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KB3TKQ
06-11-2010, 11:46 PM
I own an Ameritron AL-811h. Overall, the performance is very good, and I am happy with this unit.
The manufacturer explains that while transmitting, the plate voltage drops significantly, and that this is normal, and that rewiring the transformer for 220 volts input "Does not necessarily improve performance". So.....while looking around on various web sites, I found a few forums that claim rewiring the unit to accept 220 volts keeps the plate voltage average higer and DOES in fact improve performsnce. Has anyone tried running the 811h on 220 volts?

Bob/KB3TKQ

WB2WIK
06-11-2010, 11:52 PM
I own an Ameritron AL-811h. Overall, the performance is very good, and I am happy with this unit.
The manufacturer explains that while transmitting, the plate voltage drops significantly, and that this is normal, and that rewiring the transformer for 220 volts input "Does not necessarily improve performance". So.....while looking around on various web sites, I found a few forums that claim rewiring the unit to accept 220 volts keeps the plate voltage average higer and DOES in fact improve performsnce. Has anyone tried running the 811h on 220 volts?

Bob/KB3TKQ

Sure. I no longer have an 811H, but did for a while several years ago and my "main day to day amp" is the AL-80B, kind of a "big brother" to the 811H.

Whether the internal transformer performance is any different on 240V vs. 120V, doesn't really matter. The big difference that many operators will see in terms of HV stability is based on the line itself having less variation. If your shack is six feet from your electric service panel, it may not make any difference one way or the other. But in my case, my shack is more like 75 feet from the panel so the wiring is pretty long. The "household" outlets are all 15A circuits wired up with only 14AWG copper. A 75' run is really 150' of wire in the circuit, and it has a lot of voltage drop at 15A. My 240V wiring isn't any shorter, but it's 12AWG and the current demand is half as much, so the voltage drop in the wiring is much less.

The more stable the supply voltage is (from the outlet), the more stable the HV will be in the amplifier.

KB3TKQ
06-12-2010, 12:04 AM
My shack is approx 75 feet or so from the house. So, I am accessing power from a 60 amp 220 volt sub panel. So you are saying then that I should see an improvement if I run a 220 volt line specifically intended for my amp.....

WB2WIK
06-12-2010, 12:08 AM
My shack is approx 75 feet or so from the house. So, I am accessing power from a 60 amp 220 volt sub panel. So you are saying then that I should see an improvement if I run a 220 volt line specifically intended for my amp.....

Yes, of course. And I doubt if it's 220V, since all of the U.S. went to 240V decades ago, and in most places nominal voltage is closer to 245V (and the 120V line is about 122.5V).

When I first had the AL-811H, running it on a 14AWG circuit from the service panel 75' away its output power was about 670W CW maximum; changing to 240V and a 12AWG circuit improved that to about 820W CW maximum.

Whether anyone actually notices that change or not is another story! But it certainly did improve the HV power supply regulation.

K9STH
06-12-2010, 12:09 AM
Just by running the amplifier from the 240 volt line instead of the 120 volt line you will see just about half of the voltage drop to the primary of the transformer. This is because the current requirements when running from 240 volts is just about half of that when running from 120 volts. Since the resistance of the wires should be about the same, the "IR" drop (voltage loss) in the AC line will be half when running from 240 volts versus 120 volts.

Glen, K9STH

KB3TKQ
06-12-2010, 12:12 AM
I am finding the same results.......just under 700 watts CW. BUT...in reality, is the effort worth the payoff? It seems as though it may not be, and that I will just be working my 811 quads harder for gain that will not be noticeable.

KD0CAC
06-12-2010, 12:12 AM
I picked up a couple things , One is that is the inverse relationship of voltage & current , it this case voltage went up 120 to 240 , so current went down .
2nd is that now that power is going through larger conductors & more of them .
Both of those contribute to more stable power , less loss .

