|
1-2 hrs max...per tube. ? Alright. Then I'll do the second 3-500Z valve. Then I'll do the full voltage tests with the Drake's HT transformer -- F1AMM Fran?ois De la part de Jim VE7RF via groups.io
贰苍惫辞测é?: mercredi 26 février 2025 11:34
|
1-2 hrs max...per tube.
?
?
|
Hello ? Cooking the tubes. ? It was necessary to modify the tube polarization system. As shown previously, the HT power supply is floating relative to ground. This trick allows the cathode voltage (the filaments) to be modified relative to ground and as the grids are galvanically connected to ground, it allows the grid - cathode voltage to be adjusted. This is what happens in reception where the tubes are blocked with a grid - cathode voltage of -60V. ? To be able to positively polarize the grid relative to the cathode, in operational operation, the original diagram does not allow it. This diagram must therefore be modified. The positive polarization voltage of the grid can only come from an external source; it is shown as a green battery on the diagram ? 
? Obviously this involves some work including drilling the back panel to get the two wires out of the green source. I put in two female banana plugs and a bridge to place a short circuit in place of the auxiliary power supply to find the original diagram (0 V polarization). ? I remind you of the objective: to cook the anodes to red under a low anode voltage and a high current. All this to degas the tubes. It will certainly also be useful to improve the linearity by increasing the quiescent current which is possible since in France we are limited to 500 W HF (against the almost 2 kW that the PA can output). ? The first tests are done with a 230/230 transformer which unfortunately only makes 400 VA (it must not exceed 1.7 A on the secondary). The polarization is done from a 48 V transformer and a Graetz bridge rectifier. ? ·???????? With a polarization at 0 the plate voltage is at 688 volts and the quiescent current (since there is no HF in excitation) is 30 mA ·???????? With a polarization at 18 V DC (but it is rectified bi-alternation) the HT is 611 V, the plate current 300 mA (therefore 183 W) and the grid current (DC) 85 mA ·???????? With a polarization at 23 V DC the HT is at 593 V the plate current at 400 mA (237 W) the grid current 260 mA and I am at the limit of the transformer 1.6 A RMS ? That is not enough to make the plates red. ? I switched to a single 3-500Z tube. As a precaution, there is a load at the input and output but the system seems quite stable. ? Now it works ? Oddly enough, it only takes 20 Ω in series in the primary to bring the filament voltage back to 5.0 V. I plugged the hole caused by the missing lamp so as not to short-circuit the ventilation that I forced to the max. I placed a glass plate above the lamp box in order to leave the ventilation as when the cover is in place but being able to keep an eye on the anode of the tube (otherwise, you can't see the tubes). ? Two tests that give almost the same result: the anode in its lower part is dark red. ·???????? Bi-alternation rectified voltage on the grid Vg DC = 38 V Ig DC 110 mA plate current 390 mA under 592 V (231 W) secondary consumption: 359 VA ·???????? Bi-alternation rectified voltage + 6300 ?F capacitor so, basically DC on the grid Vg DC = 41.9 V Ig DC 120 mA plate current 400 mA under 584 V (234 W) secondary consumption: 389 VA ? I am limited by the 400 VA max of the 230/230 transformer supplying the voltage doubler. ? The measured values ??are questionable; I expected more difference when I added the capacitor. I am surprised that with 234 W on the anode, we are already in the dark red; the tube is given for 500 W of anode dissipation. I don't dare remove the anode radiator which also serves as a connector; I suppose it is this which prevents the entire anode from being red, from top to bottom. ? How long should I cook it for?
|
WRX, with 200w drive, how much grid and plate current was it running? Bob W4JFA?
Which models had 4kv on the plate?? A Triode is only going to give 10 to 12 DB of gain.??
Man, I have worked on and rebuilt pretty much all of these amps and even the later 3KA with its HD supply won't do 2kw.? It does not have 4KV on plate.? I was curious which ones did.? It's rated at 3k input and the efficiency is pretty poor.??
Henry used horrible small Fil chokes in series.? These things need to be tossed in the trash.? They get super-hot and after years of use the permeability changes.? they get harder and harder to drive.
Its so bad that the Tubes won't have the same fil voltage on them. Thats why these things always have one bright tube.? One of the tubes can be a half to a full volt off!?
The last one I rebuilt made 1800W out on low bands but needed a 200W radio to get there. It really works hard there.? ?I put a fil transformer in with a proper Fil choke.? Now each tube is spot on for voltage.? The amp runs so much better.? The blower is way
too small.? I put a Dayton ball bearing blower it. Half the noise and twice the air.?
