HRD > Bassman project! SUCCESS!!

[Dr Tony Balls]

I doubt you'll notice, but the turret board specified was 30x30. Turns out the layout requires 31x31

HA. The original board was 31!

[JSett]

I doubt you'll notice, but the turret board specified was 30x30. Turns out the layout requires 31x31

HA. The original board was 31!

Was it? classic! I stared at the plans for a good 10-20 minutes trying to see if there was a way to gain a row but I sure as shit couldn't. Cut and paste to the rescue. If I was to do this more times, I'd make my own turret/eyelet boards.

[Scout]

Almost all the parts are here now so I populated the board tonight. I find this extremely therapeutic...



It really is a nice diversion, isn't it.

[JSett]

Massive update on this.

I went and got the donor amp back yesterday morning as I had the day off to tinker with this. Obviously, as always, I'm extremely industrious.

Ready to operate...



The guts (I'll organ harvest that later )...



The cadaver...



Thanks to MattK, I sourced these adaptors from eBay China for £10 shipped (for 4) instead of $60 from Angela...



Used a lot of the existing chassis holes to mount/earth/etc things. I think, apart from the tube socket adaptors, I only had to drill 3 holes. That aside, I got the board in and stated running all the leads...



A lovely bundle of redundant wires. BUT ARE THEY?!?

It turns out that export/import models have some weirdness going on which means the colours are NOT what you'd expect. In the end I had to connect BLK/GRN to BLK/YEL together and VIOLET and BLACK were the +/-. I blew a few fuses trying different combinations...



There were a few more complications. Turns out the OT Primaries were backwards so they needed swapping. I also got 2 caps mixed up (0.01uF and 0.1uF in the tone circuit so the thing sounded awful. It took a bit of fucking about to fix that issue!!

Top panel is a mess for now, but it's functional...



But it's all in, working, and seems to sound great! I can't test it at volume until tomorrow though...







So, obviously MASSIVE thanks to Tony for inspiring and helping so much with this. This has been a much more educational effort that my last amp build - which was a little 'paint by numbers' really and wasn't a huge challenge. Not only did Tony help with the schematic and layout but he helped a ton last night with the problem solving required. Gratitude level 100.

Points of note: If I do another I will definitely make my own turret board and probably use vintage style wire for the flys. I like doing my electronics with all the nice clean angles bent in but a) I didn't have enough cloth-covered here in stock and b) seeing as it wasn't 'paint by numbers' I was more concerned with functionality.

So, several burns, a small fire, a jolt to the left hand (whoops), a tingly finger and a big old mess in the spare room later, I think its done!

[sal paradise]

That looks INCREDIBLE. Amazing work - can’t wait to hear demos!

Are you pleased with it? I’m stoked for you

[MattK]

Wowee! That looks awesome. Hope it sounds divine.

[OffYourFace]

sick

i just spotted THIS. I wish the cabinet was in better shape but it's an ideal price for a similar project.

[JSett]

Thanks everyone! Yeah, hopefully I can spend some time this evening/tomorrow with it and put it through its paces a little.

There's a couple of things I'd do differently if I was to do it again but otherwise, pending confirmation it possesses 'Le Rock', I'm a happy camper

[Scout]

Well done! As far as right angle wiring goes, being an electrician there’s always a minimum radius required when bending conductors especially those subject to high temps. Granted it’s small in a 22 gauge but I like more of a neat sweep than a hard 90, just a thought.

[Dr Tony Balls]

sick

i just spotted THIS. I wish the cabinet was in better shape but it's an ideal price for a similar project.

FUCK. These never show up this cheap in NYC.

[JSett]

sick

i just spotted THIS. I wish the cabinet was in better shape but it's an ideal price for a similar project.

FUCK. These never show up this cheap in NYC.

Thats a great price. Here in the UK you can pick them up for £250-350 pretty much any day of the week.

[Dr Tony Balls]

All I can find right now is a Pro Jr. for $250. I've done the same thing to one of those before, but its a little less utilitarian than the 30-40 1x12 guy.

What i'd really like to fuck with is one of those AC30CC things. Awhile ago i did some service on one and the guy took FOREVER to pick it up to the point where I was like "if its not picked up by this date, its mine". I was really hoping for that....was gonna gut it and make it a proper AC30.

[JSett]

Okay. So there's a problem. The amp is EXTREMELY bassy. Even on 0 it's like it's on 7.

Now, I've gone over the circuit and connections a ton of times and I can't see anything wrong. All the values seem right, the pots seem wired correctly... But it's all bass and barely enough treble

Any help would be amazing....

[JSett]

I definitely am stuck here.

After trying a million different things today and swapping parts etc there is nothing I can find that could be causing the bass-dominant tone of the thing. I lifted the mid resistor to bypass the entire tonestack and it was still there, so it's probably somewhere else.

So. I ripped the board out and remade the whole thing, checking every resistor with a multimeter out of circuit then back in. Redid all the rear jumpers too. It's now back to 'stock' as per the schematic and layout. Plugging my existing Ballsmom head into the cab & speaker proves it's the circuit that's the issue (as it sounded fine). The sheer amount of low frequency signal being let through somewhere is sapping all the power too and it's more like a 5w amp than 50w

It's a lot scruffier now I've had to redo the whole fucking thing

[Dr Tony Balls]

POST VOLTAGES!

Also what means do you have for checking bias? Bias probe or something?