Cybernet beta 1000 momentary receive & transmit issue

[MiXiN]

I've got a Cybernet beta 1000 here that will only receive & transmit for about 30 seconds to 1 minute, but only after being switched on & left for a few minutes.

After working on transmit & receive for a matter of seconds to a minute, it then reverts to the symptoms of initial switch on & doesn't receive or transmit at all.

When squelch is defeated it makes the usual noise at all times.

Anyone know where to look please?

[The Collector]

Someone will pipe up with the real answer shortly, but perhaps a capacitor has gone and it's taking a while to "charge up".

Look for any "white fluff" or bulging cap's for starters.

[MiXiN]

Thanks for the reply.

I'll pop the lids off later today & have a close inspection.

[cubwolf]

These are renowned for dry joints around the vco and pll area.
They are normally easy to spot as well.

[ChrisMagpie]

Hairdryer and a can of freeze spray, to heat and cool the different areas of the board, until you find the dry joints
Same board as the baby Radiomobile CB201. I've got three of those, and they've all had dry joints!
Nice when you get them working reliably
When you get it sorted, check out this squelch mod, which is totally worthwhile:
viewtopic.php?t=30803&start=30#p462176

[The Collector]

I bought a couple of those to stop my Petrusse Excalibur 2002 from popping. Just need to take a course in electronics now (and a bravery pill) to suss out where it goes inside "Collectors", "emitters" "Q this and that" and things like that are all gobbledeegook to the likes of me. Not that I use it, but it'd be nice to have one in there just in case.

[MiXiN]

Hairdryer and a can of freeze spray, to heat and cool the different areas of the board, until you find the dry joints
Same board as the baby Radiomobile CB201. I've got three of those, and they've all had dry joints!
Nice when you get them working reliably
When you get it sorted, check out this squelch mod, which is totally worthwhile:
viewtopic.php?t=30803&start=30#p462176

I'll do that squelch mod when I open it up later, so many thanks.

On yours, where did you find the dry joints to repair the faults, and what fault did all yours have mate?

[MiXiN]

These are renowned for dry joints around the vco and pll area.
They are normally easy to spot as well.

I had a good look around the VCO & PLL section but couldn't spot any dry joints. That said, those areas were lacking in solder.

I decided to solder over all joints on the opposite side of the wax covered area, and the rig is now working perfect.

No more waiting a few minutes just for a few seconds of receive or transmit.

Am I right in thinking the area covered in wax just in front of the channel changer is the VCO?

[cubwolf]

Yes.
It seems when they put the wax in it prevented the solder flowing correctly as everyone I have seen has the same issues

[ChrisMagpie]

Well done on the repair!
I actually caused some faults on one of these, by touching up some dodgy looking soldering, and had to do it all again, after cleaning the board with some cleaner and a toothbrush
Nice radios when sorted, though. Top quality Japanese capacitors in them, too
Whilst in the radio, look out for these two "chips" at the front of the board:

R1.JPG

Each "chip" contains seven separate 1K resistors, and they are the dropper resistors for the segments of the LED channel display. They go open circuit, and cause you to lose channel display segments.
Replacements don't seem to be available, but it's easy to replace them with individual resistors.
Here, I am halfway through the repair:

R2.JPG

A bit over-engineered, maybe
Job done:

R3.JPG

There's no way that's going to fail again
I actually think the channel displays are a bit too bright on these. If I ever have to do one of these again, I'm going to use a slightly higher resistance, to tone down the display brightness a bit

Meta tags:
Radiomobile CB201
Cybernet Beta 1000
Cybernet PTBM135AOX

[MiXiN]

Nice post Chris.

I used to have a Radiomobile 201 with a flickering display segment, so your post makes sense.

I'll keep your suggestions memorized for a later date mate.