C
It’s a well known fact that the Ameritron AL80b can obtain 1kw output ?pep?with a single 3-500. They only run 3000 volts anode voltage.? The old Henry amps made prior to the power rule change were used in some Embassies.? For that use they were running
the same amps sold to hams.? The Henry amps had choke input filers and 4000 volts anode and the?plate voltage was rock steady.? Easily capable of 2kw pep output.? Naturally the ham manuals didn’t necessarily boast that sort of power and tune up instructions
were geared towards legal limits.? Hence the CW/SSB change in voltage.? Load to 1 kwdc input on CW Carrier) switch to SSB and talk and get 2kw pep input, but dare not let down in the SSB voltage!!! You’ll break the law.? When the 1500 pep putput came in, away
went the cw/SSB switches, not need for them anymore!!
On Friday, February 14, 2025, 12:51 PM, W7WRX <clark@...> wrote:
Which henry amps were rated at 2kw out Jim???
C
Some versions of the older Henry amps were rated for 2 kw pep out on ssb.? But they also had improved cooling and also a bigger B+ supply.?
To getter older tubes, on the drake L7,? you can use the lower (1900 vdc) position, and temp shunt out any bias ( shunt out any series diodes used for bias)...and then apply a bit ( a few watts, 10-20 watts) of drive, and maladjust the tune control to put the
tank circuit off resonance...such that both tubes show some colour.?
|
Which models had 4kv on the plate?? A Triode is only going to give 10 to 12 DB of gain.??
Man, I have worked on and rebuilt pretty much all of these amps and even the later 3KA with its HD supply won't do 2kw.? It does not have 4KV on plate.? I was curious which ones did.? It's rated at 3k input and the efficiency is pretty poor.??
Henry used horrible small Fil chokes in series.? These things need to be tossed in the trash.? They get super-hot and after years of use the permeability changes.? they get harder and harder to drive.
Its so bad that the Tubes won't have the same fil voltage on them. Thats why these things always have one bright tube.? One of the tubes can be a half to a full volt off!?
The last one I rebuilt made 1800W out on low bands but needed a 200W radio to get there. It really works hard there.? ?I put a fil transformer in with a proper Fil choke.? Now each tube is spot on for voltage.? The amp runs so much better.? The blower is way
too small.? I put a Dayton ball bearing blower it. Half the noise and twice the air.?
C
toggle quoted message
Show quoted text
It’s a well known fact that the Ameritron AL80b can obtain 1kw output ?pep?with a single 3-500. They only run 3000 volts anode voltage. ?The old Henry amps made prior to the power rule change were used in some Embassies. ?For that use they were running
the same amps sold to hams. ?The Henry amps had choke input filers and 4000 volts anode and the?plate voltage was rock steady. ?Easily capable of 2kw pep output. ?Naturally the ham manuals didn’t necessarily boast that sort of power and tune up instructions
were geared towards legal limits. ?Hence the CW/SSB change in voltage. ?Load to 1 kwdc input on CW Carrier) switch to SSB and talk and get 2kw pep input, but dare not let down in the SSB voltage!!! You’ll break the law. ?When the 1500 pep putput came in, away
went the cw/SSB switches, not need for them anymore!!
On Friday, February 14, 2025, 12:51 PM, W7WRX <clark@...> wrote:
Which henry amps were rated at 2kw out Jim???
C
Some versions of the older Henry amps were rated for 2 kw pep out on ssb.? But they also had improved cooling and also a bigger B+ supply.?
To getter older tubes, on the drake L7,? you can use the lower (1900 vdc) position, and temp shunt out any bias ( shunt out any series diodes used for bias)...and then apply a bit ( a few watts, 10-20 watts) of drive, and maladjust the tune control to put the
tank circuit off resonance...such that both tubes show some colour.?
|
The Tokyo High power HL2K? with 3-500s was also such a amp. It had proper cooling(fully pressurised) On 240 VAC it could easily hit 2KW pep even though it was rated for 1.2KW PEP. Much like the TL922 which can? easily hit 1.5KW pep on 20 metres and below. The Tokyo high power HL2K was a popular RTTY? contest amp because it would not break down or melt parts and pins because of proper cooling. I think Amp Supply also had a heavy duty 3-500Z 3 or 4 holer, I cant remember.?
|
It’s a well known fact that the Ameritron AL80b can obtain 1kw output ?pep?with a single 3-500. They only run 3000 volts anode voltage. ?The old Henry amps made prior to the power rule change were used in some Embassies. ?For that use they were running the same amps sold to hams. ?The Henry amps had choke input filers and 4000 volts anode and the?plate voltage was rock steady. ?Easily capable of 2kw pep output. ?Naturally the ham manuals didn’t necessarily boast that sort of power and tune up instructions were geared towards legal limits. ?Hence the CW/SSB change in voltage. ?Load to 1 kwdc input on CW Carrier) switch to SSB and talk and get 2kw pep input, but dare not let down in the SSB voltage!!! You’ll break the law. ?When the 1500 pep putput came in, away went the cw/SSB switches, not need for them anymore!!
