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Im4jc
Intermediate Member
Username: Im4jc
Post Number: 213
Registered: 11-2005
| | Posted on Saturday, January 27, 2007 - 4:07 pm: | 
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Hey all. I want to get loud, clean audio from my Grant. It sounds good now, but I want to make it sound as good as it possibly can...tons of big audio. I have seen various mods here and other places, and have narrowed it down...I think. But before I do it, I really want your opinions. Keep in mind that I want the ALC functioning properly for SSB.
Here's what I don't want to do. I do not want to do an NPC/RC , put a switch on the AMC and volt the final [sorry Pat ;)]
Okay, there are several variations of this, and I believe that Kid Vicious has the most concise description of this. The problem is that Kid has two variations posted:
1)------------------
change R131 to a 4.7k,
change R114 to a 10k (this increases the frequency responce of your TX audio)
change C172 to a 2200uF 25volt.
change C18 to a 680-1000uF 25 volt.
and change TR41 to a 2N6487.
then give the radio a tune up, and set the dead key at 3 watts, and the SSB power at 15 watts.
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2-----------------
i did the npc mod and volted the final, but i did not remove TR24. instead i added 1.5K to the middle leg.
change R114 to 10K resistor.
change C172 to 2200uF 35 volt or higher
change C18 to 680uF 16 volt or higher
replace TR41 with NTE152
remove C207
replace R206 with a 39K resistor.
remove C232
replace R180 with a jumper
replace C163 with 3pF
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Also, here is another from a very respected technician who will remain unnamed for non-competition reasons so that I do not violate forum rules. This is the one that I am leaning towards:
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1. Jumper R180, this will increase power output and keep the bias from going negative.
2. Replace C46 with a .2 monolythic, and R114 with a 10K.
3. Remove the AM regulator (TR41?), (usually a 2SC1419) and replace it with a 2N6487.
4. Remove the 1uf (C174) in front of the 2N6487 (TR41?), and add a 1000uf from the negative hole on the board where the 1uf was and the positive lead on the 1000uf to the base of the 2N6487 (TR41?) (the lead farthest toward the back of the radio)
5. Change C18 to a 1000uf 16 volt electrolytic.
6. Add a 100 ohm resistor from pin 12 to pin 14 of the SO42P / TDA6310 transmit mixer.
7. Remove TR-26. This disables the AMC for AM, but keeps the ALC for SSB intact.
Modification explained:
Now to answer your question about removing C174, and taking the negative lead of the 1000uf cap to the negative hole where C174 was, and the positive lead to the 2N6487 which used to be the 2SC1419. It improves modulation capability quite a bit, and at the same time increases audio fidelity. If you look at the circuit (I don't have it right in front of me, all of this is off memory) the AM audio is fed from the audio IC through a 1000uf capacitor, to a 1uf that then goes to a 2SC945, which in turn "drives" the 2SC1419. What we are doing is bypassing the limitation of the 1uf, which will narrow things up quite a bit, and also any distortion that is caused or rather the end result of the 2SC945. We are still using the 2SC945 to apply bias to the 2SC1419 (which should be the 2N6487 now) to control the carrier power, but the modulation is now routed differently. You will notice that the AM peak power is now capable of 28-30 watts easily.
The 100 ohm resistor from pin 12 to 14 (ground) is there to increase the gain of the TX mixer. I have seen several times where people send pin 12 right to ground. This is 100% incorrect. They often do this in attempt to increase the gain, but they don't understand a TX mixer in general or what is going on, obviously. In this particular chassis, 100 ohms I have found is the best value to bring up the gain without any adverse effects.
This does nothing to "broadband" the TX but rather brings up the gain, and offers uniform performance across a wide range of frequencies, as the "Q" of the TX bandpass filter is high compared to exports, and therefore tend to be more narrow banded. If you have expanded the radio for more frequencies, you can easily broadband the RX and TX bandpass filters. In the bandpass filters, change the 2pf capacitors to 3pf, and it will widen it right up, but still do it's job very well.
