Ebay AL-811H, What Have I done?

[338_MtRushmore]

I meant the radio only puts out 4 to 5 watts average, but its 80 pep. I did find an obvious peak on 80m, but it was a lot lighter than the manual stated. I was just scared to turn the knob that far I guess.

Tuning is very simple, but there sure are a lot of steps and things to remember. A little overwhelming when you know you can blow the dang thing up if you screw up too bad.

 

[nomadradio]

As your band frequency goes up, the peak on the amplifier's controls will get sharper. This is normal, and to prevent the 10-meter band from being "touchy" and easy to overshoot, a reduction gear helps to smooth out a narrow peak.

But on 80 meters, this can make the peak setting seem unnaturally wide, compared to the upper bands.

Back in the day, some amplifiers would split the Plate Tune control into two sections. Both sections were connected in parallel, to get the higher capacitance needed to tune the lower bands. On 10 and 15 meters, only some of the capacitor's plates are in the circuit. Makes the amount of capacitance per degree of knob motion smaller. Serves to smooth out a too-sharp peak.

That method makes the amplifier's band switch and Plate Tune control more complex and expensive. The reduction-gear method will make the lower bands seem to have a "lazy" peak that seems unnaturally broad. Ameritron went with the simpler reduction-gear option.

IMHO simpler is better. Especially a few years down the road when something breaks and you need a replacement part. A new Plate Tune control for your 1970 National NCL2000 will not be easy to find. They used the 'split'-capacitor for that model. Does smooth out the Plate Tune control's peak on the upper bands but causes headaches if you need to replace that particular 50 year-old part.

73

 

[338_MtRushmore]

That is interesting. It seems like it would be easer to have a 1:1 knob and a reduction knob next to it. Not that that would be any easier to repair today.

For about $610 I got a broken amp, new tubes, a hand full of parts, and I learned a heck of a lot more than if I had just ordered a new one.

I also noticed the grid current needle is bent. That needle must have had some serious velocity when the amp went bang.

 

[kopcicle]

A new Plate Tune control for your 1970 National NCL2000 will not be easy to find. They used the 'split'-capacitor for that model. Does smooth out the Plate Tune control's peak on the upper bands but causes headaches if you need to replace that particular 50 year-old part.

gnorph

 

[Shadetree Mechanic]

Over couple the load control to drop the dead key down to a comfortable level. Then it will swing up from there when modulated. But maybe this is just for 11m operators, I am not sure.

 

[kopcicle]

It may seem a shame to part out a Siltronix 1011 for the dual speed knob but I've done just that several times. More than one Silly has arrived here that was so roached that a rebuild wasn't worth the effort. I have a home brew here that by virtue of it's sharp tank "Q" was very touchy on the upper bands. Enter the dual speed knob. I suppose I could have just used a reasonable "Q" to begin with but one , I wasn't that bright, and two, It's the parts I had on hand

I don't mean to promote the destruction of salvageable 1011's but if a couple come your way it's a good fix for a problem that usually doesn't exist.

If that idea doesn't appeal to you , Jackson Brothers 6:1 and 10:1 drives are still available new and used. There is even a single knob , two speed that is greater reduction in reverse. Some like it but it can be a bother finding a dip or peak .

I don't find the 811/572 Ameritron that difficult to tune. Once attached to a reliable antenna the settings are easily memorized and a final touch up takes seconds. I will admit that 10m is far sharper than 80.

Just for repetition, don't drive the piss out of it , keep tuning short and accurate, keep an eye on the grid current, beware of oscillations, don't be long winded and enjoy.

 

[Dmans]

338_MtRushmore,
I think you are on the right track and have the right help from the right members of this forum. Enjoy that amplifier, it will only lead to more of them!

For about $610 I got a broken amp, new tubes, a hand full of parts, and I learned a heck of a lot more than if I had just ordered a new one.

I am glad to know there is another way to learn. For most of my 50+ years I thought the only ways to learn were repetition and trauma impact!
If only I would have opened my wallet a little more, I wouldn't have so many scars and arthritis!!

73's
David

 

[338_MtRushmore]

I was thinking about hooking up the alc, but is there really much point? It seems it would only be useful during tuning, but I guess that might not be a bad thing.

If I were to run the amp hard then the alc could be useful, but not if I ran a reduced output?

 

[kopcicle]

https://www.w8ji.com/ameritron_alc_adjustment.htm

 

[338_MtRushmore]

I guess it's not the worst idea to setup the alc. Maybe someday I will randomly crank the power wide open for some reason. I was thinking of it as an operational safety rather, than a catastrophic safety.

 

[drgrant]

I guess it's not the worst idea to setup the alc. Maybe someday I will randomly crank the power wide open for some reason. I was thinking of it as an operational safety rather, than a catastrophic safety.

IMHO the only reason to even use the thing is its insurance against a numbskull moment, it'll keep you from over driving the amp, but it all depends on your radio and operation practices you have in play. I think with some radios its more useful than others... for example... say you're running a TS440S on SSB... well good luck with that thing if you nudge the mic gain too far or something, because the difference between nothing and full output on that radio a pretty small amount.

 

[kopcicle]

Well, do take into account that Tom Rauch designed or was heavily involved in most of the Ameritron amplifiers.
There really is no better source of information.
Spend some time on his pages learning about the 811/572b as well as the AL-811 and 811H.
Time well spent.

 

[338_MtRushmore]

IMHO the only reason to even use the thing is its insurance against a numbskull moment, it'll keep you from over driving the amp, but it all depends on your radio and operation practices you have in play. I think with some radios its more useful than others... for example... say you're running a TS440S on SSB... well good luck with that thing if you nudge the mic gain too far or something, because the difference between nothing and full output on that radio a pretty small amount.

That does bring up a question I have had for a while. It looks like the ts440 you mentioned doesn't have variable power. Everything I read says it is not good to use the Mic gain to control power. If this is true, wouldn't it be better to adjust the power through the alc jack on the radio and not use the alc with the amp?

 

[338_MtRushmore]

Well, do take into account that Tom Rauch designed or was heavily involved in most of the Ameritron amplifiers.
There really is no better source of information.
Spend some time on his pages learning about the 811/572b as well as the AL-811 and 811H.
Time well spent.

I agree completely.

 

[543_Dallas]

Over couple the load control to drop the dead key down to a comfortable level. Then it will swing up from there when modulated. But maybe this is just for 11m operators, I am not sure.

Slightly over coupled is a good thing. Better linearity and lower grid current. Too much will kill the efficiency and the toobs will run hotter. Bad idea when you don't have a lot of plate dissipation to begin with.