PDA

View Full Version : Ameritron AL811Hxce Problems ???



M5PDL
03-26-2011, 11:32 AM
Hiya all,
Im looking for some advice....

I purchased a Ameritron AL811HXCE and dont seem to be able to get more than 400watts out of it on any band. When I first got this unit home I unpacked it to find that one of the tubes was broken so had to replace that.

Let me point out at this point that I have VERY limited test equipment and the power/swr meter I am using is a VERY cheap model (watson WCN-200)

I am using a Kenwood TS570D - AL811H - Power Meter - Hustler 6BTV (average SWR 1.5:1 across the bands)

I really am scratching my head to work out weather the problem is with the Antenna, the power meter or the amp.

When I switch the amp to OPR I get a high SWR reading on the radio and the swr meter still reads around 1.5:1 (If I hit the tune button on the radio the SWR goes down ok but the output from the amp still stays the same)

The maximum output of this Amp seems to be at 400 watts regardless of weather I feed it with 40 or 70 watts input.

Is 400 watts all im ever going to get from this amp or do you think I have a problem somewhere ? (I know that my licence only allows me 400 watts but I dont want to continously drive this amp at maximum just to get the 400 watts im allowed to use, and if it has a problem id rather get it fixed)

Any help or advice would be very much appreciated..

Regards

Steve M5PDL

KR2C
03-26-2011, 01:44 PM
I have a very similar setup and have had a similar problem. I have an 811h and a TS-450. In my case, D16 was bad which caused the meters to read incorrectly. With the meters reading incorrectly it was tuned improperly which caused one of the 51 ohm resistors to burn out shutting down one of the tubes (valves).

M5PDL
03-26-2011, 04:20 PM
Ive just had the lid off the unit (didnt want to touch too much stuff in there) When I switch it on all the valves light up ok. 3 of the valves seem to have a 'silver coating' inside the glass (its not covering all the inside but its definately there) including the new one I put in.

I assume the 51ohm resistors you are refering to are the big ones on a fairly small board thats positioned above and between the 4 valves. Now, unless Im totally misreading my multimeter my 4 resistors are all reading 99.8 ohms.. Seems like theres definately something not right somewhere..

N2RJ
03-26-2011, 06:19 PM
The 51 ohm resistors are close to the chassis to the left of the valves (when looking at the amplifier from the front).

It is very likely that one of them burned out. Keep some spares around as a valve failure almost guarantees a burned resistor.

The silver coating you see on the good valves is called a "getter" which is used to absorb or react with the remaining air/oxygen to maintain the vacuum. The cracked valve has no getter because since it has air in it, the getter is all used up.

The resistors on the small circuit board are for the anode. Those are not what you're looking for.

M5PDL
03-27-2011, 05:42 PM
The valves were clear.. This 'silver coating' has appeared less than 24 hours after installing a new valve.. I only tried tuning the amp once and it still wouldnt go over 400 watts.. the valves looked like they had got very hot.. there is only 1 of the 4 valves that still has clear glass on it..
Im really beginning to wish i hadnt bothered with this amp at all..

The only 51ohm resistors I can see on the Schematic are on the same board (I think) that I refered to in my post above..

To say im very confused is a huge understatement...

WB2WIK
03-27-2011, 05:45 PM
Go back to basics:

What does the high voltage indicate in standby? What does it indicate "key down" when driving it to 400W output power?

Are you using a wattmeter of known accuracy to measure output power?

What does the grid current indicate when "key down" and being driven to 400W output power?

When it is being driven to 400W output power, after a short period the 811A anodes should start to glow red. Do they all glow red, about the same color?

M5PDL
03-27-2011, 06:13 PM
Go back to basics:

What does the high voltage indicate in standby? What does it indicate "key down" when driving it to 400W output power?

Standby.. 1.7KV Key Down.. 1.5KV

Are you using a wattmeter of known accuracy to measure output power?

Im not sure how accurate this meter is.. It was a cheapie.. its a WATSON WCN-200


What does the grid current indicate when "key down" and being driven to 400W output power?

Grid Current.. 115mA Plate Current.. 625mA

When it is being driven to 400W output power, after a short period the 811A anodes should start to glow red. Do they all glow red, about the same color?

