Yes measuring with my laser/infrared whatever temp reader, I get 60-63C. I have no idea how accurate/inaccurate this thing is.
Russellc
I don't like the IR thermometers all that much in terms of accuracy or anything else. We use thermal cameras at my job. These days you can get one that will mount to your Android (or Fruit) phone for about $300. Before those hit town, I was thinking of shelling out $2.5k for the Milwaukee thermal camera, which will focus down to 4". The Android cam only focuses down to 8", but you could get a lot of stuff for the difference in price.
Oh, yeah, I took that same resistor tested in post #20 and let it sit for a while at 20V - I got to ~99C in a lab ambient that's around 22C and a trifle breezy. This is probably the real power rating for this resistor (~1W), unless you like hot resistors ( in which case, take some precautions).
Well it only recently, after several years (I think this was a 2010 or 2011 build) got "tanned" and only on one channel. I am beginning to convince myself it was caused by the tremendous hum and intermittent "noises like pulling the jack out of an electric guitar". I am suspecting the rewire on the F-5, so have ordered new components ( forgot new CL-60s darn it, I think they are likely fine anyway) as that was the only change. I also got the remaining tidbits for Zen mod's device, and a bunch of .0033uf X-1 rated caps. I will also change out the mosfets just in case with a tight set from Ha_.
The other contributor to this problem might very well be the B-1. I am rereading the build threads on B-1, I think I may have not done grounding quite right and the change up in F-5 caused problems. I noticed most build pics showed the RCA input grounds all hooked together and a wire that I think goes to the board. I left mine floating, as each one has a spot for G on the B-1 board. I'm sure others did this for a reason. I guess some source components are grounded such that this isn't a problem, while some are not...or something fried in the B-1, which is unlikely.
I think Mr. Pass knows best, and his suggestion that this hum combined with the wide bandwidth of the amplifier causing oscillation is the likely culprit for the "tanning effect."
I have some stuffed Peter Daniels boards around here somewhere with some stiffer Caddocks on it.
Russellc
The other contributor to this problem might very well be the B-1. I am rereading the build threads on B-1, I think I may have not done grounding quite right and the change up in F-5 caused problems. I noticed most build pics showed the RCA input grounds all hooked together and a wire that I think goes to the board. I left mine floating, as each one has a spot for G on the B-1 board. I'm sure others did this for a reason. I guess some source components are grounded such that this isn't a problem, while some are not...or something fried in the B-1, which is unlikely.
I think Mr. Pass knows best, and his suggestion that this hum combined with the wide bandwidth of the amplifier causing oscillation is the likely culprit for the "tanning effect."
I have some stuffed Peter Daniels boards around here somewhere with some stiffer Caddocks on it.
Russellc
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In free air. Mounted on a PCB, it would hit 120C.
(advised mounting height of a Panasonic 3W is 1/4'' above the board)
Mine is only 1/16 of an inch. I didnt know any better at the time, and it would be easier to clamp onto for setting bias as well! Didnt think of that at the time either!
Russellc
Yeah, thermal isolation is usually mentioned, some resistors even come in both flavors (copper or steel leads) for that reason. Compared to copper steel is a bad thermal conductor and steel leads thus may help insulate the PCB tracks from the resistors' heat.
From the thermal image i would have guessed steel leads since they weren't radiating off that much infrared...
From the thermal image i would have guessed steel leads since they weren't radiating off that much infrared...
mills ww
Hello,
Because i am probably going to get myself an F 5 in the future i did come across this thread.
Long time ago i did have a tube pre amplifier that did use some 2 or 3 watt resistor because they were getting hot.
There were only six of them and i had to order something at michael Percy anyway so i did replace them by Mills wire wound 12 watts. So far this has been the biggest update for the money in 30 years of being an audiophile.
They are a bit big but by bending the leads it is easy to install them.
Even if your present resistors are not toasted i think it will be a big improvement.
If you are living in the USA it is a piece of cake to order them.
Greetings Eduard
P.s by the way i am going to make an F5 with choke input power supply with Lundahl chokes for filament. According to my German supplier the LL2733 400mH 1,7A can '' deliver '''2,4 A when ac voltage across the choke is lower. I guess with 24 volts dc it will around 20 volts. These have two coils so putting them parallel you can go for more current and less mH
Hello,
Because i am probably going to get myself an F 5 in the future i did come across this thread.
Long time ago i did have a tube pre amplifier that did use some 2 or 3 watt resistor because they were getting hot.
There were only six of them and i had to order something at michael Percy anyway so i did replace them by Mills wire wound 12 watts. So far this has been the biggest update for the money in 30 years of being an audiophile.
They are a bit big but by bending the leads it is easy to install them.
Even if your present resistors are not toasted i think it will be a big improvement.
If you are living in the USA it is a piece of cake to order them.
Greetings Eduard
P.s by the way i am going to make an F5 with choke input power supply with Lundahl chokes for filament. According to my German supplier the LL2733 400mH 1,7A can '' deliver '''2,4 A when ac voltage across the choke is lower. I guess with 24 volts dc it will around 20 volts. These have two coils so putting them parallel you can go for more current and less mH
Edit - a response to post #30
That assumption is a common mistake with thermal imaging - metal surfaces often look stone cold in a thermal imager, even if they're blazing hot, as metals in general have low emissivity. Even more counterintuitive, a coat of typist's "whiteout" will make the metal surface show up at more or less the right temperature. The stuff looks white in visible wavelengths, but not on the mid-infrared wavelengths picked up by the thermal camera. I use the trick all the time to read temperature on aluminum heat sinks. A piece of tape also works.
That assumption is a common mistake with thermal imaging - metal surfaces often look stone cold in a thermal imager, even if they're blazing hot, as metals in general have low emissivity. Even more counterintuitive, a coat of typist's "whiteout" will make the metal surface show up at more or less the right temperature. The stuff looks white in visible wavelengths, but not on the mid-infrared wavelengths picked up by the thermal camera. I use the trick all the time to read temperature on aluminum heat sinks. A piece of tape also works.
The Panasonic ERX does, Mouser also carries the steel lead type (F), twice the cost of the copper lead version (S)
For the 2W type, temperature difference between resistor body and solder pad for the steel lead type is twice as large (identical mounting height)
Of course, downside is that the resistor body wil be significantly hotter.
(a simpleton might just pick a higher power type, better on both fronts)
I usually opt for the simpleton approach, or a series or parallel combination of smaller resistors to spread out the dissipation. Somtimes placing resistors in series also makes sense if there is a lot of voltage to be dropped, as resistors have a maximum voltage rating as well as a power dissipation rating.
As well as a temperature coefficient of resistane, the resistance can also vary with voltage, a consideration that might be important in an application like a voltage divider string for a high voltage regulator (or a plate load resistor). Some resistor types are better than others for this duty, though using several inferior resistors in series would help accuracy by reducing the voltage gradient experienced by each part.
As well as a temperature coefficient of resistane, the resistance can also vary with voltage, a consideration that might be important in an application like a voltage divider string for a high voltage regulator (or a plate load resistor). Some resistor types are better than others for this duty, though using several inferior resistors in series would help accuracy by reducing the voltage gradient experienced by each part.
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