(first build) 5F6A-M Board Layout check before soldering

[Pat_rocks92]

Hello,

I'm currently building a micro bassman from rob robinette 5F6A-M

here is the layout :

https://robrobinette.com/images/Guitar/Bassman_Micro/Bassman_Micro_Eyelet_Layout_With_Rectifier_Tube_small.png

here is what mine is actualy looking (i'm just waiting for the 250uf electrolytic capacitor and the wire for the preamp ground bus)

If you could check if there is any mistake or something wrong with the board it would be kind.

I decided to use real mustard caps instead of the clones. I know that they are 400v instead of 450 but many people told me that they should be able to handle those voltages.

 

[King Fan]

Wow, that is super tidy work. Admirable.

I'm not somebody who can proofread a board against a layout, read resistor codes without a chart, or otherwise proofread amp builds from photos, so I won't try. Instead, let me share some trivial ideas.

It looks like you haven't soldered yet? Smart. Some folks would put a little slack in the component leads. It doesn't have to be full NASA S-shaped relief, but you want them able to heat up and cool down without getting taut. Some folks would wrap the resistors (but no more than 210-270° to ease revisions) while keeping the caps in the top holes -- caps wear out faster and may be swapped even before that to mod the tone.

Do you have the backside wiring in place yet? A good trick is to strip enough that it sticks a few mm out the top and gets folded over the edge of the turret. Keeps it from falling out before soldering, shows you it's there afterwards and in the future.

Finally, partly compulsive, but also useful, some folks like to rotate the caps (especially the filters) so the uF value is facing up. Oh, and if you haven't, hit the F&Ts with some clear coat -- their lettering vanishes at the sight of isopropyl or even a cleaning cloth. And most OCD of all, some folks like to arrange all the resistors with the tolerance codes the same way -- say top and left, or vice versa -- to make decoding one step easier.

Just my 2 cents. Now on to ideas that actually matter!

 

[andrewRneumann]

Looking real good. I found one mistake.

Your 400V caps should be fine. They would be in danger of over load if you test the amp with no tubes installed and your wall voltage is a little higher than the power transformer spec. A variac could be used to lower your wall voltage a little bit if you want insurance while you test things out.

 

[Pat_rocks92]

Looking real good. I found one mistake.

View attachment 982091

Your 400V caps should be fine. They would be in danger of over load if you test the amp with no tubes installed and your wall voltage is a little higher than the power transformer spec. A variac could be used to lower your wall voltage a little bit if you want insurance while you test things out.

Thanks man ! You're all super nice ! The help we can get on this forum is extremely helpful.

 

[2L man]

the wire for the preamp ground bus)

If you could check if there is any mistake or something wrong with the board it would be kind.

Since you ask and I see those quite expensive capacitors and CC resistors

I consider a mistake to make pre amp current flow thru chassis! (And possibly power tube current as well)

Now it is still very easy to install a single solid ground bus and connect it to chassis only close to the input jacks and you have made "grounding" as good as it is possible using current Mains Safery Earth wire and "poor" symmetrical instrument cable.