TRAM XL5

[crambone]

So I picked up a Tram xl5 today cheap figuring it wasn’t working, I was correct. So I open it up look inside and everything seams ok, nothing smelled or stood out as a visual issue. I power it up on my work bench and nothing. I double check the fuses and aok. I decide to pull out the large electrolytic capacitor I believe it was a 2200uf 16v, test it and reading 3400uf 16v. I then go down the line of capacitors and every one of them way over limit. 
So now comes the question, should I assume age or another underlying problem? 

[Sandbagger]

Mar 13, 2019 19:13:11 GMT -5 crambone said:

So I picked up a Tram xl5 today cheap figuring it wasn’t working, I was correct. So I open it up look inside and everything seams ok, nothing smelled or stood out as a visual issue. I power it up on my work bench and nothing. I double check the fuses and aok. I decide to pull out the large electrolytic capacitor I believe it was a 2200uf 16v, test it and reading 3400uf 16v. I then go down the line of capacitors and every one of them way over limit. 
So now comes the question, should I assume age or another underlying problem? 

Capacitor testers can be inaccurate. I would not expect that a dead radio is the fault of capacitors. There is some other failure there. If both receive and transmit are dead, then I would suspect a voltage regulator issue.

[crambone]

So i just checked power inside radio, when on off switch is off I have 13.8v between the red and black on the board were it comes in. when I turn on I loose power but then have power between black on board and chassis?

[2600]

Sounds like it may have been hooked up with the polarity of the power cord reversed.

There is a diode connected across the power input that acts like a dead short with the polarity reversed. It's meant to blow out the 2 Amp or 3 Amp fuse. Trouble is, it's a one-time protector. The diode is typically rated for only 1 Amp. By the time the fuse trips, that diode is permanently damaged and becomes a dead short even when you reconnect the polarity of the power cord correctly.

When the next (mis)step is to put a larger fuse in line, a copper foil trace on the pc board will typically blow, like a backup fuse. Sounds as if this foil trace is in the negative side of the power input to the pc board on this radio. Haven't seen one of these in decades so I can't tell you that from memory alone.

If this is the problem, replacing the protection diode and bridging the broken foil trace should get the radio to power up.

The channel selector on this radio has silver-plated contacts. Over the decades, tarnish will build up on the contacts. This shuts down the radio until the channel selector is cleaned. If it still acts dead after you get the lights to come back on, check that.

Have a close look at the foil traces where the black wire from the power cord connects to the circuit board. Good chance you'll find a severed foil trace.

73

[crambone]

Thanks I will try to take a look at that this week. Appreciate the knowledge and help! 

[Sandbagger]

Mar 13, 2019 23:47:18 GMT -5 crambone said:

So i just checked power inside radio, when on off switch is off I have 13.8v between the red and black on the board were it comes in. when I turn on I loose power but then have power between black on board and chassis?

I would concur with 2600's observation. It would seem that you have an open circuit, most likely the result of a current overload from the shorted polarity diode. Look at the circuit traces at the rear of the radio near the power leads and see if you can find an blown open trace.

[BBB]

Ask Ranger. The dusty black wire does not go directly to the dusty red wire and the dusty red wire does not go directly to the dusty black wire

But be aware, Sparky has also been fooled by the black wire with the red stripe does not equal +12VDC

[crambone]

lol thank triple B

[bobcat4109]

I am hoping you get this!   This is a snippet out of the schematic for your radio. I am not sure how you have it hooked up but I noticed you said that "when you turn it on the 13.8 goes away (or something like that!).  The protection diode is "ahead" of the switch on yours so I would thing that whether the radio switch is on or off you connect the power supply it is going to blow the fuse or "crowbar" the power supply (drive it in to current limiting).    So there may be something else inside causing the drop....

All of that said, just to the left of the choke is the protection diode.  Clip that out then carefully retry being SURE to get +  and - right... and see what happens.  You might want to put in a fuse just in case....

[crambone]

Got it thanks, haven’t had a chance to put it back on the bench yet but hopefully this week?

