Author Topic: Single Channel AB763 w/VB Tremolo (Read 4233 times)

Blind Lemon · « **on:** February 23, 2022, 01:41:01 pm »

Hello Gentlemen, doin another one of these for a good friend of my son's. Had a little trouble with the last build, distortion in the PI. Don't really think the problem was completely cured, but I think it was mask fairly well.

I am very interested to hear if this build has any of the same issues. I would love to hear from anyone that has built this layout and how it turned out for them.
Link to previous thread. https://el34world.com/Forum/index.php?topic=28060.0
I am starting with a blank BF Bassman chassis this time instead of a Twin chassis. Amp will end up in a head cab.
A few pics. I am a little farther down the road than these pics, so I'll post a few more post to get caught up. Been meaning to start a thread on this but got a little behind.
BL

Blind Lemon · « **Reply #1 on:** February 23, 2022, 01:47:06 pm »

Got the chassis punched and drilled , transformers mounted and tube sockets installed.
Figured how big of board I could get away with and how the circuit would line up with the tubes to keep the wire lengths as short as practical.
Board and layout.
BL

Blind Lemon · « **Reply #2 on:** February 23, 2022, 01:49:16 pm »

Board drilled and turrets set.
BL

Blind Lemon · « **Reply #3 on:** February 23, 2022, 01:51:56 pm »

Board populated.

sluckey · « **Reply #4 on:** February 23, 2022, 02:40:35 pm »

My computer doesn't like your pics. Are the pics those crazy Iphone proprietary "multi frame" pics that show motion when viewed?

Blind Lemon · « **Reply #5 on:** February 23, 2022, 02:59:17 pm »

They were converted to JPG from HEIC file.
Can you not see them?
Maybe I need to repost them?
BL

jamaio · « **Reply #6 on:** February 23, 2022, 03:06:13 pm »

I can see the pictures with no issues, looks nice!!

sluckey · « **Reply #7 on:** February 23, 2022, 03:43:44 pm »

Quote from: Blind Lemon on February 23, 2022, 02:59:17 pm

They were converted to JPG from HEIC file.
Can you not see them?
Maybe I need to repost them?
BL

I tried four image programs on my windows 10 PC. Nothing works for me.

Blind Lemon · « **Reply #8 on:** February 23, 2022, 03:59:54 pm »

sluckey, can you see them in the first post now?

I am on a Win 10 machine also and I could see them, but they weren't showing as thumbnails.
BL

valvetones · « **Reply #9 on:** February 23, 2022, 05:03:11 pm »

I can see them fine.
I agree,like good.
What�s the best way to punch the chassis for your power receptacle ?
Seems hard for me to grasp how to punch a shape into steel other than round? Such as the receptacle you have, or the spot for the strain relief, or sometimes fuse holes are flat on the sides not round.
Ive looked at Greeley punches but never saw any other shape but round.

mresistor · « **Reply #10 on:** February 23, 2022, 05:10:43 pm »

Then you have to ask yourself - how do manufacturers do it? I'd like to know.

sluckey · « **Reply #11 on:** February 23, 2022, 05:16:04 pm »

Quote from: Blind Lemon on February 23, 2022, 03:59:54 pm

sluckey, can you see them in the first post now?

Yes, but I was hoping for the original size. Cannot see any of the others.

mresistor · « **Reply #12 on:** February 23, 2022, 06:04:11 pm »

I can't see any photos other then the first two ..

uki · « **Reply #13 on:** February 23, 2022, 06:21:44 pm »

Quote from: mresistor on February 23, 2022, 06:04:11 pm

I can't see any photos other then the first two ..

Same here.

mresistor · « **Reply #14 on:** February 23, 2022, 06:46:36 pm »

see them all now I'm liking that red board too. I just built a 5F10 circuit with it..

Blind Lemon · « **Reply #15 on:** February 23, 2022, 06:52:31 pm »

Swapped all the pics out.

VT - I have a Greenlee punch, it's not the perfect size but with a little filing it works. I watched ebay until one came up that I thought would work and jumped on it.
BL

Blind Lemon · « **Reply #16 on:** February 23, 2022, 06:53:43 pm »

Hell now all the pics are sideways.

BL

Blind Lemon · « **Reply #17 on:** February 23, 2022, 07:14:16 pm »

Finished up all the hookups, will do the start up tomorrow.

BL

Blind Lemon · « **Reply #18 on:** February 23, 2022, 07:15:00 pm »

Couple more......

Blind Lemon · « **Reply #19 on:** February 24, 2022, 10:49:24 am »

Still sorting a few things out, but here are the voltages.
BL

EL34 · « **Reply #20 on:** February 24, 2022, 02:26:49 pm »

That's not one of my boards.,
I don't use Red board material

I am assuming Hoff is Hoffman?

Blind Lemon · « **Reply #21 on:** February 24, 2022, 03:28:44 pm »

Just giving credit for one of your layouts.
I''ll try to edit that out.
BL

Blind Lemon · « **Reply #22 on:** February 24, 2022, 03:36:16 pm »

Was able to edit my post.
Sorry for any inconvenience.
BL

Blind Lemon · « **Reply #23 on:** February 24, 2022, 05:20:47 pm »

So I wrestled with this alligator today and it ended up sounding pretty good. Had a few dumb hookup mistakes on my part but after straightening them out I had the same gravelly sound on the notes as I did with my last build of this type. I jumped straight to to PI where I experienced trouble before. I put in a jumper from V1-B6 to before the .001uf cap at the PI, bypassing the effects, trick I learnd from local hero. The distortion was still present so I scoped it before and after the PI and the fuss was present after the PI. Put a 300pf across the 220k resistors after the PI and it pretty much filtered the fuzz out. The only way I can hear anything of it is if the amp is really loud, but there will be a certain amount of distortion anyway.
So I guess the question is, what can be causing the distortion in the PI? And what exactly is the 300pf capacitor filtering out?
Schematic here: https://el34world.com/schematics.htm#Hoffman_AB763_One_Channel_

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Author Topic: Single Channel AB763 w/VB Tremolo (Read 4233 times)