Galaxy Dx-959 No Am Modulation/power/transmit

[8113 Northern MN]

I wish I had a digital wattmeter or something which read numbers better. Im using a Yaesu YS-60. Its great for showing between 1-20 on the 20w setting...but as soon as ya flip it to the 200w setting it becomes really hard to tell exact numbers. However, I have gotten it to peak over the line that would be 40watts when keying down with a 1khz signal from a frequency generator. Ive messed with the coils a bit, separating them in different patterns, moving them from side to side. Ive experimented with different size components from the install. Ive set the driver and finals all to 4.1 V and the voltage at VR 17 to 12.9v , set pots 40,42,43,44 for highest watt I could on pep. Im gonna say the best numbers Ive seen are "probably" right about 45 watts at the absolute most. At that point there were some pretty extreme heating issues when keying down for as little as 10-15 seconds. I lowered the VR 17 to 12.5 and the deadkey on AM to 3 watts. With heatsink now installed on the back and fan installed to blow air on the final section there are no more heating issues and I have it set at "about" 35 watts pep. Set up audio modulation with a local and given reports of in his words "absolute crystal clear sound". All in all I am happy with this. After I have put this radio all back together here shortly, I will be installing the same mod on my DX949.

 

[sonoma]

sounds as if you are getting it where it should be. you said you have the final and driver at 4.1 volts. is that the voltage at the gate to each. if so you may pop one after awhile. best to keep them at 3.5 to 3.8 volts . if too high they will run hot and fail sooner than normal. you can try it if that is where you have it at and if one blows you will know what could be the problem.

just to throw a wrinkle in you mods, you could even try a couple 13n10 mosfets which will give you a little more output. I have been able to get 40 to 50 and some times more out of a single 13n10 in a cobra 29. do not use the 13n10L mosfets because they only take about 1.8 volts at the gate and pop real easy. I have only done 2 so far with the 13n10 mosfets on the 29's.

 

[8113 Northern MN]

I honestly think i got a REALLY good batch of IRF520s. My DX949 blew its Final and Driver over the winter due to accidental keying up and modulation without antenna hooked up. I ordered a batch of IRF520s and ever since have been running the Dx949 with them at 4.0 with absolutely no problems at all. Ive made contacts all over the world with it and steadily get reports of great audio. Only time ive had a heating issue is when Im "competing" down on the superbowl and really getting on the mic. When I did this mod to the DX959 I took out the 520s that were inside it and put 3 of the 520s from my batch in so as to keep them all the same. Ive had weird experiences over the years with components supposedly of the same brand and size not matching up well because of being from a different batch. I know 4.1 sounds a bit high on the voltage but I really feel comfortable with where they are at with the heat sink and fan installed. The person who will be using this radio isnt a big talker and rarely shoots skip hard. We do live in a very hilly area with deep forest and Rural and he wants to be able to stay in contact with us on all his travels. Im gonna let it run with him like this for awhile and if anything happens I still have a bunch of 520s left to swap in and make changes.


Ive never heard of these 13n10 mosfets you are talking about? Are they a direct drop in replacement for the 520? And what about a Cobra 148GTL with a 2166 driver and 1969 final....? I wanna upgrade that radio to mosfets but havent found anything with good enough directions to make me feel comfortable doing it.

 

[8113 Northern MN]

I must say though.....I was honestly expecting to see higher numbers then I did with this mod. While I had no plans on leaving the radio "way up", I wanted to see what it was actually capable of with the dual finals and expected to see in the 50-60 watt range.

 

[sonoma]

it is a drop in for the 520 . has a lot more output. a friend of mine in New Jersey put me on to them a couple months ago and am going to start using those for now. Mouser has them for 43 cents each if you buy 100 pcs. he has been trying different configurations with them and he is seeing as much as 60 watts with a cobra 29. he builds them for key downs they do up in his area and people are liking them so far.

 

[sonoma]

to get more out of that radio you have to beef up the audio section from the mic circuit to get more out of it, I change a few parts in it to give a little more audio to the final section. compare the 2517 audio circuit to the 949 or 959 and you will see the difference in parts used in them. the main board is the same. since the 959 is a cb radio FCC makes them lower the audio to the finals to help keep them lower on output.

 

[Robb]

The first time I did the MOSFET mod to a 148, it worked spot on. ExitThirteen has a thread here if you search for it that makes it very easy to do. At 3.85v from a preset bias, it gets about ~24w out.

