Carlos, First off, I'm confused as to how your electrical service can be 127v or 220V. Did you mean 254/127V, with neutral, or just one or the other? Help me out here, please.
Kevin's idea of a bucking transformer must be taken in the context of where he lives, e.g. Australia/New Zealand (can't tell which), where ordinary household distribution is 240V, without a neutral. Using only one bucking transformer in that system is OK; if the electrical system in Brazil is 254/127V with a neutral, you should use two identical transformers, one for each side of the 254V line, to avoid creating an imbalance. But if you have straight (measured) 220V electrical service, by all means run your L-4B off of 220V. You'll get better HV regulation. THe main thing to watch to keep your tubes happy is the filament voltage. Measure the filament voltage at the tube socket pins with the most accurate AC voltmeter you can find. Eimac specified the maximum 3-500Z filament voltage at 5.0 VAC. Less is OK, but if you have more than this, you need to do something to lower the filament voltage (like a low-value power resistor in series with the filament circuit) if you want your tubes to last a long time. I have this exact problem now with a Johnson Thunderbot amplifier, and I am still trying to decide what to do about it. Good luck. Be safe. Let us know how you make out. regards, Mahlon - K4OQ "Kevin B. G. Luxford" wrote: > > Carlos, > > Im would go for 220 Volts. > > Current is half, and you may find regulation is better. If your Drake > demand 240 volts and you supply 220 volts, you are running your > filaments / heaters 8.3% under rating. This may lengthen their lives. > On the other hand, if you need to build the boltage up a bit, I would > suffest you get a transformer with, say, a 12 volt secondary, connect > its primary to the supply and connect one lead of the Drake transformer > primary to the supply, the other lead of the Drake transformer to one > end of the 12 v transfdormer secondary, with the other lead of the 12 v > secondary going to the supply. Measure the voltage across the Drake > transfomer primary. If it is 220 v - 12 volts = 208 volts, then reverse > the leads on the 12 volt secondary. This is a boost circuit that I > have used sucessfully. You should end up with 232 volts across your > Drake transformer primary. > > One caution, the 12 volt transformer secondary has to be able to take > the current which flows in your Drake transformer primary > > If I am not making myself clear, then let me know and I will draw you a > circuit diagram and email it to you. > > 73 > Kevin > VK3DAP / ZL2DAP > > > "Carlos Augusto S. Pereira" wrote: > > > > Dear friends, > > > > I am thinking seriously about changing the voltage in my shack. Today > > I have 126V (measured) and I am afraid it can damage or shorten the > > tubes life in my Drakes (B and C lines). Besides, my amplifiers (SB220 > > with Peter Dahl Transformer and Ameritron AL80B) would work better > > with 220V. My main problem is that brazilian energy companines provide > > 127v or 220V and Drake equipments ask for 120 or 240v. > > > > What you guys think about that? > > > > 73 Carlos PY4RO > > > > Carlos Augusto S. Pereita PY4RO > > www.qsl.net/py4ro > > E-mail: [EMAIL PROTECTED] ---------------------------------------------------------------------- Submissions: [EMAIL PROTECTED] Subscribe: [EMAIL PROTECTED] - subscribe drakelist in body Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost: [EMAIL PROTECTED] - help in body of message Brought to you courtesy of TLCHost.net http://www.tlchost.net ----------------------------------------------------------------------