[Sandbagger]

Mar 19, 2019 13:41:13 GMT -5 bobcat4109 said:

I am hoping you get this!   This is a snippet out of the schematic for your radio. I am not sure how you have it hooked up but I noticed you said that "when you turn it on the 13.8 goes away (or something like that!).  The protection diode is "ahead" of the switch on yours so I would thing that whether the radio switch is on or off you connect the power supply it is going to blow the fuse or "crowbar" the power supply (drive it in to current limiting).    So there may be something else inside causing the drop....

All of that said, just to the left of the choke is the protection diode.  Clip that out then carefully retry being SURE to get +  and - right... and see what happens.  You might want to put in a fuse just in case....
View Attachment

There are still a bunch of hazy unknowns with this radio's issue. Turning on the on/off switch causes voltage to disappear..... But where is the measurement being taken? If we knew exactly where he was probing the radio, we could come up with a likely cause. It sounds like an open or high resistance circuit somewhere. A DVM has a very high circuit impedance, and would measure 13.8V with no load across a high resistance. But put the full load of the radios circuits in line, when you turn it on, and that high resistance can't hold up the supply voltage any longer. It should not be hard to track down. Just start at the supply leads and work your way forward with the radio on and see where the voltage goes away. And there should be the culprit.

[bobcat4109]

There are things about the gentleman's test case that I don't understand.  For one, if that diode is shorted....and you hook a 13.8 supply to it... I'm not sure what.....but something spectacular is likely to happen... unless that power supply has great current limit protection.   If it doesn't... and you hook up a 13.8 power supply with enough current and either you will get some sparks OR the shorting element will announce it's presence with a POP.

If the power supply is INDEED on, and measures 13.8VDC, and then connected to the radio, and then:

1) with the switch off, the PS stays up.... I don't think the diode is shorted, and

2) turn the switch on, the PS drops to nothing.....  I think something beyond the switch is shorted and his PS is crowbar protected really well!

crambone, do keep us posted as this goes on.......

I'd be happy if I  can be of any help.

[crambone]

So I checked the diode CR701 and it tested 550 and OL so it’s good. I tested the 2200 cap C702 and that tested at 3100. I didn’t have time to go any further it was a rush check. Hopping to back to it Friday 

[bobcat4109]

crambone, when you get a chance, clarify as best as you can how you are performing this test.

Along these lines:

Connecting the power supply to the power leads of the radio (red to red, black to black) with the radio OFF and the power supply ON.

Measured 13.8 volts at (tell where you are measuring)
Then, with the meter attached, I turn the radio on and now the voltage measures

If your power supply has a current meter.... what does it read when the voltage goes away?

I hate to ask such basic questions.... but to some degree, you are going to have to be my "eyes" in looking at this.....

Thanks!

Bob

[crambone]

will do I am planning on making some time Friday HOPEFULLY!
Thanks for all your help

[bobcat4109]

Absolutely!   This is what I'd rather be doing!!!!!!!!

[crambone]

So I checked my power supply today as it’s just old on/off 12volt no meter unit. Well I’m getting 19volts out of it so I’m not sure if I should use it or not. I ordered a new one with amp/ volts that I can bring up from 0volts. I should have tomorrow. 

[bobcat4109]

Just curious, look around on it and see if it says that it is a "regulated" supply.

If it is NOT regulated....those have a tendency to "float a little high in voltage" when they are not loaded by something (meaning something is hooked to it and drawing current). If it is regulated...and it measures 19v....  I PERSONALLY would throw it as far as I can see then walk over to it and throw it again!

Another couple of questions.....

1) when you are testing it.... is there a fuse in line with it?

2) if YES, what size/rating

Attachment Deleted

3) Again, in no way do I wish to insult you,  I am sent this drawing so that things are clear.  To the left the power supply, to the right the radio.  I've shown the positive leads twisted together and the negative leads twisted together.  You may have done this a different way but as long as THIS is the idea.... we are good.   Floating above the meter with it's leads...the red hooked to the positive and the black hooked to the negative.  Over to the right is supposed to just be the front of the radio showing the volume-on switch in the OFF postition.   If you hook it this way and turn the power supply on we want to see 13.8 v (or whatever the supply feed it).