WB2WIK
06-12-2010, 12:14 AM
I am finding the same results.......just under 700 watts CW. BUT...in reality, is the effort worth the payoff? It seems as though it may not be, and that I will just be working my 811 quads harder for gain that will not be noticeable.

It's up to you. If you're having no problems now, why change anything?

I run separate 240V circuits to the ham shack, anyway, because a couple of my amplifiers are "big" and only run on 240V -- no 120V provision, because they would draw way too much current at 120V.

You'll notice it's very rare to find a "legal limit" (1500W output) amplifier that can even be operated at 120V. The reason is obvious: The current would exceed any sort of conventional wiring.

KB3TKQ
06-12-2010, 12:20 AM
I am wondering at this point if the extra 120 watts would make a difference on the other end of a qso or not. Maybe you are right....if it's working fine, leave it alone. At least this way I am staying well within the parameters of the design of the amp.

K9STH
06-12-2010, 12:22 AM
My "shack" wiring is probably "not conventional". I have at most a 4 foot run from the main breaker box to the start of the outlets. The wiring is 6 gauge to the 240 (actually more like 254 volts since my ambient line voltage runs pretty consistent at 127 VAC) outlets and then the 120 outlets "split" from the 240 outlets. Even when running virtually full legal power (my main linear only puts out a maximum of about 1400 watts instead of the full 1500 watts) there isn't much of a voltage drop!

Glen, K9STH

WB2WIK
06-12-2010, 12:26 AM
My "shack" wiring is probably "not conventional". I have at most a 4 foot run from the main breaker box to the start of the outlets. The wiring is 6 gauge to the 240 (actually more like 254 volts since my ambient line voltage runs pretty consistent at 127 VAC) outlets and then the 120 outlets "split" from the 240 outlets. Even when running virtually full legal power (my main linear only puts out a maximum of about 1400 watts instead of the full 1500 watts) there isn't much of a voltage drop!

Glen, K9STH

I'm envious! In one ham shack in a house about 7 houses ago for me (when I lived in Budd Lake, NJ -- 1978 to 1984) my hamshack was in the same room as the electric service panel. The service panel was inside the house, with the meter directly behind it on the outside. My "shack wiring" to my outlets was just a few feet. I could run 1500W amplifiers with 14-gauge wiring, no sweat!

Not here.:(

KB3TKQ
06-12-2010, 12:32 AM
Small world. I was raised in Panther Valley, Hackettstown. I know Budd lake well.

KB3TKQ
06-12-2010, 12:35 AM
I'm envious! In one ham shack in a house about 7 houses ago for me (when I lived in Budd Lake, NJ -- 1978 to 1984) my hamshack was in the same room as the electric service panel. The service panel was inside the house, with the meter directly behind it on the outside. My "shack wiring" to my outlets was just a few feet. I could run 1500W amplifiers with 14-gauge wiring, no sweat!

Not here.:(

Small world. I was raised in Panther Valley, Hackettstown. (1980 to 1991) I know Budd Lake well.

WB2WIK
06-12-2010, 12:42 AM
Small world. I was raised in Panther Valley, Hackettstown. (1980 to 1991) I know Budd Lake well.

If you know the area, I lived in the highest elevated house (at the time) in Morris County, on above the north shore of Budd Lake, about 120' higher than the top of Schooley Mountain. I could see the NYC skyline out the living room window, and the Delaware Water Gap out the bedroom window. It was quite a good ham radio location.

I had a 2 meter repeater operational from there for 7 years, including when you were in Panther Valley: WB2WIK/R on 146.805 MHz. It had coverage from Long Island to Hazelton, PA, down to Philadelphia, and up to Binghamton, NY.

KB3TKQ
06-12-2010, 01:34 AM
I know Schooley Mountain, but I am unaware of the specific residence ou are referring to. I know Budd Lake from Hackettstown, up rt 46, the old Mount Olive Inn, etc. I was not a ham radio operator at the time, But I can imagine from that area, coverage must have been amazing.

