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View Full Version : Fuses blown, need help Identifying proper replacements



opimax
06-02-2007, 10:23 AM
Hi,

I recieved my Perreaux amp last week and last night got it working, problems w/unusual connections , needed to make my own which turned out to be no problem w/input from Perreaux tech support.

Last night late I am smiling as I hear music w/test speakers , portable CD player for 30 minutes. This morning after reading the paper hook up to main speakers once before moving and finalizing connections, etc.

1 side is blown! :banghead: Started checking everything on the small speakers(l20t3 :) ). Short answer 2 rail fuses are bad, swapped with the other 2 channel sounds fine again, BIG, BIG relief!! :applaud::applaud:

Now the questions please

Amp has written on it by the fuses "8 amp, 15 amp blow." the fuses that are in it are Lucas 5 (then small print "continuous") 10A. Seems to me that theses are too small by design. I have never heard of this style. The only other thing I have heard of is "slow blow" are these the same thing? If not would Radio Shack have them or are they specialized and if so recommendations where to buy

Thanks much

Mark

Thom
06-02-2007, 11:07 AM
This won't answer your question but may explain a bit. I'm unfamiliar with said amplifier and fuses. For maximum protection continue your quest for information. Some fuses are rated at current they can carry with no ill effect. Some fuses are rated at current they should disappear at. Some fuses have very special time X current curves. Usually there is quite a bit of discretion available in replacing a fuse but if you want the fuse that will let you get the most before it becomes history and at the same time offer as complete of protection as a fuse will give you in the application then what will work becomes much narrower. I hope there was something in there for you. I'm sure a fuse number would have been more helpful.

SEAWOLF97
06-02-2007, 11:34 AM
Hi,

I have never heard of this style. The only other thing I have heard of is "slow blow" are these the same thing? If not would Radio Shack have them or are they specialized and if so recommendations where to buy

Thanks much

Mark

Since you are in contact with Perreaux tech support , ask them. I would never use "slo blo" in audio gear.

When I was getting tech support from Ohm's president , we blew fuses left and right , working to THE SMALLEST that was usuable and not blow often.

opimax
06-02-2007, 12:39 PM
Thanks both for the replys.

I do understand both replys :) I will continue w/Perreaux but being the impatient child I still am I want something today and no answer from Perreax is expected till Mon or Tuesday. I will do my Bicycling today past some high end shops in Bethesda and see if they "know" the correct answer.

For the 2-3 days I am waiting this is what I am thinking.
10 amp regular quick blow or even and 8 based on 5 blows at 10 that was in there and the writing on the amp of 8 blows at 15


Any thoughts...

Mark

Allanvh5150
06-02-2007, 02:29 PM
Hi Mark,

Depending on the amp model you have, it must be a big one, the fuses you want are just standard 1 1/4" glass fuses. Dont use slow blow. If the amp says "8Amp", go with that. The 15 amp blo rating was is confusing to say the least. Also, depending on how loud you run your system, you could just put 5amp fuses in there for a little extra insurance. I have had a lot of experience with the older Perreaux amps and I have never seen a rail fuse blow, unless someone put a very low load on it or a dead short. I have only ever seen the Mosfets fail "open", which is very good for your system. Any info that you want, give me a yell and I will see what I have. Hope this helps.

Allan.

opimax
06-03-2007, 11:25 AM
Allan

Thanks for the response. I went and purchased 10 amps for the main. I purchased both 6 and 8 for the rails starting with the 6. All of the fuses showed old age and some burning of the paper Lucas used internally. I have not seen Lucas fuses for sell here in the States thinking they might be very old.

Seems "warm", not at all familiar w/different amps but this seems accurate to what I think warm would be. I like it.

2 other issues, not liking the fan so I would think i will disable it, per a few people including Pereaux support. The other is the gigantic thump when turning off, this has to be tamed whether normal or not.

Oh and trying to find out if there is a face plate that is not rack mounted

Mark

SEAWOLF97
06-03-2007, 11:32 AM
. All of the fuses showed old age and some burning of the paper Lucas used internally. I have not seen Lucas fuses for sell here in the States thinking they might be very old.

Back when I drove English sportscars equipped with Lucas electrical running gear , Lucas was know as the "Prince of Darkness"

In fact the old joke goes..

Q. Why do the English drink warm beer ?

A. because they have Lucas refrigerators ...:applaud:


Lucas quality really improved about 10 years ago (when they started rebadging BOSCH parts and selling as their own)

hjames
06-03-2007, 11:42 AM
Back when I drove English sportscars equipped with Lucas electrical running gear , Lucas was know as the "Prince of Darkness"


Ah, you're just saying that because you never tried Moto Morelli parts!