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Okay...opinions please? |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 3468
Registered: 7-2004
| | Posted on Saturday, January 27, 2007 - 9:06 pm: |
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1 & 2 are parts of & variations of the same mod, erik. 3 is doing the same thing, just in different areas. they are both going to change audio tone, & 3 is probably widening the frequency response even more then 1 & 2. for that matter, parts of 3 could be worked into the standard npc-rc mod to improve it even more. you're in effect, storing energy in the big electrolytic, rather then adding voltage at the final. changing the regulator is to ensure enough voltage to keep the big cap delivering its 'stuff'. low voltage & you'll get wobbles & other odd audio quality issues, even on AM. and, the supposed 30 watt audio peaks from the single 1969....won't reach 30. if it ever reaches 30. i have to admit i've done the pin 12 to ground without adding resistance, can't remember how my main xl is right now-but whether it's grounded or not, it was checked for audio quality, & i went the way it sounded best. the broadband mod is standard-if the radio won't lock after expansion. if you notice, justin DOES disable the limiter on AM, something i also do-on THESE CHASSIS ONLY. they just don't go to heck unless you add a power mic fully cranked. a carefully adjusted compression-type mic such as a turner +3 or +3m can make it SMOKE, though i usually use either the stock mic or a road devil or rk70 in mobile situations.
so, my opinion? i think whichever mod the installer is more comfortable with doing would provide near equal results. especially while driving, in a noisy environment, some of the tweaks to audio quality are going to go unnoticed. i've seen & done 20+ watt XL's. my 15 watt XL has gotten by them. i've also seen my 15 watt XL get more out of an amp then a 20+ watter. with a lowpass filter on mine, it still shows 15 watts on the diamond. most of the time, as a 2sc1969 starts going over 20 watts, by adding a low pass filter, watts start dropping back into the 18 range anyway....
if you're using an amp, go the easiest route. either way, the difference between 15 watts & 30 is gonna be between antennas, or at best, too close to call |
Im4jc
Intermediate Member
Username: Im4jc
Post Number: 214
Registered: 11-2005
| | Posted on Sunday, January 28, 2007 - 12:39 am: |
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Thanks for your advice, Pat. I agree that the difference between 15 and 30 watts is negligible. I'm not really interested in the extra watts afforded by Justin's mod, just the "more audio" part. What I want is what you have been talking about for years now...bodacious audio from the Grant. Other than the receiver mod my Grant is stock, and it tx's loud and clear, but it's not like you have been describing...monster audio.
So, what would be the best way to achieve this? My tech will do whatever combo of the above that I request, but he doesn't keep up on the latest and greatest enough to recommend one or the other. I'm certainly not technically astute enough to figure it out. As for the NPC-RC mod, you almost convince me to do it (reading through your posts), but there are plenty of veterans on the Copper Forum who don't like it too. I guess it's the "RC" part of it that bothers me. I don't like the idea of Reduced Carrier, but you seem to be getting great results.
Here I go droning on and on again, but I really want to nail this down. I love my Grant and want to make it as awesome in the TX department as it is in the RX department. Man what a receiver she is! |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 3475
Registered: 7-2004
| | Posted on Sunday, January 28, 2007 - 10:17 pm: |
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where's kid vicious been hiding???? i looked in my shack for some part #'s, but there's so much stuff piled in there right now, i can't find a thing!!!
you can get it to scream without the NPC-RC complete mod. it's more the 'NPC' part that people don't like then the reduced carrier. they feel that only compressing part of the signal, rather then both peaks, shows false improvements to the signal. and on a scope, it actually dirty's it up a bit. if you want PERFECTION in the picture of the signal, very lttle modification is required-though possible. but who HEARS the picture? 3 watts of carrier is not going to cause a noticeable issue. BUT clean IN = clean OUT, to an extent. the XL chassis design is very clean to begin with, & most of the mods are values changes, with the intent of keeping it relatively clean.
as i said in the previous post, i think part of what's been posted here(mostly from the old uniden grant xl owners group). look at any mods/parts substitution in the AM/voltage regulator areas, including upgraded regulators AND electrolytic caps, & most other cap & resistor value changes in the xmit section. i think every mod without the actual change of voltage or straight removal of resistors will show audio improvement in both modes. obviously, you don't want to do any parts of the npc-rc that are 'go-togethers', but again, off the top of my head....remember, the basic 'swing mod' in itself is not a bad thing. you just have to use it right. mine will dead key as high as 7 watts or a low as zero, but i keep it around 2-2.5, because it will EFFECTIVELY swing around 15 at any carrier level. zero dead key & 15 swing looks odd, but doesn't sound bad. 2.5:15 is a 1:6 ratio, a bit more then the standard 1:4, but not like the magnum 1:45!
it'll take me a bit to find my 'stuff', so if KV doesn't add some suggestions, i'll try to dig into my cabinet next weekend. just gather up ALL the mods you can find, & skip bias moves & other voltage changes & just go with the parts substitutions. those changes with a texas star 350 will DEFINITELY open peoples' eyes when you key up! imagine a 400 or 667! |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2368
Registered: 9-2004
| | Posted on Thursday, February 01, 2007 - 7:23 pm: |
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hi guys!
