BTECH UV-2501 220 Power ON Issues

Hi All!

I got a barely used 3yr old BTECH 2501 25W mobile that seems to need to be plugged into power for an hour before powering up correctly. I have tried using the included cigarette plug in my truck, a 12.3V 8A power supply, and a 13.8V 20A power supply. After staying plugged in for like 15mins it comes on and off in sputters and clicking until enough time has passed and it runs as normal as long as it’s attached to power.

I have verified that power comes into the box and the fuses are fine. Do mobile units rely on a capacitor to function? Is there a fuse/switch that only works when warm??

Just very strange to me and needing an answer to satisfy my curiosity!



I can’t go much in detail since I’m not familiar with BTECH kit, but I’d be inclined to test/assess the DC regulator.

If you can borrow a high current variable and supply the right range of voltages (13.8V input is the nominal, fused direct connection to the battery would see around 11-15V whilst the radio is getting a suitable input voltage I’d guess. If it’s demonstrating the same sort of characteristics across the board, it’s pretty certainly regulation fault territory - I say regulation because it could be an ancillary component that’s part of setting the regulation range could be iffy.

But the stuttering points towards momentary and inconsistent regulated outputs and shutdowns or output cutout, so it’s probably sounding like a switch mode PSU if you slowed it’s switching to an audible range rate.

if you determine what outputs it normally generates (there’s bound to be a 5v/3v, possibly 1.8v depending on the internal logic at play, as well as a few higher voltages to the PA stages (higher current)), and directly supply either the correct regulate voltage that should appear directly as a bypass (it may output one supply with further changes later in circuitry) you should be able to conclude if it’s regulator or a more logic related matter (there’s some quite highly integrated complex logic mimicking some expensive DSP type logic chips within the ceramic or polymer lump.

If a basic regulator test or reg bypass fails to give clues or change, you’re looking at logic and that’s a hellish road to tread to diagnose without docs and service info.

In fact, if it’s looking seriously like logic investigation is in order, there’s a slim hope that solder reworking could correct a poor connection or dry joint cause at the logic end, since there’s almost certainly some logic loop back to regulation.

But when it comes to replacing obscure, nearly unobtainable logic to replace a component, it’s going to rapidly become a costly note viable venture beyond (if successful in fixing) the challenge.

It’s probably the reason, the fault, it got sidelined in the first place…

If it were a Baofeng, I’d not waste time beyond a rudimentary test and maybe reworking some parts as they literally aren’t viable to fix (you can still use a Duff one as a Fishguard donor up to a point). But that maybe worth trying to save as it maybe a pricey set to get new.

Well, it’s food for thought - maybe someone who’s got BTECH servicing experience can shed real light on the fault.

I had a similar fault on an aged IC-251 multimode that would randomly draw max current on power up for 5 mins like it had jumped into Full power TX, but no output. It turned out to be a supply instability to the logic, so it tried to put out an empty carrier in bypass of all front panel settings (it had real rotaries not encoders on most dials), but no output because the PLL was in an unlocked state ‘miscode’ state. It took some digging and a really good factory service manual to resolve (thankfully I was working at an LMR service center and had no shortage of solid test gear at the time).

The big difference was whilst there were some complex (relative to the 80s radio world) logic, a lot of it’s guts were fairly off the shelf TTL and non-TTL and common CMOS stuff.

Still occasionally pulls the odd random intermittent stunts, but given it’s age and sentiment (it was a fully itemised Mutek front-end modded, and aligned to LMR grade tolerances example setup by a real old school engineer and Ham who literally saw things through to the bitter end or absolutely awesome success) and the association with it’s only other owner which means it survives until it dies from old-age (being 40-something and many NFD and other contest veteran, it deserves to be a bit temperamental and mischievous).

Anyway, good luck but don’t get drawn into a wasted weeks of eventually pointless attempts to fix if it’s an internal logic flaw.

Wow! Thanks for all the info, but you are way beyond my capabilities :stuck_out_tongue:

I was just confused by the fact that all is fine if it is connected to any of my car/12.3/13.8 power sources for a long enough time…

But you are right, it’s just a Baofeng and I will probably just buy another one.

It might make a decent standby home system

Thanks again!