To be honest I havent had the lid off whilst 'driving' this amp so I cant honestly answer this question. If my problem (if a problem does actually exist) is just the watt meter not being at all accurate I would be quite happy to just use this amp. I am trying to avoid causing any real (and expensive) damage..

I do appreciate the help and advice that I am getting.. cheers guys

WB2WIK
03-27-2011, 06:27 PM
Are you sure it's fully loaded up? At 1500V and 625mA, you should have about 525W output power assuming it's loaded properly.

For 800W output power you'd need about 850mA plate current. No way to achieve 800W output at 625mA. Your grid current also seems low for "full drive power" applied. I would think on CW (key down, for tuning) at full drive it would be closer to 200mA, not 115mA.

Sounds in general like it's not being driven very hard, and as a result won't load up fully.

WB2WIK
03-27-2011, 06:29 PM
To be honest I havent had the lid off whilst 'driving' this amp so I cant honestly answer this question. If my problem (if a problem does actually exist) is just the watt meter not being at all accurate I would be quite happy to just use this amp. I am trying to avoid causing any real (and expensive) damage..



Not much you can do to harm it except kill the tubes. You can't "look inside" through the fan or anything to see the tube anode color? Maybe not, I don't have an 811H.

You can operate without the cover attached if you do it carefully. Keep the amp far back away from the rig and yourself and anything else. It would be interesting to know if the four anodes all glow about the same color. If three do and one does not, that explains the problem.

M5PDL
03-27-2011, 06:36 PM
If I drive it with 40 watts I can get 400 watts out.. If I increase the drive to 80 watts the Grid current goes to max (200mA) and the Plate current will go to max (750mA) but still only 400 watts output and the amp feels and smells hot..

WB2WIK
03-27-2011, 07:07 PM
If I drive it with 40 watts I can get 400 watts out.. If I increase the drive to 80 watts the Grid current goes to max (200mA) and the Plate current will go to max (750mA) but still only 400 watts output and the amp feels and smells hot..

You do know that when you increase drive to 80W you have to re-tune the amplifier, right?

M5PDL
03-27-2011, 07:10 PM
yes... ive done all that.. it doesnt matter what i try to do i just dont seem to be able to get more than 400 watts from this amp.. and thats on all the bands..

it all seems very strange to me..

WB2WIK
03-27-2011, 07:30 PM
Seems strange to me, too. I suspect it's not loaded fully at the increased power level, or your wattmeter is wrong.

M5PDL
03-27-2011, 07:45 PM
Thanks for your help anyway..

Would I be right in assuming that if one of these 51ohm resistors has burnt out that the valve wouldnt work at all (not light up at all) or would it still light up but just not 'work'

Please forgive my ignorance regarding all this..

my previous amp (5 or 6 years ago) was an ameritron AL80B that worked straight outta the box.. I never had any problems with that one which is why I went for another ameritron.. Shame this one isnt so straight forward..

But before I take this one back to the shop that I got it from I need to be 100% confident that there is a problem with the amp and not my antenna or swr/watt meter..

Head scratching time again.. HiHi

WB2WIK
03-28-2011, 03:11 PM
Thanks for your help anyway..

Would I be right in assuming that if one of these 51ohm resistors has burnt out that the valve wouldnt work at all (not light up at all) or would it still light up but just not 'work'




I just looked at the schematic on line. The 51 Ohm resistors shown as R19 through R22 are what ground the grids of the four tubes (they are all bypassed with .01uF capacitors which serve as the RF ground).

If one were to "open," that tube would not be able to conduct current but its filament would still light up. It just wouldn't work.

M5PDL
03-28-2011, 04:19 PM
I dont have the test equipment needed or the know how so I think it looks like a trip back to the shop..
Trying to find the time and money for all this is a hassle I could really do without..
Wish I hadnt wasted my money on this amp now !!

Thanks once again for all your help.
Regards
Steve M5PDL

N4BBQ
03-28-2011, 06:19 PM
Borrow or buy a cheap DMM, pull the cover off the amp, let the high voltage bleed off, pull the tubes, then measure pin #3 to ground on all the tube sockets and see if any measure higher than 51 ohms. Pin 3 is one of the smaller holes in the socket.

M5PDL
03-28-2011, 07:29 PM
I do have a multi meter.. Thanks for that.. I will test as soon as Ive had dinner..

