Galaxy SSB Echo Base - no modulation

[Hawkeye351]

Replaced ic8, checked pin 9 voltage, 6.69v. Not getting hot anymore now. Everything else stays cool also.

Still no modulation and receive volume still seems low, unless I key my monitor radio, then it's loud as crap and I have to turn volume down. I did flip it to PA and check for modulation, but when I turn echo on while in PA mode I can hear the echo thumping from keying up but no modulation.

 

[Dr. Frankenstein]

The TA7222P was used in older Cobra radios and probably where it came from or another radio that also used that audio IC.

Have you tried to bypass the echo board by jumping from "pin 2 (audio)" on the mic socket in the radio.....to the Mic-Gain pot (Not the ground side or the middle)?

If the beep works the only thing that looks like the problem is the echo board they both (beep and audio) get paralleled to the audio circuit.

If you are looking at the 99V schematic from 2004 (1993 is correct), the wiring from the mic socket to the echo board is WRONG (mic socket board number EPT360050Z, going to echo board number EPT0SSB50C).
It shows:
"Pin 1" as PTT
"Pin 2" as Ground
"Pin 3" as Audio
But I'm sure that just the schematic for the 99V is wrong.
It should be:
"Pin 1" to Ground
"Pin 2" to Mic I/P
"Pin3" to PTT I/P.

If yours is wired that way then you are GROUNDING the Mic AUDIO when you key the Mic.

You need to check the way the echo board is wired both going in and out, or bypass the echo board. It sure sounds like you are putting the mic audio to the ground when you key the mic. Then why does Echo work?... because the mic is unkeyed and no longer grounding the audio line. This could also be the reason for the hot Audio IC when the mic is keyed.

Hope I'm wrong.........
73

 

[Dr. Frankenstein]

Forgot to ask... Have you tried a different mic?

 

[Hawkeye351]

Yes sir, tried 3 different mics, even tried the mics on another radio, all 3 mics work fine.

Ic8 doesn't get hot anymore, I replaced it cause the voltage on pin 9 was too low and it was getting hot. I replaced it and now pin 9 has the right voltage and the IC isn't getting hot anymore.

Will try that to disable echo. Thank you.

 

[Hawkeye351]

I did use my oscope to probe for audio on pin 2 of the mic socket. I have audio there. And I also probed the mic gain for audio, it's present at the mic gain also.

 

[Hawkeye351]

Pin 2 of the mic socket directly ties straight to the mic gain. Pin 2 wire goes straight over to mic gain already.

 

[Dr. Frankenstein]

So now you just have to find the audio at pin 4 of the 4558 (IC4 on the 99V schematic). If it's not there go back, if it is there you have to keep going until it stops.

 

[Hawkeye351]

Mic gain control must be bad.
Was getting audio from pin 2 of mic socket, was getting audio off mic gain outter pin but no audio anywhere else. Removed wire from bottom of mic gain control, tied it to center of mic gain, got full audio. Even echo works fine.

Guess I'll pop in another mic gain control.

 

[Hawkeye351]

Update:

Fixed!!!

Mic gain control was bad. Replaced with new control, mic audio is back.

Volume control was bad, audio IC was bad, FT1 455khz filter was bad. Replaced all 3. Volume back up.

Both meters were stuck. Used acetone to free them up. Meters no longer stuck.

New passthrough regulator - 2SB817 (TR51)
New AF regulator - 2SA1012 (TR50)
New modulation transistor - 2SC945Q (TR49)
New 8v regulator - 2SA1012
All controls and switches cleaned

Left to do:
Replace all 10v, 16v caps.
Install the AMC Attack Time trick.
Complete alignment.
Done.

Thank you all for the guidance.

 

[Hawkeye351]

Still got this Galaxy SSB Echo Base I'm trying to figure out.

Got the mic audio issue straightened out, mic gain control was bad.

Receive audio still low. Volume control does affect volume. RF gain does bring receive up and down.

Just receive audio weak. Replaced audio IC due to bad test results. Replaced passthrough reg, AF reg, 8v reg.

I did probe the RF Gain control and got 3.3v all the way up and .74v all the way down. Removed center wire (grey) and top wire (orange) and tested those wires and got 7.74v. Replaced L6, still the same. R56 and R55 look fine. I feel it's in the first IF section somewhere.

Shaking radio has no effect,
Shaking/wiggling wires has no effect,
Flexing board has no effect,
Fiddling with parts has no effect,

If I key up nearby monitor radio with RF Gain wide open and volume wide open it pegs the meter and squeals, if I leave volume up and turn down RF Gain then the received keyed monitor station drops out as it should. Like the receive is too low, but all controls are working.

This is all I got left on this radio. I thought I had it, but after hooking to antenna, it only gets strong nearby stations, others are weak and low.

 

[nomadradio]

First question for me is whether the receiver is sensitive, but the audio is weak.

Or, is the receiver only hearing strong signals? This is what I think I'm hearing you say.

