All good points you make here Alek.
Apart from the el-cheapo design and construction economies made in the entry
level Ameritron AL-811 series amps, the 811A was indeed a good tube, as was
the 572B/160TL; the problem is the Chinese produced clones available in the
marketplace today are sadly not of the same build quality exhibiting the
same kind of ruggedness and long emission life of 811A and 572B Tx tubes of
ye days of old.
Consequently a matched pair or quad set of reputable brand vintage NOS 811A
/ 572B tubes are worth their weight in gold....and highly sought after.
It will be most interesting to see whether or not the RF Parts folk can work
through these tube manufacturing issues with their supplier(s) and someday
stock Chinese made clone tubes with an MTBF equal to or better than these
venerable oldies.
73
Leigh
VK5KLT
-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Alek Petkovic
Sent: Saturday, 24 January 2015 8:04 AM
To: Amplifier Mailing List
Subject: Re: [Amps] 5 Minutes for Ameritron 811H to warm up?
>From memory:
The plastic encapsulated output relay on the 3 holer, totally fused on 4
occasions. The little diode in the bias/metering circuit, 3 times. The
filament voltage is 10% high on both models, on the 240V tap, running on
240V, so the tubes wear out like nobody's business. The plate coupling
capacitor failed once.
Having mains AC, Filament AC, DC, RF and HV all on the same circuit
board is questionable engineering practice and makes it a PITA to
service and all but impossible to insert resistance into the filament
line, to reduce it back to a sensible level.
I agree. The 811 is a wonderful tube but the 811 amps are truly price
built amps.
It is not the tube's fault. It is the marginally rated components, the
stresses placed upon them by the designers, and the cheap charlie
construction that make those amps the POS that they are.
Also, it must be remembered, that most appliance operators have no idea
how an amplifier works or how to run it and look after it. They are
very unkind to amplifiers. Models like the 811 series, have no chance
against these operators. :-)
73, Alek.
VK6APK
On 23/01/2015 9:09 PM, Roger D Johnson wrote:
> What was breaking down? The 811 is a good tube but most hams believe
> the mfrs claims and run them way beyond their ratings.
>
> 73, Roger
>
>
> On 1/23/2015 7:09 AM, Alek Petkovic wrote:
>> You said it in one Jim.
>>
>> If you buy a AL811, you deserve what you get.
>>
>> A guy local to me had two of them. One with three tubes and one with
>> four. They were forever breaking down and he usually brought them
>> around for me to fix.
>>
>> In the end, I reminded him that he earned really good money and that
>> he had a really great station except for his amplifiers and that he
>> should just dump them and get something decent. Thankfully, he did.
>> Dunno what he runs now but I know it ain't the 811 amps.
>>
>> Alek
>> VK6APK
>>
>> On 23/01/2015 7:24 PM, Jim Thomson wrote:
>>> Date: Fri, 23 Jan 2015 13:37:00 +0800
>>> From: Alek Petkovic<vk6apk@bigpond.com>
>>> To: Amplifier Mailing List<amps@contesting.com>
>>> Subject: Re: [Amps] 5 Minutes for Ameritron 811H to warm up?
>>>
>>> Yeah. Well that is strange. Blowed if I know what he means then.
>>>
>>> Thanks
>>> Alek. VK6APK
>>>
>>> ## Buy it for a song..then spend 15 mins to repair it. What takes 5
>>> mins to warm up, the fils...or the B+ ?? I think the xfmr in the 811
has the fil winding built into the plate xfmr. It could be some shorted
winding issue, etc. It could also be a screwed up hv meter.
Jim VE7RF
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