Now, without changing anything else.... turn the CB's volume switch ON.

I am hoping that you do have a fuse in it because if something inside the radio is shorted...the fuse will blow....but ONLY if you have one in.   If you don't.....bad tidings!!!

However.......if you turn the CB ON.......the NORMAL thing to see would be that the voltage on the meter stays UP (13.8...maybe a little less as the power supply is now loaded more!).   

If it DOES stay up..... and the fuse POPS.... something is shorted.
If it DOES stay up....  but the fuse doesn't pop then either
      a) the radio should light up and come on (normal),   OR
      b) nothing happens (which means that something has opened up electronically inside and the radio is not pulling current from the power supply!)

Frankly, if the voltage drops... and the radio does NOT emit smoke.......      I'm going to be scratching my head a little....   because to pull that power supply down to zero is going to take a LOT of current draw...unless it is WAY too little to begin with.   If it is.... say... a 3 amp regulated supply and that radio pulls it down to 0 volts.....   I would expect to hear popping from inside the radio.

[crambone]

Ok got my new power supply today. I have a 1.5amp fuse in line for testing. I also set the power supply current to 1.25amps. 
I have 13.8 volts to the switch on one side when off and then both when on so I do have voltage. The amps on the power supply show under .5 amps. No light on the meter. I hooked up my watt/mod/swr meter and a dummy load. Keyed up the radio and nothing. I then started checking for voltages all over the radio and I have 13.8 and 6 volts at some points. I’m going to switch to my computer to finish this

[crambone]

OK im back.
so as I was checking voltage at various points I did find something I believe to be strange. There is was I believe to be a small transformer on the board that has a wire coming off of C10161 board and soldered to the top of that transformer. That wire has 10 volts on it at the solder point directly on top of that small transformer. I did check for any voltage to ground at several grounding points and had 0 positive voltage so I guess that can be looked at one good thing. Ok there is a 12 slot board connection that has all different color wires soldered to it and out off all of them only the 2 orange on both Pin 3's had 13.8 volts. Now I checked 2 other small boards that are screwed to the inside sides of the chassis. One board is at the back left numbered 900126 there are 5 wires connected to it and all have 13.8 volts. Now the Small board toward the front of the radio has 4 wires attached and all of the had 13.8 volts also. I tried to print out a schematic but an 8.5 x 11 is as much good as putting a paper bag over my head and trying to read anything. 
checked some voltages at the switches also:
Listed below are the switches and wires that had 13.8 volts: This was with radio on and in AM mode

Channel Selector: Middle round section: Grey, Pink, Orange
                          Outer round section: Purple and Brown (together), orange

CB/ PA: side one. Pink, White, Orange, Pink 
            side two. Red, Green, orange, brown

OFF/ NB: side one. white
              side two. yellow and green (together)     ***** so I believe this radio has a channel mod as the NB is covered with and AM sicker?

AM/ LSB/ USB: Outer Ring green, grey, red (6 volts) , yellow, white, white, pink
                       Middle ring: orange, brown, pink (6 volts) , grey, orange, green
                       Inner ring: orange, orange

Hope this helps

[Sandbagger]

Mar 21, 2019 19:18:07 GMT -5 crambone said:

OK im back.
so as I was checking voltage at various points I did find something I believe to be strange. There is was I believe to be a small transformer on the board that has a wire coming off of C10161 board and soldered to the top of that transformer. That wire has 10 volts on it at the solder point directly on top of that small transformer. I did check for any voltage to ground at several grounding points and had 0 positive voltage so I guess that can be looked at one good thing. Ok there is a 12 slot board connection that has all different color wires soldered to it and out off all of them only the 2 orange on both Pin 3's had 13.8 volts. Now I checked 2 other small boards that are screwed to the inside sides of the chassis. One board is at the back left numbered 900126 there are 5 wires connected to it and all have 13.8 volts. Now the Small board toward the front of the radio has 4 wires attached and all of the had 13.8 volts also. I tried to print out a schematic but an 8.5 x 11 is as much good as putting a paper bag over my head and trying to read anything. 
checked some voltages at the switches also:
Listed below are the switches and wires that had 13.8 volts: This was with radio on and in AM mode

Channel Selector: Middle round section: Grey, Pink, Orange
                          Outer round section: Purple and Brown (together), orange

CB/ PA: side one. Pink, White, Orange, Pink 
            side two. Red, Green, orange, brown

OFF/ NB: side one. white
              side two. yellow and green (together)     ***** so I believe this radio has a channel mod as the NB is covered with and AM sicker?

