Amptec LA1200 HF Amp made in China

Discussion in 'Amateur Radio Amplifiers' started by N2CG, Nov 3, 2015.

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  1. N2CG

    N2CG Premium Subscriber QRZ Page

    Greetings Amps Group,

    I currently see being offered on eBay (item number 272033879731) a 1000W RF linear amplifier covering 1.8 - 30 MHz using 3 each 4CX250F [Chinese FU-250] ceramic tubes in parallel. There are several picutures of this amp in various stages of assembly and it looks like high quality parts are being used. The price of $1,480 plus $400 shipping from Main Land, China; however I do not see any statement that this amp is FCC type accepted.

    Does anyone have any additional information on this amp?

    73, George N2CG
     

    Attached Files:

  2. W1QJ

    W1QJ Ham Member QRZ Page

    My friend Hsu heads up that company. He is a great fellow. I worked with him in fixing that other Chinese amp that he was in partners with. He has since left that company and started this new venture. I am not a fan of an amp that runs more than 2 two tubes in the final per se, but I'm sure it works out OK with ceramic tubes. My only concern is getting stateside repair service and parts. Although Hsu was very good about sending out parts to us via express delivery from China.
     
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I'd like to see a schematic or at least a block diagram.

    States it's AB1 but requires 40-80W drive, which drastically exceeds the drive requirement of three 4CX250Fs for full power (should be about 10W total for 3 tubes) so I'm assuming it's "swamped input" where most of the drive power is dissipated in a resistor or something. Also no details about its display and metering.

    Since I've used those tubes lots of times in AB1, I'd want to be sure that if B+ fails, Eg2 drops to nothing instantly or drive is removed instantly to keep from frying those two fragile grids. A thermal monitoring system or air pressure switch or something is also very nice to have with such tubes which can go from new to dead in a couple of seconds if the air flow stops while you're transmitting.

    In the photos workmanship looks very nice, and the price including shipping isn't bad.
     
  4. W1QJ

    W1QJ Ham Member QRZ Page

    On the other amp I worked on it had a large film type non inductive resistor on a heat sink that swamps the grid. It presents a good resistive load and probably swamps the grid heavily and keeps things stable. That was an FU-728 tetrode, that required 35 to 50 watts drive get full legal power. More drive and it went over 2KW.
     
  5. KA9JLM

    KA9JLM Ham Member QRZ Page

    That amp looks like it was made to use a different tube originally. FU-728 ?

    Not sure I would buy a amp that has Swingline Staples in its design. :eek:
     
  6. K4DSP

    K4DSP Ham Member QRZ Page

    I have no information regarding the quality or operation of this amp, but I'd be concerned about an amp like this just because of the microcontroller-based control board and the LCD color display. These are the items that often become End-of-Lifed (mfgr's term for 'obsolete') after several years, and finding replacements if they fail will be difficult in the years to come. There's a reason that many of the old Heath, Drake, Dentron, and Henry amps are still used daily despite being over 40 years old - there are replacement parts available for nearly anything that can fail in these amplifiers. But 20 years from now (heck, probably 10 to 15 years from now) you likely won't be able to buy that particular Microchip PIC CPU and you won't be able to buy that LCD display because nobody will be making them - they'll have moved on to something better/faster/cheaper. So even if the amp manufacturer is still in business you may not be able to keep the amplifier on the air if they can't get those parts.

    But I can understand why it is tempting to add a nice color LCD and a microcontroller to the design - in the case of the LA1200 it replaces a least 5 meters (forward and reflected power, plate current, grid current, and input power) and shows status info and other stuff like temperature. No front panel real estate is needed for LEDs and meters and switches to switch between what they measure. And the cost of the display and control board is probably less than the cost of a bunch of meters and switches - have you priced nice analog panel meters lately?

    Still, I'd rather not complicate what is an otherwise fairly simple amplifier design. In an amp that has auto-tune I can see the need for the smarts, but on a manual tune amp it's just more potential obsolete components and another firmware load to keep up with.
     
  7. KM1H

    KM1H Ham Member QRZ Page

    Hsu must of got a great deal on the 26.5V filament tubes which are still fairly plentiful NOS surplus as 4CX250F/7204's in the US.

    Interchangable tube decks as Ameritron does, smart move IMO and saves money when only one HV transformer is needed and are purchased in quantity.

    Carl
     
  8. UNKNOWNLISTERS

    UNKNOWNLISTERS QRZ Member

    We have the bigger brother the HF2015DX it is very well built very happy with this amp, it loafs at the legal limit with only 30 watts, it can do a lot more, and did i say its very well built, why buy the other brands when this amp is just as good or even better built, we have owned alot of amplifiers and for the price and quality you will not be diappointed.
     
    N7ZDR likes this.
  9. AC0TX

    AC0TX Ham Member QRZ Page

    To the maker of this amp:

    You need to have a Web site where schematics can be downloaded.
    We know in case of trouble, WE have to repair this amplifier, but for the technically qualified it is not such a big deal
     
  10. XZ2A

    XZ2A Ham Member QRZ Page

    Re-activating this old post, the company website amptec.cn seems to be no longer active. Does anyone have contact details for Hsu (the owner of the company)? I'm in Laos, and it's very expensive for me to import a USA amplifier - an Amptec amp might be the answer! Thanks.
     

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