Zv9 Output Resistor
Thanks Grey. I sorta figured that. I appreciate the reply.
By the way, I will probably mount the LU1014 JFET to an .125" thick small copper plate ("cold" plate) with a thermal adhesive pad used by the computer people, then mount the copper plate to an aluminum (aluminium for some) heatsink with screws. Thermal grease between the copper plate and heatsink.
Almost forgot. Thanks Grey for bringing up the Panasonic 3W resistors. Friends, do not forget they ( along with BC, Xicon, etc.) are 5% tolerances. You will have to buy more then needed, and hope they are all not from the same production batch, if you hope to get "exact" resistor values. An option would be to buy 5W and 12W 1% Mills resistors. Obviously they will cost a lot more each compared to the 5% resistors, but you may save compared to purchasing 10, 20, etc. 5% power resistors. That is if you are looking for good tolerances. Another factor is the temperature coefficient . The resistances of the power resistors will change because of the heat. Obviously the reason for the power values recommended by Mr. Pass.
Bruce
GRollins said:
Thanks Grey. I sorta figured that. I appreciate the reply.
By the way, I will probably mount the LU1014 JFET to an .125" thick small copper plate ("cold" plate) with a thermal adhesive pad used by the computer people, then mount the copper plate to an aluminum (aluminium for some) heatsink with screws. Thermal grease between the copper plate and heatsink.
Almost forgot. Thanks Grey for bringing up the Panasonic 3W resistors. Friends, do not forget they ( along with BC, Xicon, etc.) are 5% tolerances. You will have to buy more then needed, and hope they are all not from the same production batch, if you hope to get "exact" resistor values. An option would be to buy 5W and 12W 1% Mills resistors. Obviously they will cost a lot more each compared to the 5% resistors, but you may save compared to purchasing 10, 20, etc. 5% power resistors. That is if you are looking for good tolerances. Another factor is the temperature coefficient . The resistances of the power resistors will change because of the heat. Obviously the reason for the power values recommended by Mr. Pass.
Bruce
It's been a while, but I seem to remember sitting down with a medium-sized batch (30 to 50 units?) of the Panasonic resistors and finding that they were far tighter than the 5% tolerance spec would have you believe. It's always possible that their manufacturing process has changed and that current production is much looser.
On a related note, I always found that the NTE 2% resistors were much tighter than 2%. I'm not particularly fond of NTE, but they were all that was available locally unless I was willing to go to Radio Shack. These days, I just order in 100 of the Vishay/Dale 1% resistors at a time and go on with my fiddlings. At that quantity, they are actually cheaper per unit than the NTE. Given that my last decent local parts house went out of business, I can no longer stop in and pick up resistors on the way to work. If I need a part, I have to wait a week for UPS to drop it off. Bummer.
Man, I can't even find decent solder. Nelson had recommended a brand of silver solder that they use at Pass Labs, so I decided to try to order some. Couldn't find any available at retail. Contacted the company. They said talk to the Southeastern regional rep. I contacted the regional rep. They asked how much I wanted. I said a pound or two. They dropped me like a hot potato. Complete, dead, velvety silence. Harrumph! See if I talk to them when I get all rich and famous and need a half-ton of solder! (Yeah, I know...they're trembling in their shoes...) Meanwhile, I'm down to the last few turns of solder on my last spool. Guess I'm going to have to go to Radio Shack and get re-branded Kester or whoever does their OEM stuff. Actually, these days I guess it comes from China.
The problem with solder is that the blasted stuff is so heavy that it's not suitable for group buys. Shipping will eat any savings that you might get by buying in bulk.
Grey
On a related note, I always found that the NTE 2% resistors were much tighter than 2%. I'm not particularly fond of NTE, but they were all that was available locally unless I was willing to go to Radio Shack. These days, I just order in 100 of the Vishay/Dale 1% resistors at a time and go on with my fiddlings. At that quantity, they are actually cheaper per unit than the NTE. Given that my last decent local parts house went out of business, I can no longer stop in and pick up resistors on the way to work. If I need a part, I have to wait a week for UPS to drop it off. Bummer.
Man, I can't even find decent solder. Nelson had recommended a brand of silver solder that they use at Pass Labs, so I decided to try to order some. Couldn't find any available at retail. Contacted the company. They said talk to the Southeastern regional rep. I contacted the regional rep. They asked how much I wanted. I said a pound or two. They dropped me like a hot potato. Complete, dead, velvety silence. Harrumph! See if I talk to them when I get all rich and famous and need a half-ton of solder! (Yeah, I know...they're trembling in their shoes...) Meanwhile, I'm down to the last few turns of solder on my last spool. Guess I'm going to have to go to Radio Shack and get re-branded Kester or whoever does their OEM stuff. Actually, these days I guess it comes from China.
The problem with solder is that the blasted stuff is so heavy that it's not suitable for group buys. Shipping will eat any savings that you might get by buying in bulk.
Grey
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