[hotrod]

 After completing the C2 assembly and checking all the test points,which all are within 5v,it wasn't until I had a few hours of run time I began frying the resistor at R102(220 ohm) and after replacement the R101(220 ohm) fried.
 When I replaced R102 I powered up on the bench and all was fine.I screwed the bottom cover on, hooked it up in system and after 12 sec. the light turned green and I got sparks in the rectifier,powered down,popped the cover and it was R101 that fried this time.....whats going on!!
 I listened for about 4 hours last night with no issues and now today...
The resistors are 220 ohm 1 Watt carbon films and the rectifier is a GZ32 from UpscaleAudio.

[Niteshade]

Nothing after R220, including R220 fails? If that is the case, then it seems like you have either a bad rectifier tube or a bad C103. Look for solder blobs, etc.. as well. Try disconnecting the power supply from R220 and see if it happens again. You have to start a process of elimination. Naturally, try another rectifier tube first. I assume you're talking about the Cornet2 Phono preamp, right?

[hotrod]

 I do not have any other rectifiers on hand so trouble shooting is going to have to wait.I'm not sure what you are refering to concering the R220.As soon as I seen sparks,I powered down and all that happened was the R101 or R102 were fried.
 I did test the rectifier and it tested out OK,could there still be an issue with the tube?
When I tested after replacing the first resistor failure I measured .3V off both the red secondary wires...is this right?I also measured 3.7V off the green,green/yellow,green,should this be closer to 3v?
 Another reason I'm leaning towards the tube is that the first time I powered up to measure at the test points(saturday) with a Mills 1.5 ohm in R223 I measured 6.17v which is ideal.After replacing the fried R102(today) I measured again and I was getting 5.86v at R223....strange,rectifier taking a dirty one?
 I will have to get a hold of another rectifier so in a few days will have to report back.

[Niteshade]

R220, from what it says in the schematic, is the resistor in series with the main B+ output from the power supply to the main board. Did you look at the schematic and find R220? I hope we're talking about the same model phono preamp. Those resistors are acting like fuses for the rectifier's anodes.

Tube testers do not always test tubes in their natural operating environments- thus a bad tube could possibly test good.  A long time ago, a technician told me this and I can verify that he was right.

Try the new rectifier first- and then we can look at other causes if it still blows resistors.

[hotrod]

 Thanks for helping out Blair.
  The 2 R220's look alright.The tube being bad is a good bet,the whole lower half of the envelope appears to have a tint to it where I believe it was all clear aside from the getter flashing.Like I refered to it my previous post,when I first had the Cornet 2 up and running I had 6.17v after R223 and after the first resistor replacement I was meassuring 5.86 after R223,a little strange and hopefully a tube issue.
 Do you know what the two rectifier pins relate to that are connected to R101 and R102?
I will have few Bendix 6106's later in the week,also a few 5Y3gt's for guinie pigs.

[hagtech]

Yeah, bad rectifier tube.  No question about it.  They have various failure modes, one of them shorting to their filament.  The extra 220 ohms in the anodes have two functions.  1) they blow like fuses for a bad rectifier.  And they do this to protect the rest of the machine, especially the transfomer.  They are cheap and easy to replace.  2) they limit the peak current into the 47uF capacitor, thereby easing the demands on the rectifier itself, increasing lifetime.

jh

[tubesforever]

I certainly hope those wondering if they should jump into DIY take note of Jim's response.  This is just one of several reasons why I love my Hagermans.

So we all love tubes,  we want to spin up some nice sounding equipment, but the reality is that we are plugged into a power grid with issues, we are plugging in tubes (which can develop issues) and we are rolling stuff that says it tested new.....but who the heck knows for certain.

Jim designed his gear with safety first and with layers of protection built into the circuit.  If you build it, and bad things happen you are replacing a few dollars of resistors. 

There is gear out there today where hotrod would be sourcing out a replacement transformer and a bunch of passive component pieces.

Thank you Jim for building great circuits that sound great, perform better than high dollar gear, and are safe to build, roll and operate.

If you are on the fence about whether to build a certain DIY kit vs another, rest assured that the Hagerman gear will be fun, it will be economical, and it was engineered to be safe and to minimize damage during the life time of its owners. 

Cheers!

[avahifi]

Power equals voltage squared divided by resistance.  Measure the voltage on each side of the resistor in question (carefully, you are working with high voltage dangerous stuff).  Subtract the voltage on the output side of the resistor from the voltage on the input side.  This number is the voltage drop across that resistor.  Take the square of that number divided by the value of the resistor and that will tell you the power dissipated by the resistor in watts.  Compare that to the wattage rating of the resistor.  It should be less than half of the resistor's power rating for good long term reliability.  If these measurements are OK then either the voltage on the input side is going high sometimes, or the voltage on the output side is going low, in order for the voltage drop across the resistor to go so high the power rating of the part is being exceeded.  In general, one likely culprit is something downstream shorting out, pulling too much current from the circuit and causing the excess voltage drop and the subsequent resistor failure.

Check it out, and you will probably find the villain.

Regards,

Frank Van Alstine

[hagtech]

I always use a 4x on resistors for power ratings.  The thing is, some resistors can operate extremely hot without failure.  Say 250C.  That's fine for the resistor, but not for anything nearby.  Hence, you have to be wary of the specified rating.  And cooking other components.

The other criteria is distortion.  If the power load on a resistor various (as in a speaker crossover), it may experience slight dynamic shifts in value.  A form of IMD.

jh

[hotrod]

 Yup,turns out it was the rectifier, all is well.Living 30 min. from Tube World is a plus when you need tubes in a pinch.Even with about 10 hours on the C2 it sounds damn good.There is more bass impact compared to the phono section in my Mcalister tubed pre,and absolutly no hum which for sure I thought I would have to play around with to get to an acceptable level.I thought about purchasing the Inverse RIAA for break in,but I"m one of the weird ones,I enjoy hearing the changes throughout the run in process.
 Thanks for the great support here.On to the Clarinet!