BCT15X service manual ?

merlin

Member
Joined
Jul 3, 2003
Messages
388
Location
South East Idaho
OK, got a Uniden BCT15X scanner and seriously need a service manual for it or at least a schematic. 2 days searching, one site shows documentation, but must register which can't be done. Impossible to decypher the anti robot test.
Help,,please.
 

fxdscon

¯\_(ツ)_/¯
Premium Subscriber
Joined
Jan 15, 2007
Messages
5,201
OK, got a Uniden BCT15X scanner and seriously need a service manual for it or at least a schematic. 2 days searching, one site shows documentation, but must register which can't be done. Impossible to decypher the anti robot test.
Help,,please.
Uniden hasn't made their service manuals/schematics available to the public for many years now.

.
 

merlin

Member
Joined
Jul 3, 2003
Messages
388
Location
South East Idaho
Uniden hasn't made their service manuals/schematics available to the public for many years now.

.
Mods dot dk has it in their stockpile, just have to register to download. Problem I have is can't register for their anti robot test, The hiroglyphic is just not readable for the code.
Thanks
 

merlin

Member
Joined
Jul 3, 2003
Messages
388
Location
South East Idaho
The problem is power and may be a simple diagnosis and fix. Just have to get the cover off the CPU and partly stuck on with potting compound.
 

merlin

Member
Joined
Jul 3, 2003
Messages
388
Location
South East Idaho
OK, that was a quick fix. Probing around with the VOM, I found no 6 volts on the test point. Cheated it with a bench supply and fired up.
Now no cheat, cycle power switch and comes to life.Everything seems to work, save for I haven't heard anything but noise.
 

merlin

Member
Joined
Jul 3, 2003
Messages
388
Location
South East Idaho
Well, Now I know. the 6 volts has a boost chopper/L for the 20 volts. output there is 6 volts so it is the chopper circuit causing the fail.
80% of the work is done, now to fix it.
 

merlin

Member
Joined
Jul 3, 2003
Messages
388
Location
South East Idaho
The 6 volt comes from a 12v to 6v 2A regulator. Pin 4 are a on/off control.



/Ubbe
Thanks, a help, Now About the 20 volt supply. IC21 is the chopper switch, L56 is the inductance. A pinout of IC21 is worth gold.
I have mind on a swap to a switch that is far more robust and usually means a heavy duty inductor.
 

pro92b

Member
Joined
Jun 27, 2002
Messages
1,747
IC21 is a step-up DC-DC converter, not just a MOSFET. It is made by TOKO and was intended to drive up to six white LEDs in series. Schematic as used in the BCT15X is attached.

IC21.gif
 

Ubbe

Member
Joined
Sep 8, 2006
Messages
5,514
Location
Stockholm, Sweden
Check that C258 hasn't gone bad. It's the one that are closest to the corner of the pcb and you can remove it to see if it now works. Do the IC21 run unnormally hot?

/Ubbe
 

merlin

Member
Joined
Jul 3, 2003
Messages
388
Location
South East Idaho
Yea, that is what I am talking about. No, everything in this circuit seems dead other than passing the 6 volts.
The IC looks like it cooked. the diode has obviously been hot but checks good. C258 is nor shorted or leaky but no R/C timing signals on pin 4 or 5. Still dead if I pipe 20 volts to the test point, nothing gets hot. I suppose I can check all the timing components individually.
Do you have a number for IC21 and would TOKO have a datasheet for it on their site, I could compare it with some similar but stronger ICs I have in parts bin. That IC has been so hot the numbers are no longer legible. No craters or cracks. Gonna hunt for my microscope images of it.
Thanks, a big step to fixing this.
 

kruser

Active Member
Premium Subscriber
Joined
Nov 25, 2007
Messages
4,261
Location
West St Louis Cnty, MO
Do you have a number for IC21 and would TOKO have a datasheet for it on their site,
TK11880FTL-G
 

Ubbe

Member
Joined
Sep 8, 2006
Messages
5,514
Location
Stockholm, Sweden
I would just check how much current are drawn when applying an external 20v and see if that matches the specification of the IC. If too much then something are not right at the VCO. If ok then just replace the IC with the same type and check if it gets hot when used and cut power before it is cooked. It could take a lot of trial and error with component values if another IC are used. Or build a beefier design on a seperate perf board and only connect to 6v, ground and 20v. The 12v to 6v regulator can handle up to 2A so the standard Uniden external 12v power adapter would quit before that current are reached, so should be safe to build a more power hungry step up circuit.

/Ubbe
 

merlin

Member
Joined
Jul 3, 2003
Messages
388
Location
South East Idaho
I would just check how much current are drawn when applying an external 20v and see if that matches the specification of the IC. If too much then something are not right at the VCO. If ok then just replace the IC with the same type and check if it gets hot when used and cut power before it is cooked. It could take a lot of trial and error with component values if another IC are used. Or build a beefier design on a seperate perf board and only connect to 6v, ground and 20v. The 12v to 6v regulator can handle up to 2A so the standard Uniden external 12v power adapter would quit before that current are reached, so should be safe to build a more power hungry step up circuit.

/Ubbe
While this was dead and no 6 volt, the regulator got quite warm. After cheating the 6 volt, that solved what was sucking it down to 2 volts.
There was no 20 volts from the converter (IC21) and figured a short in that. The 6 volts is back now and the radio powers up but found I need the 20 volts to receive RF. Now IC21 is dead and after checking the converter circuit, I can just replace this whole circuit. there is enough room for an outboard converter and found one that will work. Coming from china so be a while before getting this thing back together. Meanwhile, I am also adding a headder for the JTAG port.
 

merlin

Member
Joined
Jul 3, 2003
Messages
388
Location
South East Idaho
TK11880FTL-G
Thanks for the number but WOW. This tiny chip can't possibly handle 600 mils. Maybe a very short duty cycle. No matter, found a replacement for the whole circuit, that one good to 2 amps. The 20 volt seems to draw about 180 Ma max. Just enough room to add this in place of the original.
I ordered this from china so a time thing getting this to work, meanwhile, I have a couple 800 Mhz duplexers I am retuning for the ham band, and a DECT6 project on the plate.
 
Last edited:

Ubbe

Member
Joined
Sep 8, 2006
Messages
5,514
Location
Stockholm, Sweden
When you use a different step up converter you have to check that it doesn't create RF interference. I once choosed a good one, I though, to be used in a remote diversity receiver I built and it sent out a smog of RF interference in the whole low-vhf band, that a repeater for the snow plow guys didn't like that sat in the same site.

/Ubbe
 

merlin

Member
Joined
Jul 3, 2003
Messages
388
Location
South East Idaho
They all create some RF from the square wave PWM, why the circuit is buried under a shield. I will just have to accommodate for that.
I can see now that a service manual, schematics, and PC overlays are in that group I call 'unobtanium'. Searched for a datasheet for the CPU and found 2000 pages of useless drivel and no pay dirt. Back to the search.
 
Top