Well, my Baofeng thoughts were actually reflecting on if it was one, i’d not invest too much time on it - I’m not actually sure what that set translates to under the skin (there are so many rebranded sets these days it’s hard to know). But as you say, in a way a bit like waiting for a valve receiver to ‘warm up’, when that set eventually settles down, it’s usable as a monitor and maybe an emergency ‘break glass when all goes pear-shaped’ fall back TxCr.

I’ve lost so many hours trying to make mostly pointless external logic bypasses and trying to sniff out the underlying logic in ‘black box’ chips that i’ve learnt the hard way, sometimes it just aint worth the hassle to tame the curiosity - especially when you’re no wiser.

So there is likely some crazy broken logic with nothing to do with temp? (Which with modern electronics makes more sense…)


Well, i can only (as an example) point out that some black box MCU based control logic in some radios have a looped logic feed that alters the regulator, via something akin to switching a set of matrixed ancillary components (which most regs use some ancillaries to set their regulation) to enable power saving and suchlike at source and use an analog input back at the MCU-element to measure the response - in such a circuit, all it needs is a foul-up on the MCU-logic element that watchdogs what part of the matrix is active and you can find your reg chopping between output and no output much like a switch mode power supply. End result, you get a varing duty cycle output of near zero output and nearly full (about 90%) of the correct DC output and if it happens harshly out of control, you could see something like you experienced, or as i have experienced, 100% loss of regulation and way too many voltage wipe out a 1.8v irreplacable ‘black box’ DSP.

I’m not even suggest it’s anything remotely that obscure or complex, but it’s one of many horror stories that modern ‘computer logic’ controlled equipment has been known to employ as a power management on the cheap.

In my experience, it could be an overheating regulator - but usually your sense of touch and language usually reserved for banging head when working under a vehicle or shifting seized sheared nuts usually results in. I’ve been there a few times more than i would care to admit to (both burns from regulators and the vehicle analogy in practise).

All i can say is, if curiosity gets the better of you - it could be as simple as a regulator swap, or a faulty ancillary component causing the regulation to be unstable (but not dangerously so), or it could be way more complex in a way you didn’t think was possible (my reaction the first time i encountered an MCU governed feedback loop to a common or garden regulator).

But since you’ll probably never use it on air now, i’ll just remind you that since you’re probably not a certified technician, you’ll kiss goodbye to it’s LMR type approval by even opening up the casing, let alone tinkering with the guts. From a ham radio point of view, now i’ve looked up the unit, it probably wouldn’t make a bad starter dual bander given it has an accessible VFO mode that can be locked out into channel-ised operation as usually used in LMR, but i certainly wouldn’t use it on air (at 25w) without doing some testing with some serious analyser kit. I know i mention in some posts that the fact some ham radio suitable VFO controlled kit has similarity or the same base or just a different degree of lockout on the control software on-board, especially those types of multi-market cros-target Chinese sets, but it’s underpinning ‘archtecture’ isn’t any guarantee it’s as pure in terms of spurious TX emission and it’s out of band harmonic purity is as in as tight tolerence as a unit built and tested for LMR market only. Some ‘brands’ actually sell their LMR QC failures (the ones that didn’t meet type approval narrow tolerance margins) into the hobby radio market and it’s not just the many branded OEM chinese stuff either - the LMR service centre i worked at, one of their revenue sources was shipping out UK market TA failures to places like India and other markets that didn’t really care about EMC conformity or RF purity and just bought the cheapest stuff they could import on mass - i kept well away from that side of the firm.

Wow, there’s a lot I didn’t know about the world commo market :blush:



Well, i guess you have to be there or know people involved to kind of be enlightened to stuff like that.

If i hadn’t got involved with the LMR market out of necessity, because i was developing some (then) early digital and hybrid tech for existing analogue equipment and repeaters, i’d probably never got past reading the RA/OFCOM and other countries legislative documents on LMR.

As much as it’s a chapter i only reflect on for the achievement really, as i did complete the project but it got sidelined for a then more cost effective commercial alternative involving integrated equipment, all that time in the workshop with access to all the service data etc, wisdom of time served engineers (including some who were hams and had other radio feathers in their caps) and eventually you just took it in and curiosity got the better of you. Having an example of each set they serviced, each set still being sold, and some old legacies i was more familar with, to hand as test beds and for reference, sort of was a bit of high pressured super concentrated nitrous oxide to the curiosity you could say.