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What size 220 service for SB-220

Two reasons.

1. For some reason, many people are obsessed with getting the last possible watt out of an amplifier. The manufacturer specified a lower figure to provide a few dB of headroom - so you could have a good, clean signal without straining the components into distortion. (Those who squeeze their amplifiers are generally the ones who obsess over "SWRS".)

2. The type of tube or the quantity of them doesn't account for the amount of power an amplifier will produce. That's all up to the power supply.

With the rumored demise of Peter Dahl transformers, it may very soon be difficult to find replacements for the power supplies that some folks insist on trying to melt down.
 
Just for 'grins'...

The rumor of the P.Dahl company closing their doors isn't a rumor. Pete is closing because of health reasons.
I sort of think that there may be a fairly large stock of some things, probably not so many of others. I also think that stock will be disposed of, along with the equipment to make them and the building etc. It wouldn't surprise me at all if the name of the company changed and those transformers will still be made/sold. Might even keep "Dahl" as a product label, since it's sold a gob of transformers all by it's self. If the new owner keep quality the same as Dahl did, I only wish I could invest in it! I'd never have to worry about eating 'newspaper' soup again. Oh well...
- 'Doc
 
I have to agree with beetle on this. There are two power levels that an amp will produce. What you CAN get out of it and what you SHOULD get out of it. I realize that in the CB world equipment life and spectral purity are not given two hoots and a holler and some may get lucky with the limits they push their amps too.A lot of guys laugh at the manufacturers ratings and strive to get that last 1/2 dB out of their amp just to be able to say that they can. :roll: One day their luck will run out. Maybe not tomorrow or next month but someday. There is a reason those SB-220's were rated as they were. The power supply is the weak point in them.A voltage doubler circuit is cheap and easy to make and does the job for what is expected from it but exceeding that by a large percentage is never a good idea. With a beefier power supply the tubes themselves can provide more power output than the ratings would suggest but then again what is another 1 or 2 dB going to really show?When one considers a piece of gear that is meant for 100% continous duty it is a real eye opener when looking at the power supply. The plate transformer alone in my 1 Kw plate modulated AM transmitter weighs more than any complete amp ever made by Ameritron and most if not all Henry's except for maybe the 5K Classic.Even the QRO Technologies HF-2500DX only weighs in at 110 pounds which is about what my transformer weighs. Why so heavy? Because it was designed to be run virtually forever and to be able to have some working headroom and be super clean while doing so.As Doc said,it looks like Peter Dahl as we know it is going out of business.Best look after that heavy iron.It may soon be in short supply.
 
QRN said:
There is a reason those SB-220's were rated as they were. With a beefier power supply the tubes themselves can provide more power output than the ratings would suggest but then again what is another 1 or 2 dB going to really show?
Click to expand...

Then it’s true. I saw in another site that the power supply in the SB-220 is only a little bit bigger than the one in the SB-200. Also I saw this (about the SB-200): :p

"is a small amp with a power supply and cooling system that keeps things operating in an OK state"

"Some would claim that the tubes are too small for the power supply, so you CAN cook a tube."

"possibly the most reliable amplifier with a good power supply"

Hummmm... there are many reasons for which i prefer / love my SB-200. :)
 
QRN said:
I realize that in the CB world equipment life and spectral purity are not given two hoots and a holler and some may get lucky with the limits they push their amps too.
Click to expand...

I'm a member of the CB world and I'm very concerned about the life span of my radio equipment and I never push any of my radio equipment to their maximum limit.
 
Yeah 194, that was kind of a general statement based on some of the figures and attitudes floating around out there. It is by no means an effort to paint everyone with the same brush. I know some hams that do the same thing.Nowhere as many mind you but some.
 
Actually, my friend Richard wrote this......

http://www.somis.org/SB220ci.html

freecell said:
Before the arrival of the SB-220, there was a popular notion that a legal-limit SSB amplifier needed a heavy-duty power-supply that required two grown men to move it about. Heath engineers knew that this idea was based more on amateur radio folklore than on sound electrical engineering principles. They also knew that the average duty-cycle of a human voice was only about 15% when no carrier was present, as is the case for SSB operation. So, why build a 100% duty-cycle, AM, "lock-to-talk" power supply when one was not required? Thus, they designed a power-supply that would competently do the job that was needed. This resulted in a considerable size, weight and cost savings, which they happily passed along to the buyers of their product. At first, some people in the ham community had negative comments about the SB-220's "wimpy" power supply. With the passage of on-the-air time, it became apparent that the power supply would do the job, and do so with a low failure-rate and with no detectable on-the-air ripple. This was no accident. Heath engineers had wisely specified a HV-transformer design that had an exceptionally low secondary-resistance of only 12.2-ohms. This minimized the voltage drop under full load in the capacitor-filter fullwave-voltage-doubler rectifier circuit. Such circuits have an extremely high peak-current to average output-current ratio. So, minimizing the transformer winding resistance is essential for good voltage regulation and to minimize the I2R heat loss in the transformer's windings.

