#183 5th Generation ODS Skyliner. Layout/Schematic discussion

[donvan]

I'm having trouble figuring out how the ground buses are used with regard to the potentiometers. Are folks soldering the bus to the cases, using a grounding washer with a tab to connect to the bus, or not grounding the cases at all?

Thanks,
Don

[dreric]

I'm having trouble figuring out how the ground buses are used with regard to the potentiometers. Are folks soldering the bus to the cases, using a grounding washer with a tab to connect to the bus, or not grounding the cases at all?

Thanks,
Don

You take a scrap lead and connect it to a heavy gauge copper bus. Here's my 183 showing how it's done:

[norburybrook]

I bend the end at 90 deg so it will go through a grounding tab directly and solder it. So the bus bar becomes an 'L' shape.


Marcus

[donvan]

Thanks Dreric and Marcus!
So I see how the grounding bus is made and how leads are used to connect to it. What about the metal case of the pots? Are the cases connected to ground by soldering a connection from the case to the bus or just by physical contact with the chassis? I can't tell for sure from the pictures.

[pompeiisneaks]

Thanks Dreric and Marcus!
So I see how the grounding bus is made and how leads are used to connect to it. What about the metal case of the pots? Are the cases connected to ground by soldering a connection from the case to the bus or just by physical contact with the chassis? I can't tell for sure from the pictures.

You don't need to ground the case, so long as you ground the right lug of the pot, if it needs grounding. Actually, soldering to the pots can do damage to them, and it's generally safer for them in the long run to not solder to the back of them. Older pots were a bit more robust I think.

~Phil

[norburybrook]

Thanks Dreric and Marcus!
So I see how the grounding bus is made and how leads are used to connect to it. What about the metal case of the pots? Are the cases connected to ground by soldering a connection from the case to the bus or just by physical contact with the chassis? I can't tell for sure from the pictures.

You don't need to ground the case, so long as you ground the right lug of the pot, if it needs grounding. Actually, soldering to the pots can do damage to them, and it's generally safer for them in the long run to not solder to the back of them. Older pots were a bit more robust I think.

~Phil

Yep, I no longer solder the braid of the coaxial cables to the back of the pots now, i solder the braid to the bus bar instead.

M

[donvan]

I'm curious what everyone is using these days for the 330uF/385V reservior capacitors. I didn't realize it but I ordered radial caps. They stick up too high. I think I can modify my board, lay the caps down, add some RTV to secure them to the board and maybe even tie them down with a tie wrap. Now that I've been looking, it seems very difficult to find radial, high voltage, 330uf caps these days. Does anyone have a source for the axial 330uF caps?

[norburybrook]

I'm curious what everyone is using these days for the 330uF/385V reservior capacitors. I didn't realize it but I ordered radial caps. They stick up too high. I think I can modify my board, lay the caps down, add some RTV to secure them to the board and maybe even tie them down with a tie wrap. Now that I've been looking, it seems very difficult to find radial, high voltage, 330uf caps these days. Does anyone have a source for the axial 330uF caps?

In the US Sprague are still available at a reasonable cost. Over the pond here I use F & T , very nice caps


https://www.tube-town.net/ttstore/Capac ... 31_37.html




M

[donvan]

https://www.tube-town.net/ttstore/Capac ... 31_37.html

Marcus,
Regarding your tube-town link, the highest value I see is 220uF. That is in line with what I am seeing on U.S. sites. 220uF seems to be the highest that are easily found. 330uF is much harder to come by.

[pompeiisneaks]

I just used a radial one for my dumble and used a terminal strip to mount it, and added some silicone under the base to keep it from vibrating etc. If you know the depth you need you can usually look around and find radials that are way cheaper from great brands for a ton cheaper. They've been building them that way for a long time now for CPU power supplies etc so the technology to make them smaller has advanced drastically. That's probably also why they're being used by builders here for the 'precision power supply' that some dumbles have. There's no difference in the quality of filtering from the axial vs the radial imo.

~Phil

[67plexi]

Precision power supply is all I use now. I started out with the Axial. Before Jason had board sets we built all our boards from scratch.

PPS.JPG

[norburybrook]

https://www.tube-town.net/ttstore/Capac ... 31_37.html

Marcus,
Regarding your tube-town link, the highest value I see is 220uF. That is in line with what I am seeing on U.S. sites. 220uF seems to be the highest that are easily found. 330uF is much harder to come by.

yo are indeed correct, I didn't read your post properly. I always use the old fashioned standard power supply so 220uf are as big as I've ever needed.

Funnily enough I've inherited a bag of old bit's from an amp builder friend and I've pulled out a precision power supply board with 2 x radial 330uF on it. They are quite short so fit no problem.

edit, I've just check and they're 220uF radials.


M

[talbany]

Thanks Dreric and Marcus!
So I see how the grounding bus is made and how leads are used to connect to it. What about the metal case of the pots? Are the cases connected to ground by soldering a connection from the case to the bus or just by physical contact with the chassis? I can't tell for sure from the pictures.

The pot casting is grounded via the star washer to the front of the chassis so the casting now acts as a shield for the pot .So by soldering the coax to the pot shield, you are just extending that shield point for that pot to the coax.
Dumble used a buss bar there to ground the preamp circuit connections to keep them further downstream from the B+ Gnd (CT) and plate caps that carry higher gnd currents. Both are perfectly legit gnd points for coax shields.I prefer grounding to the pot shields and looks neater is more secure holds the wire in place The only downside to this method is if the pot comes loose or loses connection with the chassis you lose the shielding point

BTW.I have never destroyed a pot soldering it to the pot case If you tin both the pot and the coax shield clamp them together and re-flow adding a bit more solder your iron should only be there a few seconds any decent quality pot should hande it no problem
As a general rule you usually want to ground the shields from the source end and never on both ends creates loops!

Tony

[donvan]

Thanks everyone. It sounds like I'm on the right track using the radials that I already have.

Tony, thanks for the good tips on grounding.

[donvan]

What gauge wire do amp builders generally use for the ground bus?