UNIT 399

MEDELLIN COLOMBIA

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UNDERSTANDING AND MODIFYING

THE UNIDEN PB-010 CHASSIS

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The PB-010 chassis was one of the three “export” radios manufactured by Uniden and is, in my opinion, the best. The circuit design (circa 1981) is so good that it has been copied and cloned by other manufacturers and is still used on radios being sold today. Unfortunately, these manufacturers have chosen to cost-reduce the design by using lower quality parts, as well as changing the circuitry whenever possible to make it cheaper to produce. These "clones" drift like a boat, and their audio sucks. The PB-010s are rock stable, and have excellent audio on am, fm,  and ssb. This is why they're so coveted by their owners.
 
The PB-010 was marketed as the Cobra 148GTL-Dx Mk II, and the Superstar 360fm. It uses the Motorola MC145106 Pll chip, which (with modification) allows the installation of a 5kc jump switch, so the user can get the “zero” channels (i.e. 27.405 jump to  27.410) over its entire frequency range. There are 2 variations of the PB-010 board: The PB-010AA, and the PB-010AB. Only a few hundred of the AA boards were produced. The board layouts differ slightly, but circuit-wise they are the same

 

Had the CB boom not died out in the late 70s, I think that the PB-010 would have been the basis for the next Uniden CB series after the GTL/LTD line, but without the extended freq range or FM.  Probably would have included a new Cobra base radio too. 

 

Unfortunately for us, it never happened.  

 

I have several PB-010 rigs.  My son is a diehard CBer, as are many of his friends. So, I decided to build a specially modified 360fm just for him. While working on this project, I worked up many new mods for this chassis (like the 5kc jump switch). The end result is a radio that performed better than my wildest expectations.

 

This site is a compilation of the mods and changes I developed while building the new radio.

 

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This is the radio I built for my son. I rebadged it as a PEP BOYS "Burrito-DX, to give him a radio that no one else has or can get. A little one-upsmanship, I suppose. I designed the custom faceplate, mike decal, and meter face, and had them made by a seller on Ebay. I've had several comments that the radio looks OEM. My son loves it, and that's the most important thing.

Most of the modifications shown on this site will not be found elsewhere on the net. However, I have included common mods (like the +10kc jump, Roger Beep on/off, etc.) to make this site the “go to” place for anything pertaining to PB-010 rigs.


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WARNING !!


This site is written for the experienced technician. If you do not know
what you’re doing, and you screw your radio up.

DON’T BLAME ME !!!

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A LITTLE BIT OF HISTORY

The UNIDEN PC-879 “export” chassis debuted in mid-1981. It was marketed as the Cobra 148GTL-Dx. Appearance-wise, it looks very much like the Cobra 148GTL (side mike). However, the controls on the Dx differ in that the mode switch adds CW and FM, the clarifier is now a dual control with coarse and fine tuning, and a bandswitch allows the switching in/out of 80 additional channels. The Brite/Dim switch on the 148 is replaced by a CH9 switch (???) on the Dx model.

 

It is a single final 5 watt radio, with provision for a 2nd final. The receiver is identical to the 148GTL, except that the coupling coils are changed to allow a wider receive range. As is the case with all UNIDEN radios, it has excellent frequency stability in all modes.

 

I have often wondered why UNIDEN chose to produce this rig. It was completely illegal to sell or operate in the US due to its extended frequency range and the added FM mode. In any case, Uniden built this radio, and along with the Grant-Dx and President Jackson export models, they flew off the shelves as fast as the distributors could get them. Uniden then redesigned the PLL section in the GTL-Dx, going from the MB8719 chip to the MC145106, which allowed an almost 300 channel frequency range. This is the PB-010 chassis and was marketed as the 148GTL-Dx Mark II and the Superstar 360fm. The PB-010 was the penultimate export radio built by UNIDEN.

 

Shortly after the PB-010 chassis appeared, the FCC began applying pressure on UNIDEN to cease production of these “export” models. The Commission implied that UNIDEN would have a VERY difficult time getting any of their regular cb line type-accepted if export production continued. The last several hundred UNIDEN exports were shipped in plain white boxes. They had no serial numbers, ID plates, or
brand names on the front panel. The name “Jackson” was on some, but not all, of those models. 