W8JI
06-12-2010, 01:45 AM
I own an Ameritron AL-811h. Overall, the performance is very good, and I am happy with this unit.
The manufacturer explains that while transmitting, the plate voltage drops significantly, and that this is normal, and that rewiring the transformer for 220 volts input "Does not necessarily improve performance". So.....while looking around on various web sites, I found a few forums that claim rewiring the unit to accept 220 volts keeps the plate voltage average higer and DOES in fact improve performsnce. Has anyone tried running the 811h on 220 volts?

Bob/KB3TKQ

I wrote the manual years ago but I don't recall saying the high voltage drops significantly and that is normal. I wonder if the manual changed??

The HV sag on normal power lines is about 14-15% maximum. That's typical for a capacitor input supply using an E-I lamination of good construction.

The AL811H is fused for 12 amperes on 120 volts, and normally draws about 10 amperes on peaks. With typical modern house wiring you might eliminate 100 volts or so of voltage sag under full load by changing to 240 volts, but IMO that is hardly worth it since tube dissipation is the real limit to power.

No matter what you do with power lines, you still only have about 250 watts of tube dissipation. It is still a small inexpensive amplifier with cheap tubes. It will never be a 3CX15,000A7 no matter how much voltage you apply or how big the outlet is. :-)

If you have really bad wiring or an exceptional 120V wire length and see the HV sag below 1400 volts or so, you might want to go to 240 volts. I don't think it would be necessary in nearly all cases.

WB2WIK
06-12-2010, 01:47 AM
I know Schooley Mountain, but I am unaware of the specific residence ou are referring to. I know Budd Lake from Hackettstown, up rt 46, the old Mount Olive Inn, etc. I was not a ham radio operator at the time, But I can imagine from that area, coverage must have been amazing.

Rt. 46 goes past the south end of Budd Lake and is about 1000 feet above sea level (much higher than Hackettstown!) there. But the north end of Budd Lake is much higher. My front door was at 1280 feet and the top of my tower at 1340 feet. There was nothing higher in any direction for several miles. Good for radio, terrible for weather.

I used to wear out my brakes going down the hill to Panther Valley, which was probably 700 feet lower than me.:p

NA0AA
06-12-2010, 03:00 AM
I guess my questions would be this: Is your 120 volt circuit dedicated to the amp or do you have other gear drawing on it at the same time? That will further reduce your voltage...this would be my shack, I basically have one circuit and it's shared, so if I want an amp, it's 240 volts since I HAVE to run a new circuit if I want an amp.

K3STX
06-12-2010, 10:10 PM
When I first had the AL-811H, running it on a 14AWG circuit from the service panel 75' away its output power was about 670W CW maximum; changing to 240V and a 12AWG circuit improved that to about 820W CW maximum.

Wow, that seems like alot for four 811A tubes. I thought the 3 tube AL811 would only put out about 600 watts. In fact, while they SAY it is a 600 watt CW amp, but from what I read the plates can not dissipate enough power to run it safely at 600 watts; 400 watts is about the limit. Each 811A tube can dissipate 65 watts, but at 600 watts output you are asking each 811A anode to dissipate 125 watts!! Keep the output to 400 watts, your dissipation is only 54 watts/tube). So I thought the four tube AL-811H would only be a 600 watt amp.

820 watts is getting out of the "small" amp world and into real power. I was thinking of an amp again (and I need 160 meters) and was thinking of the AL-811 again. But 820 watts for only $150 more, wow.

paul

K9STH
06-13-2010, 12:23 AM
The general consensus for a linear amplifier with 4 each 811A tubes is about 600 watts output, maybe around 650 watts on the 80 meter band and probably a bit less on the 10 meter band.

Yes, you can get more power out. But, in most cases you are grossly exceeding the plate dissipation of tubes which results in a reduced life of those tubes. Also, in the vast majority of cases the station on the other end is not going to be able to tell much difference between around 600 watts and 800 watts. As such, you can either be "proud" of getting more than around 600 watts output and replacing the tubes on a regular basis, or you can run them at a more conservative level and have the tubes last for decades.

