Tír Na HiFi

Got a second amp a few weeks ago. A bit of smoke one day which I was unsure if it was a valve going. Changed them all but it looks like one channel has given up the ghost. The power tubes are not heating up on that channel but they do seem to light up. Any ideas what has happened? I opened it up tonight to see if a resistor or something obvious was burnt inside etc but all looks fine(Am being careful not touching anything and it is plugged out).

Most likely a cathode or anode resistor gone. These can be gone and not look damaged.

Are these the amps with the fancy active "never have to adjust bias" circuitry?

Fran

Fran wrote:Most likely a cathode or anode resistor gone. These can be gone and not look damaged.

Are these the amps with the fancy active "never have to adjust bias" circuitry?

Fran

They are Fran and was hoping it is one of the resistors above you are suggesting. Do you get the smoking pipe effect when that occurs? Is that normally a dodgy valve or just a bit that decides to pack in?

Em, can be loads of reasons. Can be a valve gone, it happened me before one time when an EL84 went leaky (kinda like the one in Si's thread a little while back). It took out a few resistors at that time, but the tranformers were Ok TG. Sometimes a sudden transient can take one out. Saw that on an airtight once.

Hopefully there's not too much damage done. At least valve amps tend to be easier to repair.

Fran

Fran wrote:Em, can be loads of reasons. Can be a valve gone, it happened me before one time when an EL84 went leaky (kinda like the one in Si's thread a little while back). It took out a few resistors at that time, but the tranformers were Ok TG. Sometimes a sudden transient can take one out. Saw that on an airtight once.

Hopefully there's not too much damage done. At least valve amps tend to be easier to repair.

Fran

The Transformer word is the one I really fear.

Fran wrote:Em, can be loads of reasons. At least valve amps tend to be easier to repair.
Fran

what as compared to...............lada's..........or pinball machines..........or........hmmmm.......toasters???

MooseTrackz wrote:

Fran wrote:Em, can be loads of reasons. At least valve amps tend to be easier to repair.
Fran

what as compared to...............lada's..........or pinball machines..........or........hmmmm.......toasters???

Now your being silly..............Lada's can never be repaired!

tony wrote:Got a second amp a few weeks ago. A bit of smoke one day which I was unsure if it was a valve going. Changed them all but it looks like one channel has given up the ghost. The power tubes are not heating up on that channel but they do seem to light up. Any ideas what has happened? I opened it up tonight to see if a resistor or something obvious was burnt inside etc but all looks fine(Am being careful not touching anything and it is plugged out).

that's bad news, sorry to hear that Tony!

Now I'm starting to worry... Tony, Mark... exploding valve amps, Simon's caught in the nick of time!

Hope it all works out on the non-expensive side of things!

Good news here no need to worry too much Johnny. Resident woodturning,dac amp and speaker maker identified 3 resistors gone. Amp repaired and working fine. Havent heard it yet but looking forward to it.

Fyi Johnny spoke with a guy off wigwam who has had 4 prima luna's none have ever missed a beat. In this case it looks like the resistors that gave up the ghost were valve heaters. Not sure what happened but reckon I purchased it that way. The problem was there from the beginning as I found that I couldnt turn the amp up loud or loudish as the sound became a little distorted. I put it down to high gain maybe valves and me expecting too much performance from the amp.
The resistors were on there last legs.

No idea what could have caused this. Maybe the previous owner left it powered on too much and cooked the heater resistors.

Oh btw Many many thanks to Fran for having a look at this much appreciated.

tony wrote:Good news here no need to worry too much Johnny. Resident woodturning,dac amp and speaker maker identified 3 resistors gone. Amp repaired and working fine. Havent heard it yet but looking forward to it.

Fyi Johnny spoke with a guy off wigwam who has had 4 prima luna's none have ever missed a beat. In this case it looks like the resistors that gave up the ghost were valve heaters. Not sure what happened but reckon I purchased it that way. The problem was there from the beginning as I found that I couldnt turn the amp up loud or loudish as the sound became a little distorted. I put it down to high gain maybe valves and me expecting too much performance from the amp.
The resistors were on there last legs.

No idea what could have caused this. Maybe the previous owner left it powered on too much and cooked the heater resistors.

Oh btw Many many thanks to Fran for having a look at this much appreciated.

Delighted to hear everything worked out well for you Tony. Good work Fran too :)