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Re: what fuse do I need, yamaha emx66m

Postby James Perrett » Tue Oct 20, 2020 9:58 pm

Chances are they use the same board for a number of different models so the fuse rating depends on which model the board is fitted to.

Looking at the parts list, the 12A and 10A fuses are for the Japanese and US versions while the Northern European version uses a TSD 4A 250V SEMKO 20mm fuse.
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Re: what fuse do I need, yamaha emx66m

Postby ciarancussen » Tue Oct 20, 2020 10:26 pm

I put in a 1.25amp fuse in today and it blew straight away without time to even show a light on the mixer. So will I try a 10amp then a 12 amp?
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Re: what fuse do I need, yamaha emx66m

Postby Hugh Robjohns » Tue Oct 20, 2020 10:38 pm

ciarancussen wrote:I put in a 1.25amp fuse in today and it blew straight away without time to even show a light on the mixer. So will I try a 10amp then a 12 amp?

I wouldn't... That path leads to smoke and flames!

It's really important to know if it ever worked reliably, in your ownership, with the original fuse fitted?

I fear not and that you've picked up a second-hand dead mixer-amp.

There is some evidence that it might be intended to use a T4amp fuse (time-delay or anti-surge 4 amp), so it would be worth trying one of those, but definitely NOT a 10 or 12 Amp fuse of any description.

But the fact that it came with a dead fuse and blows a similar replacement instantly suggests a catastrophic fault condition.
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Re: what fuse do I need, yamaha emx66m

Postby ciarancussen » Tue Oct 20, 2020 10:40 pm

It never worked in my ownership. I’ll try the anti surge 4 amp fuse.
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Re: what fuse do I need, yamaha emx66m

Postby ef37a » Tue Oct 20, 2020 11:02 pm

ciarancussen wrote:It never worked in my ownership. I’ll try the anti surge 4 amp fuse.

No! That powered mixer has a consumption rating of 300W which would indicate a 1.25A fuse for a 240V supply. You could go to 2A (and slow blow as Hugh thinks) but I am pretty sure that will blow as well and you have a serious fault with the mixer.

Fusing equipment is far from an exact science and often ratings have to be changed, almost always increased after gear has been out in the real world a while. It should be remembered that fuses are NOT there to save the electronics so much as to stop fires! Well they do tend to save very expensive things like power transformers.

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Re: what fuse do I need, yamaha emx66m

Postby James Perrett » Wed Oct 21, 2020 1:24 am

ef37a wrote:
ciarancussen wrote:It never worked in my ownership. I’ll try the anti surge 4 amp fuse.

No! That powered mixer has a consumption rating of 300W which would indicate a 1.25A fuse for a 240V supply.

4A anti surge is what the service manual says Dave.

Personally I would do a few checks with a meter first before replacing the fuse.
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Re: what fuse do I need, yamaha emx66m

Postby ef37a » Wed Oct 21, 2020 8:33 am

James Perrett wrote:
ef37a wrote:
ciarancussen wrote:It never worked in my ownership. I’ll try the anti surge 4 amp fuse.

No! That powered mixer has a consumption rating of 300W which would indicate a 1.25A fuse for a 240V supply.

4A anti surge is what the service manual says Dave.

Personally I would do a few checks with a meter first before replacing the fuse.

But it also gives the 240V mains consumption as 300mA? 4 amps is getting on for a kW and a 4A T would need near ten amps to blow. There clearly IS some confusion here and fitting such a fuse rating before checking things could destroy many more components, even blow print away.

The OP might be lucky and the fault nothing more than a shorted 100nF mains filter cap although if the right type, X or Y is fitted they rarely fail in my experience.

https://www.cricklewoodelectronics.com/ ... 7xEALw_wcB

^ Shows the rear panel of a 300+300W amplifier and the fuse for 240V is T2A. Since this is a mixer maybe T2.5A? 4A is for 110V operation.

