<I understand the differences in class and imd. However. 13 volts won't cut the tube off to 100 ma. I have <the amp here with the triode board all the way up at 225 ma.? Turn it down and its 300 ma.? -100 <suggests the class c bias point. At 39, what the bias board is maxed is 225.? Would 50 or 60 volts not <be required?
##? I just looked at the constant current charts for the? 3-10000Z? in GG.? ? At? 4 kv..and ZERO bias, it should be aprx? 280 ma.? ? ?At? 5 kv, and zero bias, its then? ?350 ma.?
##? at 4? kv,? ?to get the idle down to 100ma, requires? ?aprx? 12.5 Vdc of bias.?
##? At? 5 kv,? to get? 100 ma of idle requires? ?13.-? 13.5 vdc.?
##? are u sure you have your metering done correctly?? ?You could also TEMP insert a fluke dvm in series with the B-? ?to verify? idle current.? ?Beware, a fluke or analog ammeter inserted into the B-? from the? ?HV supply will? indicate? cathode? current? =? sum of plate + grid current.? ?That's a mott point if just wanting to measure idle current, since tube is not being driven.? ?You have something amiss? some where.? ?Is? your? B+? ?HV metering fairly accurate ??
##? I would not mess with any? EBS circuit.? ?They typ are quick enough between words? but not between? syllables.? ?Then u get the switching transients? over the air.? ?If u want to lower? idle power, reduce the idle current down to 100 ma..which is ample for that tube.? Vox? SSB? +? 100 ma of? idle current? is the ticket.?
##? 20 x 1N5408's? in series will easily provide for? ?14.2? vdc? of bias, +? handle loads of current.? Come? glitch time, they will? handle? a? 200A? surge.? ?Bias gets tweaked? by jumpering some diodes.? ?Then it's all dead simple.? ? 20? x? 6A10's? also works? good.?
##? IF? you want to operate? CW,? ?you can reduce the idle current a bunch more, but? not down to zero ma..... other wise you will get? key clix? on? a GG? triode.? ? You can easily drop it down to 25 ma? for CW use if you wanted..... but you require a tiny bit more drive to overcome the added bias V required.? ?20 vdc of? bias? would/ should result in 25 ma of idle current with 4 kv.? ?20vdc? /? .71 =? ? ?28 x diodes.? ?To? switch between? ?CW? and? SSB,? use a spst toggle to shunt out the last? 8 x diodes.?
##? Buddy used that same bias board? you have.....? in fact two of em, on the? 2 x GS35B? ?6m? GG amp you see on the home page of this site.? ? ?One per tube..so each tube? could have it's respective? idle current adjusted individually.? ?The plate current meter? could be switched from? tube #1..to? both tubes, to? tube? #2.? ? That bias board has been used in a LOT of amps? with? zero issues.?
##? The? BTI amp never used a chimney, but the cooling tower? scheme.? ?If you pour through the dayton? catalog,? you will probably find the blower you want, but it's a tedious process.? ?They? initially rate em all at XXX? cfm? @? zero back pressure.? ?Then you have to bring each one up that's close to what you want, then? download their? ?graph, which depicts? ?CFM? vs? back pressure.? ?25? cfm? @ .43"? is not that big an issue.? They have several blowers that will provide those specs.?
Jim? ?VE7RF