 

The damage was done, however, as other marketers commissioned different manufacturers to build “clones” of the UNIDEN sets. The first of these, the Galaxy 2100 was a somewhat decent radio, but the build quality was not even close to UNIDEN standards. It only got worse from there.
 

Today, many of the radios on the market are still clones of this 1980s design. The cutting edge exports are almost all out of China now, and getting info on them (service manuals, schematics, programming, etc.) is like pulling teeth. 

 

The PB-010 is, in my mind, the best export radio ever produced. People who own them are very reluctant to sell. If you do find one in good condition, be prepared to pay dearly
 

    

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GETTING STARTED

Your radio must be operational. Do not work on it without proper test equipment, dummy load, factory service manual and schematic (there is no Sams for this chassis). Mark any changes you make on the schematic for future reference. You can download the 148GTL-DX service manual here. This link is connected to the CB Tricks website. The Service manual is missing some pages which are accessible elsewhere on the site.

 

If the radio you have has any of the limiters removed, replace them. If it has a frequency expansion or a “swing kit”  installed, remove it. In other words ... start out with a stock radio.

 

The following basic modifications/changes are very important (especially the installation of Bergquist insulators), and should be done to any PB-010 chassis rig to eliminate shortcomings and improve overall performance. 

 

The important thing to remember is that PB-010 rigs are getting harder to find. A rig in mint condition will set you back a pretty penny ... IF you can get the owner to part with it. So, protect your investment. Some of the following mods may seem trivial, but they will help make your PB-010 perform at 100%+ for a long time.

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BASIC MODS

 

The first thing to do is to replace all of the thick white ceramic insulators from between the power transistors  and the heat sinks. These insulators were used as replacements for mica insulators because the exhibit better thermal conductivity and their thickness (0.5mm to 1.5mm) reduces capacitive coupling between the device and the chassis. The drawbacks are that they are stiff, crack easily, and require the use of heat sink compound which is messy. Both the insulators and the compound contain berrillium which is highly toxic. Replace these insulators with Bergquist SIL-PADS. They are flexible, exhibit superior thermal conductivity, handle high voltages, and are virtually puncture-resistant. They do not require the use of heat sink compound. 
 

I prefer to use Bergquist type 800 insulating material. This is available in 12”x12” sheets, and can be cut to fit any transistor or tabbed IC. It has double-sided adhesive which eliminates the need for any mounting hardware. AVAILABLE from DIGI-KEY.

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Replace all of the electrolytic capacitors. These radios are over 30 years old, and the stock caps are well beyond their rated life. Use high quality capacitors and not Chinese Junk !! When replacing the tantalum capacitors, KEMET and MURATA caps are suggested brands.

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Bridge a piece of buss wire across C236, C237, C238, C239, and C271. These caps are connnected between the main board ground plane and the chassis mounting points. Their only function is permit installation of the transceiver in a vehicle with a positive ground electrical system. Also bridge a piece of buss wire across C508 (connected between the negative terminal on the DC power jack and the chassis).
 
Connecting the chassis to circuit ground will improve shielding and reduce receive noise.

 

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Remove L503 and L504 inductors, and replace them with #14 insulated wire. The holes in the circuit board will have to be enlarged. Do this by hand NOT with an electric drill. Remove C508 (.01uf across the dc power jack) and replace it with a 220pf NPO. Change C227 to 5000uf/35V and C228 to 3300uf/35v. The inductors are there to remove any stray rf on the dc power lines, but the 24ga wire in these coils can become current restrictive when the radio is modified for higher output. The 220pf NPO will shunt any rf on the power lines to ground, and the big electrolytics will clean up any other noise on the DC input.

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 Replace VR5, 6, 10, 11, 12, 13, and 14 with Cermet (or equiv.) multi-turn PC mount variable resistors of the same values. This will permit more accurate setting of the FM deviation, transmit frequency, driver & final bias, SSB ALC, AM deadkey, and AM AMC. These resistors are available from DIGI-KEY,  MOUSER, and other suppliers.  

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Replace D1, D2, D21, and D22 with 1N6263 schottky diodes. This will improve receive sensitivity appreciably. A lot of folks suggest replacing TR17 (2SC1674L) with a 2SC2999 transistor. I think a better solution is to replace TR17 with a 2SC1730L. This will provide a bit more sensitivity, and a slight improvement in noise factor (BUT ...probably will not audible to the average listener.)

