I have an AL-80B amplifier that has a high input SWR on 40 meters of three to one and I can only get 500 watts into a dummy load.
I have adjusted the tuned input slug and the SWR only goes down to 3 to 1.
I have cleaned the band switches and the dummy load has tested good with a another amplifier.
I get 800 to 1000 watts on all other bands.
Any ideas to fix it?
Thanks
Dale (KD0GES)

I get the impression that the only way to test a tube is in a known to good amplifier.
Thanks
Dale (KD0GES)

Last night I pulled the tubes out of the amplifier.
One tube had a ball of glass rolling around inside.
The heating elements would light up on both tubes.
Except for the heating elements all the other pins had showed as an open circuit on my ohm meter.
I,m assuming both tubes are bad.
I went over the wiring and found no obvious problems.
I am going to buy a new set of tubes for the amplifier.
RF parts looks like a good place to buy tubes from.
Dale (KD0GES)

I have a manual.
I am going to take the amp apart again and check everything I can and make sure everything is wired correctly.
I have asked on local ham nets a few times if anyone living near me knows how to work on the amplifier and have had no responses.
I will check into your suggestions and see if one of these solves the problem.
Thanks
Dale (KD0GES) 

Update I put in a harbach power supply.
Now I have 2500 volts on the meter but at idle it has no grid or plat current.
Would this indicate the tubes are bad?
Thanks
Dale (KD0GES)

I came up with a good way of testing the transformer.
I hooked my o-scope to the high voltage output and with the amplifier switched on.
Then I touched a 9 volt battery across the plug and the o-scope shows a 35 volt spike output from the transformer.
I believe this is a reasonable indication the transformer is OK without running high voltage.

I am going to put a harbach power supply into the amp.
Dale

Good
Thanks
Dale

I removed the high voltage output wires from the power supply board for the transformer and checked the resistance and got 13.2 ohms.
My guess is it should read 0 ohms on the secondary side of the transformer with an ohm meter.
Would this indicate the transformer is bad?
Thanks
Dale (KD0GES)

Is there a good way to test the HV side of the transformer?
Dale

Upon further investigation I found some wires that have gotten hot enough to melt the coating.
When I turned it on before the tubes would light up.
I am now replacing the bad wiring and while I am at it I probably will put in new capacitors in the power supply.
My guess is the rectifier diodes are bad.
I did find the diodes for the meter protection at radio shack.
I am assuming the transformed is OK if the tubed light up.
Thanks for the help.
Dale (KD0GES)

My electronics is a little rusty.
I had 2 years of votech training 25 years ago and never got a job.
If I remember correctly diodes have .7 volts before current will floe
Dale

Thanks for the help.
Does radio shack hove the diodes to put across the meter?
And what type of diode should I use?
Thanks
Dale

I have a sb-200 that the meter does not work.
I deoxit the meter selector switch and it didn't help.
I can get movement of the meter by putting my ohm meter across the terminals.
Any help of what to look for will be appreciated.
Also can I run the amp using an external power meter to tune it for max output?
Thanks
Dale (KD0GES)

On 40 meters the tuning capacitor is on 15 meters.
I need to open the case to findout what is arcing tonight.
The plate current is what I was referring to.
The gridcurrent is around 15 mA
Thanks
Dale (KD0GES)

Last night I tried it on the lower portion of 80 meters and the tuning capacitor ends up on the high side of the 80 meter band and the load is on 1 and I got 500 Watts out.
On 40 meters it acts the same as 80 meters with 500 watts out.
on 20 meters the amplifier starts to arc at 200ma of drive current.
Tonight I am going to tune it into my antenna in-case my dummy load is getting a high swr under high power.
Thanks for the help.
Dale (KD0GES)