house voltage

[M Fowler]

I only check my wall voltages when I take amp voltage readings and it has been 117 to 118 each time.

Mark

[Ken Moon]

At my house in Jacksonville, the range is between 121 and 124 volts.

It seems that very few people have 115V coming out of the wall in the states anymore (Mark seems closest at 117-118).

I've gone to using PTs spec'd for 120V (Hammond 300 series), I always put 0.1R/5W resistors in series on both heater legs, and I even buy PTs with lower-than-normal secondary windings to get the proper voltage readings on cloned vintage amps.

For instance, a 290-0-290 can be replaced with a 275-0-275, and the voltage readings will match the original specs pretty closely.

But really, what a PITA - the main worry I have is that I get a heater voltage of about 7 volts at my house with no dropping resistors, and that''s already 10% high - if someone is running even higher, you'd be looking at up to 7.5 volts on the heaters. I don't know if this will cause problems but I don't want to take the chance...

[Andy Le Blanc]

if you have 1000r load...

120v will be .12a, or 14.4w.... 345.6wh

128v will be .128a. or 16.38w.... 393.12wh

the stronger the state mandate for conservation the higher the
power rate per KWH and the higher your wall voltage will be.
The share holders of the power company must make a consistent margin.

The corporation that owns the subdivision that controls the American branch
in Florida that manages the power distribution franchise where I live...
Is somewhere in Spain...

Most of the old gear was rigged for 110 -117 ac, new iron has to conform
to current, current standards. A couple dropping resistors, or an adjustable
fil. voltage should fix the heater issues, but a higher voltage means you'll
run through more tubes, which means greater consumption and market demand
for vaccum tubes, which will help reduce the cost of tubes for everyone in the long run.

Not so bad really.... Today my wall ac is 124, it gets worse.

[rp]

I've gone to using PTs spec'd for 120V (Hammond 300 series), I always put 0.1R/5W resistors in series on both heater legs, and I even buy PTs with lower-than-normal secondary windings to get the proper voltage readings on cloned vintage amps..

Ken, I only build with euro taps now for when/if I move to Italy, so those 300 Hammonds are in my future. I've ran away from the 200 series since they are wound for 115V and have always f'd up my amps. I guess from enough complaints Hammond added a 120V tap - great, so now your choice with that series is correct filaments and under-voltage on the HV secs, or correct HV secs and over-voltage on the filament! I hate kluging my nice new builds with resistors on the filaments! So screw Hammond. Why not just wind transformers that work correctly for the USA in 2010? Arggg! I'm ranting again!

Anyway - are those 300 series giving you proper voltages for 120V? Filaments in proper range and HT as spec'd when plugged into an outlet in modern day America?

... if someone is running even higher, you'd be looking at up to 7.5 volts on the heaters. I don't know if this will cause problems but I don't want to take the chance...

I posted a rant and questions about high filament voltage on AX84 after I built a P1 w/ the spec'd hammond and had 7.1 on the filamnts. I got a lot of very informed replies and a long white paper from the 1950s detailing tube life with respect to filament V - it matters a lot, and 7V and over is really bad. Funny, at AX84 everyone was, "big deal, just use resistors" but to me that's more space, more parts, more heat, more stuff to fail and not a proper solution. Solution is get the right PT and that Hammond wasn't it.

[Ken Moon]

I hear ya!

[IMG870]http://i514.photobucket.com/albums/t346 ... ndmill.gif[/img]

The 300-series Hammonds do bring the voltages pretty much in line, even though they're still a tad high at my house, and they don't run nearly as hot as the equivalent 200-series, so I like them a lot, even though they have a bunch of extra primary leads I have to tape off, and they can get expensive.

I still use the series 0.1R resistors just in case - I've never seen a problem with them causing too low heater voltages - I guess I've just gotten used to making room for them, like I have for limiting resistors before a tube rectifier.

