson]

hi Homer,
check your audio output power Transiters Q7511, Q7512 A1264 or Nte37,
Q7513,Q7514- C3181 or Nte36 fuse FU1101 6.3a 125v this use come from full
volum without speakers attached hope this help.

You need to tell the OP.

 

[Arfa Daily]

You need to tell the OP.

And not top post. This is how confusion like has happened here, as to who
you're replying to, occurs. Homer was not the original poster, just one of
the respondents ...

Arfa