Bearcat BC-350

[brfischer1]

I have an old Electra Bearcat BC-350. The display is stuck at 00. When I press a key, it shows some digits in the alphanumeric section (not very bright). It must be a problem with the digital module. Upon opening the unit, I discovered several proprietary integrated circuits, in addition to the 6504. Does anyone have any repair suggestions, or the service manual?

 

[trimmerj]

Shotgun the Electrolytics

 

[brfischer1]

Thanks trimmerj, I'll check the electrolytic capacitors. But there's another important piece of information. Previously, when the scanner would freeze, I would flex the processor board and they would work again. Currently, this no longer works. I've already completely resoldered this board and it didn't solve the problem. If there's no other solution, I'll compare the various schematic diagrams of other Unidem scanners and see if I can infer how the analog control works. Then I can design a new digital display and keyboard control using the ESP32. I believe this will be a way to solve the problem. Because without the schematic of this model, the solution will be very difficult. Not to mention that there are three proprietary ICs on the logic board, in addition to the 6504 processor.

 

[wtp]

my wife did this for the ones that died
we have two entertainment centers and i got a shelf !
that is for the dead radios that are in good enough shape for showing.
the background is the motherboard from a zaxon game, and that one worked when i put it in there.
my pro2001 is on its way to the 'center'.
the only other thing i can share is the manual, and it does not have a reset or anything.

RigPix Database - Bearcat/Uniden - BC-350A

 

[I_Am_Infinite]

Thanks trimmerj, I'll check the electrolytic capacitors. But there's another important piece of information. Previously, when the scanner would freeze, I would flex the processor board and they would work again. Currently, this no longer works. I've already completely resoldered this board and it didn't solve the problem. If there's no other solution, I'll compare the various schematic diagrams of other Unidem scanners and see if I can infer how the analog control works. Then I can design a new digital display and keyboard control using the ESP32. I believe this will be a way to solve the problem. Because without the schematic of this model, the solution will be very difficult. Not to mention that there are three proprietary ICs on the logic board, in addition to the 6504 processor.

@Ubbe must not have this scanner because he knows everything about scanners and circuits etc. So he might know even of he dont have it, u can try to dm him cudnt hurt.

 

[pro92b]

The Electra Bearcat 350 was made in 1982 before Uniden bought Electra. The BC350A is a completely different unit.

 

[Ubbe]

I have an old Electra Bearcat BC-350.

So it is the Electra Bearcat 350, the vintage one.

Previously, when the scanner would freeze, I would flex the processor board and they would work again. Currently, this no longer works.

That's no good, a mechanical failure. Google says it is mostly the 6504 CPU that fails. "Processor Issues: Users have noted that the BC350 often suffers from processor failures or firmware bugs, causing it to lock up, display blank screens, or show random characters."
When flexing the board it could be the internal of a component that flex so resoldering will not help and the faulty component must be found. One way could be to heat up components using a hairdryer or cool them down using freeze spray. Anything that makes the internals of components to move a little. I could be using double layer circuit boards, as it uses those CPU 6504 components, and it's a hidden copper layer that are broken inside the circuit board. Then a schematics are needed to try and ohm measure between different points but it seems there's none to be found on the internet.
When it's a double layer circuit board it should have rivets going thru the circuit board to connect to that inner layer. The Realistic Pro2004 had that rivet issues in some scanners that could be solved be soldering on those rivets to make them connect again to the foil.
There's some help found in a Wiki at BC300 - The RadioReference Wiki

/Ubbe

 

[brfischer1]

my wife did this for the ones that died
we have two entertainment centers and i got a shelf !
that is for the dead radios that are in good enough shape for showing.
the background is the motherboard from a zaxon game, and that one worked when i put it in there.
my pro2001 is on its way to the 'center'.
the only other thing i can share is the manual, and it does not have a reset or anything.

RigPix Database - Bearcat/Uniden - BC-350A

Thanks for the tip, but the BC-350A is very different from the BC-350; I believe it's about 10 years newer. It has a proprietary IC that replaces about 4 other proprietary ICs from the old 350. As for the shelf of dead equipment, I'm fighting to keep my 350 from going there. Although sometimes I manage to resurrect some. The last one was a Kim-1 board computer.

