Marantz PM230 amp

[rockolagirl]

Hi, for some years I have successfully used this amp. Then it started to blow when switched on. I replaced all fuses x 3 times and although it looked likely as soon as volume was increased it blew. I read that it would not be financially viable to have it looked at. So I bought a replacement from Ebay,plugged it in and when volume was over a third it blew. Help please

[paulsherwin]

This suggests that there is something wrong with your speakers or the associated wiring.

[rockolagirl]

Hi, thank you. I will check the wiring. I have tried two different pairs of speakers and the amp still blows. Actually the problem started when I changed from original speakers to replacements. I have since put the original Marantz speakers back but blew again. Simple question, should the lined wire from speaker connect to plus on amp

[paulsherwin]

It doesn't matter which way round you connect the speakers so long as both are the same.

[TonyDuell]

Normally the marked wire (lined, whatever) is usd for the positive (plus) connection.

But unlike a lot of electrical things where it does matter which way round you connect them, in this case if you wire a speaker up the wrong way round it will not damage the speaker, it will not damage the amplifier. All that will happen is that you won't hear much bass because the sound from the 2 speakers will cancel out

[AC/HL]

Were the replacements the same impedance, probably 8 ohms?

[Michael Maurice]

It should but I think there is something more fundamentally wrong.

Check your cables to see that there are no short circuits or strands of wire from one terminal to the other.

Check the length of the cable to see if there is any damage.

If you have a test meter remove the wires from the amp and test the resistance of both cables buy putting the meter on each pair of wires at a time.

The meter shold read approx 6 ohms. If it reads 0 ohms then have have a short circuit.

[rockolagirl]

Hi. Thank you all. Mr Maurice. I have 6 ohms on one and 0 on other speaker wire. Oh dear. Just checking the wire under the carpet

[tri-comp]

Originally Posted by rockolagirl

Then it started to blow when switched on. I replaced all fuses x 3 times and although it looked likely as soon as volume was increased it blew.

Certainly the speakers and the speakercables should be checked as advised.
What strikes me is that you write the fuses starts to blow when the amp. is switched on.
If this is to be taken literally the problem likely should be found elsewhere as the overload caused by defective speakers and/or shorted wiring is only present when the amp outputs a signal.
Did you replace the fuses with new ones of the correct rating?
The two fuses pos.no.: F801 & F802 are rated at 3,15A of the type Slow-Blow.
Another common fuse rating is 315mA which will allow for 10 times less current before blowing and if this type was mistakenly used, I imagine it would be too small to handle the power-on surge current.
So, you need the check what was advised above AND the rating on the replacement fuses used.

Rgds,

/Torben

[Michael Maurice]

Originally Posted by rockolagirl

Hi. Thank you all. Mr Maurice. I have 6 ohms on one and 0 on other speaker wire. Oh dear. Just checking the wire under the carpet

The one with 0 ohm is the faulty one it should also measure 6 ohms.

[Techman]

I think she said it blew the fuses when the volume was turned up, indicating speakers or their wiring or connections shorting.

I should go without saying that wires should never be put under carpets - they always end up being rubbed through and short out. This particularly applies to any mains cable - a fire may start when you're fast asleep in your bed!

[rockolagirl]

Please don't be impatient. I am at the end of my tether too. I have replaced wires to the speakers, using either pair of speakers or either Marzntz amp ....they still blow

[Radio Wrangler]

Understood.

The shorted speaker wires may have done damage to the amplifier, and the amplifier could then blow fuses without any connections being made.

I suppose the next thing to do is to measure the resistances at the amplifier ends of the wires once more to check that the short circuit which caused the trouble has been fixed. Otherwise it will sit there waiting for the next amplifier or if this one is fixed.

David

[ajgriff]

Originally Posted by rockolagirl

Actually the problem started when I changed from original speakers to replacements.

This may be a clue. Can you post a photo of the speaker wire connections at the back of an amplifier as they are currently configured? Also have all three fuses blown whenever you've tried something different? I'm assuming that one fuse relates to incoming power and that the other two are the output fuses - one for each channel. Is that correct?

Alan

[Diabolical Artificer]

Sounds like you have a short circuit, when the fuses blow, what do they look like? Are they clear or black/silver - ish. Try and make a lamp limiter if you can and use that to power the amp up on next test might save on fuses and will be indicitive. Do you have a meter?

If you get stuck and you have transport your welcome to drop it off here, am about 1 hour from Kings Lynn or a courier would be about £8. Actually, come to think of it I might have a PM230 somewhere, will look.

Andy.