2017-04-17
This is the story about a BEKO HLV-1500 PA for 144 MHz and its performance and communication with BEKO.
In February 2017 I bought a BEKO HLV-1500 PA from Hannu, SM5KWU. The reason why Hannu wanted to sell the PA was that he found it to fragile compared to a tube PA. It had also been at BEKO for repair due to the lack of output power, probably because of the output relay Hannu told me even if the PA has a protection circuit.
So before I applied mains power and keyed the amplifier I decided to do some initial inspection. I could easily tell that the PA had been disassembled a number of times because when removing the screws many of the threads had been damaged. My first focus was the output relay which is a TOHTSU CX-531N. The datasheet reveals that this relay is rated for 200 W at 144 MHz. This is only 13% of the rated output power of the PA. What is also worrying is that the isolation, when running 1,5 kW, may be a lot less than 65 dB thus a preamp can be damaged especially when the SWR may be less than perfect.
TOHTSU CX-531N RF properties. Source: TOHTSU datasheet.
View of the output relay the BEKO HLV-1500 - TOHTSU CX-531N.
So I decided to write BEKO and find out if this was the original design or something else.
Copy of my e-mail, entered in BEKO webform, to BEKO.
BEKO's e-mail to me.
I am flabbergasted - in more than one way!
So using an output relay 7½ times above its rating is intentional. Even if using a sequencer this is a big problem.
Well, am I a less gifted than the average ham? I don't think so given my university degree in electrical engineering, then five years as senior development engineer at the Motorola lab in Copenhagen, and two other university degrees in business management.
So to operate a BEKO PA you have to be skilled way above average.
Keep in mind that the PA had been at BEKO for repair.
Finally, if you have such a problem with communication maybe you shouldn't be in the communications industry.
I also decided to write the relay manufacturer TOHTSU about the specification of the relay.
My e-mail to TOHTSU.
TOHTSU's email to me.
Wow, even the manufacturer does not suggest to use the CX-531N at its rated power. Of cause TOHTSU would like to sell more expensive relays but still the current use by BEKO is then 10 to 15 times above what the manufacturer suggests.
On the other hand perhaps BEKO means that also TOHTSU is at the same competence level as I am.
For a PA in this price range I had not expected to find a heat sink hanging by the legs of a transistor. During transport this can easily break off and short circuit something. The ribbon connectors have been glued probably to prevent them from coming out/falling off during transport. Also had I not expected to find a fan glued with silicone rubber to the chassis. In my view this PA looks like a late prototype. Anyway, below are some pictures so you can decide yourself.
Inside view of the BEKO HLV-1500.
View of the hanging heat sink in the BEKO HLV-1500.
View of the fan attached using silicon rubber.
View of the control board in the BEKO HLV-1500.
View of the RF PCBs in the HLV-1500.
End of document