Many hams initially labeled as "inferior" the capacitor-filter fullwave-voltage-doubler rectifier circuit. They did not realize that this circuit has some advantages over the traditional, fullwave-bridge rectifier circuit. These advantages are:

1. Low ripple-voltage. This is due to the fact that, as one capacitor bank is charging, the other capacitor bank is simultaneously discharging, thus, cancelling each other's 180º out-of-phase, sawtooth waveforms.

2. It allows the transformer to have only half as many secondary turns which yields a more efficient transformer design. Here's why: Since a layer of insulating-paper is required between each layer of wires, fewer turns means fewer layers of paper. This allows the transformer to use less paper and more copper. The net result is a transformer that has a high ratio of copper to paper. This makes for a very capable transformer.

3. Excellent voltage-regulation during current-transients, due to the fact that no swinging-inductance filter is used. This is exactly what's needed for CW and SSB modes of operation.
Click to expand...
 
Hulkster,
Your conclusions (powerful/durable) may be correct, but not because of the filament circuits alone. The rest of the circuits making up those two thingys, and 'how' they are run have lots more to do with that.
I tend to take the tube manufacturer's word about what a 'good' filament voltage should be. A 0.3 voltage increase doesn't sound like much, but if it means doubling, or halving, the life of the tube, I think it's a sort of an 'odd' way to try to get more power from the tube. Especially since that 'more power' doesn't amount to anything significant, except to your wallet, in the long run.
That doesn't mean to say that there isn't a difference in output between the two amplifiers (SB-220/Henry), there certainly can be. That difference is also sort of indicated by the weight of the two being compared. The difference in weight is typically in the power supply. And like it or not, the power supply is one of those 'bigger is better' thingys, to some ridiculous point. If it costs more for concrete than the amplifier to build the foundation to sit the thing on, thats ridiculous!
It's also certainly possible that I misunderstood your post. If so, then all the above is sort of ridiculous too. Oh well, no coffee yet, that's my excuse...
- 'Doc
 
Take it easy, you are correct.
There are a lot of things (voltage, power supply size, input drive,:shock: etc) to make a few more watts. But, like Beetle say: "For some reason, many people are obsessed with getting the last possible watt out of an amplifier" Certain words.
Those few more watts only affect the life of the amplifier in general, those few more watts doesn´t represent any change in the signal strength, so i don´t understand what´s the "deal" with this. I´m a tube amplifier guy, precisely a few weeks ago i put a new pair of tubes in my Heathkit, and I respect all the parameters of factory: input power, grid and plate current (that´s two things are very important for me) That´s the way i like to operate an amplifier (and it runs more cooler and happier). :p
 
Hulkster said:
Then, why manufactures like Heathkit, Drake or Swan rated its linears with two 3-500Z for 2000 w PEP INPUT, if they can generate more power output? Why a Ameritron, like the AL-80B, with single 3-500Z is rated for 1000 w PEP OUTPUT from factory?
Click to expand...
Back when the Heathkit, Drake, and Swan amps were being manufactured, the FCC rules listed INPUT ratings. Those rules were changed in the late 70s and the current production amplifiers are using the OUTPUT rating from the FCC.

The INPUT rating (power used by the amplifier) is different than the OUTPUT (power output to the load) are two very different things!
 
Master Chief said:
Hulkster said:
Then, why manufactures like Heathkit, Drake or Swan rated its linears with two 3-500Z for 2000 w PEP INPUT, if they can generate more power output? Why a Ameritron, like the AL-80B, with single 3-500Z is rated for 1000 w PEP OUTPUT from factory?
Click to expand...
Back when the Heathkit, Drake, and Swan amps were being manufactured, the FCC rules listed INPUT ratings. Those rules were changed in the late 70s and the current production amplifiers are using the OUTPUT rating from the FCC.

The INPUT rating (power used by the amplifier) is different than the OUTPUT (power output to the load) are two very different things!
Click to expand...

Also don't forget that while the tubes may be capable of more power output they first need a power supply that can deliver more power input. The transformer in the Ameritron is larger and capable of providing more current than the Heath while maintaining a higher average voltage to the tubes.A voltage doubler circuit is OK to a point but it just cannot maintain good dynamic range unless VERY high values of capacitors are used. The full wave bridge type power supplies can provide a better plate voltage regulation especially the old choke input supplies with decent filter caps.
 
it's a sooner or later kind of risk. You can drive without a seat belt for years and one day get caught. One day your amp might fry a power supply.
 

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