ODS-101-HRM 100W Scratch Build w/ Pics [In Progress]

[benoit]

As the wealth of questions I've recently asked might imply, I have a build underway.

The chassis is one I had a friend bend up in the metal shop he works in from .125" aluminum. Drilling it all out was the biggest PITA in history, but rewarding as well. I don't think I'm going to put a faceplate on, as I'd have to find front panel controls with longer frames.

Boards are all 1/8" garolite from McMaster-Carr, some of which have 1/16" backing boards, also garolite.

The schematic is the ODS-101-HRM found here:
http://www.ampgarage.com/forum/viewtopi ... ight=final

The only major deviation is in the relays, which are not present in ODS101HRM.

I've been following Funk's excellent build order guide, found in this thread:
http://www.ampgarage.com/forum/viewtopi ... s+threaded

Relay and bias supply are installed and I've just installed OT and choke.

More pics, info, and questions to fallow.

[benoit]

More Pics

[ic-racer]

Looking good!!

I am working on a schematic for the HRM I hope to eventually build. It seems like you have most things figured out already, but I'll post it if you want to have a look. Basically it is 101-HRM with the details filled in from little tidbits of info that have been posted.

[Deric]

Lookin' good!

[heisthl]

Looking good!!

I am working on a schematic for the HRM I hope to eventually build. It seems like you have most things figured out already, but I'll post it if you want to have a look. Basically it is 101-HRM with the details filled in from little tidbits of info that have been posted.

Don't use the bottom leg of the presence pot in your revised 101 schematic - the way you have it changes the DC resistance to ground in parallel with the 390. It makes a difference

[benoit]

Looking good!!

I am working on a schematic for the HRM I hope to eventually build. It seems like you have most things figured out already, but I'll post it if you want to have a look. Basically it is 101-HRM with the details filled in from little tidbits of info that have been posted.

Don't use the bottom leg of the presence pot in your revised 101 schematic - the way you have it changes the DC resistance to ground in parallel with the 390. It makes a difference

So just come right off the wiper to the cap, and from there to ground?

[ic-racer]

Looking good!!

I am working on a schematic for the HRM I hope to eventually build. It seems like you have most things figured out already, but I'll post it if you want to have a look. Basically it is 101-HRM with the details filled in from little tidbits of info that have been posted.

Don't use the bottom leg of the presence pot in your revised 101 schematic - the way you have it changes the DC resistance to ground in parallel with the 390. It makes a difference

Good pickup. Thank you! I see the same error in my #124 schematic.

[heisthl]

So just come right off the wiper to the cap, and from there to ground?

Right

[Structo]

Man that is some thick aluminum!
Should be a very stout amp!

[benoit]

Man that is some thick aluminum!
Should be a very stout amp!

I know! I'm bummed I can't get a faceplate on there though...

[benoit]

Progress. It's debatable whether the amount of pictures I'm taking (much less posting) borders on obsessive. So be it.

Wishing I had something other than incredibly beefy 5W Cement screen resistors but I guess it works.

Does my OT primary lead dress look ok? Or anything else for that matter?

[heisthl]

This could be the start of something good, seriously it looks great so far.

[ic-racer]

Are those your 1ohm bias reistors coming from the tube sockets? They look like 1/2 watt. All the pictures of real D amps I have seen show seriously large resistors in this position.

[benoit]

Are those your 1ohm bias reistors coming from the tube sockets? They look like 1/2 watt. All the pictures of real D amps I have seen show seriously large resistors in this position.

You're right about that, and I'm wondering if I can get away with half watt. If not it's no big deal, I'll just skip the resistors and go with plain wires. I'm not too worried about being original for originality's sake, at least not in trivial places but if those won't work due to power handling needs I'll yank 'em. Anyone care to weigh in on this?

[heisthl]

Power = E x I or P = (R X I) x I so if your tube was running at anything less than 223ma you would have (1 x 223ma) x 223ma or .49watts.