I bought a professional ZHC Chinese transmitter - here's what happened

[OgreVorbis]

Back again for a brief update: The Chinaman told me to record a video of the parameters on the LCD for the engineer. I did. When I was recording, after that I managed to catch the cap C3 exploding. It finally went. Right on video.

So I'm thinking at this point I might use that as ammo to start an alibaba refund process. Don't you think this warrants asking for a full refund? Honestly, I just want a replacement, but knowing how things go...
Or should I just keeping going back and forth with this guy and hope he sends me a replacement board?

[King Croccy]

Tbh I would go for the full refund. I don't know how much you paid but I don't think the build quality is all that compared with what I have seen from other professional transmitters. I have even seen some pirate rigs that were better than this!

Here's a few other things I'm not keen on (from just looking at the pictures)...

1. Cable carrying the forward and reverse voltages dragged right across the main power amplifier. Surely that will cause noise to be induced in the unsheilded cables?! The 300w Telefunken one I have uses screened coax for all connections (forward, reverse, temperature) and they are all routed well away from the high power amplifier.

2. The bias board for the amp looks like it is free floating in mid air and I'm pretty certain its the same one I bought off Ebay a few years back! I'm not saying it's a bad bias circuit but just another clue that the "designer" doesn't know exactly what he's doing.

3. Strange over use of soldermasking on the filter, I doubt the coils are very stable as they've had to blob solder to bridge the connections to each other. The soldermask needs to be removed close to the inductor legs to have a good connection.

4. No screening between any stages, you wouldn't expect that with a "pro" rig.

5. Copper heat spreader looks like its cut in two/three sections?! How will it spread heat if its separate pieces?! Also there are screw threads either side of the mosfet which is telling me its a board that had a different mosfet in that they have recycled?

Get your money back pal

[BriansBrain]

It's a very sad story......... good luck

[radium98]

As i know , something , this guy will ask you to pay also again . beleive me and let see .wish NO >I said aagin rubbish >100 time to fund in some kits and not to get this .I could be wrong...only GOD know.

[radionortheast]

I understand why you went for this, it can be hard to make a transmitter, i’ve only over the past week been able to get a signal generator working only a particular type of pll, I was only able to encode stereo with stereo tool, with an audio buffer, a stereo encoder I made, with resistive mixing has the best sound i’ve ever heard, only go to a few watts, miles better than an all in one chip. Radium dose driver boards might be worth asking him, getting the soldering iron out to built your own stereo encoder.

There are only 2 things I can think of with this only speculative, sounds to me you don’t quite know whats going on with this transmitter, only tests of the individual components different parts, different stages, will reveal whats going on, might be better sending it back for a refund get the defective part fixed.

It should be easy to check continuety with a meter resistence for the enambled issue, Sounds to me like the capacitor on its own couldn’t cope it needed 2 in parallel, i’ve seen capacitors in parallel on transmitters in the past, only low power, might be the make up the value. I stole the idea on my own filter, I had some 30pfs soldered on one side, some of simliar values on top

[OgreVorbis]

I understand why you went for this, it can be hard to make a transmitter, i’ve only over the past week been able to get a signal generator working only a particular type of pll, I was only able to encode stereo with stereo tool, with an audio buffer, a stereo encoder I made, with resistive mixing has the best sound i’ve ever heard, only go to a few watts, miles better than an all in one chip. Radium dose driver boards might be worth asking him, getting the soldering iron out to built your own stereo encoder.

There are only 2 things I can think of with this only speculative, sounds to me you don’t quite know whats going on with this transmitter, only tests of the individual components different parts, different stages, will reveal whats going on, might be better sending it back for a refund get the defective part fixed.

It should be easy to check continuety with a meter resistence for the enambled issue, Sounds to me like the capacitor on its own couldn’t cope it needed 2 in parallel, i’ve seen capacitors in parallel on transmitters in the past, only low power, might be the make up the value. I stole the idea on my own filter, I had some 30pfs soldered on one side, some of simliar values on top

It's not so much that it is too hard to make. I've made my own TXs before. The reason I bought this specifically is cause it's a DDS exciter. I can't find another DDS exciter and I'm totally not able to make one myself. I only have the skills for PLL or single chip design. I don't know how to deal with all this I/Q stuff. That's why I bought it. I wish PCS or somebody would make a DDS exciter board, but nobody does as far as I'm aware.
I have a soundcard that has AES output and I was going to test that functionality with this ZHC transmitter. With what I have now, it's all analog. Given that high EMF environments introduce noise into the audio lines, I was super excited to have pretty much zero noise in my signal.

[jvok]

It should be easy to check continuety with a meter resistence for the enambled issue, Sounds to me like the capacitor on its own couldn’t cope it needed 2 in parallel, i’ve seen capacitors in parallel on transmitters in the past, only low power, might be the make up the value. I stole the idea on my own filter, I had some 30pfs soldered on one side, some of simliar values on top

Issue with checking continuity is if its only a weak connection (not enough enamel removed for example) it will test fine on a continuity buzzer but still get red hot when you try to put 300w through it. I think you're right though the cap is the more likely problem.

Now you know the filter board is just a filter and not part of the match, you could try swapping it for one of the DutchRfShop filter boards. If it was me though I'd be getting a refund

[OgreVorbis]

Issue with checking continuity is if its only a weak connection (not enough enamel removed for example) it will test fine on a continuity buzzer but still get red hot when you try to put 300w through it. I think you're right though the cap is the more likely problem.

Now you know the filter board is just a filter and not part of the match, you could try swapping it for one of the DutchRfShop filter boards. If it was me though I'd be getting a refund

Yeah, the smoke and melting solder was originating right next to the cap C3 (which ended up burning out in the end). It didn't appear to be coming from the coil. On top of that, I ran it for a while, turned off, and quickly felt the first coil; it was body temperature. So it looks like that cap was just not adequate to put up with the voltages there. Potentially a ton of standing waves from all the reflected harmonics (cause as I said - there were a ton coming from the driver board).

Can't even swap in a new filter (at least not easily without cutting PCBs). The problem is the intelligent power AGC must read stuff from the SWR coupler in order to control the driver to give output, and that coupler is located on the same board.

Anyway, here's the news: Right as I was about to press the "get refund button", the guy finally got back to me with news and photos from the engineer. It shows him testing a new transmitter on the bird meter on my frequency with what looks like 290W - not bad. So I suppose I'll give them a few more days. Not sure if he's planning on sending me a whole new TX or what. The talk earlier was to replace the board or module.

[radium98]

My question , how theses brillant guys test there tx in there labs , and give out a warranty and testedok tooo

[radium98]

I am so far from china , maybe it is the most beautiful and number one people in the world , But i assume they could not make an RF transistor in any kind , and if i am wrong convince me and tells me why all the kits to (pro) tx have japenese and other quality transistor inside .They could make software and good exciter and maybe best pcb high quality , but airf no

[rigmo]

The LPF Filter should be adjusted with the nanoVNA, calibrated before adjusting the operating range. The LPF is not properly adjusted. I haven't seen anything crazier so far.