London Power ad

Search the Forum

(Advanced Search)

Bogen CHB-20A Rebuild
(06-11-2024, 08:43 PM)K O'Connor Wrote: Hi Guys

You cannot test your setup without using real cards.

Got it, so that confirms my suspicion.

(06-11-2024, 08:43 PM)K O'Connor Wrote: The Cambion and any setup that requires a bottom holder is not the right approach for eyeleting a card - it may be okay when setting eyelets into floppy material, but not for a card.

Most arbor presses come with a flat thick steel bed which is preferably polished so the eyelet card can slide freely on it.

I see. I had thought it might be preferable for alignment to have the single point for the eyelet to rest against with the center guide pin. However it does get fairly inconvenient trying to keep the card balanced and level on the small support block I've been using while also operating the cambion press, and I assume that is why you don't recommended it. Using the Dake press which has a table like you mention, though not polished, is much nicer.

(06-11-2024, 08:43 PM)K O'Connor Wrote: The arbor press will definitely work better bolted to a sturdy table even though you do not have to apply high force to install eyelets.

Yeah, keeping the cambion from tipping has been getting annoying and cumbersome.

(06-11-2024, 08:43 PM)K O'Connor Wrote: Regarding the card layout: have you seen the inside of an old Fender? The layout is designed for the parts to be used, arranged in now classic shapes that make recognising the circuitry very easy. The point is really to use the space wisely with a minimum of jumpers on the card. Generic cards with two or three rows of eyelets or turrets makes tracing and repairs much more difficult later even though it looks neat.

Noted. I suppose that means the swiss-cheese practice card will only be suitable for breadboarding throw-away stuff.

Based on your above input, it sounds like the cambion isn't going to offer much advantage over just the Dake press, despite being made for terminal swaging, and it'd be a better idea to focus on getting things working with the Dake, which does have the nice big table and doesn't require precise vertical positioning of the work to perform at it's best. Magnet chuck here we come.

Thanks for the feedback! Also for you patience, I imagine it's probably a headache on your end watching this unfold.
I spoke too soon. What I thought were good swages with just the tools and manual tapping were not, upon closer inspection. I found a way to get a good swage, but again it involves using a center punch before applying the staking tool.

Here is one of what I thought was a good swage obtained with just the tool and swiveling it around while tapping it with a small steel block:

Closer observation, and pausing during the swage process to check on the eyelet progress, revealed that it's not actually flaring outwards and instead is sort of folding itself in half as depicted below.

I was able to get a good swage that rolled outwards, but only after I first did the swiveling motion with a 1/4" center punch to get a nice even flare before following up with the staking tool. Comparison between the center punch + 1715 (left) and only the 1715 (right) in the picture below. The stuff sticking out of the left eyelet is just some debris that got caught inside while handling, and isn't an artifact of the swaging process.

So, back to the drawing board it seems. Current guess is that I'm leaning the 1715 too much while swiveling it, meaning that instead of the cone contacting the edge and flaring it the circular groove is smooshing the edge inwards so that it starts rolling in on itself as seen in the drawings. This whole thing feels like when you miss a negative sign early in a physics problem, but everything else checks out so you end up chasing your tail until you find where you flipped the sign. I wonder where I dropped the sign, metaphorically, in this problem... At least I've got a good puzzle to work through.

Forum Jump:

Come in where it's warm!
A warm welcome to tube amp modding fans and those interested in hi-fi audio! Readers of Kevin O'Connor's The Ultimate Tone (TUT) book series form a part of our population. Kevin O'Connor is the creator of the popular Power Scaling methodology for amplifiers.
Please remember these three principles: respect, sharing, community.
Not familiar with The Ultimate Tone book series? See discussion topics, or click here to visit London Power/Power Press Publishing.

Tube Amp Forum Hosted by London Power
London Power logo