Third build underway - 6V6 KF60

[gktamps]

Happy New Year, All!
Started this build last week, with some helpful input and advice from Mark and Richie.
It's going to be a KF60-inspired, 6V6-tubed amp with GZ34, choke, PPIMV and Hall VVR3, in a bare JTM45 chassis (using parts that I've picked up here on TAG). I'm using multi-section can-caps for the 20uF and 8uF sections, with the large, series caps on a smaller board inside. Transformers are ClassicTone 18watt, and using turrets instead of eyelets. Also running a 2-pos. switch for NFB. It's going into a Komet cab, tolex with wood face, but I have to come up with a panel while I'm waiting on more parts to arrive.
Not sure of my voltage targets and therefore power rail resistor values, which I assume will require tweaking from the normal build values. Also hoping to replace the fast/gradual switch with a relay board, but need to do some homework there, or maybe Dana will sell me one.
Should get more completed after parts arrive on Wednesday...
Best to you all, and thanks for being a great bunch.
Greg

[Structo]

Cool amp!

I did a 6V6 Rocket that sounds pretty good.

[M Fowler]

Greg you have a good start.

It's hard to tell if the amp will need tuning or not, might fire right up with good voltages and you'll love the tone

Mark

[gktamps]

Thank you, Tom! I'd love to see your build thread on the 6V6 Rocket, by the way...
Thank you, Mark. I've been spending a couple of hours searching posts for the fast/gradual switch options and have been reminded, like every other time I go through this, that you guys have done all this before - many times - and I'm a real neophyte. It must get tiring breaking in newbies...
Now I am thinking of incorporating either Roberto's or Tictac's approaches for the split plate load selection:
https://tubeamparchive.com/viewtopic.ph ... l&start=15
My wife is telling me to stop searching and moaning about not being able to decide and start soldering so she can read in peace.
Greg

[gktamps]

Had to wait for parts, so slow going.
Front panel painted hammer dark grey, pots installed (waiting on the MV pot), choke installed, switches, pilot light, preamp board and can caps in place.
Next, have to mock up the main filter (using F&T caps) and bias supply board and location, then make one. Will be running the VVR3 board at front panel, very close to CMOS.
Taking bias supply from one leg of B+, since this transformer has no dedicated bias tap. Thinking I'll start with 220k dropping resistor to bring it down around 60v - does this sound about right?
Cheers,
Greg

[Structo]

Thank you, Tom! I'd love to see your build thread on the 6V6 Rocket, by the way...

Greg

Be careful what you wish for!

My "amp" started life as a Hammond organ amp.

First I tried a Deluxe circuit and was underwhelmed by that, then a Plexi style circuit then finally a Rocket.

It was an exorcise in cramage.

But believe it or not, it's real quiet and gets a fair amount of hair when cranked up.

I added the second stage cathode bypass and switch it with an old footswitch I had around.
Adds a nice boost in gain.

The Hammond PT was high in voltage so I added a 25w Zener on the center tap to lower it.

[gktamps]

Hah! Well, Tom, you aren't exaggerating about the cramage, but it looks very well executed.

Thanks, Tom,
Greg

[M Fowler]

Nicely done Tom.

Greg your not done yet what about required hammertone painted transformers

[gktamps]

Mark,
Believe me, I thought of it, especially considering I have several cans of the correct color. Since this is a tribute, OK a bastardization, really, I thought it would be more authentic to let all the family lineages show!
Cheers,
Greg

[Reeltarded]

Nice work! I need to stay focused on Rocket, must stay focused on Rocket.. must focus on Rocket..

Hammertone all the way. Lookin good.

[gktamps]

Reeltarded - thanks.
Rocket's on deck, waiting to find a correct chassis. I've got a couple of nice A470s pulls from an old Dynaco to choose from, and a Pacific PT sitting there, but this one's gotta be right first!
Got more parts, so more progress to report after tonight.

[gktamps]

Parts, parts, where's my parts??
Slow progress waiting for odds and ends, but here's the main filter cap board and an auxiliary board that will hold the gain switching transformer and power supply boards I'm getting from Dana Hall. Made the aux. board oddly shaped to take advantage of transformer bolts, extended with standoffs, but also make room for switch wiring. Lots to fit into this smaller chassis.
I made the main filter board larger to handle the VVR3 at the top extension, and the bias supply resistors and diode at the left extension, which will sit over the bias can cap.
Bias pot is in, some of the front control wiring.
Can't even play guitar waiting for parts - sliced my finger open on the milling machine!
Greg

[gktamps]

As usual, working for a living and waiting for parts has slowed me down, but also given me time to re-think my layout, and has reminded me that it's a lot tougher to modify the heck out of something that someone smarter than I designed!

Using a smaller chassis meant things got a little cramped, and my boards were taking up lots of real estate, so I cut down the main filter board, mounted the bias supply circuit onto that, then cut down the board I was going to use for Dana Hall's switcher board, and stuck the VVR3 onto that. The switcher will get installed on the side wall after I get this thing up and running.

Also made a change to the fast/gradual circuit, adapting Roberto's 1ML potentiometer circuit to replace the switch. That meant modding the preamp board a little for different caps and layout.

Next change was more substantial; I had originally mounted the can capacitors for the bias supply and preamp board next to the PT, but realized I was going to have some pretty long wire runs to the preamp caps. So, I cut a hole over the preamp board, added some turrets, and wired up the dropping string onto the preamp board, right over the can cap. Much shorter runs now. The connection from the main caps will be the 10k resistor across the adjacent turrets on each board.

One big OOPS was that when I had the idea of running a can cap for the bias circuit, I blanked out on the fact that these things share grounds. Because I was committed to my basic layout and had little room left, I decided to make my own can cap using individual capacitors, which I installed into the can of a bad cap that I dug out (that was a bitch). Used 10uF in place of 8uF, which I couldn't find in the voltage rating I wanted, and wired them to turrets on a small piece of board I siliconed into place. Looks like the real deal, and gave me discrete solder connections for both + and - of each cap.

Tonight I'll wire up the signal cables, the final power rail resistor across the two boards, and check all my connections and runs, then fire it up without tubes and see how many things I've messed up.

If anyone sees something that looks wrong, please feel free to let me know!

Cheers,

Greg

[vibratoking]

Lookin good and tight in there!

I like the can cap creativity.

I also like the extra features that you are designing. I'd love to hear it when you wrap it up. Thanks for posting your progress.

[Reeltarded]

Yeah! Amp looks like a winner!