[n_maher]

If it were me I would at least measure the value of the resistor now and check it vs. what it should be based on the color bands. This is for two reasons, one to see if any drift has occurred already due to stress and two so that if you have to replace it in the future you know what value to get.

I also wouldn't feel all to comfortable about the resistors showing these signs after so little use (50hrs) if it were my amp. I'd certainly be asking the manufacturer if this is typical.

My 2¢,

Nate

 

[jamato8]

I am referring to a cathode resistor for bias in a driver tube. If you feel that this is not a place to use a cap or not depending upon whether a designer wanted it there or not I do not agree with you.

 

[jirams]

All this thread is achieving is to push the OP into more and more disatisfaction with a product that he has only had a short time. He would be well advised to 'close the bonnet' and ignore areas that he is unfamiliar with. Use the amp as an amp and see what develops with the resistors and any other areas that may develop 'problems' and then deal with these through the folks who sold him the kit. I don't know how many of these amps are out there but I am sure that this one will be fairly typical, for better or worse. From what I can see of the innards, it looks like a competent piece of hardware - its sonic properties, I cannot comment

Good luck anyway

 

[jirams]

Quote:

Originally Posted by jamato8 /img/forum/go_quote.gif I am referring to a cathode resistor for bias in a driver tube. If you feel that this is not a place to use a cap or not depending upon whether a designer wanted it there or not I do not agree with you.

Your opinion is acknowledged and valued

 

[jamato8]

I see that you have been into valves for a long time. That is great. I used them in the Navy as that is what we had to use. The radioroom would heat up like a second hell but I always liked the glow of tubes. I have a friend who designed tubes for RCA and has patents, though RCA really has them, on his wall. I love talking about tubes with him. He knows them to the finest detail of course and what so many think as new to tube uses he has already been through. Not too many people around who did the actual design and implementation of these wonders.

As to the hot resistor, I agree, they can get hot as blazes and they keep on going. I have had what I thought to be a resistors with too small a wattage rating they went on for years. They get hot, that is what they do when working with current.

 

[jirams]

Quote:

Originally Posted by jamato8 /img/forum/go_quote.gif I see that you have been into valves for a long time. That is great. I used them in the Navy as that is what we had to use. The radioroom would heat up like a second hell but I always liked the glow of tubes. I have a friend who designed tubes for RCA and has patents, though RCA really has them, on his wall. I love talking about tubes with him. He knows them to the finest detail of course and what so many think as new to tube uses he has already been through. Not too many people around who did the actual design and implementation of these wonders. As to the hot resistor, I agree, they can get hot as blazes and they keep on going. I have had what I thought to be a resistors with too small a wattage rating they went on for years. They get hot, that is what they do when working with current.

Hey - I trained as a Radio Officer in the Merchant Navy in 1963 - in these days we even used Morse code radiotelegraphy. Satellites ended all that just as solid state ended (almost

) valve (tube) technology.

I got tired of maintaining valve amps - I generally used KT88 beam tetrode Class A push-pull topology - getting decent valves which stay stable for any length of time has become a problem. I occasionally hook up my remaining amp (loudspeaker) and enjoy it for a week or so then have to put in a screen feed resistor when a KT88 develops an interelectrode short and burns up.

Nice to reminisce

 

[atbglenn]

Looking with a flashlight the colors are red-red-black-black 1% (purple) 220 ohm. Looks like a 3 watter?. What I'll probably do is replace the resistors with the same rating but I'll space about a half an inch above the circuit board so it doesn't get burned over time. What do you think?

 

[jirams]

Quote:

Originally Posted by atbglenn /img/forum/go_quote.gif Looking with a flashlight the colors are red-red-black-black 1% (purple) 220 ohm. Looks like a 3 watter?. What I'll probably do is replace the resistors with the same rating but I'll space about a half an inch above the circuit board so it doesn't get burned over time. What do you think?

Spacing it the way you describe is correct practice - also change for both channels and up the wattage. However, if it was me I would wait for a longer period to see what transpires (for the reasons already described).

Good luck whatever you do

 

[jamato8]

I was a code specialist. When we couldn't get out by other methods, which was often, everything was encoded and I had to send it out with a bug.