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Replace the 2SC2312 RF final transistor with a 2SC1307. The 2312 has a max collector current of 6 amps, while the 1307 maxes out at 8 amps. This will provide the additional headroom needed to
accommodate the speech clipper and high power mods shown later.

 

note: I know that 2SC1307 transistors are hard to find, and expensive when you do find them. However, I feel that it is absolutely necessary to have the highest available power output potential.

 

 

******************************************************************************************************************************* This next modification is optional as it eliminates the SWR function from the radio

An SWR meter in a 5 watt CB radio is worthless. It is not very accurate. The SWR sampling circuit siphons off a small bit of the output power, and we need every milliwatt we can get. Right?? If it is removed, the S-RF/SWR/SWR CAL switch and the SWR cal control can be used for something more worthwhile. Besides, if you run a linear, are you going to use the SWR feature to measure your linear’s input impedance ???

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Remove the wire connected between the circuit board and the center pin of the SO-239 antenna connector. Then remove the SWR board from the main board. Remove R255 and R256 from the main board. No replacement. 

 

Desolder the blue and the brown wires from the s-rf/swr/swr cal switch. Slide a piece of heat shrink tubing over one of the wires, and solder the two wires together. Insulate the joint with the shrink tube.
This will make the S-RF meter operational 100% of the time. Remove and discard the violet and gray wires connected between the switch and the SWR cal pot. Remove the red and orange leads connected
between the switch and the main board and discard them too. There are two black leads still connected to the SWR cal control. Desolder them from the control and separate them. Slide a piece of shrink tubing over the longest lead, and solder them together. Slide the tubing over the joint, and shrink it down. 

Refer to the diagram. CAREFULLY, drill a hole large enough to accommodate a #14 wire at the point indicated.  Scrape off all of the green solder mask from around the hole. Solder a piece of #14 stranded wire to the board at this point. Solder the other end of the wire to the center pin on the SO-239 connector.

 

 

Mod complete.

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Add a heatsink to the rear of the chassis so that it covers the area where the driver and final are mounted. I use the sink from an RCI 2950, as it is a perfect fit and readily available. Make certain there is a good flush fit between the sink and the chassis. Use Bergquist insulating material or heatsink compound between the sink and chassis. Bolt the sink in place securely. 

 

Fabricate a two square inch heatsink, and fit it to the chassis so that it covers the area directly behind the AM modulator pass transistor (TR51). This guy will get pretty hot with some of the mods we’re going to do, and it needs all the cooling it can get. Again, make it a good flush fit, and use Bergquist mat’l or compound. Mount the sink to the chassis using counter-sunk screws. The radio covers have to be modified for clearance. I use a nibbling tool for this, but use whatever method works best for you. Make the covers a nice tight fit around the sink for a “factory” look.

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The stock power switch not very reliable. After having several fail due to internal arcing, I developed the following mod which uses a relay to switch the power on/off. The relay is controlled by the original power switch. 

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At this point, the basic mods are complete. The transceiver can now be aligned (xmit and recv), and the AM deadkey, SSB peak output, and AM modulation adjusted (just a hair over 100%.) If you have the
proper equipment, adjust the FM deviation to factory spec (5Khz).

 

You will now have a radio that will kick ass on-the-air, and be as reliable as the day is long.

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OPTIONAL MODIFICATIONS

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+ 10KC JUMP SWITCH

The channel spacing on US cb radios is 10khz. However between channels 3-4, 6-7, 11-12, 15-16, and 19-20 the spacing is 20khz. The missing channels, designated 3A, 7A, 11A, 15A, and 19A were used for
old 27mhz “radio-controlled” devices (model cars & planes, garage door openers, etc.) To operate on these “A” channels, perform the following mod.

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Remove JP54 and put a 4.7k ohm resistor in its place (located by IC6).  On the solder side of the board, connect a wire to pin 9 of IC6. Run the other end of the wire to a pole on a spst switch. Then connect the other pole on the switch to a suitable 8v supply on the board. When the switch is thrown the rig will go up one channel (10KC's)

 

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ROGER BEEP ON/OFF w/ continuous tone option

The diagram shown below is the Uniden roger beep circuit used on the Cobra 148GTL-Dx and Superstar 360FM.

 

TR33 is the roger beep oscillator and operates at 1200-2000Hz (depending upon component values). When the radio is keyed up, the oscillator starts, but its output is shorted to ground thru diode D92. When the key is released, oscillator output is enabled, and the C270/R206 combo holds the unit in transmit for a few milliseconds and the beep is broadcast.

