Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: AndrewD on May 21, 2023, 11:54:23 pm

Title: Rob Robinette Champ Micro Build
Post by: AndrewD on May 21, 2023, 11:54:23 pm

I'm building my first amp: a Rob Robinette Micro Champ (https://robrobinette.com/Champ_Micro.htm) with an EF80, SS rectifier, and toroidal PT. I have the Turret Board populated and drilled out the chassis.

When I started this project, I really wanted to make sure I took my time with it, double-check everything, and generally make it look great.

As you can see by the photos, that plan didn't go well, haha. All's good though, I learned a lot building out the chassis and getting everything mounted. I'll definitely be able to do a much better job next time. I debated getting a new chassis and trying again, but I'm sure I'll make more mistakes, so I'm just going to live with the swiss cheese box for now.

I'm feeling pretty good about the turret board, but the Champ Micro site recommended posting the board before soldering everything, so here we are. I also posted photos of the chassis with everything dry-mounted in case I'm doing something silly there as well. (I'll be adding grommets to the chassis holes.. just waiting for them to arrive)

Thanks for any and all help!

Title: Re: Rob Robinette Champ Micro Build
Post by: AmberB on May 22, 2023, 12:07:50 am

The chassis kind of looks like what happens when you repurpose an old Bogan PA amp for guitar use...there's always holes in the chassis where you remove stuff that's not needed for the guitar amp.  It doesn't hurt anything.

Title: Re: Rob Robinette Champ Micro Build
Post by: bmccowan on May 22, 2023, 05:12:41 am

As you said, board looks pretty good. Watch the polarity of the power tube bypass cap. Assuming the grounds are all running along the north side, that one looks backwards. The speed bumps in the leads are not needed, but they look cool and do no harm.
Agree with Amber on the holes unless there might be curious kids around. Check Doug's Miscellaneous Hardware page for Hole Blocker Plates.

Title: Re: Rob Robinette Champ Micro Build
Post by: mresistor on May 22, 2023, 06:32:35 am

If the holes seem unsightly and you want to plug them these might work  https://www.ebay.com/itm/260951077606


If its inside a cabinet and not seen then sometimes I use 3M aluminum foil tape, just cut a piece and cover up the hole. The tape is the same color as an aluminum chassis.

Title: Re: Rob Robinette Champ Micro Build
Post by: AndrewD on May 22, 2023, 11:10:08 am

Great catch on that capacitor, thanks!

Thanks for all the advice on the chassis as well. I feel like it's 50/50 I'll need to drill more holes anyway, so I'll just leave them for the time being. Good to know about the plate covers and aluminum foil is a great idea too.

Thanks again all. Will post updates as I slowly get this thing knocked out.

Title: Re: Rob Robinette Champ Micro Build
Post by: scstill on May 22, 2023, 04:31:26 pm

Here is my version of Swiss cheese.
Some great patina and cool holes for viewing - just don't touch :-)
Its a 5F1 built in the cabinet and chassis of vintage Silvertone tube radio
Sometimes you need to fill a hole too. In this case, solder in a metal plate.
Here is link to its build history:
https://stillampd.com/silvertone-champ

Title: Re: Rob Robinette Champ Micro Build
Post by: kagliostro on May 23, 2023, 06:45:35 am

To fix the top of that chassis is very simple

Just cut an aluminium foil at the top measures

fix it on the top of the chassis using pop rivets

new holes in proper position and all will be fine to look with a more professional aspect

Franco