Alignment is the first diagnostic step for a weak receiver. The ferrite tuning slugs in all the RF and IF transformers will exhibit a characteristic peak response with a steady WEAK signal applied to the receiver. Sometimes, alignment proves to be the whole problem. Other times, a tuning slug that doesn't react in a normal way when it's turned can point to the circuit with the fault causing the symptom.

The 10mm "cans" with the skinny black tuning slug can fail in one particular way. When this happens, the slug will appear to show a peak with the top of the slug DEAD EVEN with the rim of the hole. If you see this, it's not really a resonant peak like you should get. The peak should always occur with the slug at least (or nearly) two full turns below the rim of the hole. The "even with the rim" symptom is caused by failure of a built-in capacitor inside that coil.

Naturally you can replace the can when this happens. Sometimes you can cheat and solder a trimmer capacitor to two of the can's foil pads on the solder side of the pc board. Takes the place of the failed internal cap.

Sometimes. This failure is not unique to radios made by RCI, but your Galaxy is the second-oldest "black" radio. Old enough to have developed this kind of fault.

Maybe.

73

 

[Hawkeye351]

Thank you nomad for jumping in.

Here is what I've discovered since fiddling with this issue:

I can adjust all the IF coils and barely hear it changing, weak but they are doing something.

I checked the voltage on both sides of R66 and got 2.02v on the RF Gain side with gain all the way up, all the way down its 1.56v. On the other end of R66 I get 0.37v gain all way up, 0v all way down.

I then checked the outter leg of the RF Gain control and only got 2.2v max. I unsoldered that wire and checked just the lifted wire and got 8v. But with wire attached to the RF Gain control that same wire drops to 2.2v.

Just idling on the dummy load with RF Gain and volume wide open I can hear it, but you have to get closer to hear it. If I key up a nearby radio it's loud as hack. The volume is the same with or without any antenna/dummy load/coax hooked to it.

I don't understand the 8v wire on the RF Gain showing 8v when it's unhooked and dropping to 2.2v when hooked up. The wiper goes from 1.56v to 2.2v. I don't get it? Could a bad pot do that? And the RF Gain seems to work, from what I can tell on strong signals. I did ohm out the pot, it goes from 0 ohms to 1.2k ohms.

 

[Dr. Frankenstein]

Hawkeye351,

I got you to find the bad Mic Gain potentiometer before, now for the RF Gain problem.

Again looking at the schematic for the 99v.........

Have you checked or replaced capacitor C333 (10uf at 25v), it is the only other thing in the circuit between R66 and the "wiper-wire" to the RF Gain potentiometer. If it is bad it will drag the voltage going to R66 down toward ground.

That is the 2nd mistake on the "new" schematic for the 99v......it shows two C333 capacitors in the same RF Gain circuit, and the "old" schematic shows only one. Both schematics are from CBTricks.com.

You say you checked the "end-wire" going to the RF Gain for 8 volts, but there is also a resistor, R190, in series with the 8-volt "end-wire" from the receive circuit. Now you would need to check R190 for 1.5K (1K5) ohms, and not just for the voltage. Again that same "end-wire" has to be disconnected (just like unsoldering and lifting one side of R190) then check across R190 for 1.5K ohms or so.

You know the problem is in that area, so what is bad?
a. Capacitor... C333
b. Resistor... R190
c. Bad... RF Gain potentiometer
d. Or... none of the above

Now "imagine" R190 not being in the circuit at all (or bypassed) and at the same time C333 being bad (shorted)...... When you turn the RF Gain the 8 volts would get shorted directly to board ground, and something would burn up. So be careful if you decide to bypass R190 just to test the RF Gain circuit.

Remember only the person working on the radio is responsible for any mistakes made while repairing said radio.

Let us know............
73

 

[Hawkeye351]

There is no C333 in this radio. There is C44 right at the R66. I yanked that cap, tested the ESR on my esr tester and the uf value on a capacitor tester. The ESR states .97 ohms, the value shows 11.34uf. The cap is stamped 10uf 25v.

Looking at the galaxy ssb schematic, the wiper of the RF Gain goes through no caps before it gets to R65. After that it goes through R66 and then to L6.

R66 = 984 ohms
R65 = 991 ohms
R190 = 1.4k ohms
RF Gain = 0 ohms to 1.2k ohms
C44 = 11.34uf with an esr of .97 ohms

All 3 wires are now unsoldered from RF Gain control.
Black (bottom leg) = ground
Light grey (wiper) = R65
Orange (top leg) = 8v

But when all 3 are soldered to the RF Gain control, then the 8v on the orange wire drops to 2.2v. Like something is sending the 8v straight to ground when connected to RF Gain control.

This has the ept360010a board in it.

 

[Hawkeye351]

So, with R65, R66, R190 testing good and close to proper values, and with no C333 or any other component being between the wiper and R65, that would leave the problem in the potentiometer itself right?

Would a potentiometer that measures the proper resistance drop an 8v supply down to 2.2v upon connecting to said pot?

I know electronics can be some real head scratchers at times, but I've seen stranger things than this, lol...