It is like back in the 1930s and 1940s when some amateur radio operators ran 1000 volts (or more) on a single 6L6 tube. Just to hold down the heat to an excessive level some operators immersed the tube in oil, in water, etc. But, I have been told that most of those operators sent CW at a pretty good "clip". Why? Because a short "dah" turned the plate "red hot" and a long "dah" melted it!

Glen, K9STH

AG3Y
06-13-2010, 01:34 AM
The original question was operation on 110 vs 220 volts. If you are pushing the amp to its limits in either case, you are going to see "cleaner" output if you supply 220 to it. The drop in HV on peaks is contributing to the amplifier's non linear performance, a symptom known as "flat-topping", which can result in spurious products being generated. These spurs would be extra sidebands, somewhat like a square wave output as opposed to a sine wave one.

If you are going to push it till the voltage sags, run it on 220. There will be less voltage drop for any given RF output level you operate at. And more linearity is good !

W8JI
06-13-2010, 01:51 AM
Wow, that seems like alot for four 811A tubes. I thought the 3 tube AL811 would only put out about 600 watts. In fact, while they SAY it is a 600 watt CW amp, but from what I read the plates can not dissipate enough power to run it safely at 600 watts; 400 watts is about the limit. Each 811A tube can dissipate 65 watts, but at 600 watts output you are asking each 811A anode to dissipate 125 watts!! Keep the output to 400 watts, your dissipation is only 54 watts/tube). So I thought the four tube AL-811H would only be a 600 watt amp.

820 watts is getting out of the "small" amp world and into real power. I was thinking of an amp again (and I need 160 meters) and was thinking of the AL-811 again. But 820 watts for only $150 more, wow.

paul

The AL811H is rated at 600 watts output on CW, basically the same as the Collins 30L1 was rated.

In IVS (intermittent voice service) the AL811H is rated at 800 watts, primarily IMD limited. IMD was in the mid -30 dB range below PEP when the amp is heavily enough loaded at 800 watts PEP. It can easily handle that with unprocessed voice because average power would only be a few hundred watts.

The steady carrier power is only 400 watts and that is based on retuning the amp for maximum efficiency at 400 watts out, which is about 630 watts input. At that point the tubes are dissipating under 50 watts each. The plate efficiency is about 70%, and the tank circuit and other component losses bring that down to about 65% efficiency overall. The anodes are responsible for 190-watts of heat.

Anyone running 800 watts on steady carrier (or even 600 watts steady carrier), however, is a fool.

The AL 811 with three tubes is good for 75% of that power.

73 Tom

W8JI
06-13-2010, 02:20 AM
The original question was operation on 110 vs 220 volts. If you are pushing the amp to its limits in either case, you are going to see "cleaner" output if you supply 220 to it.


110 and 220 hurts my head. We haven't had 110 or 220 since the 30's. In 1940 we had 117/234, and by the 50's we were changing to 120/240. The 120/240 is typically run on the high side.


The drop in HV on peaks is contributing to the amplifier's non linear performance, a symptom known as "flat-topping", which can result in spurious products being generated. These spurs would be extra sidebands, somewhat like a square wave output as opposed to a sine wave one.

If you are going to push it till the voltage sags, run it on 220. There will be less voltage drop for any given RF output level you operate at. And more linearity is good !

Voltage fluctuation is being far overplayed here. The voltage drop from power mains is usually a small percentage of the overall drop. There are exceptions, but in most cases power line drop is insignificant at the power levels of this amp. Not only that, any harmful IMD would be caused by the mixing of lower and higher frequency components. The filter caps remove that issue and all that is left are syllabic variations.

I doubt anyone would see an additional 3 dB of IM degradation even with some pretty loose lines.

