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811 H question.

SMILEX2692002

SMILEX2692002

Well-Known Member
Oct 26, 2011
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Bought a used 811H.
Intial test on 40 meters with 20 watts drive shows no power out on my watt meter. The plate current shows nothing. The hv meter also dosent drop when the amp is keyed in cw. But the HV reading is good.
The amp does have grid current when keyed in cw.
What could be my issue?
Seems like the tubes are not getting any rf to and from them.
 

One of the tubes was broken in shipment so my amp only has socket 1-3 with tubes installed. I was told the amp would still function missing one tube untill a replacement arrives.
 
It will still function however the position of the tune and load knobs will be considerably different than with all tubes installed. I don't think one missing/faulty tube is the issue. There should be some RF out and plate current with just three tubes. That is unless one tube had a short and was shunting drive power to ground I suppose.
 
Ameritron

Here is the manual download it if you like and there is also a schematic in it.

Be careful working on that amp high voltage is present in the PS.
 
Captain Kilowatt said:
It will still function however the position of the tune and load knobs will be considerably different than with all tubes installed. I don't think one missing/faulty tube is the issue. There should be some RF out and plate current with just three tubes. That is unless one tube had a short and was shunting drive power to ground I suppose.
Click to expand...

It seems like the tubes are not warming so the issue is in that area. The tubes only light up.
It was an Ebay purchase. Seller said it was working completely. Just my luck.
 
I can tell you from experience that if the 811 wasn't shipped in the original bullet proof factory carton with packaging your amp was probably dropped and damaged in shipping. Look for loose components and replace all three tubes. 811's are cheap. Were the tubes in their sockets when shipped or wrapped separately?
 
RatsoW8 said:
I can tell you from experience that if the 811 wasn't shipped in the original bullet proof factory carton with packaging your amp was probably dropped and damaged in shipping. Look for loose components and replace all three tubes. 811's are cheap. Were the tubes in their sockets when shipped or wrapped separately?
Click to expand...

The amp was not shipped in the factory box. To my dislike the tubes were left in the sockets. When I received the amp I could clearly see the tubes had been shaken out of the sockets and were just laying near them. One tube had also broken.
I don't see any loose components by sight.
I bought a brand new 811a tube to replace the broken one.
Installed the 4th tube and see the same results.
 
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SMILEX2692002 said:
It seems like the tubes are not warming so the issue is in that area. The tubes only light up.
It was an Ebay purchase. Seller said it was working completely. Just my luck.
Click to expand...


If the tubes light up then they are warming up. The filaments light up and generate enough heat that after a few minutes you won't want to remove them with bare fingers. tubes will only get real how with plate current drawn and that seems to be the issue:no plate current. If it was beat around that bad look at the plate choke. It could be broken and if it is no HV will get to the tubes. The meter sample is upstream from the tubes closer to the actual filter capacitors.
 
Captain Kilowatt said:
If the tubes light up then they are warming up. The filaments light up and generate enough heat that after a few minutes you won't want to remove them with bare fingers. tubes will only get real how with plate current drawn and that seems to be the issue:no plate current. If it was beat around that bad look at the plate choke. It could be broken and if it is no HV will get to the tubes. The meter sample is upstream from the tubes closer to the actual filter capacitors.
Click to expand...

Loose or faulty T/R relay...Make sure all your cables are correctly hooked up...don't discount the relay in the radio...is it closing the contact going to the amp.
All the Best
Gary/W9FNB
 
Captain Kilowatt has given the correct answer to this problem and from the description of the symptoms it's 100% spot on. The key in this description was only having grid current with 20 watts drive applied and keyed. If there is no plate current at all under this condition it means plate voltage is not arriving at the tubes. There is an open on one side of this HV supply. Otherwise we would at least have bias current showing and plate current increasing with drive.

The sure thing that tells us drive is arriving at the tubes is the presence of grid current when 20 watts is applied. When plate voltage is missing grid current rises rapidly because all drive power is being dissipated by the grid since there is no current path to the anode. Do not continue to key the amp like this because you can ruin the grids inside the tubes.

If this amp was turned on with the broken tube installed, it caused a short to be applied to the HV supply. I would check L4 and L7 with an ohm meter to make sure they are not open. It's more likely that R9, the cathode current shunt resistor has opened. It should read .6 ohms. It's also possible for D16 to short. One leg of this diode must be lifted to test it since it's across the .6 ohm shunt resistor.
 
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Shockwave said:
Captain Kilowatt has given the correct answer to this problem and from the description of the symptoms it's 100% spot on. The key in this description was only having grid current with 20 watts drive applied and keyed. If there is no plate current at all under this condition it means plate voltage is not arriving at the tubes. There is an open on one side of this HV supply. Otherwise we would at least have bias current showing and plate current increasing with drive.

The sure thing that tells us drive is arriving at the tubes is the presence of grid current when 20 watts is applied. When plate voltage is missing grid current rises rapidly because all drive power is being dissipated by the grid since there is no current path to the anode. Do not continue to key the amp like this because you can ruin the grids inside the tubes.

If this amp was turned on with the broken tube installed, it caused a short to be applied to the HV supply. I would check L4 and L7 with an ohm meter to make sure they are not open. It's more likely that R9, the cathode current shunt resistor has opened. It should read .6 ohms. It's also possible for D16 to short. One leg of this diode must be lifted to test it since it's across the .6 ohm shunt resistor.
Click to expand...

The amp was not powered on with the broken tube. I have a multi meter but the presence of leathal voltage makes me not want to probe around with components with the unit powered on.
Just my luck. I contacted the seller about a doa unit. Waiting to hear back.
Its most likely a easy fix for some. But for me its not worth the risk of shock from the high voltage.
 
SMILEX2692002 said:
The amp was not powered on with the broken tube. I have a multi meter but the presence of leathal voltage makes me not want to probe around with components with the unit powered on.
Just my luck. I contacted the seller about a doa unit. Waiting to hear back.
Its most likely a easy fix for some. But for me its not worth the risk of shock from the high voltage.
Click to expand...

The seller is not wanting to work with me on a refund or return.
I have found a local who can fix this amplifier. I have taken it there and waiting for his diagnosis.
I will be going after the seller for any repair charges at the least.
 
Tony, what good would Paypal do? It is obviously shipping damage. If you file a claim with paypal due to shipping damage, or blame the guy wanting him to compensate you for shipping damage, you are the one doing the ripping off and a snake in the grass!

What he needs to do is to contact the shipper, and BOTH of them work together with the shipping carrier on filing a claim. If he is patient, he will probably get reimbursed for the cost of new tubes, some upgrades to the amp and then some.

The package will need to be inspected, and it is a process, but that is the *RIGHT* thing to do.
 
Ebay sellers should always insure what they sell. When you sell an item on eBay, YOU are responsible if it is lost or damaged in shipment. It is the SELLERS responsibility to purchase insurance.

If an item is lost or damaged and you did not insure the package, YOU are responsible. Most eBay sellers are still unaware of this policy. You used to be able to make insurance optional and charge extra for it. Now, your supposed to add this extra cost within your S&H charges.

Since this was an eBay transaction and the seller did not insure the item, then the seller will likely lose this claim.

Go ahead an file a PayPal claim. The dumbass should have done a better job packing it anyways.

http://community.ebay.com/t5/Review...rance-Policy-Buyer-Refund-Policy/td-p/1313758

If I sell something for $100 or less, I usually just self insure it, but not always. Sometimes, it just depends on what kinda vibes I get from the buyer. Transactions over $100 are always insured.
 
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