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Old 13th Aug 2019, 7:04 pm   #161
julie_m
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Default Re: More Chinese AM radio kits

What do you expect when you go borrowing words from other languages willy-nilly? Just as English has different names for an animal when it's alive in a field and dead on your plate, so it has picked up different words for "bonding metals using a molten metal filler" depending on the particular subdomain of engineering. "Welding" and "Soldering" are the same word in many languages.
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Old 13th Aug 2019, 10:57 pm   #162
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Default Re: More Chinese AM radio kits

Useful, but only if you already know what a superhet is and how it does it!
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Old 14th Aug 2019, 9:50 am   #163
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Default Re: More Chinese AM radio kits

Thanks, Avid Nerdlinger for your handy tip. As it happens, The P.C.B. is marked with the component values, and the Chinglish assembly instructions given in the original ad on Ebay (but, sadly, not with the kit) give the colour/function of the I.F.T.s and transistors, so I should be well away with those clues.

Herald 1360, what you say is very true. I think, given the available instructions, a beginner would be very lucky to successfully build this kit without some help from a knowlegeable person.
Fortunately, this project is only being done out of of academic curiosity. Tony.
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Old 14th Aug 2019, 10:17 am   #164
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Default Re: More Chinese AM radio kits

I’m not exactly a beginner (just built a working superhet from scratch and a K2) and I’ve built two of these Chinese radios and neither of them worked properly so you’re right

I was hoping to modify one a little bit and try and add a BFO.

On the IFTs I found a chart of Chinese symbols for colours on the web and used that. Appears the RF side of mine both worked but the audio didn’t.
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Old 22nd Aug 2019, 3:23 pm   #165
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I put the kit together over the weekend, and it does not function. The problem is in the audio section (uses the one transformer (driver) configuration). Some real jobs have come in meanwhile, so it has had to be put on the Roundtuit shelf for a day or two.
Further investigations will be made shortly. All currents drawn are within the specified limits. Tony.
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Old 22nd Aug 2019, 4:30 pm   #166
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Default Re: More Chinese AM radio kits

Have you bridged all the test point breaks on the PCB? Is the transformer the right way round?
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Old 22nd Aug 2019, 5:04 pm   #167
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Quote:
Originally Posted by boxdoctor View Post
I put the kit together over the weekend, and it does not function. The problem is in the audio section (uses the one transformer (driver) configuration). Some real jobs have come in meanwhile, so it has had to be put on the Roundtuit shelf for a day or two.
Further investigations will be made shortly. All currents drawn are within the specified limits. Tony.
Had similar fault, radio works but weak audio. Scope shows only one output transistor working but non-working transistor is OK. Output from driver transformer does not look very good, definitely not equal and opposite . Suspect transformer so the whole thing will go into the junk box for when I need I.F. transformers etc.. No big deal, have plenty of LW/MW radios here, fun building apart from lousy circuit board with poor track adhesion.
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Old 27th Jan 2020, 6:08 pm   #168
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In relation to the long-term reliability of the HX 108-2 kit radio, I am happy to report that mine is still working a year after I successfully built it. It would be interesting to know if other members who built this radio also have had a similar experience.
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Old 27th Jan 2020, 7:31 pm   #169
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Default Re: More Chinese AM radio kits

Mine is still working well after 10 months and with the same batteries. Some of my ceramic capacitors were pretty rubbish when tested before building the radio, so replaced from my stock, otherwise no other problems.

Mike
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Old 28th Jan 2020, 4:22 pm   #170
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I had the same experience with the ceramic caps. I didn't use any of the supplied ones.
@bc312: did you make any modifications to the circuit ?
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Old 29th Jan 2020, 12:40 pm   #171
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No mods to the circuit, however given that other members had experienced problems, I tested every component in the kit - especially caps, transistors, IF transformers and audio transformers - all ok apart from said ceramic caps. The radio worked first time and only needed a tweak of the oscillator coil in order to match the dial frequency markings. I suspect that the kit components are probably manufacturers rejects, so some parts may be near ok, whilst others are out of spec. For the money it was worth a punt and perhaps I was lucky.

