RCI 2995DX power issue

[Crambone]

I’m only seeing 1.7 - 10 watts output on AM and 0 - 10 on SSB
I checked Q66 VR (2SB754Y) and I’m seeing 12v at all 3 legs. I popped off the legs and I’m seeing on the CPU Pads 13.7V, 1.2V & 1.4V???
Should I be seeing voltage on the 2 contacts? I know the 13.7 is ok but not sure about the other 2?
I also checked Bias and it seems like my mA are low on Q62 across TP7 & TP9.

Any suggestions?

Drew

 

[brandon7861]

I checked Q66 VR (2SB754Y) and I’m seeing 12v at all 3 legs

In AM or SSB?

 

[OldTech03]

Ok what about the variable power control on the front of the radio does it vary the power levels when adjusted?
I assume you mean the circuit board not the CPU board, Anyway there should not be 13+ volts on all three legs so I assume you have tested the (2SB754Y) this being the main modulated supply for the final section would show full power readings if there is as you say 13+ volts on all three legs of the (2SB754Y) when the power level is adjusted total counter clockwise it would most likely be around 2 watts depending on how the limits are adjusted for low and high power.
Next I would ask what does the Modulation levels look like if that is good and the front panel power control is functioning as it should and the voltage levels at the collectors of the driver and final are going up with modulation levels then the issue may be elsewhere in the RF chain from the before the mixer stage or after.

 

[nomadradio]

First thing I check is to unplug the two-wire lead that serves to key the amplifier in the rear. Need to know what power the barefoot radio delivers before looking deeper. Got a pic of that somewhere. I'll see if I can find it.

73

 

[Crambone]

Ok what about the variable power control on the front of the radio does it vary the power levels when adjusted?
I assume you mean the circuit board not the CPU board, Anyway there should not be 13+ volts on all three legs so I assume you have tested the (2SB754Y) this being the main modulated supply for the final section would show full power readings if there is as you say 13+ volts on all three legs of the (2SB754Y) when the power level is adjusted total counter clockwise it would most likely be around 2 watts depending on how the limits are adjusted for low and high power.
Next I would ask what does the Modulation levels look like if that is good and the front panel power control is functioning as it should and the voltage levels at the collectors of the driver and final are going up with modulation levels then the issue may be elsewhere in the RF chain from the before the mixer stage or after.

First thing I check is to unplug the two-wire lead that serves to key the amplifier in the rear. Need to know what power the barefoot radio delivers before looking deeper. Got a pic of that somewhere. I'll see if I can find it.

73

Hello Nomad, I should have stated that I unplugged the amp keying 2 wires.

 

[Crambone]

In AM or SSB?

AM

 

[Crambone]

Ok what about the variable power control on the front of the radio does it vary the power levels when adjusted?
I assume you mean the circuit board not the CPU board, Anyway there should not be 13+ volts on all three legs so I assume you have tested the (2SB754Y) this being the main modulated supply for the final section would show full power readings if there is as you say 13+ volts on all three legs of the (2SB754Y) when the power level is adjusted total counter clockwise it would most likely be around 2 watts depending on how the limits are adjusted for low and high power.
Next I would ask what does the Modulation levels look like if that is good and the front panel power control is functioning as it should and the voltage levels at the collectors of the driver and final are going up with modulation levels then the issue may be elsewhere in the RF chain from the before the mixer stage or after.

Variable RF Power control
CCW .2 watts
CW 1.4 watts

VR 2SB754Y tests good

I tested voltages on the following also

Q62 IFR520
RX. TX
G. 35mV. 4.3V
D. 6.26V. 6V
S. 0. 1.1mV

Q60 IFR520
RX. TX
G. 28mV. 3.5V
D. 6.26V. 6V
S. 0. 1.1mV

Q63 2SC2314
RX. TX
B. 0. .68V
C. 67mV. 7.9V
E. 12mV. 1.37V

 

[Crambone]

OK to make sure it wasn’t in the amplifier I totally removed and connected one of the coaxes from bottom side to main board. I just wanted to make sure the amp wasn’t in the chain at all. Still same results as I assumed but it does make it easier to move around now.

 

[nomadradio]

If this is the pre-2006 version with two 2SC2290 in the amplifier, you shouldn't see more than ten or twelve Watts PEP from the barefoot radio. That's really all it takes to drive the heck out of two 2290s.

Had a customer years ago who liked his Galaxy Saturn Turbo. He had a friend ask for him, how much to install that second final in the radio circuit board. When that radio's main circuit board was used in a mobile model, it had two final transistors in parallel. But in the Turbo, one of the two spots is empty. Told him five hundred bucks. The added drive would just make it sound bad and wear things out prematurely. If I make it sound that bad with my name attached, you'll make it worth my while. He wisely declined my offer.

73

 

[Crambone]

If this is the pre-2006 version with two 2SC2290 in the amplifier, you shouldn't see more than ten or twelve Watts PEP from the barefoot radio. That's really all it takes to drive the heck out of two 2290s.

Had a customer years ago who liked his Galaxy Saturn Turbo. He had a friend ask for him, how much to install that second final in the radio circuit board. When that radio's main circuit board was used in a mobile model, it had two final transistors in parallel. But in the Turbo, one of the two spots is empty. Told him five hundred bucks. The added drive would just make it sound bad and wear things out prematurely. If I make it sound that bad with my name attached, you'll make it worth my while. He wisely declined my offer.

73

Unfortune

If this is the pre-2006 version with two 2SC2290 in the amplifier, you shouldn't see more than ten or twelve Watts PEP from the barefoot radio. That's really all it takes to drive the heck out of two 2290s.

Had a customer years ago who liked his Galaxy Saturn Turbo. He had a friend ask for him, how much to install that second final in the radio circuit board. When that radio's main circuit board was used in a mobile model, it had two final transistors in parallel. But in the Turbo, one of the two spots is empty. Told him five hundred bucks. The added drive would just make it sound bad and wear things out prematurely. If I make it sound that bad with my name attached, you'll make it worth my while. He wisely declined my offer.

73

Unfortunately it’s the 4 R5 transistor's that I believe may be IRF520’s also? It was putting out 7 watts dead key and 23 watts modulated with the amp keying 2 wires disconnected. Something went wrong?

 

[nomadradio]

This is where the 30-buck chinesium fleabay tranistor tester pays for itself. Odds are most of the four linear MOSFETs are croaked. No good way to test them with only a multimeter. Got in the habit of calling that linear stage the firestarter junior.

But they can fail and still look okay on the outside. Time to find out.

73

 

[Crambone]

Well I found the issue it was the voltage regulator, tested good with cheap Chinese tester but when bench tested with power supply no good.

 

[Crambone]

On another note it has the R2 adjustment for the “fire starter” and was wondering if that is what’s set wrong causing the issue with the amp board?

 

[nomadradio]

Excessive bias current leads to excessive heat and eventual breakdown.

73