Hello all , tonight my trusty 811H developed a problem, when I turn it on the plate voltage / currant meter almost swings into the red. Then slowly drops down to 0 when turned off . Thanks Brian KG6WIK
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Ameritron 811H trouble
- Thread starter pipe layer
- Start date
You can try disconnecting the anode connections from the tops of the tubes. Make sure they aren't going to short out on anything and power it up.
If the plate current meter doesn't peg out you may have a bad tube. Power it down, discharge the caps and connect the the tubes one at a time. Repeat until you find the bad one.
If the plate current meter doesn't peg out you may have a bad tube. Power it down, discharge the caps and connect the the tubes one at a time. Repeat until you find the bad one.
OK I disconnected the anode connections, powered it up and got the same result. No change
I'm not familiar with that amp so I can't help more than that. Hopefully someone else will know more about it.
Well I took the old girl out to the garage blew out the dust with my compressor and now shes back to normal. So im guessing something is loose.
Do yourself a favor and join the Yahoo Ameritron amplifier group. The designer of the amp is on the group and you will have all the help you need to diagnose the issue and repair it. There isnlt much that can go wrong in an amp so you will probably have an answer stat!
I though he was saying the plate current meter pegged out when he turned the amp on. Maybe he was talking about the volt meter???
I know little to nothing about amps. I wouldn't think dust could cause the type of issue your amp is having. But then again amp issues go from the complicated to the so simple they get over looked. Your diagnosis of something possibly being loose seems logical. I'm assuming if your compressor has enough compression to easily move wires and possibly components around (especially if they are loose).
Have you considered the possibility that unplugging then plugging the amplifier from its buffer (if used) or the wire that supplies voltage from your transceiver to the keying Circuit may have been dirty. And unplugging then plugging the connectors back in might've removed some dirt/residue/gunk build-up. Unintentionally taking care of the problem?
Does your transceiver require a keying buffer?
I am reaching. I hope that you post the definitive answer to what caused the initial issue.
I am interested in the 811h and Hope you wouldn't mind sharing your working conditions.
What transceiver are you driving it with?.
I asked that question because I know some people like to drive it with the maximum rated input and others prefer driving Them Softly with less. The reason driving it with a lower output than the amplifier is capable of is usually tube longevity. Even though those tubes are fairly cheap I'd have to guess that many owners don't want to have to purchase and then change out tubes once every 6 months when one would only probably get a few hundred Watts more driving it with the maximum allowed input.
Are you using your 811h for SSB and CW?
The 811h is on my short list. Thanks and good luck. 73
That particular amp sometimes has that issue, the power switch is often the cause (due to oxidation...?? yeah I know, it doesn't make sense, but....).
cycle the switch a few times and observe the meters.
cycle the switch a few times and observe the meters.
Err, the plate-voltage/plate-current meter has a switch that select which of these two readings you will see.
In the "HV' position, what you see is normal. Should be at the bottom portion of the red zone at the top of the scale. The power supply's bleeder resistors will cause the reading to slowly drop to zero when powered down.
In the "Ip" position you should see NO reading at all until you key the amplifier.
So, which way was the switch set when you saw it read in the red on standby?
Big difference.
73
In the "HV' position, what you see is normal. Should be at the bottom portion of the red zone at the top of the scale. The power supply's bleeder resistors will cause the reading to slowly drop to zero when powered down.
In the "Ip" position you should see NO reading at all until you key the amplifier.
So, which way was the switch set when you saw it read in the red on standby?
Big difference.
73