F5 power amplifier

[Diomedian]

what about BER131-ND? are cheap

BER131-ND are made of "Q-Pad 3" material, which is electrically conductive. This may be fine in some cases though - it certainly has good thermal ratings.

-j

 

[ichiban]

quote:
Originally posted by samsagaz
what about BER131-ND? are cheap

BER131-ND are made of "Q-Pad 3" material, which is electrically conductive. This may be fine in some cases though - it certainly has good thermal ratings.

-j

These seem to be similar for only $US 0.25 each

Mouser Part #: 567-175-6-230P
Manufacturer Part #: 175-6-230P
Manufacturer: Wakefield
Description: Heatsink Accessories TO-220 .006" KAPTON

 

[Tea-Bag]

These seem to be similar for only $US 0.25 each

Mouser Part #: 567-175-6-230P
Manufacturer Part #: 175-6-230P
Manufacturer: Wakefield
Description: Heatsink Accessories TO-220 .006" KAPTON

to-220
too small, except for to-220 devices.

I am still looking for the ultimate mica to-3p to-247 insulator part # myself.

 

[woodturner-fran]

Plus they're TO220 - you would need something a little bigger I think for Q3/4.


Mouser do have this one:

link


I think its the same size. TO247 is meant to be 16mm x 21mm (0.625"x0.875") and this pad is apparently 0.6" x 1".

I'm not sure if the holes will all line up correctly. I'll be placing an order with mouser and might buy a few just to see. Probably worth it at only 0.06c each.

Could someone have a look at this and confirm what I'm seeing?

Fran

 

[enzedone]

Thermal pads

Fran

I bought a 400x400 sheet a couple of years back and have been sitting on it. Give me your sizes and i'll cut some up for ya. And send it over.

Way to go, for sorting the amp out...........

Brett

 

[woodturner-fran]

Wow, thanks Brett.


Look, I'll probably buy some of those ones from Mouser. At least then we'll know if they work ok. I'll PM you my addess but look I don't want to put you out....


Fran

 

[Nelson Pass]

I am still looking for the ultimate mica to-3p to-247 insulator part # myself.

I use the ones made by Keystone.

 

[labjr]

I'm searching for an enclosure and heatsinks. Does anyone know if the enclosure has to be all metal for shielding from noise and feedback etc. ?

I'm considering using a partially wooden enclusure.

 

[Phil Townsend]

Tell me why...

Nelson, why do you like the Mica insulators over the various other types...

Enquiring Minds and all that stuff.

 

[AndrewT]

to protect against electric noise/interference you must (completely) surround the circuit with a conductive cage/box. It does not have to be metal.
Wood is a fairly good insulator, so can't give any help.

To protect against magnetic fields you need something quite different. I don't know enough to give advice.

 

[Tea-Bag]

I use the ones made by Keystone.

I'm not to sure exactly which one's. Spec sheet looks to fit quite tight, with little wiggle room on the sides. I could be overlooking an obvious one.

 

[sekess]

mica

Hey Tea-Bag,

I'm not 100% sure, but it looks like Keystone's 4661 would do it. It's made for a TO-3 package. But, I think the TO-247 will fit. You will have to cut is some though.

Steve

 

[max426]

mica

I ordered 4671, looked like a good fit to me.
I am very much a rookie at this. When all my parts arrive i'm sure i will have plenty of questions for everyone.

jim

 

[Tea-Bag]

Re: mica

Hey Tea-Bag,

I'm not 100% sure, but it looks like Keystone's 4661 would do it. It's made for a TO-3 package. But, I think the TO-247 will fit. You will have to cut is some though.

Steve

I have some of those, and the Berq band-aid looking pads.
The 4661 has a hole where the FET where some goop may get through, not sure if it may make contact with the sink and short.



The Mica's I've used on To-220 projects I like working with better than the silicon pads. I think having goop keeps the pad from moving around.

 

[Diomedian]

Keystone 4663 is the one you're looking for I think. It'll fit to-247 packages. Digikey seems to be out of stock, but at Mouser it's part number 534-4663.

-j

 

[labjr]

to protect against electric noise/interference you must (completely) surround the circuit with a conductive cage/box. It does not have to be metal.
Wood is a fairly good insulator, so can't give any help.

To protect against magnetic fields you need something quite different. I don't know enough to give advice.

I realize that a traditional metal amplifier looks cool.

However, I'm trying to save a ton of metal work. Maybe make a nice cube-shaped walnut wood box with heatsinks on the sides. I just don't want to get it all together and have an oscillation problem.

 

[JimT]

I have the Keystone 4661's and put a IRFP240 on it to check. The two small holes in the mica are low enough down that they are under the plastic part of the case just at its lower edge. The holes should not be an electrical problem.

Jim

 

[woodturner-fran]

ok, so it seems that with keystone 4661 or 4663 will both work ok.


Good work guys!

Fran

 

[bobodioulasso]

labjr
why not to stick aluminium paper on the inside of your wooden box?

 

[Ed LaFontaine]

Yes, aluminum foil and spray adhesive, or there is peel 'n stick copper sheeting sold as flashing. It is available from your building materials supplier.