Ameritron AL82 stresses tubes

[W8JI]

Really, do we think anyone is still reading a two year old thread?

Weird!

[KX5JT]

Really, do we think anyone is still reading a two year old thread?

Weird!

I am now!

[VE7RF]

Really, do we think anyone is still reading a two year old thread?

Weird!

##  why didn't you just tell the fellow in question, the 1st time around that no, 250ma @ 3 kv is NOT normal idle current..and 1 or both zener's  are shorted.  750w= blast furnace.   You can always tell when the 5 v zener in a SB-220  has shorted.  The idle current [zsac]  goes from 180m up to 250 ma every time.  The fix?  Just fix it.

later... Jim  VE7RF

[VK4TUX]

Really, do we think anyone is still reading a two year old thread?

Weird!

##  why didn't you just tell the fellow in question, the 1st time around that no, 250ma @ 3 kv is NOT normal idle current..and 1 or both zener's  are shorted.  750w= blast furnace.   You can always tell when the 5 v zener in a SB-220  has shorted.  The idle current [zsac]  goes from 180m up to 250 ma every time.  The fix?  Just fix it.

later... Jim  VE7RF

Well its good to get some advice from somone who knows the circuit. I would stay with ptt actuated bias control for a cleaner signal in any case.  A W8 I think came up with that rf actuated design, but I dont see any advantage to it, as you have the tube amplifying during small segments on non-linear bias levels at the on and off edges of operation. During qsk you need bias on, all of the the ptt on period.


Adrian ... vk4tux

[KG6YV]

Interesting discussion on the need for 3-500Z's to show some "red".  I have an L4B that never shows any red with zero signal in SSB (~150ma total IP) and seldom shows any red when transmitting @1100-1200W PEP. 

Is there any sentiment in the group that I should consider "something" to drive these tubes a bit harder to insure some level of gettering?  I can't get any more drive from my TS-820S which is already putting out 120W to get 1100-120WPEP output from the stock L4B.  The tubes are 1year old Taylors from RF Parts.

Any suggestions?

Thanks

Greg

[WB2WIK]

Interesting discussion on the need for 3-500Z's to show some "red".  I have an L4B that never shows any red with zero signal in SSB (~150ma total IP) and seldom shows any red when transmitting @1100-1200W PEP. 

Is there any sentiment in the group that I should consider "something" to drive these tubes a bit harder to insure some level of gettering?  I can't get any more drive from my TS-820S which is already putting out 120W to get 1100-120WPEP output from the stock L4B.  The tubes are 1year old Taylors from RF Parts.

Any suggestions?

Thanks

Greg

They never show any red when transmitting?  That's unusual.  If you hold only brief transmissions on SSB, it would be understandable.  But if you hold a 5-minute SSB transmission, or even a 1 minute RTTY transmission (or AM, or anything producing a carrier) I'd expect the tubes to be showing "red."  Mine always have.

[K6AER]

Steve,

I will be ariving in LA on the 23rd of Feb. Got to drop off some cats in San Diego and then I will be staying in Woodland Hills until the following Monday. Lunch would be great. Any locals want to join us.

Mike