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Re: what fuse do I need, yamaha emx66m

Postby Mike Stranks » Wed Oct 21, 2020 10:19 am

I think this has moved beyond an interesting discussion that we've all been having about fuses...

The O/P has said that the mixer-amp has never worked in his ownership. It's blowing the specified fuse straight away.

Time either for the O/P to start negotiations about getting his money back if that's possible or to have the amp properly checked out by someone who can determine where the fault lies. We've even made a service manual accessible! :)

... any other route risks a merry blaze or a possible minor fault becoming a 'fit only for the scrapheap' one.
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Re: what fuse do I need, yamaha emx66m

Postby Hugh Robjohns » Wed Oct 21, 2020 10:45 am

Yep -- completely agree with Mike.

And Dave makes a good argument about the T4A fuse...

This really isn't the time for random fuse swapping. If it has never worked under the current ownership then it should be assumed to have been sold with a fault.

Fitting ever larger fuses is likely to convert what might be a minor fault into a catastrophic failure that is extremely uneconomic or even impossible to fix.

I'd recommend either returning the unit to the vendor or find a competent technician and be prepared to spend a load more money on it!
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Re: what fuse do I need, yamaha emx66m

Postby BJG145 » Wed Oct 21, 2020 11:44 am

Mike Stranks wrote:The 'blacked-out' info on the circuit board is stating a 1.2 amp 250 volt fuse

But the circuitboard and diagram say "10A" and "12A", not "1.2A". Is it common to leave out the decimal point...?

The other circuitboard shows "2A" for that other fuse, not "20A".

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Re: what fuse do I need, yamaha emx66m

Postby Hugh Robjohns » Wed Oct 21, 2020 12:04 pm

That first PCB is just a mains-input-to-power-switch-to-transformer board. As such, it is probably used in a range of products with wildly different power ratings -- it certainly looks like it has tracks capable of carrying 10A or more!

Hence the wide range of acceptable mains-voltage ratings for F101 printed on it, and the need to cross out the ones not relevant to that specific product.

So T4A would appear to be the correct rating here for this specific product...

The second PCB receives the output from the transformer and feeds the rectifiers and regulators. That uses two smaller fuses (F102/F103) to feed separate power supply chains, both with T2A ratings.

As Folderol and others have said, armed with the excellent service manual which Mike found, and competency in electronic fault-finding of mains-powered equipment, it should be fairly straightforward to check for faults with the transformer or power supplies and/or locate any faults.
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Re: what fuse do I need, yamaha emx66m

Postby BJG145 » Wed Oct 21, 2020 12:09 pm

Hugh Robjohns wrote:So T4A would appear to be the correct rating here for this specific product.

OK, sounds sensible...
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Re: what fuse do I need, yamaha emx66m

Postby James Perrett » Wed Oct 21, 2020 2:00 pm

BJG145 wrote:But the circuitboard and diagram say "10A" and "12A", not "1.2A". Is it common to leave out the decimal point...?
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According to the parts list they really are 10A and 12A for the US and Japan. I haven't gone through the rest of the circuit to find out why they need such large values but presumably there's a large inrush current on power up or high peak currents.

However, it definitely sounds like this unit needs someone to look at it who knows what they are doing.
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Re: what fuse do I need, yamaha emx66m

Postby Hugh Robjohns » Wed Oct 21, 2020 2:53 pm

James Perrett wrote:I haven't gone through the rest of the circuit to find out why they need such large values but presumably there's a large inrush current on power up or high peak currents.

From page 26 of the user manual:

For European Model
Purchaser/User Information specified in EN55103-1 and EN55103-2.
Inrush Current: 85A
Conformed Environment: E1, E2, E3 and E4
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Re: what fuse do I need, yamaha emx66m

Postby BJG145 » Wed Oct 21, 2020 3:38 pm

James Perrett wrote:According to the parts list they really are 10A and 12A for the US and Japan.

Well in that case -

Doctor Watson. You're fired. :D

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