 

Change the values of C154 and C156 to vary the beep frequency. Change the value of C270 to shorten or lengthen the beep time. To transmit a continuous tone, install switch S2 as shown. Opening S2 prevents the oscillator output from being shorted out, and a continuous tone is transmitted whenever the key is down. This is handy when aligning the unit's transmit section. Also helpful when tuning up tube amps, matchers, or for just plain agitating.

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AM MODULATOR UPGRADE

Want “kick-ass” audio ??? Do this mod.

Replace TR51 with a 2SB754 transistor. Take the 2SA1012 transistor removed from TR51, and use it to replace TR53. Replace TR52 with a 2SD471. Replace R295 (150 ohm-1/2watt) with a 47 ohm-1watt
resistor. Mount this resistor off the board for cooling. Put small clip-on heatsinks on TR52 and TR53.
 
Solder one end of a length of #14 insulated stranded hookup wire to the positive (+) terminal on the dc power plug. Run this wire between the chassis and the circuit board and solder the other end to the
emitter of TR51. Solder another piece of #14 hookup wire to the collector of TR51. Run this wire along the solder side of the board, and solder it to test point 9. Make both wires as short as possible.

 

Adjust the driver and final bias until they are spot on. Then, using a piece of #14 buss wire, connect test points 7, 8, and 9 together on the solder side of the board..This will eliminate the possibility of any poor
connections between the test point standoffs and the bridging board. 

 

Next, take the stock bridging board used to connect the test points, and throw it into the nearest trash can. Fabricate a new board using high copper content double-sided PC board. Make this board as large  as possible without shorting to any components. 

 

This mod doubles the output of the AM modulator.

 

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5KC JUMP SWITCH

NOTE: Although I would like to take credit for this modification, I must give credit where credit is due. Sue Nguyen is the person responsible for figuring this out . She is a technician extraordinaire, and her knowledge is second to none. In addition, she is a really great person. Sue, thanks for all of your help on this mod.
 - 399

The UNIDEN PB-010 chassis was marketed as the Cobra 148GTL-DX Mark II and the Superstar 360fm. This modification applies to them and to many other export radios that use the MC145106 PLL. This modification does not permit the radio to switch channels in 5kc steps. However, it allows the installation of a "5kc jump" switch, which gives the user the "zero" channels (i.e. 27.400, 27.410, etc.) without changing the position of the clarifier. 

 

First up, make these 4 changes:

1) Isolate all of the PLL programmable divider pins (9 through 17 inclusive) by cutting the PLL traces as close to the pins as possible

 

2) Connect them back up with wire jumpers as below:

- Connect the trace that went to pin 17 to PLL pin 16
- Connect the trace that went to pin 16 to PLL pin 15
- Connect the trace that went to pin 15 to PLL pin 14
- Connect the trace that went to pin 14 to PLL pin 13
- Connect the trace that went to pin 13 to PLL pin 12
- Connect the trace that went to pin 12 to PLL pin 11
- Connect the trace that went to pin 11 to PLL pin 10
- Connect the trace that went to pin 10 to PLL pin 9 .

 

3) Put the PLL into 5Kc mode by connecting pin 6 to ground.

 

4) Install a 5.1k ohm resistor between pin 17 and ground.

Moving all of the PLL PD lines over by 1 pin is binary multiplication by 2. In other words it doubles the "N" value. Each pin is now shifted twice as much. BUT putting the PLL into the 5kc mode DIVIDES the "N" value by 2, so that each pin is now shifted by exactly the same amount as it was before the mod. The radio will now operate over the same frequency range as it did stock. There is ONE difference though.
Pin 17, which adds "1" to the "N" value (increasing the output frequency by 5kc) is no longer connected to the channel selector.

 

Now if we connect pin 17 to 8Vdc through a switch, the output frequency will increase by 5kc. For instance, channel 40 mid band will "jump" from 27.405 to 27.410 at the flick of a switch. Connect switch
S1 as shown in the diagram above to complete the PLL portion of the mod.

 

Unfortunately, this mod may permit some phase noise to make it through the PLL loop filter, allowing an annoying whistle on AM and FM, as well as distorting SSB audio. To prevent this, the cutoff (corner)
frequency of the loop filter needs to be reduced by about 50%. On the PB-010 chassis this can be done by changing the value of R126 from 27K ohms to 36k ohms. 