M5PDL
04-06-2011, 10:12 PM
I think I'm gonna need to phone the shop I got it from and see what they say about it.. I took it along to my local radio club tonight and we hooked it up to a different wattmeter and a dummy load and it reads exactly the same as my wattmeter was reading.. Something definitely ain't right with it. At least I know my wattmeter is ok.. So much for quality control before it leaves the factory..

WB2WIK
04-07-2011, 12:22 AM
I think I'm gonna need to phone the shop I got it from and see what they say about it.. I took it along to my local radio club tonight and we hooked it up to a different wattmeter and a dummy load and it reads exactly the same as my wattmeter was reading.. Something definitely ain't right with it. At least I know my wattmeter is ok.. So much for quality control before it leaves the factory..

We always say:

-Price
-Quality
-Delivery

Pick two!

K3STX
04-07-2011, 01:23 PM
If it were ME, I would buy a new set of four 811A tubes. You will probably want them anyway, and it would be a good way to see if the problem is with the tubes or something else. The fact that you replaced ONE of the four tubes makes me wonder, not so much about neutralizing the "new" circuit but that one (or more) of the other three tubes is weak. A new set of good tubes will help you and it's not like it would be a complete waste of money, 811As are cheap.

paul

W8JI
04-08-2011, 01:48 PM
If I drive it with 40 watts I can get 400 watts out.. If I increase the drive to 80 watts the Grid current goes to max (200mA) and the Plate current will go to max (750mA) but still only 400 watts output and the amp feels and smells hot..
Smelling hot is not good. :-)

Before you get all worked up, and other people start to fuel your angst with smart comments, you probably have a simple problem.

Some of the stuff about neutralizing is bad advice. Good advice about the diode. Generally good advice about the resistors, except on later amps the resistors are GONE. They have been removed.

Read the manual a few times. You may just need to get a feel for how to tune. As drive is increased the loading control has to be rotated clockwise.

Do you have the ALC connected??

The single biggest problem with 811H amps by far is bad tubes, and the single biggest cause of bad tubes by far is improper tuning and heavy-handed tuning.

Also read this page and links:

http://www.w8ji.com/al811h_schematic.htm

M5PDL
04-13-2011, 10:07 PM
Thanks for all the advice.. I do not have the ALC connected.. It says in the manual that I dont need it if im driving it with less than 70 watts input..
I took the amp to my local radio club to have them test it for me (different power meter, dummy load etc etc) and we did connect the ALC and we still couldnt get more than 400 watts from it..
The little red stickers (I assume quality control stickers) on all the boards etc insde the amp all have 'SEPT 2010' written on them.. Would I be right in assuming that this was a later model that does not have the 51ohm resistors that you were refering to ??

If I leave the amp in standby mode and key the radio the SWR on the radio reads low just as I would expect, however, when I place the amp in OPR mode the SWR on the radio shoots off the scale, pressing auto tune on the radio will bring this back down ok.. Didnt know whether this was significant to my problem or not..

I have owned a amp before so im pretty confident that Im tuning it ok..

KB3HRO
04-15-2011, 12:16 PM
my best guess is that tube with no silver at the bottom is a defect,didnt take a seal at the factory?.try a new one,maybe borrow one? and if it comes up in power some, id get all new.if you had the plates(anode?thing in the middle??) glowing red,they will show discoloration .them original tubes are gonna be tired.i'd be upset if i had my new tubes glowing..thats a good amp when you have good tubes the alc is supposed to catch over shoot from the driver? it still gets thru mine.

my 811h can push 800 into a dummy load driving with 90 watts (on cw),however in real life im happy to see 450ssb driving with 70 or so . its quite an art to tune ssb...73 Rick

M5PDL
04-15-2011, 06:18 PM
im happy to see 450ssb driving with 70 or so . its quite an art to tune ssb...73 Rick


I'd be very happy to see more than 350-400 on any mode from my amp.. HiHi.. It just really annoys me that I spent 1000 on an amp that doesnt work properly.. Anyway.. Im sure it will make a nice paperweight HiHi

W8JI
04-18-2011, 02:58 PM
Thanks for all the advice.. I do not have the ALC connected.. It says in the manual that I dont need it if im driving it with less than 70 watts input..
I took the amp to my local radio club to have them test it for me (different power meter, dummy load etc etc) and we did connect the ALC and we still couldnt get more than 400 watts from it..
The little red stickers (I assume quality control stickers) on all the boards etc insde the amp all have 'SEPT 2010' written on them.. Would I be right in assuming that this was a later model that does not have the 51ohm resistors that you were refering to ??