The only significant worries here are what the amp does to other things on the line, or if the breaker does not hold because of a sum of loads. This is around a 10-amp load on CW. On voice it averages much less.

73 Tom

W0UZR
06-13-2010, 03:35 AM
All of you running the 811H? Wow! This makes a good survey.

Anyway My 811H was wired for 120v and I didn't change anything. I get around 760 watts on a dead key down. But I'm on line where nothing else is being used on when I'm operating and I'm closer than 75 feet to the breaker box. I'm just shy of 500 watts on peaks when I'm running the net. My average power is around 250/300 watts. And people don't hear me any better when the needle is saying 600/700 watts anyway so I don't push anything.

My 922 Kenwood amp, I tried a comparison of 300 watts and 1200 watts with many people and they all said that they didn't notice any higher reading on the needle from me. Although the audio was louder. (Hmm, I can get the same thing by turning on my processor and keep it at 300 watts)

I see some voltage drop when I PUSHING it over 500+ but it doesn't drop much when I'm running 300w

WA7PRC
06-13-2010, 04:41 AM
My Heathkit SB-220 (about 1KW output) pulls close to 10A at 240V, on its own circuit. If I ran it on 120V, it'd suck up nearly all the capacity of a 120V/20A circuit. In order to run the other gear, I'd still need two circuits. That's the main reason I run mine on its own 240V circuit.

Echoing what others have said, the voltage drop in the AC mains wiring can be an issue if you're running it on 120V with a long run and/or smaller-gauge wiring. At 10A & 12ga wire over a 40' run (80' roundtrip), my estimated voltage drop is 1.27V. At 240V nominal, this is about 0.5%, which translates to about 16V at the plates of the 3-500Zs. I cheated and used a handy spreadsheet calculator (http://www.rst-engr.com/rst/jimsdata/wirecalc.xls). ;)

73,
Bryan WA7PRC

KM3F
06-13-2010, 05:00 AM
Hello Bob, got in on his thread late.
Another way to look at it I believe is the answer, is the voltage drop on the long length of your AC power facilty to your shack reguardless if it is 240 or 120 vac feed.
Wireing an amplifier for 240 results in 1/2 the amperage drawn through the AC line therfore 'less' voltage drop. It's just ohms law.
Now the total power drawn is still the same. 120 v times 15 amps is 1800 watts from the power line. 240v times 71/2 amps is still 1800 watts.
Less voltage drop generally means less drop in plate voltage to
the tubes when under full load.
The overall difference is efficiency of not losing power heating the ac line as much from the voltage drop and having it show up in plate power output where you want it.
To back it up, you will see that your manuel tells you to install smaller fuses in the amplifier when using the 240 input option. The option must be changed inside the amp first.
That means the amplifier will draw about 1/2 the AC current it would on the 120 vac option.
Less current means less voltage drop, so it is overall better to run off a 240 ac supply line.
Now if the overall AC supply is on wire size to small for the current and distance involved, then you would not gain as much from the 240 option because you would still experience more voltage drop than there should be.
Another thing, if your shack lights and radio lamps etc tend to flicker a noticeable amount when running the amplifier, you need to address the total AC issue in some manner.
Get on 6 and 2meters more often and don't try to wear out the HF bands.
They will be there for a long time. Hi Hi.
73 Ken.

W8JI
06-13-2010, 12:50 PM
All of you running the 811H? Wow! This makes a good survey.

My thoughts exactly. :-)

The AL811H only draws about 5 amps on short term peaks of average current on SSB even when pushed. On steady lockdown carrier when hammering it hard to the point of nearly melting the tubes, around 10 amps or so on 120 volts.

Comparing it to behavior of amplifiers with 4 times the tube dissipation capability isn't really applicable. Also improving the % of line regulation by four times isn't meaningful when the % of regulation is largely determined by amplifier internals, and they don't change a bit going from 120 to 240.

