New Build: 18watt Richie TMB Head - pics uploaded.

[Plexi]

Nik: I have another TMB circut i like, its different than the one posted..
And it would keep the normall channel totally stock. I have most of that one drawn up, I left off the power supply and hookups to the output tubes,depending on what amp it would be used for. So i'd have to finish that part,but all the rest is drawn up. Its very simple,and easy to build.

I can e-mail you a copy to look over.

Richie

[Gabi]

All right all!

Back from camping.... ready for normal life.
ugh

Norm: I posted your TMB layout in the Richie's TMB section in the DOWNLOADS. Right here:

http://www.18watt.com/modules.php?name= ... oad&cid=30

Cool drawing, BTW!

Richie: Some are talking on this thread of a mistake in one of the schematic... Which one is that? IS this the one? http://www.18watt.com/Storage/18wTMB_Richie.pdf

Then I can do the corrections...

gabi.

PS: I missed the Forum in Cheesland

[jhguitarlab]

jersey-aaron et al,
I also have built the TMB (as a combo) and worked for awhile with input from Richie, Norm, and BKing (I left out the master volume). When complete the amp worked on power-up which was exiting but it is quite noisy. I too refered to the schematic to document layout changes such as the V2/V3 reversal. The amp works, it's loud with beastly gain, and it looks great in the Swanson cab but it's still noisy and I suspect my tone stack and pre-amp wiring. I have your layout to compare and have posted the one I did in the troubleshooting folder (JHTMBR2layoutDraft). I had been away for awhile but I'm ready to dig back into this one fresh. It looks like lot's has happened in the meantime. Any input to the layout would be helpful. Certainly some differences from the latest TMB layout on file.

Thanks all
JH

[jersey_aaron]

JH - I don't know much about electronics, but I *DO* know that my amp is quiet as a mouse, so I will just point out some differences between your layout and mine.

The most obvious thing that comes to mind is that all of the components on your board are sharing the same ground point as your 32/32uf cap. This, from what I have heard is not a good thing. You should seperate your signal ground. In my layout, the 32/32uf cap is connected to a ground at a transformer bolt, along with my 5w resistor and 470 electolytic cap that comes off the board. Also, my transformer is grounded here as well.

Another thing is your pot grounds, they are all grounded to themselves. I would ground these pots to the bussbar with the rest of the signal grounds.

The last thing I noticed is the 68k resistors you have going to each jack. I don't know the significance of these, but I don't have them at all.

On a side note, I would recommend (along with Phil) that you bump your 25uf and 50uf caps on the cathode bypass on V1 both to 1uf. Its just a much better sounding amp this way. Also, The master volume pot works wonders and doesn't affect the signal like you think it would.

Jersey Aaron

[jhguitarlab]

Thanks for the reply Aaron!
Grounding could be an issue though I used a star grounding scheme. In reality the pots are not to the housing but to the star ground per the photo (TMBstarground) I just added to 'troubleshooting'. I maybe should isolate the pots from the chassis if I have it this way. Keep in mind since the photo I have added the second filter stage and the output wiring is no longer way over on the input end.
The 68k are a hold-over from a bassman type attempt and they are gone from the TMB channel. After seeing the MV pot in one jack location I may give it a go. I don't need two inputs. Once I address the noise I'll look at doing this.
There quite a few component differences compared to the latest Norm layout drawing. I will compare with yours tonight (when I can get out of work;-]

This troubleshooting gallery was a great idea.
JH

[jersey_aaron]

That star grounding in your photo looks pretty frightening. I would probably say, without a doubt, that is the cause of your noise (although I'm no expert).

[jhguitarlab]

mmm... well everything about it frightens me;-] but that star grounding is intended to provide a common grounding point and eliminate ground loops and thereby minimize noise. I've always been mixed about it as I have have some old amps that have grounds points all over the place and the're pretty quiet and I have built other amps using the star grounding that are also quiet. I can't help thinking I have something just plain wired wrong??
JH

[jersey_aaron]

From what I understand, star grounding is far more bizarre than your description. Its all about grounding certain elements in positions on the chassis that get progressively closer and closer to the power supply. I swiftly discarded any inclination to messing around with that kind of crap and just did a simple buss bar. It worked for me. Where are the experts?

[Plexi]

I like the buss bar. I used it in the first 18 i built,and took pics of it. Seemed to have caught on. Many other amps use them,and not much different than haveing the buss bar on the back of the pots like in the early amps. Sound city amps used the back of the pots also. I do like to have a my buss attached to ground on each end..and one mounting lug close to the middle. But there are many options of how people use them,and they work very good. Some people want to use the star ground,and try to run everything to one ground..like a big tree,and wires run from everywhere. It would be neater,and probably work better to run maybe 2 or 3 lugs for the star grounds,in this amp that would cover most all of the grounds from the board..and pots.
And use a lug on the transformer bolt for grounding the center tap,and parts of the power and cathode resistors off the end of the board.
This would seperate most of the sections to there own ground.
Paul Ruby has a very good board layout that includes the grounds along the back. Those long run grounds and every ground to one star can cause some noise problems. I know some guys when working have used an alligator clip for a temporay ground,and you can hear alot of noise when it gets move close to something. I like the short as possible ground connections.. Ok enough rambling..

Richie

[zaphod_phil]

There's nothing bizarre about star grounding at all. Basically. you just need to make sure that ground currents from the power stage and power supply sections don't share the same ground paths with the preamp. You also make sure there is only one connection between the amp's ground and the chassis. It all needs to be kept as simple as possible. You can do this with a nice fat bussbar as well, which acts as a stretched star point, provided you lay things out in a sensible order and have all the power stuff soldered onto the far end of the bar from the preamp.

Some old amps have funny grounding arrangements, it's true. If you have a lot of time and patience these schemes can be made to work through a process of trial and error, and the hum can be made to cancel too. However, for DIY builders it's easier, less frustrating and more sensible to use an electrically sound grounding scheme from the very beginning.

[uplandpaul]

I've decided that the TMB is the variation to build. Which is the best schematic or layout to use? The layouts and schem in circuit variations | TMB (richie) don't match yet. Am I looking in the wrong place?

BTW, I thoroughly enjoyed Arron's description of his TMB 18 watter.

Thanks,
Paul

[jersey_aaron]

Hi Paul. You aren't looking in the wrong place, I used the non-matching schematic and layout too. Someone is working on fixing the files as we speak..

P.S. If you want to hear my 18watter, just go to the Zounds section on this website.