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Old 10th Feb 2020, 10:45 pm   #172
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Default Re: More Chinese AM radio kits

Dug my HX108-2 out the other day and ran it for a few hours with no problems at all.

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Old 10th Feb 2020, 10:55 pm   #173
Jolly 7
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Thanks. Hopefully the set will stand the test of time over the years. Given the sad and worrying situation in China with electronic production lines starting to be affected, we can only hope that we do not see the last of such interesting and useful kits in spite of their limitations.
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Old 25th Apr 2020, 9:16 am   #174
Neil Purling
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Default Re: More Chinese AM radio kits

In the context of these kits I built the HX108-2 with 2N3904's in the IF strip which tend to be much higher gain. Too much signal going through I think.

The HX-6B would probably benefit from the use of a 2N3904 as V2 (IF), to give as much gain as possible.
I was wondering about if the same transistor is viable as local osc rather than the stock 9018.

I am waiting for some more kits that seem to have become delayed somewhere between the PRC & the UK.

The image is for guidance. This kit is in full working order.
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Old 25th Apr 2020, 5:10 pm   #175
Neil Purling
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Default Re: More Chinese AM radio kits

Stuck a 2N3904 in the KX-168 at BG2 (IF) & re-peaked the cores of B1 & B2. It has made quite a difference & would be well worth doing in Europe where the station density & signal levels aren't so high. Therefore it suggests that the S66, HX-6B and other 6 transistor kits will all benefit from the same mod.
The KX-168 had the proper specified 9018H as BG2. Sometimes you don't even get the transistors with the particular gain suffix.
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Old 31st Aug 2020, 11:50 pm   #176
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Default Re: More Chinese AM radio kits

I finally got round to building the HX207 that's been waiting for me to get round to it (I got a dose of Covid so I'm a captive audience at the moment).

It seems to have "worked first time" apart from a slight niggle with a broken track - probably caused by my cack-handedness. The current drawn by all the stages was about double what they should have been - I'm hampered by not having my full workshop available, just a B&Q multimeter so that might be what's at fault?

I was quite surprised when it burst into life without too much fiddling around. I did substitute the main 100uF cap for a 220uF as the ones that came with the set had quite a poor ESR and I suspect that is what causes a lot of the motorboating and misbehaviour?

My daughter loves it and has taken it to bed with her!

I'd really like to get it tuned up though. At first Five live (909Khz) appeared on the dial at around 1400 with absolute (1215) at around 1600 with an image of Radio leeds 774 appearing in between.

After some (fairly random) fiddling I manage to pull them down closer to where they should be but not great without my signal generator.

Does anyone know what the IF frequency should be?

D
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Old 1st Sep 2020, 8:36 am   #177
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Default Re: More Chinese AM radio kits

IF will almost certainly be 455 kHz. Once you've peaked that, getting the LO cct correct and any basic aerial cct trimming done it should be ok.
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Old 1st Sep 2020, 10:31 am   #178
dominicbeesley
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Thanks ian, now to find a sig gen.
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Old 28th Dec 2020, 10:41 pm   #179
mirceacra
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Default Re: More Chinese AM radio kits

Hello, today i finished my HX-108 - 2, all 223 capacitors was defective and i replaced them, the sensivity is very good but i have some motorboat sound on lower frecvency about 540khz and on 900khz. I replaced c15 capacitor, what else i can do? the bateries is new alkaline .
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Old 9th Feb 2021, 2:29 pm   #180
Neil Purling
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Default Re: More Chinese AM radio kits

The HX-108 is push-pull output. I was wondering if substituting the driver and output transformers for a LT400 and LT700 would help the horrible sound quality as they have larger cores. Even speaker substitution did little to fill out the awfully 'tinny' sound.

Given the innaccuracy of the scale 540Khz is close to the IF and 900Khz is the 2nd harmonic of the IF.
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