BMWCCA
06-04-2007, 06:05 AM
Or, perhaps, Magneti-Morelli?

hjames
06-04-2007, 06:28 AM
Or, perhaps, Magneti-Morelli?

There ya go makin' sense of it all ..
hey I never let accuracy get in the way of good drinkin' !

Allanvh5150
06-05-2007, 02:16 AM
Hi Mark,

Out of curiosity, wht model Perreaux do you have? I am pretty sure they were all rack mount.

Allan

opimax
06-05-2007, 04:33 AM
Hi Allan,

It is a 6000b. only 2 issues left , disabling the fan and turn off thump. the fan I can deal with the thump I need help with

Mark

Earl K
06-05-2007, 05:20 AM
It is a 6000b. only 2 issues left , disabling the fan and turn off thump. the fan I can deal with the thump I need help with

Mark,

If that was my amp, I would worry most about the "thump". It sounds to be a discharge wave that includes a large amount of DC based energy. This could eventually cause damage to your speakers. I'd suggest that you take your speakers "offline" before shutdown and replace them with an 8 ohm load resistor before powering down the amp ( until this thump is minimized ). I'd go with a 20 watt / 8 ohm resistor ( fwiw ).

- This discharge thump is ( IMO ) what's causing your rail fuses to prematurely blow. I think the amp overall needs some maintenenace & tweaking in the area of all the internal DC offsets .

- I'd recommend you register at the diyAudio website (http://www.diyaudio.com/) . Once a member, create a thread listing your amps problems. "Anatech" ( Chris ) is a moderator there who's a very skilled tech. / who "may" just respond to your query with some self-help directions ( if you want to open up your amp ) .

:)

opimax
06-05-2007, 09:58 AM
Earl,

I agree the thump is an issue, I thought that is what I posted, :)

let me clear something. The fuses don't blow on a ongoing bases, they blew only one and that was after the 1st time I used it. The fuses were 5 amp and 8amp is what is printed. I used 6amp this time, I do have 8 amp available. the old ones were very old.

All that being said I have only turned it off 3 times , 2 thumps 1 not. My unit is kept on currently, it is no big deal to leave on. On the otehr hand I want all my equipment "right" so I will happily follow your suggestions, athough in my usual slow process :). I am also waiting for next response from Perreaux on the manual, I will be asking them about the thump also if I haven't already

Allanvh5150
06-06-2007, 02:56 AM
Hi Mark,

It is unusual for these amps to make a thump, on or off. Does it still do it when you turn the attenuators right down? Putting a timer circuit and a realay to disconnect the speakers would solve the problem as well.

Allan.

opimax
06-06-2007, 06:46 AM
Allan,

If I can get it fixed properly rather than a work around, that would be my 1st choice. Also want to verify this is not a sympton of something else with the amp. I am writing to marty from Perreux in another window currently and I will leave it on till fixed. I don't like turning it on and off, the sound makes me fell like I am listening to fingernails on a blckboard, hopefully you have heard that analogy. I will try the gains all the way down next time I do turn it off and report back :)

thanks for your on going help

Mark

Earl K
06-06-2007, 08:56 AM
- If I can get it fixed properly rather than a work around, that would be my 1st choice.
- Also want to verify this is not a sympton of something else with the amp.

Mark,

- You can make a start by measuring for symptoms of illness. Look for DC offset across the amps output terminals. ( Amp on , with a load, idling with no input ).

(A)
- Use a DMM ( auto-ranging is handy but not necessary ) / start by setting the multimeter to measure DC volts using a low voltage scale / something like 3 volts. Hopefully not much of anything is registering at this scale. Switch to milliVolts and write down the measurements for both channels .

- With this knowledge in hand / someone at Perreaux ought to be able to tell you if your measurements are within normal tolerance for that model .

(B) Do the above again / ideally, use a dummy 8 ohm load .

- This time switch the amp off and try to make note of the maximum DC swing across the outputs as the amp discharges .

- Having a meter that does a "Peak & Hold" function is extremely useful here.
- Since the "thump" is momentary, visually following the DMMs' display will be difficult without the audible cues from a speaker load .
- Restoring the "audible cue" of the thump would be helpfull for this test / though I would then limit the exercise to a less valuable speaker .

- Again, write down your results of this test so that you can pass them on to a qualified tech ( or Perreaux ) .