If you are going to replace it then go with a higher wattage while you are in there. Getting it off of the board is good and you will give it more freely exposed surface area.

 

[jirams]

Quote:

Originally Posted by jamato8 /img/forum/go_quote.gif Please visit my photo gallery at: www.pbase.com/jamato8

Superb Photographic work !! A privilege to visit.

 

[feifan]

Quote:

Originally Posted by jirams /img/forum/go_quote.gif Superb Photographic work !! A privilege to visit.

Jirams, thanks for the tip re John Amato's (Jamato8's) photo gallery. I can't recall the last time I spent a more enjoyable hour. His photography is art -- of the human kind. Each shot is complete in itself, a whole world captured in a single frame. I wasn't able to view them all. With every picture, time stands still, and I lose track of how long I've been a part of each world. In audio terms, we're looking at an extremely wide soundstage with vivid clarity and separation throughout the spectrum, and with infinite, glowing warmth and depth throughout. I was especially pulled into the picture of a lone worn sandal made out of an old tire. I'll have to return, again and again.

 

[mbutter]

Quote:

Originally Posted by atbglenn /img/forum/go_quote.gif Looking with a flashlight the colors are red-red-black-black 1% (purple) 220 ohm. Looks like a 3 watter?. What I'll probably do is replace the resistors with the same rating but I'll space about a half an inch above the circuit board so it doesn't get burned over time. What do you think?

I pulled the 'hot' resistors from my Little Dot II++ to replace them. I must admit the bands looked like red-red-black-black but when I checked them with a meter they are actually 330 ohm which means the bands must actually be orange-orange-black-black. The bands are hard to read because they are very thin.

Interestingly though, the print on the circuit board under the resistors says 220 ohm 3 watt. So the resistance was increased for some reason after the initial design phase. I am in the UK where mains voltage is 230 - 240 volts. Could this change be to accomodate the higher mains voltage or were the values increased to reduce the amount of heat generated or for some other reason ?

Anyway the nice Kiwame 220 ohm resistors I ordered are now consigned to the parts bin and some 330 ohm ones are on order.

 

[Dept_of_Alchemy]

Quote:

Originally Posted by mbutter /img/forum/go_quote.gif I pulled the 'hot' resistors from my Little Dot II++ to replace them. I must admit the bands looked like red-red-black-black but when I checked them with a meter they are actually 330 ohm which means the bands must actually be orange-orange-black-black. The bands are hard to read because they are very thin. Interestingly though, the print on the circuit board under the resistors says 220 ohm 3 watt. So the resistance was increased for some reason after the initial design phase. I am in the UK where mains voltage is 230 - 240 volts. Could this change be to accomodate the higher mains voltage or were the values increased to reduce the amount of heat generated or for some other reason ? Anyway the nice Kiwame 220 ohm resistors I ordered are now consigned to the parts bin and some 330 ohm ones are on order.

That's very interesting...

Is this the same issue that the LDII++ v.2 fixed? If so does anybody know the value and wattage rating of the resistors on the ver2?

 

[penguindude]

Quote:

Originally Posted by Dept_of_Alchemy /img/forum/go_quote.gif That's very interesting... Is this the same issue that the LDII++ v.2 fixed? If so does anybody know the value and wattage rating of the resistors on the ver2?

No, ver2 changed much more than just the two resistors. Even the potentiometer changed to 50k instead of 100k. It's not possible to mod it to ver2 from ver1 without chaning the entire PCB.

 

[jamato8]

Quote:

Originally Posted by Dept_of_Alchemy /img/forum/go_quote.gif That's very interesting... Is this the same issue that the LDII++ v.2 fixed? If so does anybody know the value and wattage rating of the resistors on the ver2?

The transformer would drop the voltage to what is needed or raise it. The resistors would have been increased to change an operating point or they were handy. Some reistors, it depends on the current draw can have a fairly good tolerance but then I don't even know where the ones are you are talking about but I would use the same value. I like to rate the resistor at 5 or more times that needed. Audio Note UK uses this ratio on stuff that may only require a 1/4 watt and they have noted, as I have, that the larger wattage resistor in critical positions, sounds better. This could be from less thermal noise that can hang around on the DC carrier signal which will of course degrade the sound, even if just a tiny bit.