help needed with valve amp issue

[mmar]

my valve integrated amp has developed a fault after the intial soft start up it is sending a loud hum to both speakers , unplugged my cd player and interconnects and still the same so deffo the amp , all valves are glowing and no nasty noises internally from the amp or the transformers , forgive me if this all sounds a bit ignorant but i dont have a clue

i live near newcastle [ in the north east ] could anyone direct me to someone with the technical know how to take a look at the amp with a view to repair

[Dingdong]

Which amp is it?
I take a first guess at a dodgy cap.

[mmar]

mark the amp is a consonance m100s plus running 300b,s

[Dingdong]

Are there a couple of pots on the amp for adjusting hum?

[mmar]

yep thanks the pots make no difference and the hum isnt low level

cheers mick

[lurcher]

I am happy to take a look at it, but Halifax is not that close to you, so you may find someone that is close enough to not require posting the amp.

[jantheman]

My first instinct is to say that one of the valves is faulty. Had one not too long ago where the resistance between heater and cathode (i think) went low...hummed like buggery, changed valves and all well again. Best advice dont use it until its fixed. If its a duff valve than it may blow and take other stuff with it.
AnthonyTD was the guy I spoke to and gave me that advice. As far as most are concerned on here, his word is sacred. maybe he will answer here, if not, pm him and see what he says.

[Spectral Morn]

Give Ian Large at Alium audio a ring, they are the UK distributors for Consonance. Hes a nice guy and very helpful.

If the amp was bought recently (from new) then assuming its the amp and not a valve, then rectification of the problem will be covered by the warranty.


Regards D S D L

[mmar]

thanks guys

the amp is about 3 years old an purchased second hand so warranty out of the question

if it where a faulty valve would it affect both channels as the fault is at the mo , unless i have two faulty valves ?

obviously someone local for a check over / repair would be better but happy to pack and send the amp

thanks again mick

[Marco]

Who's Mick - or are you thanking yourself? :scratch:

;)

Marco.

[Reid Malenfant]

if it where a faulty valve would it affect both channels as the fault is at the mo , unless i have two faulty valves ?
From what little i know about valves some small signal valves can have two in the one bottle so yes it's possibly a valve gone duff ;) Personally i'd think it more likely that some part of the PSU is snafu, possibly some low current but high voltage circuit feeding the front end?

Put it like this, it does narrow things down a bit so it shouldn't be too difficult to find the problem & rectify it :)

[mmar]

just a general curtisy thank you in advance for any additional info or advise , from me , mick !

[mmar]

agree the valves would be a good place to start , am i right in thinking the fault could only be due to the smaller pre stage valves ? with a total of 8 valves to possibly replace including a quad of 300b,s it could be costly if it didnt turn out to be a fault with any said valve

[Reid Malenfant]

Sorry i just don't know... Put a transistorised amp in front of me & i'll fix it, but i know next to naff all about valves.. In fact i think i have learn't more on here about them than anywhere else.

Yes the front end & small signal valves would be a good place to start looking. Check up what each valve type is & if one of them is two in one bottle you may be onto a winner. As i say though, i'm more inclined to think it's a PSU issue ;)

[anthonyTD]

Hi,
as others have stated, it could be a valve, and because the amp shares a common power supply, the hum could be carried to both channels, to start, i would remove all valves from one channel and switch on, if the hum is still present, then remove the valves from that side, and replace the ones in the other side and try again, if the hum is still present then i would sugest either a power supply fault, ie; capacitor, or a rectifier fault.
hope this helps.
Anthony,TD...

[mmar]

thanks anthony ill give that a try tonight !

[mmar]

thanks again anthony did as you said and it is a fault with the amps right channel which must affect both channels when all the valves are in situ

took the valves out of the left channel and the hum remained on the right , swapped the valves from the right channel to the left no hum , swapped the valves i had not used for the exercise into the left channel and no hum , swapped them out of the left channel again back into the right channel and the hum is back [ try saying that after a few beers ]

at least i know i have no issues with the valves , anyone local or otherwise happy to take a repair job on ! cannot imagine it being anything major as i mentioned no pops or bangs or nasty noises or smells , possible resistor or cap failure ?

[Ali Tait]

Mick, I suggest you take up the offer Nick (lurcher) made to have a look at it. He knows quite a bit about these kinds of things.

[mmar]

I am happy to take a look at it, but Halifax is not that close to you, so you may find someone that is close enough to not require posting the amp.

hi mate can i take you up on your very kind offer i have origanal box and packing

mick

[lurcher]

Yep, I have PM'd the address. I will post here when I find what the problem is in case folk are interested.

[anthonyTD]

hi Mick,
glad to help.
well,,, thats some good news, i too would recomend taking Nick up[lurcher] on his kind offer, he will sort it no problem i am sure.
Anthony,TD...