"IBAM" Module Design Almost Finalized For 500-C!

Hi Guys ,
As some of you may already know I have bee agonizing over this one for quit a while now

Well, I think I have my plan! :yes:

I wanted to do this as compact as possible and with no cutting or drilling if possible. I have decide to use a little wood to mount things on. A nice short block cut from one of the blank dividers from one of Daddy's old cigar boxes, some nice tiny screws to mount the "IBAM" board vertically, and a small piece of Mahogany to actually attach it (the little square Radio Shack PC board and block assembly) to the chassis (location yet to be determined) on the horizontal plane. We'll use either silicone adhesive, canopy glue or similar or nylon screws and nuts, depending on where it goes.

I also want all four tip jack test points as well as a jack for the meter's ground connection. And I want/wanted it all in one location, so they will also be mounted on the little Radio Shack board. We are building an "all in one" module. I think this will do it.

We will run the bias feed, the (4) wires from the pots to the grid resistors and the ground wire for the meter up through one of the holes already on the chassis. To do this I will use some nice, thin solid core #20 Teflon coated wire.

My question here today is; will it be "OK" to run ONE (1) wire from one of the lugs on the chassis (I was thinking one of the ones where the a fusitor is attached and simply jumper the "IBAM'S" ground to that up top, on the back of our little board. Result? The "IBAM" circuit AND the meter test point will be sharing the same ground point
This would allow us to not have to run so many wires through the holes and route them underneath.

Any problem with doing it like this? Would that spot, and sharing a ground there, be "OK" from a hum, accuracy or any other reason? In other words, any detriment to doing it this way?

Thanks to all and I hope everyone is doing fine and having a lot of fun! Summer is almost here!

Thanks you all!
Phyllis

I'll be watching with interest as I want to do something similar for an IBAM install on my 500C. I've got all the parts to include most likely the same Radio Shack board that you mention.

Was leaning toward mounting everything in a small black plastic box with holes cut out for the trim pots and test points. The problem with this is of course finding space to put this on the top side of the chassis.

Looking forward to solutions from this thread.


-Paul

There are several inventive solutions to IBAM mounting, both internal and external. In fact, too many to cite. Do a quick search and you'll find a number of solutions to the mounting question. I did both an internal and external mount; here's the external:



In this version, everything is reversible. Note the green wire popping up through the case. That is the IBAM ground wire that is simply attached to a chassis screw. I recall reading a post by Drew that the IBAM ground was not finicky. Of course, he was right. All the wiring was run through the vent holes in the bottom of the chassis and protected by the 1/4 board.

I guess the point is that so long as your wiring is done correctly, you could mount the IBAM pots and test points anywhere you could squeeze out room.

notdigital said:

There are several inventive solutions to IBAM mounting, both internal and external. In fact, too many to cite. Do a quick search and you'll find a number of solutions to the mounting question. I did both an internal and external mount; here's the external:

In this version, everything is reversible. Note the green wire popping up through the case. That is the IBAM ground wire that is simply attached to a chassis screw. I recall reading a post by Drew that the IBAM ground was not finicky. Of course, he was right. All the wiring was run through the vent holes in the bottom of the chassis and protected by the 1/4 board.

I guess the point is that so long as your wiring is done correctly, you could mount the IBAM pots and test points anywhere you could squeeze out room.

Click to expand...

Thank You!
I understand. My only concern was if there was any reason not to let the two grounds share the same spot; the ground for the meter and the IBAM's ground.
Theoretically I guess they are one in the same, the chassis! :yes:
Only asked as we are going to use the very nice little test jacks and wanted to consolidate things as much as possible. We plan to tie both ground wires to the back of the little test jack.
Thank you again for your nice and thoughtful replies!

Phyllis

It's Built!
It's on the Chassis!
And it performs FLAWLESSLY!

Thank you Mr. Drew Bolce! :yes:

I DID remove the capacitor C86 (it was a 716P from the initial overhaul, I was already un-soldering and jusr wanted to neaten things up under that S.D.S board).

I would like to know though what that cap's function was in the STOCK design?

The one ROASTING E.H. is still touchy to adjust (not as much range left as with the others), but at least now it's at a proper value and stable, just floats a point or two. It was pulling crazy current with GOOD numbers on all pins after only 6 months BEFORE the "IBAM"; another one was like an ice cube (I already posted a question about that one) ...............so, I don't have a lot of love for Russian or chinese tubes no matter who's selling/"matching" them. Our 40 years old G.E. worked better with the stock bias set up than the E.H.s. The G.E. with NO getter flash!

Sorry to ramble; about that C86 and what it did/does?

AND, thank you again Mr. Bolce, you've MADE MY DAY! :yes: :yippy:
Now I KNOW that my tubes are dialed ACCURATELY
Not depending on trust with some cheesy L.E.D.s either like our friend's "new" Conrad-Johnsons he bought at an estate sale. Very nice amplifiers but what a cheap way to do something that important on an amplifier that costs over $7000! And they are MONO BLOCKS!

Phyllis
P. S. : Going to let it cook on the kitchen table over night before putting it back in the system. Can't wait to hear the sound now that I have REAL P/P PAIRS!!!!!!!!!!! :yippy:

Hi!
In a word BEAUTIFUL! This "IBAM" deal is the cat's pyjamas!
Thank you guys: Larry, Don, Drew and everyone else that pitched in to help me with this project.

I could not have done it without you and you have not only helped me retain a wonderful connection with Daddy but you have also taught me a great deal; not to mention the fact that this thing KICKS ASS! :yippy:

Most importantly you've demonstrated to me just how kind and generous smart (and busy) people can be. I have some new views on things now after this project.

Didn't mean to get all deep on ya!

I hope you all enjoy a great July 4th and thank you to all the members here that have served our Country!, I know many of you have, (so dummies :arrow: like me can have the time and the privilege to play with and learn about old Fisher 500-Cs! instead of worrying about where my next meal was coming from) :yes:

Thank you all again so much! I Love You Guys! :boink: This is a special place and a special bunch! :yes:

Phyllis