If I leave the amp in standby mode and key the radio the SWR on the radio reads low just as I would expect, however, when I place the amp in OPR mode the SWR on the radio shoots off the scale, pressing auto tune on the radio will bring this back down ok.. Didnt know whether this was significant to my problem or not..

I have owned a amp before so im pretty confident that Im tuning it ok..

It would be around January 2011, I do not know the exact date, that the resistors were removed. You should be able to see the resistors on terminal strips near the tubes.

M5PDL
04-23-2011, 03:48 PM
I thought these resistors were underneath the valve sockets.. ??

KM1H
04-23-2011, 05:02 PM
On 2 small terminal strips on the far left side with 2 resistors apiece to ground.

You can check tubes one at a time, with the others removed, on 40 or 80M. Use only 20W of drive and a tuner if your rig cant handle the VSWR. I use an old TS-830 hybrid and it doesnt care what it loads into.....within reason

With 20W drive good tubes should yield 200W which is 10dB of gain.

Ameritron now has an AL-811HD model with guess what....572B's :eek: which will give a very long life if not dropped or driven with 200W. Its a direct swap into other models. With 100W of drive you should get 800W out but the power transformer will be unhappy except during very casual use.

Its a fine little amp for the price and takes up where the Heathkit SB-200 left off. Neither one is contest rated or idiot proof but it sometimes seems that every SB-200 built is still in existence. Id rather have seen a 2 572B amp that ran a bit less HV than the SB-200 and was deliberately limited to 600-650W out however build cost won out I suppose.

Carl

M5PDL
04-23-2011, 09:50 PM
I have posted 3 pictures onto my webpage of the valves from my amp, please have a look.. www.m5pdl.co.uk

I still cant see the 51 ohm resistors..

This damned things never worked since the day I got it.. I should of just taken it back to the shop !!

Im at a loss to know what to do next..

N4BBQ
04-23-2011, 10:44 PM
I have posted 3 pictures onto my webpage of the valves from my amp, please have a look.. www.m5pdl.co.uk

I still cant see the 51 ohm resistors..

This damned things never worked since the day I got it.. I should of just taken it back to the shop !!

Im at a loss to know what to do next..

You've had a lot of good advice in this thread - it seems you want someone to snap their fingers and fix the problem. Look at this photo, the four resistors in question are in the photo. Two on the left, and two on the right (next to the red inductor). Get your DMM out and measure them (if your model has them) and see what you come up with.

M5PDL
04-24-2011, 08:47 AM
I dont want someone to just snap their fingers and fix the problem for me.. I just want to be sure that I was doing the right thing thats all..

Thanks for the pic of the resistors.. I have been trying to establish their exact location and your picture certainly helped.. Mine does not have these.

I will check each valve and see what output I get with each of them..

N4BBQ
04-24-2011, 11:23 AM
I dont want someone to just snap their fingers and fix the problem for me.. I just want to be sure that I was doing the right thing thats all..

Thanks for the pic of the resistors.. I have been trying to establish their exact location and your picture certainly helped.. Mine does not have these.

I will check each valve and see what output I get with each of them..

Well I'm sorry for my comment; I'm sure its frustrating. Good luck on the search. 811s are good tubes, but they do not like to be driven hard. I've never put more than 60W into my four. And one other fellow made a good comment about testing each tube individually, but I'd not drive more than 15W per tube if it were me testing in that fashion. Just be careful with the B+ while you're in there messing around.