:)

opimax
06-06-2007, 09:42 AM
Earl,

I can do this, thanks!!!! I have my fluke 77, might have peak hold on it even. Gimme a week, I move slowly through projects :)

choosing the "safe" speaker, do you think the 18" 2245 is safe just because it can take it or something else? I don't have lots of bad speakers to blow up, 1 maybe 2, lol the rest are decent enough to save

Earl K
06-06-2007, 10:54 AM
Mark,

- Don't risk your 2245H ( or any decent JBL for that matter ) .

- You just want to make an audible cue system so that your eye/brain coordination tracks the shutdown thump. Therefore, anything will do that makes sound .

- Find a 16 ohm 6" or 8" junk woofer ( get it from radio shack if need be ) / parallel it with an 8 ohm load resistor ( total load is still over 5 ohms ) and do the shut down test ( at your leisure ) .

opimax
06-06-2007, 02:03 PM
a friend of mine read this thread and has an 8" woofer to use for this purpose :applaud::applaud:

Mark

opimax
06-06-2007, 03:58 PM
Is a turn off thump a standard symptom of more serious problems? Did I get a lemon that I should be dealing with the seller about? not much help probably, nice but ebay, transaction complete...


Mark

Earl K
06-06-2007, 05:00 PM
- Is a turn off thump a standard symptom of more serious problems?

- Some form of discharge noise is quite normal for many hi-powered amps.
- How much noise is relative to the design of each amp.
- This is why you've been asked to make some basic measurments so that you can compare notes with the manufacturer.



- Did I get a lemon that I should be dealing with the seller about?
- It's impossible to tell until measurements are made and you get expert advice on what the results mean.


<> Earl K

opimax
06-06-2007, 05:18 PM
1st observation, thump is is minor at 2 on their scale of 1-10 (thier 1 is at 7 on a clock dial and their 10 is about 5 on a clock dial)

Next to measure idle current
Amp on(ok), with a load(?, speakers attached?), idling with no input(removing input plugs)



I will measure with at "0" "2" and "8" on their numbers

.083-.094 at all levels DC volts left channel
.190-.204 at all levels DC volts righr channel

Using the peak hold function and setting the gains at 2 where the pop isn't bad, it wont actually measure the pop. I tried it without the peak setting because it does actually read when the pop hits, I got OL , don't think this 1970s (maybe 80s) fluke 77 series 1 can handle the big jump, still playing around testing, thinking how big the jump is with gains turned up ....

Mike Caldwell
06-09-2007, 07:24 AM
Hello
As for the turn off thump, are there other connected pieces of equipment that are turning off at the same time as the amp. The normal sequence for powering is preamp and assorted equipment turned on first and power amp last. For power down amp off first and everything else last. If that's the case there are a few good power sequencer units available that with the flip of one switch everything turns on and off in the correct order.

Mike Caldwell

Earl K
06-09-2007, 08:14 AM
Sorry Mark, I missed reading your last post until Mike brought this thread back up ( Thanks Mike ).
-I don't subscribe to threads / therefore I don't get notifications about new activity .


I will measure with at "0" "2" and "8" on their numbers

.083-.094 at all levels DC volts left channel
.190-.204 at all levels DC volts righr channel

- Since I'm not a qualified amp tech. / these numbers for dc-offset ( at idle ) don't mean much to me.
- They are higher than I've measured in other amps but all the other amps types had different design topologies ( and that does matter some ) .
- For instance, the highest offset I've measured on a Bryston 2BLP is around .050 millivolts ( & Brystons are typically biased quite hot which will drive up those numbers ).

- As mentioned earlier, you'll need to run these numbers past, a qualified Perreaux tech.


Using the peak hold function and setting the gains at 2 where the pop isn't bad, it wont actually measure the pop. I tried it without the peak setting because it does actually read when the pop hits, I got OL , don't think this 1970s (maybe 80s) fluke 77 series 1 can handle the big jump, still playing around testing, thinking how big the jump is with gains turned up ....

- Did you ever succeed in obtaining a meaningful measurement when measuring this "thump" ?

:)

opimax
06-09-2007, 08:38 AM
As I said my Fluke is tired , old, cranky, oops thats me :) . Fri I borrowed a newer and 1 model up 87 from work, will test this weekend again, most likely tomorrow.

The thump doesn't seem to care about other equipment, with or without, BOOM :)

I had the top off the amp, not sure if this is good but I didn't see or smell anything funny. Its good nothing is burnt but If I saw something broken or not right we would have a good idea what to fix. I did disconnect the fan. Unit does get warm but not hot now, seems ok heat wise

Thanks for following up

Mark