6G3 Deluxe build completed

[TitaniumValhalla]

I thought I would share this 6G3 Deluxe build I just finished. My aim for this build was basically a "reissue" (since Fender has never reissued them) that externally looks like the original, using modern components and design principles, while staying true to the original circuit. I opted to create my own layout that deletes the cap can and the brass grounding plate, adding a bus wire on the board for the preamp grounds, which terminates at a dedicated bolt near the normal input. The noise floor of the finished product turned out to be extremely low so this arrangement seemed to work well.

Doug made the boards, the transformers are from Pacific, the chassis and cab are from Mojotone, and I splurged on the spendy faceplates from eBay that include the original logos. There are definitely a few things I would do differently now if I were to build it again, but I couldn't be happier with the results. I tacked in a trim pot to work out the bias value and then set it with a resistor when done - I originally planned to leave a pot in it, but the trim pot felt flimsy to me and I like the peace of mind knowing it can't be turned or vibrate out of spec. I did change the filter cap values slightly from 8/16/16/16uf to 10/22/22/22uf just because I had them on hand and figured they were close enough. Everything else is true to the schematic.

I spent equal or more time in the planning of this build than in the actual work itself, which I recommend to anyone undertaking this kind of project where you aren't just working from a known layout or kit. It ended up coming together without any issues. I read every 6G3 build thread I could find to try to prevent issues others have experienced which I think was a big part of that. Enjoy.

[Latole]

Very nice job, congratulations!

I have never had a problem using a good quality bias pot.
I have often used multi-turn cernets.
For me, a bias pot is a must.

[TitaniumValhalla]

Very nice job, congratulations!

I have never had a problem using a good quality bias pot.
I have often used multi-turn cernets.
For me, a bias pot is a must.

When I had a little single turn trimpot tacked in, only one of its legs was in an eyelet which would probably have been fine in practice but just didn’t feel sturdy enough for me. I think if I need to change it in the future I might do a full size chassis mount pot for it to be more solid. I got the bias dialed in right at 60% idle and the trem works great though so I don’t plan to touch it until these 6V6’s give out.

[Latole]

60%. that's are my choice too

[emerson909]

Nice work, looks amazing!

[Lectroid]

Outstanding work.  That soldering is among the very cleanest I've ever seen.  Great job!

I think if I need to change it in the future I might do a full size chassis mount pot for it to be more solid.

I'm with Latole that a bias pot is a must, and I'm pretty new here.  I once mounted a small PCB-mount bias pot onto a square of perfboard screwed onto the main board, overhanging it slightly.  Painfully ugly to look at, but safe.  And well-secured. 

Like you said, lack of planning on my part... 



 

[bmccowan]

Nice work.
Doug has a bias pot that works great.

[mresistor]

Beautiful amplifier   well done  and congrats!

[sam]

Hello, Most excellent build. 
Any chance that I could get a copy of the layout of the eyelet board? I like the idea of the filter caps w/o the cap pan.

Sam

[TitaniumValhalla]

Hello, Most excellent build. 
Any chance that I could get a copy of the layout of the eyelet board? I like the idea of the filter caps w/o the cap pan.

Sam

Sure - here are the DIYLC files I used for the board itself (compatible with Doug's DIYLC Analyzer) along with a full layout for the build. If you prefer turrets to eyelets you can swap those in with DIYLC and have Doug make it that way for you.

[sam]

Hey, that was quick... Thanks so much for the DYI files, I can see that you spent a lot of time creating them. It is greatly appreciated.
I have ordered the eyelet board.
One more quick question... Using the Brownface PT from Pacific Audio, what is your B+ voltage?

[TitaniumValhalla]

Hey, that was quick... Thanks so much for the DYI files, I can see that you spent a lot of time creating them. It is greatly appreciated.
I have ordered the eyelet board.
One more quick question... Using the Brownface PT from Pacific Audio, what is your B+ voltage?

Good question - I ended up with about 425v at the plates with a GZ34 rectifier which is obviously way higher than the imaginative figures in the schematic but it seems they used a few different PTs in the 6G3 and none were ever as low as the schematic indicates (some good reading material on that here: https://el34world.com/Forum/index.php?topic=31403.0). Mercury makes a reduced voltage 6G3 PT (#FBDP-M) which I considered but the Pacific was claimed to be a clone of an original so I went that route. If I were doing it again I'd probably get the Mercury just to make life a little easier on the caps, 6V6s, etc. but it sounds perfect to me so I am happy with the results.

[sam]

Thanks, I believe I'll get the lower B+ voltage Mercury PT for the 6G3. I've built a 6G6B Bassman and a 5G9 Tweed Tremolux both with the lower B+ voltage PT's and the B+ voltage comes out within 10 volts of Fender specs.

[jojokeo]

...adding a bus wire on the board for the preamp grounds, which terminates at a dedicated bolt near the normal input.

Negative. Technically you have ground loops there. Each set of Input Jacks' are grounded at their chassis points. These points are signal ground going to the chassis. Then you have the speaker output, tremolo switching, neg bias/heater CT, B+ CT, etc. All totaled, I count 8 various grounding points for power, speaker, and signal grounds directly to chassis. Good for this build, but not ideal for others. Nice build and great looking amp!