KB3HRO
04-24-2011, 04:55 PM
yep if swr is high between the rig and amp that will back off drive power for sure..not sure of the reasons for it..tune it out? ,check coax feeds? another meter to confirm?? i know, all a pain in the ass..we all know,damn gremlims..now them tubes are lookin a lil smokey,looks like 11mtrs??? just kiddin.im gonna say it again. the clear one is a leaker.and the others look tired,shouldn't be so smokey looks like they got toasty? and should be silver just on the bottoms?.. these 811 tube troubles are like a rash all over the net..send them back they will give you new..

its also worth mentioning because it always seems to pop up in these 811 threads.when replacing 4 811s with 572s you only need 3..im almost positive?

have patience and good luck,you will be a better ham when you fix it, Rick

KM1H
04-24-2011, 05:17 PM
And one other fellow made a good comment about testing each tube individually, but I'd not drive more than 15W per tube if it were me testing in that fashion. Just be careful with the B+ while you're in there messing around.

The amp is rated at 80W drive for 2 reasons, keep the tubes happy as well as the transformer. The Collins 30L1 and Dentron 160-10L (early version) is regularly driven with 100W+ but that was with USA tubes.

Anyway the idea is to establish a baseline. I test tubes individually in most amps and am surprised when i get comments that it cant be done, etc.

Carl

W8JI
04-25-2011, 11:00 AM
I dont want someone to just snap their fingers and fix the problem for me.. I just want to be sure that I was doing the right thing thats all..

Thanks for the pic of the resistors.. I have been trying to establish their exact location and your picture certainly helped.. Mine does not have these.

I will check each valve and see what output I get with each of them..

Then you have the lastest amp with the grid resistors removed and the HV fault clamps added.

About the only thing that can go wrong is bad tubes either from tube manufacturer defect, shipping, or from operator error.

If it is a new amp and you have not melted the anodes, they should just give you an exchange set of tubes. Why screw around with things so much, when you can probably get replacements for free?

M5PDL
04-25-2011, 02:50 PM
I would have to send the whole thing back to the shop and then wait for them to send it back to me.. The cost of shipping would probably be about the same as the cost of 4 replacement tubes..

I'll phone em tomorrow and see what they say..

Thanks for all your help and advice guys.. Much appreciated

MM0IMC
06-01-2011, 04:05 PM
I've been following this thread, how did you get on in the end?

73,

Ian - 2M0ISM.

M5PDL
06-26-2011, 10:31 AM
I now have new tubes for the amp.. I replaced the 811a's with a set of 572B's...

The problem I have now is the Grid Current meter swings right over to the left when I switch the amp on (no reading at all)

I dont seem to be having any luck at all with this amp...

W0UZR
06-26-2011, 02:30 PM
I have an 811 H here. Now what your problem reminds me of is what I have experienced and in what my antenna system situation is from time to time. What does your amplifier tune to in a good dummy load? If you can give it the 60/70 watt drive and then have around 475 on the plate and under 200 ma on the Grid and the watt meter reads 750/800, then there is nothing wrong with your amp.

Now if I turn into an antenna, then I might not have the same results. Not unless my antenna is cut exactly to the frequency I am using it on and it is resonant with good SWR. I can have a SWR of 2.0 on an antenna, and I can't get any power out of the amp or the radio to speak of. And the lower I go down on frequency the lower the SWR is and the power will read better and better. And another antenna will read where I'm putting out too much power even though the SWR reads about the same. And to get to a flatter SWR I will have to go higher in frequency and the SWR and power out will read lower and lower. So is your antenna too long for the frequency you are using it on or is it too short? This has happened to me.

Well, as a general rule, when I have a situation like yours I see everyone copies me well and if they do I call it good ignoring the watt meter. But keep the Grid BELOW 200. I wouldn't say that there is anything wrong with your amp until you tune it into a good dummy load. Then if it reads the same thing, then I would say that there is something wrong.

W0UZR
06-26-2011, 02:42 PM
I now have new tubes for the amp.. I replaced the 811a's with a set of 572B's...

The problem I have now is the Grid Current meter swings right over to the left when I switch the amp on (no reading at all)

I dont seem to be having any luck at all with this amp...Oh Boy!! It looks like you have a bad brand new tube. They should work at least as good as the 811's Send em back explaining the amp doesn't work with them at all and they wiil send you a new set

KB3HRO
06-26-2011, 03:41 PM
well its been a while. did you just get the tubes? and put them in without looking for other damage caused by the beating on the original tubes? check out the w8ji site, maybe 10 mins of your time..meter protection diode?

