Hi All,
I truly enjoy all the useful info on here. I'm NC Hawkeye, 351 AM, 592 SSB, KM4VAZ Ham. I recently acquired several radios from a broken down, collapsed barn. The roof was caved in and the floor was collapsed. The radios I got from there were laying in a pile in the dirt, but dry and hasn't been used in years.
1 Cobra 2000 GTL
1 Teaberry Stalker XV
1 Teaberry T Command
I chose to start on the 2000 GTL first.
Cobra 2000 details:
1. Receive low but does receive.
2. Transmit fine at 2.5 watt key swing to around 14 watts peak on AM and up to 16 watts on ssb.
3. Signal/rf meter stuck in receive, but works on xmit.
4. Controls and switches need cleaning.
5. Meter lights dim slightly on xmit, am and ssb same on AC, but dim dramatically on DC power with a substantial power drop.
6. Clarifier strapped, course tune must be all the way right and fine tune dead at 12 o'clock.
7. Amc and alc removed.
8. Channel kit installed at Tone Control position (expo kit).
9. Constant hash sound (sounds like a fan on an amp) coming from speakers when volume is turned all the way down.
10. Frequency counter shows 92.0002, but clock and alarm works fine.
11. Anytime I touch the base of the mic im using (Turner +3B) then the frequency on ssb shifts.
12. No mods to the audio or mic circuit.
13. Original pll (MB8734), regulator, audio IC, bridge rectifier, driver (1306) and final (2166).
Need to do first:
1. Replace all caps (already ordered them).
2. Replace filter cap on power supply side on bottom, and cap on power supply board.
3. Remove heat shield and apply new compound on bottom of shield and corresponding parts (driver, final, audio IC, regulator and rectifier).
4. Replace AMC and ALC components.
5. Adjust 3 transformers to align clarifier up to 12 o'clock on both fine and course tune.
6. Clean switches and controls.
7. Remove any old glue (not much in it).
8. Realign IF and RF stages.
9. Replace meter (already ordered).
10. Apply any upgrades for performance.
My questions are:
Why does the radio xmit better on AC power rather than DC power, lights dim bad and low xmit power on DC?
What causes the constant hash noise (like a fan running) through the speakers with the volume turned all the way down?
Why does ssb frequency shift when I touch the base of the mic I'm using on it?
Why are the lights dimming slightly when transmitting on AC power?
Everyone says the radio is loud with the Turner +3B mic. Great reports on audio sound and swing. But I would like some of y'alls best audio/mic circuit mods that are proven to improve the sensitivity and clarity of the xmitted audio. Hifi is welcome if it's proven as a benefit not only for AM but also for SSB. I will not be hooking any eq's or the likes to this radio, no direct inject or volting of the final.
Can anyone answer the above questions, and give recommendations for circuit improvements on this radio? Not looking to hack it up, just fix it and improve it.
Thanks in advance.
Goldfinger
Kid viscous
Patzerozero
Etc...are all welcome to chime in please.
I truly enjoy all the useful info on here. I'm NC Hawkeye, 351 AM, 592 SSB, KM4VAZ Ham. I recently acquired several radios from a broken down, collapsed barn. The roof was caved in and the floor was collapsed. The radios I got from there were laying in a pile in the dirt, but dry and hasn't been used in years.
1 Cobra 2000 GTL
1 Teaberry Stalker XV
1 Teaberry T Command
I chose to start on the 2000 GTL first.
Cobra 2000 details:
1. Receive low but does receive.
2. Transmit fine at 2.5 watt key swing to around 14 watts peak on AM and up to 16 watts on ssb.
3. Signal/rf meter stuck in receive, but works on xmit.
4. Controls and switches need cleaning.
5. Meter lights dim slightly on xmit, am and ssb same on AC, but dim dramatically on DC power with a substantial power drop.
6. Clarifier strapped, course tune must be all the way right and fine tune dead at 12 o'clock.
7. Amc and alc removed.
8. Channel kit installed at Tone Control position (expo kit).
9. Constant hash sound (sounds like a fan on an amp) coming from speakers when volume is turned all the way down.
10. Frequency counter shows 92.0002, but clock and alarm works fine.
11. Anytime I touch the base of the mic im using (Turner +3B) then the frequency on ssb shifts.
12. No mods to the audio or mic circuit.
13. Original pll (MB8734), regulator, audio IC, bridge rectifier, driver (1306) and final (2166).
Need to do first:
1. Replace all caps (already ordered them).
2. Replace filter cap on power supply side on bottom, and cap on power supply board.
3. Remove heat shield and apply new compound on bottom of shield and corresponding parts (driver, final, audio IC, regulator and rectifier).
4. Replace AMC and ALC components.
5. Adjust 3 transformers to align clarifier up to 12 o'clock on both fine and course tune.
6. Clean switches and controls.
7. Remove any old glue (not much in it).
8. Realign IF and RF stages.
9. Replace meter (already ordered).
10. Apply any upgrades for performance.
My questions are:
Why does the radio xmit better on AC power rather than DC power, lights dim bad and low xmit power on DC?
What causes the constant hash noise (like a fan running) through the speakers with the volume turned all the way down?
Why does ssb frequency shift when I touch the base of the mic I'm using on it?
Why are the lights dimming slightly when transmitting on AC power?
Everyone says the radio is loud with the Turner +3B mic. Great reports on audio sound and swing. But I would like some of y'alls best audio/mic circuit mods that are proven to improve the sensitivity and clarity of the xmitted audio. Hifi is welcome if it's proven as a benefit not only for AM but also for SSB. I will not be hooking any eq's or the likes to this radio, no direct inject or volting of the final.
Can anyone answer the above questions, and give recommendations for circuit improvements on this radio? Not looking to hack it up, just fix it and improve it.
Thanks in advance.
Goldfinger
Kid viscous
Patzerozero
Etc...are all welcome to chime in please.