 

[brfischer1]

So it is the Electra Bearcat 350, the vintage one.

That's no good, a mechanical failure. Google says it is mostly the 6504 CPU that fails. "Processor Issues: Users have noted that the BC350 often suffers from processor failures or firmware bugs, causing it to lock up, display blank screens, or show random characters."
When flexing the board it could be the internal of a component that flex so resoldering will not help and the faulty component must be found. One way could be to heat up components using a hairdryer or cool them down using freeze spray. Anything that makes the internals of components to move a little. I could be using double layer circuit boards, as it uses those CPU 6504 components, and it's a hidden copper layer that are broken inside the circuit board. Then a schematics are needed to try and ohm measure between different points but it seems there's none to be found on the internet.
When it's a double layer circuit board it should have rivets going thru the circuit board to connect to that inner layer. The Realistic Pro2004 had that rivet issues in some scanners that could be solved be soldering on those rivets to make them connect again to the foil.
There's some help found in a Wiki at BC300 - The RadioReference Wiki

/Ubbe

@Ubbe, I tried heating the logic board, and in another test I also put it in the freezer, but it didn't work. I don't believe it's a firmware failure, as it has two processors and circuits from Rockwell, made for Electra. So these would be ROMs written during the chip manufacturing process, which would only lose data if the chip were defective. Unlike current BIOS, there is no way to rewrite them.
The logic board has a sub-board interconnected by a wire strip, where the ER-3400 GI8133 HHA EEPROM, from General Instrument, is located, with 4kbits, arranged in the form of 1k Nibles. This EEPROM is what allows saving the frequencies and their alphanumeric description. Interestingly, in addition to the 6505 microprocessor, there is another microprocessor, the ND58-701 R14A9-11 8133 from Rockwell, which is a single-chip microcomputer with CPU, RAM, and ROM programmed at the factory (making its replacement practically impossible). This chip probably interfaces between the EEPROM memory and the display. Another interesting fact is that the ND58 has P-MOS technology and works with negative logic. Level 1 is close to 0V and level 0 is close to -15V. This prevents the use of a conventional logic state analyzer. The logic board also has the ND58-601 in its 52-pin version. Another microcontroller with internal ROM, possibly used to write to the display and read the keyboard.
Since I don't have the schematic diagram of the scanner, I will try to replace this entire part with an ESP-32. I only have to decipher the interface with the VCO. Below I am attaching two photos of this logic board. Another observation is that the entire project is riddled with factory corrections, using jumpers and components soldered on top of each other. This indicates that the project had to be corrected many times. I saw somewhere on the internet that this is the worst scanner ever produced by Electra. It even has a pair of resistors soldered onto a diode, causing the diode's temperature to reach 94 degrees Celsius (measured with a thermal camera).

 

[Ubbe]

I have extremely bad experience from that grey flat cable type from the 70's, that uses solid wires that breaks off as soon as the ribbon cable flex a little. Look for breaks in the wires, also inside the plastic, and solder an external wire between points that do not measure to have contact from one end of the ribbon cable to the other.

If possible replace that ribbon cable with another more flexible one or take the long route and use single wires.

/Ubbe

 

[brfischer1]

@Ubbe thanks for the tip about the flat cable, the cable connecting the digital module to the memory module did indeed break in some places, I'll have to resolder it. I focused on the diodes and resistors of the -31V power supply because there was a hot spot on that line. Since this spot didn't disappear when I disconnected the display cable (the display uses VFD - Vacuum Fluorescent Display technology) and since the digital module didn't use -31V, I focused on the memory module. And indeed, the EAROM ER-3400 had a short on the -31V line. I removed the memory and the display started scanning, although it always stops at the same number, even when I enter a different one. I believe this is because the frequency must be stored in the memory. I've already ordered the memory from AliExpress. Thanks to everyone in the group who helped me. Below is a image of the scanner working, but still without the memory.

 

[JASII]

Delete.