Problem to be solved

[basil]

I have an EAR 864 pre amp and Opera Audio Cyber 800 amps driving B&W CDM 7 NT speakers.
After 8 months of performance of the set-up, a static sound from the left speaker alerted me to the fact that something was going on and soon the preamp quickly overheated, evidenced by the smell of burning plastic and smoke! I sent it off to a highly recommended techno-head who repaired the pre amp by replacing some component or other(The details escape me) and it has been returned "in 100% working order"after he had tested it.
6 hours into playtime...... static returns and feint burning smell again......

Being reluctant to have him attend to it again, my limited common sense suggests that the problem could be one of compatibility between the components(Amps and Pre amp) and not the equipment per se. Why though after 8 months only?
If it is incompatibility between amps etc how does one test for/determine this?
Any informed suggestions/opinions will be welcomed.

Basil

 

[markw]

Take it to another tech.

I think if it were a compatablity problem it would have reared it's ugly head well before eight months.

Since it worked for only six hours after being "repaired", it sounds to me like the guy replaced the burned out part, a symptom of the problem, but never chased down the cause of the problem in the first place to cure the disease that caused the symptom.

IOW, he put a band-aid on a bullet wound without removing the bullet and searching for internal damage.

Find a better tech or send it to the factory if you can't find one locally.

 

[TLS Guy]

I have an EAR 864 pre amp and Opera Audio Cyber 800 amps driving B&W CDM 7 NT speakers.
After 8 months of performance of the set-up, a static sound from the left speaker alerted me to the fact that something was going on and soon the preamp quickly overheated, evidenced by the smell of burning plastic and smoke! I sent it off to a highly recommended techno-head who repaired the pre amp by replacing some component or other(The details escape me) and it has been returned "in 100% working order"after he had tested it.
6 hours into playtime...... static returns and feint burning smell again......

Being reluctant to have him attend to it again, my limited common sense suggests that the problem could be one of compatibility between the components(Amps and Pre amp) and not the equipment per se. Why though after 8 months only?
If it is incompatibility between amps etc how does one test for/determine this?
Any informed suggestions/opinions will be welcomed.

Basil

This is not a compatibility problem. Preamp to amp is voltage amplification, with negligible current passing between them.

Your preamp was not repaired correctly. If the unit was only 8 months old, why was it not repaired under warranty?

 

[sawzalot]

I have the same thoughts why not send back to the manufacturer , at this point you may have voided any warranty that you did have by letting someone else tinker around inside that may not be qualified to work on said product, good luck with your set-up.

 

[TLS Guy]

I have the same thoughts why not send back to the manufacturer , at this point you may have voided any warranty that you did have by letting someone else tinker around inside that may not be qualified to work on said product, good luck with your set-up.

This might be why he did not send it to the manufacturer.

{11-02-09: Jeffb28451
Very reliable and well built. God help you if you need repair, though. When I needed help, the distributors were very helpful and apologetic, but "Tube God Tim" intervened and took the time out to thoroughly insult me by email because I dared to simply ask his distributor if they were taking time off, as I couldn't get anyone on a telephone to order the part for three days. You'd have thought I said something about his mother.

Mind you, not due to a three day delay or lack of contact: three days where no one answered or returned phone calls about a broken unit. They didn't deal with email back then and encouraged telephone calls for contact.

I immediately sold that piece after repair and will never have another Tim P designed piece in my system, even though it sounds pretty good and looks nice in its way. Too many other guys like Nelson Pass, George Wright (rip) Gordon Ranken and tons of others who make great stuff and are gentlemen.

I'll be happy to provide details rather than being flamed by pro-P fans who don't have any knowledge of this transaction. Mr. P's ego and attitude are well-known in the audio industry.}

The above is a lesson to avoid tubes. Bad fry ups are more common with tubes than solid state. There is also no advantage. Decent modern op amp chips will beat the pants off any tube. The designer of his preamp is one of the arch priests of the loony crowd.

 

[basil]

Guys

Thanks for your advice and commenst.
I should have more clearly explained the issue of warranty on the pre amp. I have had it for 8 months it is 2nd-hand and the warranty was not transferable.
It was acquired via the EAR agent who vouched for its original purchase date etc. So the option of getting it to the manufacturer is closed.

Perhaps if I described the noise....It is intermittent occurring whenever it feels like it...
It's a hissing sound like rushing water or heavy rain, interspersed with crackling like cellophane paper being crumpled. It is on a different "level/plane" to the music and therefor doesn't distort or interfere with the sound other than to be a constant in the background. when it appears. It occurs both when the system is playing music and when on without music playing.
It only appears in the left speaker(the speakers have been swapped- still only left). There is no hum(ground loop-- Thanks Clint) nor is it volume related/affected.

