Silvertone Meteor 1430 Amp

[angelodp]

Looking at this Iso T

[angelodp]

sluckey, hi... you pulled down the schematic you so kindly put up?? Can I get you to put it back?

A

[sluckey]

sluckey, hi... you pulled down the schematic you so kindly put up?? Can I get you to put it back?

I pulled it to minimize confusion when you posted some pics of your actual amp, revealing that schematic was not accurate for your amp.

[angelodp]

Screen Shot 2021-12-19 at 6.51.11 PM.png

I understand. Looking more deeply I have discovered that the Wards Airline Model GDR-8511A - is exactly my amp, even though it's a Silvertone 1390 Meteor by name. Ok I think I can get going on this now. I reckon Danelectro made these for a number of differing name sakes.

[angelodp]

More info

[sluckey]

The resistor you labeled as 150Ω is really 160Ω.

[martin manning]

I have discovered that the Wards Airline Model GDR-8511A - is exactly my amp, even though it's a Silvertone 1390 Meteor by name.

It was common to see rebranding like that, particularly on department store amps. A curiosity is the use of a ceramic trimmer cap to AC ground the screen. It seems redundant, and an extravagant expense for a low-cost amp when a much cheaper ceramic cap would do.

It will probably need new electrolytic caps, and some of the others might be leaky, and check all the resistors for drift. Measure the filament voltages to see where they are on modern line voltage. If they are high, I'd put an additional dropping resistor between the line and the existing one to bring them down. The string should drop 50 + 35 + 12 = 97VAC at 150 mA. The schematic shows a 100Ω dropping resistor, so it was sized assuming 112 VAC. With a 120V line it needs to drop 23V, which would be 23/0.15 = 153Ω. I'd add a 50Ω at 2W or greater.

[sluckey]

I loaded the corrected schematic in my original post.

[angelodp]

Thanks much, will be looking at all those values.

[angelodp]

Well, finally got the missing power tube and put it on a limiter.... no shorts. Amp sound pretty cool as is. The Tubes seem to be getting a bit hot. I'll check the voltages and take it from there. The amp is remarkably quiet ()hum or buzz) and has a sweet tone, 50's 60's noodle amp. The amp belonged to a Hughes EE that worked on micro wave radar and has passed away. Joe always demurred at the widow maker title and thought he amp was fine the way it was. I think it is prudent to make this amp as safe as possible.

A

[angelodp]

Guys, my home, where I am playing this amp, is wired correctly. Would this method suffice, if playing at my home only, to be considered safe?

I found this on a site.

You can make the Widowmaker safer (but not completely safe), by installing a 3-conductor power cord with ground to chassis, and utilize the death cap and current return resistor of the original design. (You should absolutely replace the “Death Cap” with a Class Y Safety Capacitor. The Class Y cap is designed to fail open). Here is a Class Y capacitor:

This modification does two things: first, it fixes the polarity of the line cord, so the neutral is always incorporated into the chassis ground, and second, it keeps the functionality of the AC capacitor and current return resistor, in the event of a line-to-ground fault, limiting the current just as it was designed to do in the original circuit. If the Class Y capacitor should fail, it will fail open, keeping full AC off the chassis in the event of reversed polarity.

The only potential problem arises if the wall outlet itself is wired with reverse polarity, and this is more common than you might think, so it pays to always have an outlet polarity checker, especially when playing at a new venue with unknown power quality. A polarity checker is an invaluable $10 insurance policy.

[sluckey]

If you wired it like the schematic I posted, the amp is as safe as it can be.

[angelodp]

Ok, Steve, in your schematic you say ok to jumper the cap and resistor (death cap), is it equally ok to just leave the two components in place?

A

[sluckey]

Ok, Steve, in your schematic you say ok to jumper the cap and resistor (death cap), is it equally ok to just leave the two components in place?

JUMPER! JUMPER! JUMPER!

[martin manning]

If you wired it like the schematic I posted, the amp is as safe as it can be.

Note the schematic Steve posted includes an isolation transformer.

After some more thought, I believe that the ceramic trimmer cap is for hum reduction. It feeds a bit of the ripple voltage on the reservoir into the input tube's screen, which creates an inverted version of the ripple at the output tube's plate.