Regal Model 30 Tube Amp Filter Caps and More?

[misterc57]

Another oldie I picked up. It has 120 Hz hum and I want to replace the filter caps.

Schematic would really help but I have not found one yet.

Having a challenge with the filter caps wiring, values, pin locations, etc...

Tube line up is

6SC7
6J5GT
6V6GT
80

The large 40 uF 450V orange Sprage is loose and not connected. I cannot determine where it was connected but I suspect it went to one of the pins on the plug going to the speaker which is where the OT is located.
Wondering where this one is supposed to go? Also wonder if this one was thrown into the mix and not part of the original layout.

The multi cap has the following values and where I suspect they go. I cannot judge most of the colors because of 70 years of aging and I am a bit color blind.

red/white 15 uF 350V - either going to pin 1 of 6J5GT or to OT
red 15 uF 350V - either going to pin 1 of 6J5GT or to OT
blue 10 uF 25V - maybe pin 8 of 6V6GT. Is this a bias cap?
black common to ground
yellow 10 uF 25V - pin 8 (cathode) of 6J5GT. Is this a bias cap?
brown negative - what is this? - maybe pin 8 of 6V6GT

There is a wire that looks "white" coming out of this cap that is taped off. Cannot really see a blue wire on this cap, or I cannot tell the diff between blue and brown.

6J5GT pin 1 is listed as the "sleeve". I assume no internal connection to the tube?

Thank you for any help or schematic! MC

[The Dude]

I couldn't find anything. It might be just as easy to sketch out a schematic and post it. The amp looks relatively simple. It must be hell to read resistor color codes being color blind!

[g1]

Someone said this national schematic was close to their Regal. Looks like yours is a lower power version of similar. Maybe have a look around the prewaramps.org website.

[The Dude]

My bet is that it's very similar except for the single ended output section. Don't forget to clip out the death cap and install a grounded power cord.

[Enzo]

Draw up your own schematic. I could probably do ti from the photos, but don't ask me. SO much easier when you have it in your hands.

[misterc57]

.... Don't forget to clip out the death cap and install a grounded power cord.

I will also add an inline fuse.

Thank you everyone. Will let you know how it goes.

[mozz]

Going to say a 40uf at 450v is probably not original to that amp. I have some Regal schematics but nothing with that lineup. Nothing in Riders. Probably made by Valco.

[misterc57]

All quiet now. I ended up with a new 22uF 450V on either side of the field coil and two new 10 uF 50V bias caps.

New 3 prong cord and inline fuse also installed.

That National Dobro schematic helped.

Thank you to all! MC

[Jon Snell]

Someone said this national schematic was close to their Regal. Looks like yours is a lower power version of similar. Maybe have a look around the prewaramps.org website.

Anyone else noticed the drawing error with the rectifier valve?

[Chuck H]

I'm confused. Bias caps? And it looks like an electrolytic capacitor has been added to the tube sockets second from right and second from left.?. FWIW the tube socket is not the best place for electrolytics because they are heat sensitive. And why not replace that old preamp power supply filter when you're already at this? Paper and oil coupling caps should ALWAYS be tested for DC leakage too.

[Helmholtz]

Anyone else noticed the drawing error with the rectifier valve?

Oh yeah, the 5V heater winding with the grounded CT would short the HT to ground.

[misterc57]

Hmmm.... so I still have a noise issue.

There is a background humming-buzzing-vibration which I think may be coming from the PT. It is showing up as 120 Hz on my tuner app on my phone. It is not coming through the speaker. I snugged up the PT screws/bolts (no difference). If I push down on the rectifier tube I can feel the vibration and I can muffle the sound a bit. I think the vibration at the chassis is being amplified by the wood cabinet as this was not as noticeable when I had the chassis outside the cabinet.

[Chuck H]

Many transformers are microphonic to some degree. But since 120Hz should be DC I'm more suspecting the rectifier tube. Taking your word that it's not coming from the speaker.

[Helmholtz]

Many transformers are microphonic to some degree. But since 120Hz should be DC I'm more suspecting the rectifier tube. Taking your word that it's not coming from the speaker.

Transformer vibration is caused by magnetic forces between the laminations and between adjacent wire turns.
As these forces are always attractive (in each half-cycle) the result is frequency doubling.
So the fundamental frequency of vibration is 120Hz.

[misterc57]

I'm confused. Bias caps? And it looks like an electrolytic capacitor has been added to the tube sockets second from right and second from left.?. FWIW the tube socket is not the best place for electrolytics because they are heat sensitive. And why not replace that old preamp power supply filter when you're already at this? Paper and oil coupling caps should ALWAYS be tested for DC leakage too.

I meant to say bypass caps on those two tubes, 6J5GT and 6V6GT. Since the sockets are below the tubes I thought I would be okay on heat dissipation, no?

Good advice on the other sections. At this point I am just trying to get it to work noise free.

Thank you. MarkO