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RCI 2995DX CF troubleshooting help needed

LOL forgot this was an SMT chassis. you'll have to pull the parts out all the way.

If you don't have experience working with SMT components, i hightly recommend sending the radio out to be repaired at a place that does this type of work.
LC
 
I also looked at voltage on the 3 SM capacitors C265 is showing no voltage readings, C265 shows 13V towards C263 and 2v opposite,
I'm a little confused here. Is there voltage at C265 or not??

Also check capacitors C223,224,225,226 They go from TP7 to ground. If one of them is bad it could be loading down the collector voltage of Q60.
 
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C265 shows 13Vdc on one end and 2Vdc on the other.
Ok will do thanks guys but we ended up with the grandson today, 3yrs old and there isn’t anything getting done when this wild one is here!
Not that I’m complaining I ouldnt want it any other way!
 
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Well I hate to keep stomping this dead horse but I’ve been checking this RCI in my spare time and had yet one more question,
After checking many parts I found this little tiny cap C227, when I pulled and checked it I came up with 1400pf and from what I see in the manual it looks like it should be 470pf. Could this be causing my issue? I ordered a new one today anyway.
Am I reading the service manual correctly?
 
A bad Q66 raises the possibility that Q67, the transistor that drives the base of Q66 will also be damaged. Q67 is a surface-mount power transistor. It has a large (relatively) foil pad directly under it where the collector lead is soldered.

This one has visible damage.

2vbhs6.jpg


It won't always offer a visual cue when it fails. If replacing Q66 doesn't restore AM transmit carrier, Q67 may be the culprit. If the base voltage on Q66 never falls more than 6/10 of a Volt lower than the emitter voltage, this is a sign Q67 was damaged.

Removing Q67 always seems to damage the foil pad under it. Could be our crude tools are to blame, but if the part gets too hot when it breaks down, that can destroy the foil pad under the part.

We replace Q67 using a TO-220 PNP transistor with the plastic mounting surface. Can't remember the part number right now. Same part shows up as the 9-Volt regulator in newer Galaxy/Connex radios with EPT3600 boards. Saves the trouble of putting an insulated washer under the new part. We put a teflon-insulated wire on the new part's leads. They will reach to Q66 and to the main circuit board and take the place of the croaked SMT part.

zg2GaP.jpg


It mounts in a random extra hole in the heat sink near Q66. The brown wire (collector) and yellow wire (emitter) go into the gap under Q67.

iq81y5.jpg


The collector wire (brown) from the new Q67 lap-solders to the center pin (collector) of Q66. The emitter wire (yellow) goes to the base lead of Q66, the lead nearest the rear of the radio.

nKyenv.jpg


The blue wire from the base lead of the new Q67 will go to the component side of the main pc board.

Hejbla.jpg


It goes to the center leg (collector) of either Q65 or Q69. Can't remember which of those this one is.

fdN8W1.jpg


So far this has done the job when both Q66 and Q67 both fail.

And when the foil under Q67 is damaged, you can't just replace the original part where the old one went.

Something we have adopted as standard policy when servicing this type radio is to install a separate fuse to protect the radio circuit board. You wouldn't hook up a 4-Amp mobile radio to a 25-Amp power supply with no fuse, right? But that's what the factory put inside this cabinet. A fuse for the circuit board could minimize the damage when Q66 fails, or when IRF520 transistors fail as a short.

4hAhX1.jpg



We call it cheap insurance.


73
 
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Hey, you're welcome.

And the part in the Mouser link looks perfectly suitable.

73
OK I replaced Q66 & Q67 exactly as you stated and showed. Now when I key the radio with NO modulation I see a small wave form and 0 watts forward, when I apply modulation I see good modulational and a swing to 2 watts peak on my BIRD. That's with RF Power full and Mic Gain Full. In LSB & USB I see slight a Sine Pattern not a flat when keyed with 0 watts forward and with modulation I see good modulation and 4 watts peak?
 
You should see a lot more from a 2995DX than that.

Makes it sound as if the final transistor on the radio circuit board may have failed. Could be what damaged Q66/Q67.

Maybe.

See what the DC voltage is on the "mirror" board, the bias-test jumper. If it's around 6 Volts or more, it's time to check the final and driver on the main circuit board.

73
 
It got nicknamed the "mirror" board. It's a small piece of double-sided pc-board material with shiny tin plating on the foil both sides. It's inserted into three fork-shaped spring contacts just to the front of the driver and final transistors.

73
 
Ok that’s what I thought it was but just wanted to confirm I will give it a look tomorrow. I know I was only getting around 2.5V to tp7 with the board pulled before I replaced Q66 & 67. I should have checked it again today!!
 

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