[Amps] What Old Amp to Buy?

[Carl]

The DTR-2000L doesnt even meter grid current of the 8877 and there is no 
tube fault circuitry.
Mods exist.

Early models used a muffin fan to cool which were later changed to a real 
blower. Stock amps will barely do 1400W due to low B+ and there is no tuned 
input network. Built during the days of 1000W Input on CW and 2000W PEP 
Input on SSB.

The octal based time delay relay is becoming expensive and scarce so more 
mods are needed.

Other than that it works well; Ive had one sitting on a shelf mostly doing 
nothing for 25 years other than an occassional run as an AM linear and to 
keep the filter caps formed in case I suddenly need it as a backup. It is 
completely stock with original 8877 but at 20-25W of drive the grid is safe 
from mistuning.

Dont laugh too hard but a Clipperton L or Clipperton QRO can be turned into 
an excellent amp with a little work. Runs 4 572B's and with that work even 
Chinese tubes run cool and stable. Im finishing one up now that runs 
1100-1200W out  with 100W drive, 160-10 with a new set of direct from China 
tubes.
They come with 3 input circuits
1. None
2. So-So tuned input
3. Better tuned input also used in the QRO, none are adjustable so some SS 
exciters require an external/built-in ATU or an all new input board.
Outputs differ a bit but none work as is on 12 or 17M or both. The Ameriton 
plate choke takes care of that.

An Alpha 76 CA or PA is a fine amp if it comes with excellent tubes which 
are three 8874's. Drive it light to 1200-1300W and they will last a long 
time. Not a WARC amp without mods. The 2 tube 76 version is straining to 
make 1200W which is why I dont suggest the Alpha 78 either or the earlier 
274/374 2 tubers.
None have grid protection so always watch the meter.

If money is tight an AL-80B will do about 800W on 160-10. The AL-80A and 
SB-1000 clone is a bit light on the transformer and a few other areas. The 
LK-450 is a rugged single 3-500 ampas a are a few lesser known models that 
quickly came and went.

The B&W PT-2500A is another low production amp that easily does 1500W with a 
pair of 3-500Z's, early parasitic and low band arcing problems were fixed 
but serial # before about 35 are suspect as to being upgraded. Under 300 
total were built in the US and a small earlier run as the Viewstar 2500A 
fron Canada. Viewstar made a few other models that were seldom seen in the 
US.

Carl
KM1H



----- Original Message ----- 
From: <n8de at thepoint.net>
To: "Pete Smith N4ZR" <n4zr at contesting.com>
Cc: <Amps at contesting.com>
Sent: Tuesday, March 12, 2013 7:40 AM
Subject: Re: [Amps] What Old Amp to Buy?


> Pete,
>
> If you can find a Dentron DTR-2000L in good condition .. or even a 
> Clipperton-L .. they make good 160m amps .. as long as you don't run  RTTY 
> there.
>
> Some guys on here will put those amps down, but, for the usual 'used' 
> price, they are a bargain.
>
> Oh ... of you find a DTR-2000L that has NOT been retrofit to some  other 
> tube, and you decide NOT to buy it, CALL ME, as I am interested!
>
> 73
> Don
> N8DE
>
> Quoting Pete Smith N4ZR <n4zr at contesting.com>:
>
>> With Dayton 2 months away, I'm pondering whether to try to buy an
>> amplifier in the flea market, in order to add 160M QRO to my
>> repertoire.  If you were looking, what would you be looking for?  Don't
>> have bags of money, and am very happy with my SB-220, so maybe I should
>> leave well-enough alone?
>>
>> What would you do?
>>
>> -- 
>>
>> 73, Pete N4ZR
>> Check out the Reverse Beacon Network at
>> http://reversebeacon.net,
>> blog at reversebeacon.blogspot.com.
>> For spots, please go to your favorite
>> ARC V6 or VE7CC DX cluster node.
>>
>> _______________________________________________
>> Amps mailing list
>> Amps at contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>
>
>
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 10.0.1430 / Virus Database: 2641/5664 - Release Date: 03/11/13
>