Silvertone Meteor 1430 Amp

[angelodp]

Here is my layout for the changes

A few questions

1. Can I take the Red Iso T leg that I now show at pin 3 of the 12Au6, to the node where the R6 &R5 are grounded?

2. I have removed R4 &C3 and replaced with two jumpers. Can I loose the C3 jumper?

I have not shown the additional Resitor that martin siuggested to bring down the line voltage, as I am running the amp on a variac at 110v

Any other notes appreciated.

Ange

[sluckey]

This heavy black line is chassis ground. Everything connected to the heavy black line is now earth ground, including the PT red wire. I would connect the PT red wire to the negative side of those filter caps, but anywhere along the heavy black line is OK.

[angelodp]

I checked for voltage on the Variac switch while using it with this amp, sure enough I see 120v!! Even with the two prong plug reversed I see 120v on the on/off switch for my Variac.... no bueno. Thats between the amp switch and the variac switch.

Gonna order the stuff to convert shortly.

A

[angelodp]

Since this amp uses a half wave rectification, do i need to consider adding a solid state full wave rectifier in addition to what I have?

[martin manning]

Your 35W4 vacuum rectifier only has one diode. If it were me, I'd do only what is necessary to eliminate the safety hazard.

[angelodp]

Can you please explain what the 15M bridging pin 1 & pin 7 on the 12AU6 does?

[martin manning]

Can you please explain what the 15M bridging pin 1 & pin 7 on the 12AU6 does?

It's grid leak biased. Basically developing the negative grid voltage wrt the cathode by virtue of grid current and the high impedance to ground. Note the cathode is connected directly to ground, with no bias resistor.

[angelodp]

Thank you

[angelodp]

That 15M has drifted to 20M. I only have 8.4M on hand, would two of those in series 16.8M suffice? Close enough?

[angelodp]

I need a bit of input. I have modified this cab to more fully support the chassis. My plan is to mount the ISO Tranny on the bottom pan. I have the amp upside down in the pic to line things up. I am also planning on running the three prong cable from the bottom along side the ISO Tranny so that I don't have the big hump of a thick cable out the back.

Question is, will the ISO so close to the Alnico magnet create any issues? Am I better off positioning the ISO on the floor of the cab and running lines up into the chassis.

[angelodp]

Went ahead and mounted the ISO, with rubber grommets installed for the wires. With the wooden spars as support its feeling pretty solid. I may just run the three prong from the sideb and put in a good strain relief, trying to avoid a clunky cable off the back side. I have replaced all the internal components save the 100 ohm 5W. Once I get up, and running I will see about adding that extra dropping R that Martin suggested. I also did some repairs on the edges of the speaker, minor tears. I use a stuff that is designed for tent repairs, goes down like an amber bead glue and solidifies pretty quickly and is somewhat rubbery.

Still waiting for a 2.2M 3W to complete.

[angelodp]

I am thinking of taking a page out of Dave's Bassman build and use wire nuts for the connections to the switch/ISO, Neutral/ISO, where each connection has three wires. I will solder, then wire nut, then shrink wrap, seems like the best way to go.

[Colossal]

I am thinking of taking a page out of Dave's Bassman build and use wire nuts for the connections to the switch/ISO, Neutral/ISO, where each connection has three wires. I will solder, then wire nut, then shrink wrap, seems like the best way to go.

Hey Ange,

Good to see around. I laughed when I saw this thread. When you get on one of your arcane projects, you hunt it to the end. Your point-to-point rebuild looks great.

Here is the Bassman you mentioned:

wirenuts.png

[angelodp]

Hey Dave, good to hear from you old friend, yeah I am a bit like an old dog with bone and won't let go. This amp is an homage to a dear friend that just went to the other side. He left me this little amp and a 1958 U2 Silvertone guitar, black with silver edge work. Killer guitar. So I want to get this just right and safe. Have to say TAG is still a safe harbor even for those of us that are perennial beginners. Hope you are well and safe in these nutty times.

[Colossal]

Hey Dave, good to hear from you old friend, yeah I am a bit like an old dog with bone and won't let go. This amp is an homage to a dear friend that just went to the other side. He left me this little amp and a 1958 U2 Silvertone guitar, black with silver edge work. Killer guitar. So I want to get this just right and safe. Have to say TAG is still a safe harbor even for those of us that are perennial beginners. Hope you are well and safe in these nutty times.

Ah, that's a cool story. Always sad to lose a friend, but that's a nice way to honor his memory and gift. Yes, I am doing well, thank you, and I hope you are too. I have managed to avoid the virus thus far, but I did get verbally threatened this morning, so yep, everything seems completely normal