I just don't build in enough volume to justify spending a bunch on a run of custom PTs- I wish I had a good solution

[rp]

I just don't build in enough volume to justify spending a bunch on a run of custom PTs- I wish I had a good solution

Heyboer. I go custom with just about everything now. They only tag on about $25 over the retail price you see at Mojo, Weber etc. for a one off. That's incredibly fair and I'm amazed they do one offs, totally worth it to avoid surprises.

Great pict.

[TheGimp]

I hear ya!
...snip...


I just don't build in enough volume to justify spending a bunch on a run of custom PTs- I wish I had a good solution

Contact EDCOR, for a $40 setup charge they will make what you want.

Friendly folks, good prices, and great quality.

I stick 2.5R NTC thermistors in series with each leg of my heater supply to the tubes.

[Cliff Schecht]

BAH! I finished up my somewhat snazzy looking bucking transformer box complete with line filter, fuse and old rusty Stancor 12.6V CT transformer. I wired up the transformer with the two outer legs connected together and the CT going to the other side (obviously flawed thinking, see below). Plugged it into the function generator and got the winding polarity right on the first try (YES!). Ok cool. I plugged the box into the wall and plugged in the amp, flipped the standby switch and measured a slowly rising 120V, and much better heater voltages (5.4V, 6.7V IIRC). Then I start hearing a slow fizzling coming from my feet (where the new bucking box is). I quickly flip off the amp and rip out all of the cords. I now see that wiring the two secondaries together on the bucking unit was a mistake and have a most likely ruined filament transformer to prove it. It definitely dripped everywhere..

I may go to an 8V transformer if I can find one, that would be ideal for actually hitting the target 117V.

[Cliff Schecht]

My second attempt at the bucking box worked better than my first it seems. I used a bigger transformer and didn't hook up both sides of the 6V winding this time. Knocks the wall voltage down to about 120V and I finally was able to fire up my Rocket build. For some reason this amp was making me nervous, I guess the building process went too smoothly. But after all of the fuss about getting the voltages in spec, I flipped the amp on and it sounded awesome. The PPIMV I rigged up worked like a charm and everything was idling where I was expecting it to. I'm super excited to break this amp in during Christmas. I only heard it with "test" tubes but once I get a proper set of 84's and throw in some known good preamp tubes, it'll be a nice sounding amp for sure. I'll post some pics and soundclips in a thread when it's all buttoned up.

[Dr-Joned]

You could incorporate this with every build.

http://www.tripplite.com/en/products/mo ... delID=2010

[M Fowler]

Wall voltage tonight is 119.8, I had to check since I was so low compared to rest of you.

Mark

[rdjones]

Wall voltage tonight is 119.8, I had to check since I was so low compared to rest of you.

Mark

Still, you should consider yourself very fortunate.

Voltage here in Nashville consistently runs quite high,
usually 127- 130. (128.8 right now)
That's at several locations over the past 20 years.

I will say that it doesn't vary over a wide range, it's just that it's always high.

rd

[rdjones]

What do you guys usually do? I'm tired of tacking in resistors on the heaters to keep those voltages right while the B+ runs too high and alters the amps sound. A resistor in the primary is a no no and variacs aren't safe to have around drunken bandmates.. I'm thinking a permanent bucking transformer in a breakout box would be the safest solution.

My concern is to protect the screen voltages and just let the plates run a bit high.
Adding or increasing values of screen limiting resistors, or tapping the screen supply further down the B+ string is my approach.

rd

[rdjones]

I posted a rant and questions about high filament voltage on AX84 after I built a P1 w/ the spec'd hammond and had 7.1 on the filamnts. I got a lot of very informed replies and a long white paper from the 1950s detailing tube life with respect to filament V - it matters a lot, and 7V and over is really bad. Funny, at AX84 everyone was, "big deal, just use resistors" but to me that's more space, more parts, more heat, more stuff to fail and not a proper solution. Solution is get the right PT and that Hammond wasn't it.

I was under the impression (apparently wrong) that low filament voltage is harder on tubes than a high filament voltage.
This may be worth looking into more in depth.

rd

[dobbhill]

My house voltage hovers around 124vac +/- 3vac. It puts my filaments at 7vac on some of my vintage amps. ?Dangerous??
D