SLO100 AC-DC HEATERS?

[ViperDoc]

I combined some existent SLO100 schematic drawings into a proposed placement for the V1/V2 DC heaters. I've never done DC heaters. Is it possible to place the DC power supply in between V2/V3 instead of running a whole separate supply across the chassis? See attached. Thanks.

[FILE DELETED--CORRECTED FILE BELOW]

[martin manning]

Only one ground reference in a mixed AC/DC heater circuit, please. Regarding the location of the bridge rectifier and filters, I'd prefer to keep that junk close to the power supply end of the chassis. Leads carrying DC to the V1 heater are not going to bring any significant noise.

[ViperDoc]

Thanks, Martin.

This is the schematic I saw:

https://imgbb.com/QXCkrLT

I see the AC heaters center tap is connected to a 100K/47uF 100V cap to ground. Is that a form of "elevation" that allows the DC circuit ground?

[martin manning]

I see the AC heaters center tap is connected to a 100K/47uF 100V cap to ground. Is that a form of "elevation" that allows the DC circuit ground?

Yes the heater winding is elevated, maybe 45V, and so the whole bridge rectifier circuit and filters for the DC heaters are as well. The DC ground is there. The ground between the 4700u caps next to the DC powered heater is an AC ground, so all good.

[ViperDoc]

Here's perhaps a better version?

SLO HEATERS ACDC HTRS 2.pdf

[martin manning]

From the layout associated with the schematic you linked above, it appears both the AC and DC grounds are taken to the main filter ground.

[ViperDoc]

From the layout associated with the schematic you linked above, it appears both the AC and DC grounds are taken to the main filter ground.

Is that bad?

[martin manning]

From the layout associated with the schematic you linked above, it appears both the AC and DC grounds are taken to the main filter ground.

Is that bad? :mrgreen:

No, just pointing out that in your drawing the heater AC ground should be labeled “FCG” if it is at the same location. That DC filter set up is not original to the SLO, is it?

[ViperDoc]

No, just pointing out that in your drawing the heater AC ground should be labeled “FCG” if it is at the same location. That DC filter set up is not original to the SLO, is it?

Gotcha. I took that circuit off the schematic above, I have no clue if it reflects the SLO original.

EDIT: Here's the SLO100 SCH for reference.

https://el34world.com/charts/Schematics ... slo100.pdf

[danman]

The original SLO ran all AC heaters but the newer models produced by BAD are using DC on the first couple of tubes.

[bepone]

6.3VAC rectified heaters never give clean heaters supply, it is rather impulse and spiky full of artifacts, which will be inserted throught cathode insulation back to circuit and amplified.

It is beter to use separate 14.5VAC 0.5A transformer, rectified and regulated with 7812, then suppied first 2 tubes with 12VDC (heaters connected to 12V, or using only pins 4-5)