The valve connectivity of the valves in the amp has been checked...all OK.

I guess that a techy will need to do some kind of systematic, electronic process of elimination to arrive at the AHA-moment.

Once again thanks for all your assistance. I threw this out in to the Forum thinking that perhaps it was a problem that someone else may have experienced or may have been awatre of, with EAR and had found a solution.

Otherwise the sound quality/staging, imaging etc of the current system is great....

Regards

Basil

 

[TLS Guy]

Guys

Thanks for your advice and commenst.
I should have more clearly explained the issue of warranty on the pre amp. I have had it for 8 months it is 2nd-hand and the warranty was not transferable.
It was acquired via the EAR agent who vouched for its original purchase date etc. So the option of getting it to the manufacturer is closed.

Perhaps if I described the noise....It is intermittent occurring whenever it feels like it...
It's a hissing sound like rushing water or heavy rain, interspersed with crackling like cellophane paper being crumpled. It is on a different "level/plane" to the music and therefor doesn't distort or interfere with the sound other than to be a constant in the background. when it appears. It occurs both when the system is playing music and when on without music playing.
It only appears in the left speaker(the speakers have been swapped- still only left). There is no hum(ground loop-- Thanks Clint) nor is it volume related/affected.

The valve connectivity of the valves in the amp has been checked...all OK.

I guess that a techy will need to do some kind of systematic, electronic process of elimination to arrive at the AHA-moment.

Once again thanks for all your assistance. I threw this out in to the Forum thinking that perhaps it was a problem that someone else may have experienced or may have been awatre of, with EAR and had found a solution.

Otherwise the sound quality/staging, imaging etc of the current system is great....

Regards

Basil

Thanks for the further info.

It sounds as if there is a grid bias problem. This is very common in tubes.

Really if you are going to own tubes you need a boat load of test gear. Tube gear wanders, and should be put on test gear two or three times a year to check things like grid bias. In the old days we had to go through that routine all the time to keep gear in peak condition.

I suspect there is a component pushing the bias high and periodically the cathode/anode current gets too high on one of the tubes. Hence a hot resistor and the burning smell and noise. I would not use that unit until fixed, you likely will extend the damage.

Now knowing that designer, I bet he has pushed everything to the limit, to even get in the ball park of a good solid state unit. That makes this "modern" tube gear even more temperamental.

Now in defence of the tech, I did a careful search of the Net and could not find a circuit or service manual for your unit. Unless one is forthcoming no tech can service it properly. If you don't know the grid bias voltages for instance you have to guess and you will likely be wrong and further problems will occur.

In the hey day of tubes every instruction book came with the circuit with all critical voltage points clearly marked. In these money grubbing days; fat chance. A great many enthusiasts, myself included had all the test gear required to maintain and service Hi-Fi tube gear. Those that did not always had a local competent service tech to turn to. Now they are all dead, or as in your case struggle for lack of information, because the loony set manufacturers say the information is a vital trade secret.

The above alone is a very good reason for not owning tube gear. At the very least anyone contemplating purchasing tube gear should only do so if it comes with a good clear circuit diagram and ALL critical voltages clearly marked.

Unfortunately you problems are a classic case study.

 

[highfigh]

OTOH, the data for virtually every tube model is available on the internet. As long as the circuits aren't trying to shove excessive voltages toward the tubes, they really should be fairly happy. The tens of thousands of tube amplifiers still in use with few problems testifies to that. However, as TLS mentioned, values drift, techniques aren't what they were and specific information may not be available.

It does seem like it could be a resistor issue in the grid bias- have you looked inside of the amp (don't do this when its power cord is plugged in)? The ones in question may be soldered onto the output tube socket pins. As an example, if the output tubes are 5885/6L6 type these would be on pins 4 and 6. These resistors are sometimes sized WRT wattage so they'll fail in the event of a tube issue and while they won't necessarily look bad, they may have failed.

What does the amp use for output tubes?

 

[TLS Guy]

OTOH, the data for virtually every tube model is available on the internet. As long as the circuits aren't trying to shove excessive voltages toward the tubes, they really should be fairly happy. The tens of thousands of tube amplifiers still in use with few problems testifies to that. However, as TLS mentioned, values drift, techniques aren't what they were and specific information may not be available.

It does seem like it could be a resistor issue in the grid bias- have you looked inside of the amp (don't do this when its power cord is plugged in)? The ones in question may be soldered onto the output tube socket pins. As an example, if the output tubes are 5885/6L6 type these would be on pins 4 and 6. These resistors are sometimes sized WRT wattage so they'll fail in the event of a tube issue and while they won't necessarily look bad, they may have failed.

What does the amp use for output tubes?

It's a preamp.

 

[highfigh]

It's a preamp.

Thanks-