amplifiednation wrote:
Are you guys drilling an extra hole for the tag strip that the 7805 mounts to? I can just mount the 7805 to the chassis with thermal grease, right? Or do i need a true "transistor mounting kit" from Shack?
Assuming it's a CE chassis, I use the left most transformer mounting hole for the terminal. If I'm using a relay PT, I also mount the terminal on the same through bolt for the PT leg.
I use the insulator/#4 bushing to isolate the 780x tab from the chassis so it's only grounded at one point on the chassis. I've also floated the relay supply ground as well on some builds too.
Here's a terminal mounting pic, no PT.
TM
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TM,
How do you get the tabs of the 7805 to reach the terminal strip? All the ones I have aren't long enough. On my 102 I had to bend the strip forward to reach.
I thought I had seen some builds with the regular floating in mid air...but that can't be good as there would be no heat transfer.
Tom cool PCB! I think I'll probably drill an extra hole like Ultra did. It will take about 45 seconds.
Structo wrote:
I make a little eyelet board and mount a heatsink on it.
.
Tom, you don't need to mount a separate heatsink as the huge chassis surface area naturally acts as the heatsink for the tab. In reality with any of the 780x series, as long as you keep the input voltage within 2-4 volts over the target voltage, they can supply up around 300-320mA of current or so without a heatsink at all.
amplifiednation wrote:TM,
How do you get the tabs of the 7805 to reach the terminal strip? All the ones I have aren't long enough. On my 102 I had to bend the strip forward to reach.
I thought I had seen some builds with the regular floating in mid air...but that can't be good as there would be no heat transfer.
I bent pins 1 and 3 out at an angle and I don't have to bend the terminal tabs. My first 3 builds I mounted them standing up and they don't run hot. I only started chassis mounted when I started using Jason's boards.
Folks have a tendency not to read the application or datasheets, the 780x can supply up to 1.5A with a heatsink and has a max input of 36-37 volts. So you don't automatically need a heatsink. Now if you run 24V into a 9V regulator, that extra 15V will be dissipated as heat. Thus, you most likely will need a heatsink for longer life. With a 6.3V PT configured doubler relay supply, about 18V will be at the input of the regulator. Using this with a 5V regulated relay supply, I would mount it to the chassis. Whereas, if you used a 6.3V AC tap and a bridge rect, 8.8-9V into a 5 or 6V regulator will give off very little heat and no heat sink is needed. I use a 6.3V tap, LM7806 and 5V relays.
TM
Last edited by ToneMerc on Thu Jun 07, 2012 2:21 pm, edited 1 time in total.
amplifiednation wrote:TM,
How do you get the tabs of the 7805 to reach the terminal strip? All the ones I have aren't long enough. On my 102 I had to bend the strip forward to reach.
TM
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Yeah, it's over kill but it is such tight quarters in that corner that I made the little board so I could do most of the soldering outside the chassis confines.
Taylor,
You can solder the legs of the 7805 to the holes in the terminal (strip) which are lower down, then solder the wires to the upper terminals.
Structo wrote:Yeah, it's over kill but it is such tight quarters in that corner that I made the little board so I could do most of the soldering outside the chassis confines.
Taylor,
You can solder the legs of the 7805 to the holes in the terminal (strip) which are lower down, then solder the wires to the upper terminals.
That is exactly what I was thinking but I still don't think it's gonna reach! Maybe my 7805 has shorter than normal leads?? I'll upload a pic later tonight.
Structo wrote:Yeah, it's over kill but it is such tight quarters in that corner that I made the little board so I could do most of the soldering outside the chassis confines.
Taylor,
You can solder the legs of the 7805 to the holes in the terminal (strip) which are lower down, then solder the wires to the upper terminals.
That is exactly what I was thinking but I still don't think it's gonna reach! Maybe my 7805 has shorter than normal leads?? I'll upload a pic later tonight.
Ok I will not be uploading these pictures...because it actually does reach those bottom lugs. Man, I am moving too fast or something!!
Anyway, here's my boards.
I need to figure out what NFB resistor value to use. I have 3.3k in there now, but i think that needs to come up for a 50w (vs 100) Maybe 4.7k?
Also, I might pull the brown NTE's out for 6PS..
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Structo wrote:Yeah, it's over kill but it is such tight quarters in that corner that I made the little board so I could do most of the soldering outside the chassis confines.
Taylor,
You can solder the legs of the 7805 to the holes in the terminal (strip) which are lower down, then solder the wires to the upper terminals.
That is exactly what I was thinking but I still don't think it's gonna reach! Maybe my 7805 has shorter than normal leads?? I'll upload a pic later tonight.
Ok I will not be uploading these pictures...because it actually does reach those bottom lugs. Man, I am moving too fast or something!!
Anyway, here's my boards.
I need to figure out what NFB resistor value to use. I have 3.3k in there now, but i think that needs to come up for a 50w (vs 100) Maybe 4.7k?
Also, I might pull the brown NTE's out for 6PS..
Looks great Taylor
Can you measure the capacitance of the caps?
You can always change out the NTE's later...up to you I think they
break up the color schem and add that mojo look...
FWIW looking at the files/layouts(Tony's) the original 2/3 gens had 820 Ohm NFB resistors
amplifiednation wrote:Yes I can measure the caps. Should i be doing that??
Taylor
Up to you...doesn't hurt
I measure resistors and caps...
I think most are pretty close, but I have found some caps more than 10% off.(could make a difference in the end)
My cheapo meter probably isn't real precise but gives consistent reads
I always measure the resistors...and now I will start measuring the caps (and I know I should be doing the pots too!!). If anything it is way "more Dumble" to write the cap values on the sides!