dont have near as much free time as i used to these days, so forums havent been getting checked.
to put my .02 worth in;
i am currently using the last of your listed mods, the one done by JD.
so far, i really like it, and i will probably leave my radios like this unless some new hotshot comes along and re-engineers the whole TX audio chain.LOL
seriously, this i my favorite, and i really like the audio response.
remove all NPC and volted final mods.
put radio back to stock.
make sure TR24 is fully intact, as is R131.
remove TR26 (i put mine on a switch on my base station, just in case of TVI. switch the base lead)
jumper R180.
change R114 to 10K
change C46 to .22 monolythic disc cap
remove C174.
put the negative leg of a 1,000uF cap into the negaitve hole left by C174, and the positive lead to the base of TR41 (closest to the rear of the radio)
replace TR41 with a 2N6487
replace C179 with a 2200-4700 25v cap.
replace C18 with a 1,000uF cap.
run a 100 ohm resistor from pin 12 to pin 14 of S042P TX mixer IC.
not that the volted final with the NPC mod isnt loud as heck, i just happened to do this mod to my 148gtl after reading about it online, and i REALLY liked the way it sounded!
hey pat!
how goes tings?
you should definitely do one of your MB8719's up like this and see how you like it.
check the specs on the 2N6487!
also, things are alive and well over at the group of the way too complicated mods.LOL
you should come by and say hi once in a while.
hope this helps,
matt |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2369
Registered: 9-2004
| | Posted on Thursday, February 01, 2007 - 7:42 pm: |
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sorry!
TYPO in my last post.
C172 should be changed to 2200-4700, NOT c179.
also, removing C232 is not for the audio response, removing it will stop the silencing when changing channels; something that always annoyed me.
much smoother without it.
matt |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 3481
Registered: 7-2004
| | Posted on Friday, February 02, 2007 - 6:47 pm: |
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that was my thoughts, too, matt, leaving out the voltage changes. sounded like a good mod when i 1st saw it, but, like you, free time lacks right now. i recently picked up 2 brand spankin' new XL's, so as soon as my house is done, i definitely have a few projects to get going on! as for the 'group of way too complicated mods', i am signed there, just haven't looked in a long while-free time, remember!
there ya go, erik! give it a shot, & have a smokin' 8719 radio like those in the know  |
Im4jc
Intermediate Member
Username: Im4jc
Post Number: 215
Registered: 11-2005
| | Posted on Sunday, February 04, 2007 - 5:10 am: |
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Sorry for the long delay in responding. As you guys know, I'm only home one day a week.
Man, I REALLY appreciate the feedback from both of you!
Kid...I'll do it just like you posted.
Pat...I'm saving up for a 667 (after I get past the XYL barrier, that is). My dream setup is a Grant/667 combo.
I just hope I can turn down the Grant far enough after this mod to work properly with a 667. That's the one reason I was shying away from JD's mod...I really don't want 28 watts PEP from the Grant. 15 would be perfect. If not, I wonder if 7/28 would adequately drive a TS 500V?
Kid, after the above mod that you say is your favorite, what is the PEP after modding? |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 3484
Registered: 7-2004
| | Posted on Sunday, February 04, 2007 - 2:24 pm: |
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while all these mods strive for maximum output, you could always add a variable output control(i use the squelch or rf gain control)to turn things down-or just readjust the internal pot downwards a bit. turning down the mic gain turns down swing/PEP in both AM & SSB modes. after modding, you'll be surprised how low you can turn the mic gain & still have LOUD audio. turning the amp on increases apparent audio again!
7/28 would be fine with the 500v. it takes a wide range of input & gets roughly the same output with it. doubt you'll see much if any difference in PEP from the amp with 28 watts PEP input or 40 watts PEP input. the 667v with a driver is different, you'll see different output with 8-12-15 watts PEP in. on a good sounding XL, with either amp, they'll KNOW you're coming
as for barriers....YOU'RE the man of the house, buy what you want, just pick it up at the PO, don't send it to the house  |
Im4jc
Intermediate Member
Username: Im4jc
Post Number: 219
Registered: 11-2005
| | Posted on Sunday, February 04, 2007 - 3:17 pm: |
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Lol...yep..I WEAR THE PANTS IN THE HOUSE.
She just tells me which ones to put on. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2374
Registered: 9-2004
| | Posted on Tuesday, February 06, 2007 - 12:47 am: |
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i have some things i buy shipped to the office. LOL
then i sprinkle dust on them and tell the wife i got it at a garage sale. JUST KIDDING!!!
i have thought about doing that though.LOL
im4jc, i set my deadkey right at 5 watts and i have a PEP of about 25 watts.
