Ex HiFi repair engineer, advice given

It is very simple. If you dont agree with Bloo, by all means put your argument forward, however all he is doing is offering his advice. You dont have to take it but i, for one, am very grateful of anybody who can offer help on projects/keeping kit running etc.
FOX was right, IMHO, to question the need to replace components before trying other things.
Lets keep this civil folks. we are all adults and hi-fi enthusiasts.

Welcome to the forum Bloo

 

Is it just me or wasn't Bloo saying that changing the transformer is probably the quickest way to fix the problem most of the time.

Perhaps that comes from working in a commerical environment where you just don't have time to go through all the options. Just my opinion and I'll piss off now just like Bloo has...

 

As I understand it Bloo is saying change the transformer, Mr Fox is saying......you should be establishing why the TF **** up in the first place?

Doesn't Mr fox a have point (if a little tactlessly put at times...?).

Its good of all yoiu guys to put your thoughts in for poor prunes....like me.....but agreed, lets try and keep it nice huh?

No one knows everything....

 

As David says, the first part of any debug should be to assertain the cause.
As Fox said, the Tx hum may well be due to external influence.

 

Ooh, I'm glad to hear some more moderate offerings - this was getting uncomfortable! I come on here to relax!

 

I'd like to offer a thread proving expensive cables are rubbish from my years of experience...

(only joking, put down the stones and rotten tomatoes)

 

:gatling::chainsaw: :chop:

whoops..... sorry........

 

DC on the Tx primary

Take the offending box to a friend (preferably as few miles away) and see if it still hums, and to roughly the same degree, when running on their mains. If so you should probably look to replace the transformer. If all is well, or the hum drops significantly then you know your mains is at least partly at fault.

Having said that, some transformers are better at dealing with DC on the mains than others so you may end up replacing it anyway.

 

Very good advice from RobHolt.

Any debug engineer (IE repair type chap) should first find the cause, not just suggest replacement without actually examining all evidence.

I have worked in electro/mech failure analysis for the past 9 years and I can still get caught out by assumption.

 

So's amazingtrade. heh heh.

 

That's what I was thinking. Changing a £60 transformer in an hour may be better VFM than 4 hours labour fixing it...with unknown results... who knows? not me

Also, maybe mr Bloo had presumed that things such as humming dimmer switches and the like had already been eliminated, and the hum was definately a transformer fault.

Anyway, glad to have a repair man on the forum. Who knows when any of us may be glad to use a well-priced repair.

 

Yep, that's what I was getting at.

 

So one is saying what heppnes if the replacement one packs up as well.....

The other is saying no it shouldn't..........if my experience serve me correctly......and this is the fastest way of solving it.

Ho hum.

 

Thanks guys - it seems airtight agree with the different approaches suggested on this thread (ie could be the traffo, could be the mains and that replacing the traffo wouldn't necessarily cure the issue (ie not cheap but no guarantee) - its with a chap who has it on a variac at the moment and whilst I havent heard it myself he says on the lower voltage he has to put his ear to the box to hear it so perhaps the higher voltage is causing the laminates to vibrate

the engineer chap seems to think there is somehting wrong with the tranny (ie in his experience it makes more noise than he would expect) but he thinks if we use a variac or step down then this will (to pick up on bubs point) make it negligible

any suggestions re putting an aitotransformer in the circuit - if suitablly overrated will it degrade matters - on another forum it seems this could be a potential issue deoending on impedance but I dont understand such things well enough to know if the airtight pre will suffer from this - an autotransformer won't be cheap by the time I have one fitted (ideally in the other room and wired through into the lounge)

rgds
Darren

 

One of my power amp trannie hums.
The hum varies at different times of the day, sometimes disappearing altogether others, usually teatime, its bloody loud.

 

Well my voltage is a bit over 250V and the air tight pre should be run at 220v - word on the streets is some trannies would cope with this but others won;t - you pays yer money etc - air tight are suggesting a new tranny may not fix the issue (but it might make it better)

so looking for a Variac now - any clues where I might get one in the stoke area? autotransformer is another option but I thought having a variac around might come in useful for other jobs and would give better adjustment

looking at a 15amp one to give a bit of headroom and hopefully the possibility of running the denon Jap TT off it as well

seen one on ebay but any other suggestions as to where I might get variacs gratefully received

rgds
darren

 

cheers fox - got a second hand one on ebay at the weekend for £95 15A so should be big enough

waiting for it to arrive

rgds
darren

 

Help on some Old Kef Drivers

Hi Everyone...just joined today

I am looking for some advice please? I have a paid of large speakers that have flat and large KEF drivers. I have owned them for 10 years and before that my father in laws friend had them built for around £2500. I am told the drivers alone are £600??

I am trying to find out the model numbers of the drivers and as well as mid range and tweeters....any suggestions?

Cheers

 

Post some pictures.

Are the bass drivers an oval shape rather than round?