These MOSFETs are supposed to be most efficient @ 4v; but that is hearsay. But 4.1v is pushing it a bit much even with a heatsink. Best set at 4v or slightly less. I see 30w with a single MOSFET in a Galaxy after the tx coils are peaked; 50w should be seen in two unless everything isn't right. 60w is the breaking point.

 

[8113 Northern MN]

Ok. Perhaps I will have to take a look at the audio section when doing my 949 this evening. Id really like to get the most out of this radio.

Robb, I tried following ExitThirteens post on my OLD 148 that has now turned into a parts radio since my acquisition of a new working one. Perhaps there were other problems but I just could not get the radio to transit with the MOSFETs in it. I did admittedly hand make the EKL parts instead of purchasing them so its possible that was the cause. But ive also seen claims of people getting it to work without them and just modifying other areas of the final section, but have never found proof of it or any steps. So Cobra to Mosfet is still a WIP for me and my modding career lol.

 

[Robb]

it is a drop in for the 520 . has a lot more output. a friend of mine in New Jersey put me on to them a couple months ago and am going to start using those for now. Mouser has them for 43 cents each if you buy 100 pcs. he has been trying different configurations with them and he is seeing as much as 60 watts with a cobra 29. he builds them for key downs they do up in his area and people are liking them so far.

Have you tried it in a SSB radio like a 148 yet?
Gate voltage needs to be 1.8v?
Interesting . . .

 

[sonoma]

not on the 13n10 version. the 13n10L has to have 1.8 gate. the straight 13n10 runs higher. it is a direct dropin for the 520 fet. only been messing with them on 2 cobra 29 radios so far. the guy in New Jersey has even used them in the kl203 amps with good results even when driven by a ssb radio

 

[ExitThirteen]

I've known about the 13N10's for a while now, but if you run them in a SSB radio, the AM pass regulator circuit will need to be modified to withstand the extra current draw from the 13N10's. This is very critical in the older Galaxy radios, like 33/44/55/66/73/77/88/99 boards where the audio path for SSB runs thru the AM pass regulator. On the regular AM radios, like the 29, they use a modulation transformer, so it's usually not a problem. You could install one on a 148 and be ok, as long as you don't install an Asymmetric/NPC mod, since SSB audio takes a different path and does not go thru the AM pass regulator circuit. If you install any kind of a swing mod or compression mod, you'l have to modify the AM pass regulator circuit, or you'll smoke the pass regulator in short order.

If the OP decides to install the 13N10's in the 949/959's, the AM pass regulator circuit will need to be upgraded if running dual finals.

~Cheers~

 

[8113 Northern MN]

Exit, by modifying the AM pass regulator circuit would simply upgrading the Voltage regulator at Q55 be sufficient? I did change it from a 2SB827 to a 817 and also upgraded Q54 from the stock 1869 to a 2SA1012-0. It was my understanding these mods would beef up the ability of the radio to handle more voltage while staying stable and also allowing much better modulation.

 

[ExitThirteen]

The 2SB817 with the 2SA1012 will be fine with the IRF520's, but not with the RQP13N10's. As long as you use the 520's you should be fine.


~Cheers~

 

[Robb]

Just ordered ten fqp13n10; going to change out the MOSFET in the 148 and see if it picks up a few watts. From what I understand on YouTube, they also run cooler - which is a bigger plus.

Thanks for that tip . . .

 

[Robb]

I've known about the 13N10's for a while now, but if you run them in a SSB radio, the AM pass regulator circuit will need to be modified to withstand the extra current draw from the 13N10's. This is very critical in the older Galaxy radios, like 33/44/55/66/73/77/88/99 boards where the audio path for SSB runs thru the AM pass regulator. On the regular AM radios, like the 29, they use a modulation transformer, so it's usually not a problem. You could install one on a 148 and be ok, as long as you don't install an Asymmetric/NPC mod, since SSB audio takes a different path and does not go thru the AM pass regulator circuit. If you install any kind of a swing mod or compression mod, you'l have to modify the AM pass regulator circuit, or you'll smoke the pass regulator in short order.

If the OP decides to install the 13N10's in the 949/959's, the AM pass regulator circuit will need to be upgraded if running dual finals.

~Cheers~

As in just changing out the AM Regulator for a beefier part; or would its companion part also need to be upgraded beefy as well?