SSB is right about 22-25 watts also.
i like the higher deadkey and so does my amp.
i run a homebuilt 2X2879 that is basically the same as a TS350 on the inside.
the 2879's like a bit more deadkey than the other popular "pills".
i wouldnt go over 5 watts for a deadkey, just so you can be a bucketmouth and not worry.
i understand that you are trying for a perfect 4 to 1 figure (7/28 watts), but that ratio isnt the primary thing you should be using to determine how you want your setup to run.
the 4 to 1 ratio is a good rule of thumb when it is used to determine whether or not the PEP power you are generating is actually on the frequency you want it on, or if it is all hash and harmonics. (wattmeters dont know the difference)
if you have a friend who says his radio will key at 2 watts and swing to 50 watts, you can be sure that some of that PEP wattage is on some harmonic of the channel he is on. try hooking up a low pass filter after the amp and before the wattmeter.
you will magically see his PEP figure go down dramatically.
this is the only way in which we operators without scopes and spec. analyzers should only be using the 4 to 1 ratio as a rough basis for tuning our radios and as a way to dispel cb myths.
so, dont worry so much about setting the deadkey so high just to get the proper swing ratio, just set the deadkey to wherever the amp will like it and let the radio do its thing.
like pat said, you will be surprised how much you will be running the mic gain at 12:00 and the gain on your power mic at 25%.
seriously, you wont need all the gain you will have, but if you want it; it is there.
like its mentioned in the mod you posted:
its hard to go too crazy when this mod is done, because the AMC is still intact.
and just to help you in your amp search, remember that although it is very disappointing to realize; these numbers are the actual truth when it comes to power out related to S-meter readings:
if your radio puts out a deadkey of 5 watts, and the station you are transmitting to is receiving you with a meter reading of S-5 then:
if you increase your deadkey to 10 watts, he will read you at S-5.5
if you increase your deadkey to 20 watts, he will read you at S-6.
here's the rest of the story:
80 watts = S-7.
320 watts = S-8.
1,280 watts = S-9.
so you can see that going from 5 to 80 watts will give you a 2 S-unit increase, but to get 2 more S-units, you have to invest alot of money and run BIG power.
if it were me; i would set the deadkey of the grant to 4 watts, let the radio do its swing, and get the 667.
you will be very happy.
matt |
Im4jc
Intermediate Member
Username: Im4jc
Post Number: 221
Registered: 11-2005
| | Posted on Friday, February 09, 2007 - 10:49 am: |
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Thanks Matt. By the way, what kind of PEP do you see from your 2x2879's? Maybe all I really need is a TS350. Anything over 250 watts out of 2x2879 is pushing it, isn't it? I'm pretty sure that the 2sc2879 is a 120 watt device, unless of course you are reading from a Davemade spec sheet, lol.
Also, isn't 25 watts from the radio WAY to much for a TS667? I would think this mod would be better paired with a straight 4x2879. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2380
Registered: 9-2004
| | Posted on Tuesday, February 13, 2007 - 10:52 pm: |
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i have no experience with a 667, but knowing that its a 1 pill driving 4 i would say yes, maybe 25 watts is a bit much for that amp.
the question is: would 12 watts PEP into a 667 give me more watts out than 25 watts into a 500?
i dont know the answer, but i imagine the difference is not that noticable on the receiving end.
i am getting about 220-250 watts out of my 2879's with about a 20 watt swing out of the radio.
on SSB i do almost 300 watts. i think the radio does just over 20 watts out on SSB.
the amp i have is biased differently for SSB and AM.
Class C for AM and class AB1 for SSB.
i dont know of any commercial amps that do this, which is one of the reasons i built this one. (its the lou franklin plans)
so my results may be different than what you would get with a TS amp.
best of luck to ya,
matt |
Johhn
Member
Username: Johhn
Post Number: 77
Registered: 8-2007
| | Posted on Thursday, October 18, 2007 - 8:28 am: |
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Did you clip R-131 at the begening..Audio Cut.... |
Hyperno_1979
Intermediate Member
Username: Hyperno_1979
Post Number: 464
Registered: 12-2005
| | Posted on Saturday, October 20, 2007 - 8:27 am: |
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I am no expert but what i have found to be the best and cheapest mod is a GOOD power mic. The Grant and it's cousins Washington, Madison etc had a heap of grunt from stock. A good quality power mic just seemed to put the cherry on top.
CEFFFCEF
Bob
CEF703/CVC26
269 Hunter Valley
NOT allowed to hold a passport....
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