As I said before, if the power line is really lousy or on the edge of being overloaded, a different circuit would be advised (either 120 or 240). That would not be a common case, however. In addition, some components (like the power switch) will have significantly shorter life on 240.

That's why the owner's MANUAL does not push for 240 operation.

73 Tom

AG3Y
06-13-2010, 02:17 PM
110, 220, Tom, they are good round numbers ! 117, 234, now THOSE numbers make MY head hurt !

I think everybody knows what I mean, even if I don't quote exact figures. Besides, are those latter voltages actually STANDARD across the country? Maybe so, but I really don't know.

Besides, 110 and 220 were the words the OP used.

Just the "mindless babbling" of an OF ! :eek: :rolleyes: 73, Jim

K9STH
06-13-2010, 03:35 PM
Actually, most of the major electric companies are now using 125 volts +/- 2 volts as their "target" voltage. In fact, during the summer months when the electricity demand is the highest (due to air conditioning), they generally go for the 127 volt level.

In this area, TXU (operating as ONCOR) usually runs at the 127 volt level most of the year. When I was with TXU I was also a member of the "speakers bureau" which supplied speakers to all sorts of groups on all sorts of topics. But, no matter what the topic of the speech, there would be a question from the audience about why their light bulbs didn't last very long. The answer is that the vast majority of bulbs purchased at Walmart, at home improvement centers, etc., are rated for 120 volts maximum. There are bulbs available for 130 volt operation and using that type of bulb extends the life of the bulb by a very large factor. However, most stores do not "push" that type of bulb because their sales of bulbs drops dramatically. You have to either ask for the 130 volt bulbs or go to a store, like a lighting center or an electrical supply, which routinely have the 130 volt bulbs.

Glen, K9STH

W8JI
06-13-2010, 11:27 PM
Why not turn it up to 150/300 volts and be done with it?

K9STH
06-14-2010, 12:03 AM
Too many "older" items still around. The voltage has been "inching up" for decades. First 110 VAC, then 115 VAC, then 117 VAC, then 120 VAC, now 125 VAC, with 127 VAC being common during the warmer months. As new consumer devices are being manufactured the "target" design voltage is increasing. If you look at the labels things say 120 VAC and some are even now saying 130 VAC.

A lot of the radios made during the 1930s and into the 1940s actually were designed to work from voltages as low as 100 VAC and as high as 140 VAC. That was back when persons living fairly near the generating station could have voltages at least as high as 140 VAC and those out in the "boondocks" were lucky to have 100 VAC.

Although the "indicated" voltage on the Collins equipment was 115 VAC, the equipment was actually designed to work from about 105 VAC to at least 130 VAC. This was because a lot of the equipment was used by the military and the generators used by the military could vary all over the place. National also was pretty conservative in their specifications. Hallicrafters, where their receivers were concerned, equipment could also handle a a pretty good voltage variation. But, where their transmitters were concerned, Hallicrafters tended to run them on the "ragged edge" and even with only 115 VAC input transformers in the HT-32 and Ht-37 series fail on a regular basis. Although I don't usually recommend replacing the tube rectifiers in most "boat anchor" equipment, I definitely recommend not only replacing the tube rectifiers in those particular units but also completely disconnecting the 5.0 VAC rectifier filament windings completely. Doing this gives enough "slack" that the power transformers in the units do not "self destruct".

It is the same with the Collins 32V- series transmitters. Getting the filament load of the rectifiers off the power transformer as well as getting the rectified B+ (which goes through the filament windings) off the transformer greatly improves the chances of not having a power transformer failure.

Glen, K9STH

W8JI
06-15-2010, 02:44 AM
variation. But, where their transmitters were concerned, Hallicrafters tended to run them on the "ragged edge" and even with only 115 VAC input transformers in the HT-32 and Ht-37 series fail on a regular basis. Although I don't usually recommend replacing the tube rectifiers in most "boat anchor" equipment, I definitely recommend not only replacing the tube rectifiers in those particular units but also completely disconnecting the 5.0 VAC rectifier filament windings completely. Doing this gives enough "slack" that the power transformers in the units do not "self destruct".

