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I have a few 520s, I thought I had read somewhere that the 13n10 was A stronger mosfet which is why I bought 50 of them. I'm still learning a lot about electronic theory and practice, so forgive any stupid questions or assumptions. Is the easiest way to adjust the gate to do the tip120 hooked...

Changed r123 back to a 10 ohm and now gate voltage is about 3.78 which is a little too close to MAX. Would dropping this down to a 5 ohm lower the gate a little bit more?. Also, the modulation is back but weak. 10w dk swing to about 16w. Turning vr4 didn't seem to make any difference

Hmmmm. Put a new final in and replaced what appeared to be a cooked r123 10ohm with a 22 ohm. Got good receive but now I'm not getting any modulation, dk @ 2w. The gate voltage is now a steady 4 volts when keyed. Which resistor do I bump up to lower the gate? One of the ones in the 1230...

I removed the final, the transformers are no longer heating up when powered on. I'm probing the far right solder pad when looking at the solder side of the board for the final. When I key the Mic it shows zero volts, then jumps to 4.5 volts for just a moment when the Mic is unkeyed. This...

Right on! I'll check her out in the morning. Thanks much!

So the fried final could cause the transformers to heat up?

I had a gate voltage of about 2.2vdc, which I believe is a fair margin less than the recommended max of 4vdc. I guess we'll see if it goes into BBQ mode again.....

It's the straight 13n10 from Fairchild. I did not check gate voltage. Would the cooked final cause the transformers to heat up? At what level of modulation do I check voltage? Deadkey or full Mod?

I pulled out the wimpy 2078 along with r55, r56. C61 did not appear to have ever been installed in this radio. I built a en1230 from through hole components and placed it with the positive side towards the front of the radio in r56's holes. Replaced original final with 13n10 mosfet. I...

I had some issues with mine cooking all the Mosfets a week ago. Took it apart, replaced the unidentifiable Mosfets (sanded off id numbers) with 13N10s, and replaced the relay with a Avicom unit. I'm now getting 200w+ on SSB and about 175w on AM. Being driven with a 4w carrier and 9-10w swing...

This is on an old workman p5000. I've checked a lot of different units with the meter and even an amp pushing about 200w on SSB. It seems to be reasonably accurate from what I've been told to expect from various stock rigs and those that were modified with mosfet finals. Shows a dead solid 4...

The 5 pin Mike works as it should, radio functions are restored. Just need to figure out why it's only modulating on SSB now, am had no mod. Never mind, turned the Mike gain all the way off while I was fidgeting. Dk @ 4w, swinging to 10w. This appears to have a Mitsubishi 1969, is it worth...

Well I'm at a bit of a stumbling point. I crossed pins 2 and 4 in to pin 1 of the cobra connector and hooked everything else up as I think it should be according to wire functions. Now I've tried 5 different 4 pin mics and they all seem to do something different. I tried a cobra ca73, a...

I crossed 2 and 4 from the 5 pin radio to pin 1 (top left facing the solder side with the notch up) of the cobra connector. I must have done something backwards because now the Mic acts like a speaker when I key it. If there is good news, it's that the Mic doesn't squeal when keyed. What...

It appears the switch wire changes the radio state from rx to tx independent (and perhaps redundant) from the tx and audio wires. I extended the board the original 5 pin was mounted to with some 4" leads to make experimentation a little easier. Going to try the 3 shortcut options first, then...

Wow. Thank you for the thorough response, you don't get those very often in today's world of "k" text messages. I guess I'll try it the easy way first (or all three easy options) then proceed to the copper board and the acid wash. Maybe I'll get lucky. This is the first 8719 board radio...

I'm not going to order the adapter plug because I have spare 4 pin sockets. I got this radio without a mic but it powers on and everything seems to be working as far as I can test it without a mic. I've done a lot of searching and it seems I need to join pins 2 and 4 (shield and switch wire)...

Actually it's not a pot but a variable air gap cap. I'm thinking maybe it emits a test tone for aligning a radio?

Really not sure what this thing is. I got such a good deal yesterday on 2 generations worth of CB equipment from a widow on craigslist for $75. Bunch of pre amps, antenna switches, ext speakers, 3 portable SSB units and 5 base stations. I also got this small enclosure that doesn't have...

So I just got my tech license and am modifying a Cobra 139XLR to play on 10M and CB frequencies. I was able to procure a NIB 1970s Avanti Astro-Plane Antenna which is 12' tall but 8' of it hangs below the top of the mast. This antenna radiates from the top at an upward angle. I'm planning on...