Like many homebrewers, I've always built a timer into my amps that powers the blower for a couple of minutes after killing power to the amplifier. Today, however, in a conversation with another build
Hi Jim, I have always used a manual "timer" (me) to turn the blower off a couple of minutes after killing hv and filament. My homebrew amps have three power switches; air/water on, filament/heater on
Graphite plate tubes retain heat a long time and the glass temperature does rise. Carl KM1H _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesti
<snip> I must admit, I tend to agree with your reasoning. Dave, G8WRB _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinf
My amp, which is an Emtron DX-2sp which uses an external anode tube (Chinese equivalent to a 4CX1500B) ramps up the filament and HV using a Triac. On shutdown the instructions are to let the tube idl
Some tubes, such as TH327/347, caution in the data sheet to not run the filament without air flow. In their case, the filament power is about 200 watts. If 200 watts is bad for a tube then it seems l
The anode might not get hotter when the blower is turned off, but the other parts of the tube will, as heat from the anode is conducted into them and they no longer have the cooling effect of the air
There is a bit of thermal inertia for the plate, and probably lesser amounts for the grid and screen if it has one, but the critical points are the seals. The cathode is the hottest part of the tube
Like many homebrewers, I've always built a timer into my amps that powers the blower for a couple of minutes after killing power to the amplifier. Today, however, in a conversation with another build
If the filament transformer is sized properly it should provide sufficient inrush protection at ham tube power levels. The 3-500Z certainly isnt known for open filaments nor are any of its tetrode co
Does running the blower after shut down apply to a tube like the 4CX1500A [5V @ 42A]? I don't see any thing about that in the Eimac spec sheet. I've wondered about that for the amp I am building. I h
Hi Carl, I have read/heard that about filament transformers before. I am not sure where that idea started but have some doubts about the validity in all cases. The cold resistance of a filament is cl
Another caution, this time about constant voltage transformers. I had one of these and tried to use it to stabilise the mains to a signal generator to improve drift. It sort of worked but the main pr
The stock Kenwood TL-922 which is 2X 3-500Z ran the fan for about 3 mins after shutdown. Mine is heavily modded including a step-start to protect the tubes even more Tom - AB3FL _____________________
I never saw that happen with a constant voltage transformer (transducer). Are you sure yours is based on transformer/choke and not an inverter? However, how do you measure AC with a moving coil meter
Gerald, that has been around for many decades. The SB-220 is a prime example of a current limited filament transformer. Henry, Johnson, Ameritron, Amp Supply, Drake, and others using the same 5V/15A
Gents: I asked a former co-worker (WA5LFY) how our "big" rigs were shut down; he was still working on them after I left the company. Here is his reply: I think that response would be of interest to t
Another caution, this time about constant voltage transformers. I had one of these and tried to use it to stabilize the mains to a signal generator to improve drift. It sort of worked but the main pr
100% convinced that ramping down the fil V is less stressful on big fil's. It would certainly reduce thermal stress and shock. Emtron does the ramp up sequence...dunno if they do the ramp down part o
As I recall, both Collins and Continental included an SCR-based ramped filament regulator in the majority of their high-power designs. During my college years, I worked at a station that used this d