It is the same with the Collins 32V- series transmitters. Getting the filament load of the rectifiers off the power transformer as well as getting the rectified B+ (which goes through the filament windings) off the transformer greatly improves the chances of not having a power transformer failure.

Glen, K9STH

When we replace a high vacuum tube rectifier in a capacitor input supply with a semiconductor diode transformer heating goes up, even despite removing the filament load.

http://www.w8ji.com/power_transformer_stress.htm

I'll add a little to that showing the change from a vacuum tube to a semiconductor rectifier.

73 Tom

AG3Y
06-15-2010, 05:10 AM
Tom, I didn't read your page ( shame on me ) but wouldn't replacing the tube rectifier with SS diodes also raise the B+ voltage, possibly to a higher level than the tubes are meant to handle? I have heard that if you intend to replace tubes with semiconductors, that you should install a rather high value/high wattage resistor following the diodes to compensate for the increased conductance of the solid state units.

Wouldn't this help the transformer, as well as the rest of the radio, a bit ?

Thanks for all your expert advice. It is always appreciated. 73, Jim

K9STH
06-15-2010, 03:32 PM
Replacing the tube type rectifiers does increase the voltage. In some units this can definitely be in excess of the voltage ratings of other components.

The failure in the case of the Hallicrafters HT-32 series and HT-37, and in the Collins 32V- series, is usually caused by a failure of the insulation on the 5.0 VAC filament windings. There are 2 such windings in each of these transmitters. Whether or not this failure is directly caused by the heat generated by the current drawn by the rectifier filaments, by the fact that the rectified B+ is present on these windings, or by a combination of these 2 factors, the result is still the same. The power transformer WILL fail unless the filament windings for the tube type rectifiers are completely removed from use.

The WRL Globe Champion 300 series and the WRL Globe Champion 350 series have a similar problem. Also, the Johnson Valiant series have similar failures but, fortunately, not to the same degree as the other transmitters. In both the WRL and Johnson transmitters the filament winding for the 866 rectifiers are included on the main power transformer. The insulation on the rectifier filament windings will eventually fail which, in turn, "takes out" the power transformer. Disconnecting the rectifier filament winding and changing the tube rectifiers to solid-state extends the power transformer life considerably.

Glen, K9STH

KC9PRE
06-15-2010, 04:16 PM
I just converted my 811-H to 240 dedicated line.I had too as the 120 line was not dedicated to the amp. Only thing I noticed and maybe this is my mind playing tricks on me,was it seemed to take less power from my Icom to drive the amp.It is easy to do if you want to do it.

AG3Y
06-15-2010, 04:57 PM
It would be interesting to see what the HV was on the 240 volt line as compared to what it was on the 120 volt line. I would think that if it were higher, the tube probably would display more "gain" and be able to achieve a certain amount of power out with less drive. How much less is the question, but you are probably seeing a real result.

KC9PRE
06-15-2010, 07:59 PM
Thanks for the answer.

WB2WIK
06-16-2010, 12:26 AM
I just converted my 811-H to 240 dedicated line.I had too as the 120 line was not dedicated to the amp. Only thing I noticed and maybe this is my mind playing tricks on me,was it seemed to take less power from my Icom to drive the amp.It is easy to do if you want to do it.

If your 120V line was dedicated and 12 AWG with reasonably short wiring, there'd probably be no difference at all. But many are using "original house wiring," which is typically 14 AWG and could be 100 feet long, and a non-dedicated branch, in which case there could be substantial line voltage sag when you add a 10A+ load to it.

Yes, I agree you're probably now seeing higher voltage under load, which would provide more tube gain.

Collins ran 811As at excessive voltage in the 30L1, evidently (as I've heard) condoned by RCA, who manufactured their tubes at the time. I wouldn't try that with the Chinese tubes today!

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