 

With more operators using the "zero" channels on SSB, this is a quick and easy way to get them on the PB-010 chassis.

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DUAL FINALS FOR THE PB-010 BOARD

The Cobra 148GTL-DX Mk I (PC-879) was introduced overseas in mid 1981. This model was never sold (new) in the US. It was superceded by the 148GTL-DX Mk II and Superstar 360FM (PB-010) in April 1983.
Production continued until mid-1985, and then it was discontinued due to pressure from the FCC. 

 

I always wondered why UNIDEN chose to produce this radio. Because of its extended frequency range as well as its FM and CW modes, it was completely illegal to sell in the US.  Uniden must have had big plans for it. Although it was a 5 watt single final radio, UNIDEN made provision for a second final with the extra component holes and circuit traces already on the board. Component locations for the 2nd final circuitry were silk-screened on the board also.  I'm certain that a high power base model was in the works. We'll never know.


The 148GTL-DX/Superstar 360FM, along with the Grant-DX, and Jackson models were the only multi-mode “export” radios ever produced by UNIDEN. The Jackson model with its high power Motorola final transistor should have certainly been the most popular. However, UNIDEN chose to equip this model with a low level am modulator which turned off a lot of potential buyers.

 

This writeup shows how to update the MKII and SS360fm to the dual final configuration.

 

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Parts Required

 

      To add the 2nd final, the following 10 parts are required
     
      QTY            DESCRIPTION
    
        1    2SC2312 RF POWER TRANSISTOR
        2    390pf disc capacitor
        1    560pf disc capacitor
        1    150pf disc capacitor
        1    .01uf disc capacitor
        1    1 ohm - 1/4 watt resistor
        1    47 ohm - 1/4 watt resistor
        1    100 ohm PC potentiometer
        1    ferrite bead

        1    150ohm 1/2 watt resistor
        *    a few inches of uninsulated pc jumper wire

Note: This mod utilizes the 2SC2312 rf power transistor for both finals because it is readily available. I chose to use a pair of 2SC1307 transistors in my personal rig. Along with the high power audio mod shown earlier, my 360fm deadkeyed 15+ watts with a 50 watt swing on AM, and cruised along at almost 60 watts pep on

ssb. For even greater power and reliability, 13N10 FETs can be used as finals. I will post this mod soon.

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The schematic on the right  shows the PB010 dual

final circuit. The parts to be added are highlighted in

the yellow box. The new parts and their component

designations screened on the board are as follows:

      QTY            DESCRIPTION      DESIGNATION

        1         2SC2312 transistor

        1         560pf disc cap                  C197

        1         MV1Y diode

        1         390pf disc cap                  C198

        1         .01uf disc cap           See image below

        1         1 ohm resistor                  R259

        1         47 ohm resistor                R261

        1         150ohm 1/2W                   R262

        1         Ferrite bead                       L48

        1         Jumper wire                      JP16

 

Clear out all of the holes for the new parts. Look at

the installation of the original final and install the 2nd

final and the MV1Y diode together

using a berquist insulator between the

chassis and the transistor. Use heat

sink compound between the diode and

the transistor, 

Next, install the jumper wire. Then

finish installing all of the remaining

parts. 

Replace C204 (470pf) with a 390pf cap.

Replace C196 (220pf) with a 150pf cap.

Check your work, and then check it

again. No room for errors. If it checks

OK, the mod is complete.

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     ALIGNMENT

The transmitter alignment is the same as the 148GTL-DX MK II on CB TRICKS. The only difference is the 

final bias adjustments. To adjust the final bias, put the rig in USB, and set the selector to Chan 19 mid band.

Remove the bridging board connecting Test Points 7, 8, & 9. Set VR9 and VR10 to MINIMUM resistance.

Connect a milliammeter between TP9 (+) and TP7 (-). Keyup and adjust VR9 for 50ma +/- 5ma. Then adjust VR10 for 100ma +/- 5ma. Reinstall the bridging board and complete the alignment. 

 

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MORE TO COME FROM UNIT 399 

VISIT MY OTHER SITE

"UNDERSTANDING AND MODIFYING THE UNIDEN 858SSB CHASSIS"

HERE:

https://unit399.wixsite.com/858ssb

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