On Friday, February 14, 2025, 12:51 PM, W7WRX <clark@...> wrote:
Which henry amps were rated at 2kw out Jim???
C
Some versions of the older Henry amps were rated for 2 kw pep out on ssb.? But they also had improved cooling and also a bigger B+ supply.?
To getter older tubes, on the drake L7,? you can use the lower (1900 vdc) position, and temp shunt out any bias ( shunt out any series diodes used for bias)...and then apply a bit ( a few watts, 10-20 watts) of drive, and maladjust the tune control to put the
tank circuit off resonance...such that both tubes show some colour.?
|
Which henry amps were rated at 2kw out Jim???
C
toggle quoted message
Show quoted text
Some versions of the older Henry amps were rated for 2 kw pep out on ssb.? But they also had improved cooling and also a bigger B+ supply.?
To getter older tubes, on the drake L7,? you can use the lower (1900 vdc) position, and temp shunt out any bias ( shunt out any series diodes used for bias)...and then apply a bit ( a few watts, 10-20 watts) of drive, and maladjust the tune control to put the
tank circuit off resonance...such that both tubes show some colour.?
|
Some versions of the older Henry amps were rated for 2 kw pep out on ssb.? But they also had improved cooling and also a bigger B+ supply.?
To getter older tubes, on the drake L7,? you can use the lower (1900 vdc) position, and temp shunt out any bias ( shunt out any series diodes used for bias)...and then apply a bit ( a few watts, 10-20 watts) of drive, and maladjust the tune control to put the tank circuit off resonance...such that both tubes show some colour.?
|
The 3-500zg tube with the graphite plate can handle 600ma ICAS ? The regular 3-500 rated 450ma CCS! ?With enough cooling (very important factor) you could run 2000 watts pep output SSB with a pair of tubes. ?Most vintage amps do not have the transformer capability of this anyhow except for the older Henry amps that can do this. ?
On Friday, January 31, 2025, 12:50 AM, Fran?ois via groups.io <18471@...> wrote: > Attached, please find a great book about tubed amplifiers. ? Hello ? Thank you for this communication. ? Even if it does not answer my question, this document is very interesting, both at the technological and implementation level. ? I reformulate my initial questions: ·???????? What is the maximum anode current (reasonable) for a 3-500Z tube ·???????? What maximum current can be used in a Drake L 7 to bake the tubes (not in RF operation), compared to the transformer capacity for example. ? I measured some characteristics of the HV transformer (measured in short circuit) ·???????? Transformation ratio o?? In CW: 2.95 o?? In SSB: 4.14 ·???????? Resistance brought back to the secondary o?? In CW: 13.4 ? o?? In SSB: 18.6 ? ? ? De la part de HaL Mandel via groups.io
贰苍惫辞测é?: jeudi 30 janvier 2025 21:30
|
The original? C41 cap (47 pf) is failure prone.? ?Replace it with a 50 pf TX doorknob cap.? ?The original cap? was made from pc board.
C42? ( 307 pf)? is used to pad the TUNE cap on 160m only.? ?It's failure prone too.? ?Replace it with a 300 pf doorknob.
C39 and C40? will eventually fail.? ?Replace? with a pair of 1000 pf @ 5/7.5 kv doorknobs.? ?The original caps were discs types.?
|
> Attached, please find a great book about tubed amplifiers. ? Hello ? Thank you for this communication. ? Even if it does not answer my question, this document is very interesting, both at the technological and implementation level. ? I reformulate my initial questions: ·???????? What is the maximum anode current (reasonable) for a 3-500Z tube ·???????? What maximum current can be used in a Drake L 7 to bake the tubes (not in RF operation), compared to the transformer capacity for example. ? I measured some characteristics of the HV transformer (measured in short circuit) ·???????? Transformation ratio o?? In CW: 2.95 o?? In SSB: 4.14 ·???????? Resistance brought back to the secondary o?? In CW: 13.4 ? o?? In SSB: 18.6 ? ? ? De la part de HaL Mandel via groups.io
贰苍惫辞测é?: jeudi 30 janvier 2025 21:30
|
Dear Francois,
?
Attached, please find a great book about tubed amplifiers.
?
’73,
?
