Ameritron 811H no grid current
I just received a brand new AL 811H. I removed it from the box and opened the amp a removed the packing material, installed the 12 amp fuses, made sure the tubes were seated, replaced the cover, hooked it up and turned it on, the plate voltage is 1800 volts but when I tried to tune the amp "by manual instructions"the grid current meter remains zero. No power output at all. Need help. Thanks
Are you "keying" the amplifier? It sounds like the amplifier is still in the "standby" condition. You have to apply a ground to the "keying" jack on the rear of the amplifier.
You don't give much to go on . Let's start with the obvious . Do you have a footswitch or keying cable hooked up to the amp ? If so , can you hear the relay inside the amp when it is " keyed " ? The AL-811 does not have a rf detection circuit , so you have to either use a cable between the rig and the amp or use a footswitch to " key " the amp . You can use any type of momentary switch , but most ( myself included ) prefer a footswitch . If that's not the cure then we may need some more info . Also make sure the amp is in operate and not standby . Hope this helps . The 811h is a really nice amp for the money .
Randy #( KB5WX )
FISTS ## #10542
Member of SPAR
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Tubes being seated is nice. Did you also attach the four plate caps on the tubes?
Originally Posted by NZ4L
Is the amplifier "keying" (XMIT LED turns red when you do...with or without any drive)?
you didn't say so I have to ask - is your xcvr in CW or FM mode? in other words, is it actually driving RF in to the amp? if it's in SSB or AM mode, try yelling in to the mike and see if the grid current needle moves.
No I don't have a footswitch, I have the relay and alc cables from the 746 Pro connected to the amp. When I try to tune the amp up in the CW mode the operating light comes on and I can hear the relay keying but there's no output. The plate voltage is 1800 and when the switch is put in the Ip position the meter falls to zero as the manual says it's suppose to. The standby/operate switch is in the operate position. When the xcvr is keyed the plate current meter moves up a little but the grid current meter doesn't move no matter what the radio output. The coax is connected between the xcvr and the amp out to a inverted L vertical 1.8 swr. As far as I know I have done all the manual says to tune the amp but it still doesn't work. All four of the tubes seem to be seated good and the caps are all on good and they all light up. Hope this is a better description of the problem. Thanks.
Originally Posted by KB5WX
Actually, it does sound like you are doing all the right things. If you can test the output wattage of your driving radio and it's anywhere above 0, then it's time to return it to the place of purchase and have a little chat with them about an exchange.
Originally Posted by NZ4L
What MODE are you using to do this?
Is your coax jumper from the radio to the amp on backwards? Jumper has to be connected to the RF IN on the amp?
Is your radio connected to the "RF IN" on the amp, and the antenna connected to the "RF OUT" ??
If you hooked it up wrong, don't feel bad. I have connected amps and antenna tuners wrong several times before. And when the amp is connected wrong, It don't work at all.....
Last edited by W0UZR; 11-20-2009 at 01:51 AM.
I also have the AL-811H and am quite happy with it. As another post said "it is a great buy".
However, the QC at MFJ just plain stinks in many cases.
The first AL-811 I bought had been dropped hard (pre-packing, box and packing perfect condition, so obviously at the factory) such that one rear corner of the chassis and cabinet was deformed badly...right back to the radio store it went. I have had other MFJ products with joints that had never had solder applied, cold solder joints, etc. In some cases it is like building a kit.
I think it sounds like you have given it a 'fair shot'. You might try one last thing.
!. be sure that it is "deader than a hammer" electrically.
2. take the cover off...be sure it is dead, again.
3. give it a thorough 'exam' - mechanically and electrically.
if no findings, take it back...won't be the first piece of MFJ they got back.
don't give up on it - they are good property.
SOWP, QCWA(50), OOTC, Navy Amateur Radio Club, ex USN Aviation Radio Op. (there was a time when it was ALL CW)