KB3HRO
06-26-2011, 05:23 PM
ok its been a while since i have visited Toms site. it has changed some and i cant find what i was thinking of. its d16 on the shematic. 1n4007 diode that went bad,most likely..on my amp from the early 90s its near the meters on the board ? tiny little tube, black in color with a silver band on one side.there is only one like it in that area. you should be able to make out the numbers..if bad you will have power on both sides (diodes are directional) but you knew that right? did you get 3 or four of these tubes?

KB3HRO
06-28-2011, 11:35 AM
well looks like uzr has the right answer for you..googled it(grid current negative),took 5 mins. shorted tube..try to isolate by pulling out one at a time..do not forget to ground the top of the tubes when going in and out of there..if you bought 4 you are in luck as it should play well on 3. just take your time..to bad you got rid of your 80b 73 Rick

M5PDL
07-16-2011, 10:13 PM
hiya.
sorry for the delay in replying to you. I took all the tubes out and then put them back 1 at a time and all seemed to be ok.. I hooked it back up to the radio and a dummy load.. Switched everything on and s9 of interference on radio.. switched the amp off and the intereference stopped.. so something aint right there..

M5PDL
07-17-2011, 04:47 PM
And still no more than 400 watts output.

M5PDL
07-17-2011, 04:51 PM
well looks like uzr has the right answer for you..googled it(grid current negative),took 5 mins. shorted tube..try to isolate by pulling out one at a time..do not forget to ground the top of the tubes when going in and out of there..if you bought 4 you are in luck as it should play well on 3. just take your time..to bad you got rid of your 80b 73 Rick


I agree.. I should never have got rid of my old amp.. This new one has been a pain in the backside ever since the day I got it. It's never worked properly and I'm beginning to think that It probably never will..

M5PDL
07-18-2011, 10:26 PM
Spoke to shop I bought the amp from and I'm taking it back to let them sort it out.. So hopefully it will be fixed soon and then I'll know exactly what is/was wrong with it.. I'll update you as soon as I have some answers..
Thanks for all your help and advice guys

MM0IMC
07-29-2011, 03:04 PM
I'm following this one with interest as I'm planning to perhaps buy this model of amp at some point...

KB3HRO
07-29-2011, 03:16 PM
well there is alot of interest here? these troubles are not the norm, well maybe with chinese tubes and heavy handed tuning
...i like the old al 82 myself.

KM1H
07-29-2011, 05:08 PM
I wouldnt waste my money on a new AL-811 of either type. Pick up a used one with bad tubes and otherwise OK and use 572B's. Then make the various published factory mods (call Ameritron for the latest) that correct the initial design problems.

Since the transformer is the same the AL-811 is the better bang for the buck as it can be run hard as long as grid current isnt exceeded which is 150ma with either type tube.
The slight power difference isnt worth the price premium of the 811H.

Something I havent tried with a straight AL-811 is adding another stage of filtering to increase the voltage rating and then going into boost mode on the transformer. Id expect 800W with a ~20% boost and the 572B's would be loafing. This would also require reducing the filament voltage to spec with a resistor.

The creative can think about an external transformer and 6 filter caps resulting in about 2200V, I think the tank circuit would take ithttp://files.qrz.com/static/images/smilies/eek.png

Carl

M5PDL
08-12-2011, 09:46 PM
Hi,
I took the amp back to the shop and foolishly left the 572B's in it.. They said that 1 or more of the 572B's were faulty and I should send them back for a refund. They claim that they put some new 811A's in it and it worked fine. because they couldnt test my original tubes that came with the amp they couldnt replace them (which is a fair enough) so I travelled all the way back to the shop to collect the amp and Ive just tested it and as far as I can tell three of the 572B's are ok. I still couldnt get more than 400 watts out of it though. I have 8 x 811A's in total (the 4 original tubes plus the 4 extra ones I brought) amd Ive tried lots of different combinations of these tubes and still no more than 400 watts.. The amp tunes to an output of 400 watts and no more.. Im at a complete loss of what to try next.. Maybe I need to just accepot that this is all the output power im gonna get and just get on with it..

I do know that I will never buy another thing from Martin Lynche and sons again.

Like I said in a previous post.. This was a very expensive paper weight.. HiHi

Ive learnt a very valuable lesson here..

Thanks for all your help and advice guys.. It was all very much appreciated.

ad: giga-rw