Hal Mandel
W4HBM
|
I am still studying a way to cook my 3-500Z which have not been hot for at least 15 years. The idea is to cook at high current with a low anode voltage, without HF. ? The maximum rating of the cathode current is not clear in the Eimac specifications. There are examples with a current of 0.4 A (for one tube). ·???????? Does this current (0.4 A) seem acceptable to you? ·???????? Can we go beyond that? This requires a grid voltage of around +30/+40V 100 mA. So 4 W and the tube is given for 20W ? I am considering using, temporarily, another transformer, with a lower secondary voltage, upstream of the doubler. ? Is this a bad idea?
|
Yes, a “single diode path” would have made it clearer. Thanks for the clarification. What I understood is that these diodes are used to protect the galvanometers in the event of an arc in the PA De la part de Peter Voelpel
贰苍惫辞测é?: jeudi 30 janvier 2025 00:42
|
Yes, a “single diode path” would have made it clearer.
Here more then 0.7V are clamped, depends on the meter or meter shunt for grid current.
Zener diode can be used as well or a germanium diode for less then 0.7V.
I was also referring to the “green” diode of your drawing.
?
73
Peter, DJ7WW
?
?
?
?
?
-----Original-Nachricht-----
Betreff: Re: [ham-amplifiers] Drake L-7
Datum: 2025-01-29T20:36:58+0100
Von: "Fran?ois via groups.io" <18471@...>
An: "[email protected]" <[email protected]>
?
?
?
>That clamp diode is typically a single diode.
http://radiojim.exofire.net/pages/Glitch%20diodes.html
De la part de Peter Voelpel
贰苍惫辞测é?: mercredi 29 janvier 2025 18:37
? ?
|
>That clamp diode is typically a single diode. http://radiojim.exofire.net/pages/Glitch%20diodes.html De la part de Peter Voelpel
贰苍惫辞测é?: mercredi 29 janvier 2025 18:37
|
That clamp diode is typically a single diode.
?
73
Peter, DJ7WW
?
?
?
?
-----Original-Nachricht-----
Betreff: Re: [ham-amplifiers] Drake L-7
Datum: 2025-01-29T13:33:50+0100
Von: "Jim VE7RF via groups.io" <jim.thom@...>
An: "[email protected]" <[email protected]>
?
?
?
A diode clamp is simply? a pair of REVERSE connected diodes, like 1N5408 / 6A10 / PM-600? type diodes.? ?They are wired between the B-? and the chassis.? Then the B- can never wander more than +/- .7 vdc? from chassis potential.
IF the? B+ anode ever arced to the (grounded) grid, the fault path is then through the chassis....and up out of the chassis, through one of the diodes...and back to B-? which completes the loop...and the HV fuse opens up asap, in < 1 msec.?
I use a 750 ma HV fuse in series with the B+ output ( instead of drakes .82 ohm resistor)....then a 50 ohm @ 50 watt wire wound resistor.? The 50 ohm resistor will? LIMIT the fault current to just 2500/50 ohms = 50 amps.? And 50 amps of fault current will OPEN OFF? a 750 ma rated? HV fuse in < 1 msec every time.?
Without the RVS connected diodes wired between? ?B- and chassis (I install em in both the L4PS / L7PS? HV supply....and also the RF deck) what happens is the fault current will flow into the chassis (anode to grid arc)...then up out of the chassis...then through the grid shunt,? grid meter pegs backwards.......then? through the plate current meter (plate current meter pegs forward)...then? back to the B-? of the HV supply, destroying both meters in the process.?
? ?
|
> A diode clamp is simply? a pair of REVERSE connected diodes, […] ? Does the following diagram correspond to your proposal? ? 
? What is the green diode used for? -- F1AMM Fran?ois De la part de Jim VE7RF via groups.io
贰苍惫辞测é?: mercredi 29 janvier 2025 13:34
|
A diode clamp is simply? a pair of REVERSE connected diodes, like 1N5408 / 6A10 / PM-600? type diodes.? ?They are wired between the B-? and the chassis.? Then the B- can never wander more than +/- .7 vdc? from chassis potential.
IF the? B+ anode ever arced to the (grounded) grid, the fault path is then through the chassis....and up out of the chassis, through one of the diodes...and back to B-? which completes the loop...and the HV fuse opens up asap, in < 1 msec.?
I use a 750 ma HV fuse in series with the B+ output ( instead of drakes .82 ohm resistor)....then a 50 ohm @ 50 watt wire wound resistor.? The 50 ohm resistor will? LIMIT the fault current to just 2500/50 ohms = 50 amps.? And 50 amps of fault current will OPEN OFF? a 750 ma rated? HV fuse in < 1 msec every time.?
Without the RVS connected diodes wired between? ?B- and chassis (I install em in both the L4PS / L7PS? HV supply....and also the RF deck) what happens is the fault current will flow into the chassis (anode to grid arc)...then up out of the chassis...then through the grid shunt,? grid meter pegs backwards.......then? through the plate current meter (plate current meter pegs forward)...then? back to the B-? of the HV supply, destroying both meters in the process.?
|
Bob
HaL Mandel