AM/ LSB/ USB: Outer Ring green, grey, red (6 volts) , yellow, white, white, pink
                       Middle ring: orange, brown, pink (6 volts) , grey, orange, green
                       Inner ring: orange, orange

Hope this helps

Out of curiosity, where is the negative lead for your voltmeter connected to when you are making these measurements? If it is at the negative terminal of the power supply, try moving it to the ground traces inside the radio. I suspect you may have an open ground somewhere......

[2600]

Maybe it's time to ask where you connect the black probe on your meter.

It should go to the black power lead. Preferably inside the radio.

If you have clipped it to the metal chassis, this may cause misleading readings from the meter.

The chassis won't necessarily be connected to the negative side of the power supply. The power supply's negative side is the "ground" where the meter's black lead should connect.

73

[crambone]

I had the ground connected to the chassis. 

[bobcat4109]

I, too, suggest finding a good DC ground inside the chassis, in the power supply area or a shield to clip on to.  Too many times I've seen the board ground tied to the chassis with a bunch of ceramic caps.   That might make it an RF ground but not necessarily a DC ground.   I might be confused....but I think it is safer.....

[crambone]

Next time I get a chance I will do just that and test everything over again. Spoke to person that sent it to me and he said it was working when 100% when he shipped it. I believe him he’s a friend of mine so I’m thinking something came loose. 

[2600]

Decades ago there were diesel trucks with the positive side of the battery grounded to the vehicle chassis. The need to operate a CB in either kind of vehicle, either positive or negative ground prompted adoption of a "floating ground" standard in the design of mobile CB radios.

The radio's metal chassis would not have a direct connection to the power leads. Multiple disc capacitors placed between the circuit-board ground and the chassis all around the edge of the circuit board provide an AC-voltage-only (not DC) ground for the RF signals going to and from the antenna. This allowed you to use the radio with either the positive or the negative side of the battery connected to the vehicle's chassis ground.

As a result, you have to find a proper "DC ground" inside the radio to make a reliable measurement of DC voltages in the radio. The negative wire on the power cord will serve this purpose.

There are other spots inside that will serve this purpose, but the chassis of that model is not a reliable DC ground connection for making DC-voltage measurements.

73

[crambone]

Thanks for the knowledge I’m learning a lot over these past few days. 

[321 treeclimber]

Me too. 321

[bobcat4109]

Mar 22, 2019 21:19:02 GMT -5 2600 said:

Decades ago there were diesel trucks with the positive side of the battery grounded to the vehicle chassis. The need to operate a CB in either kind of vehicle, either positive or negative ground prompted adoption of a "floating ground" standard in the design of mobile CB radios.

The radio's metal chassis would not have a direct connection to the power leads. Multiple disc capacitors placed between the circuit-board ground and the chassis all around the edge of the circuit board provide an AC-voltage-only (not DC) ground for the RF signals going to and from the antenna. This allowed you to use the radio with either the positive or the negative side of the battery connected to the vehicle's chassis ground.

As a result, you have to find a proper "DC ground" inside the radio to make a reliable measurement of DC voltages in the radio. The negative wire on the power cord will serve this purpose.

There are other spots inside that will serve this purpose, but the chassis of that model is not a reliable DC ground connection for making DC-voltage measurements.

73

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Very cool bit of history that I did  not know but it makes perfect sense!   Thank you!

[crambone]

I haven’t given up or abandoned this I’ve just been VERY busy. Hoping to get to it next week one day.