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Message |
    
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 248
Registered: 9-2004
| | Posted on Thursday, March 03, 2005 - 12:36 am: | 
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this is my new favorite radio! i got one bone stock off of ebay, and it has the best quality receiver ive ever heard! this is going to be my number one so the mods must be top notch. (no clipping out TR24 here). i have found three different mods to the audio circuit for the radio. two are some parts value changes, one is the npc-rc mod posted on this forum by adshare64.
here they are:
1. replace the resistor in front of TR26 with a 270ohm. add 800 ohm resistor to the collector of TR24. it also says that if these dont provide enough boost, then replace R126 with a 4.7K.
to me this mod seems to just stress out the parts in the circuit. maybe a tech can lend some info as to what this mod is actually doing.
2.this is adshare64's npc-rc mod, i wont repost it here so here's the link.
http://www.copperelectronics.com/cgi-bin/discus4/discus.cgi
i want to do the npc part of the mod, not the rc part. any ideas on this are appreciated.
3. here's a new one! remove R166. add an 8.2K resistor from emitter of TR26 to 8 volts constant.
change R228 from 560 ohm to 33K.
change R159 from 18K to 33K.
C109 should be 10uf, if not, replace with 10uf.
well there you have them! which one is the best?
any experience with any of these? im not looking for teh best way to drive a linear. im looking for the highest fidelity audio that i can get.
one idea i have is to remove R131 and add the 10uf cap. from the npc mod. what are the thoughts on this?
thanks in advance for any and all input.
think about it. if we get enough responses on this post, maybe we'll save some bandwidth by eliminating more repetative posts.
EVERYONE INTERESTED SHOULD POST AT LEAST THEIR OPINION!
matt |
Tech808
Moderator
Username: Tech808
Post Number: 5072
Registered: 8-2002
| | Posted on Thursday, March 03, 2005 - 1:00 am: |
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Kid_vicious,
Ok you said I could post. 
If it is Bone Stock, Leave It Alone and add a DM-452 mic and you will be HAPPY! 
If you do not have the equipment to properly Adjust & Align it after the Mods then Don't do them.
There are 1000's of Junk 2000's out there that people have messed up and very few that are still 100% stock.
Like the old saying goes it its not broke then don't fix it.
Just my personal thoughts.
Lon
Tech808
CEF808
Tech808 |
Racer_x
Member
Username: Racer_x
Post Number: 78
Registered: 2-2005
| | Posted on Thursday, March 03, 2005 - 7:36 am: |
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Lon is right - leave it alone. Butchering one of the best all time CB radios isn't something I'd do.
If you really want to sound loud then buy a desk mic with some compression. My nod goes to a Turner +3, but there are others. |
Tech291
Moderator
Username: Tech291
Post Number: 111
Registered: 11-2004
| | Posted on Thursday, March 03, 2005 - 7:15 pm: |
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I third that motion!the 2000 would use the +3b turner.if you can find one a turner SSK is another good choice.
tech291
CEF#291
kc8zpj |
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 250
Registered: 9-2004
| | Posted on Thursday, March 03, 2005 - 10:09 pm: |
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ok guys, while i appreciate the sentiment, and i did ask for opinions, i was hoping for some technical explanations of what these mods are doing.
my goal is not to "be the loudest on the channel".
i am looking to learn more about the hows and whys of these mods.
that being said, my ego is a little bruised here guys; have my past posts given you the impression that i've never successfully modded a radio?
while its true that i know VERY little about circuit theory, i am very confident in my abilities to align and change out parts in a radio. i have been a ham operator for the past 16 years, and have done my fair share of channel mods and alignments. think of me as that mechanic that you dont let near the diagnostic maghine, but can tune a carburetor like nobody's business.
so in closing, maybe i should rephrase my question.
is there anyone out there who still finds it interesting to discuss modifications in depth; particularly ones for the audio section of the cobra 2000gtl?
matt |
Racer_x
Member
Username: Racer_x
Post Number: 93
Registered: 2-2005
| | Posted on Friday, March 04, 2005 - 7:09 am: |
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Perhaps you misinterpreted my use of the word butchering. I wasn't referring to your abilities - I was referring to the modification you were asking about.
Swing mods are crap in my opinion. Taking a nice radio like a Cobra 2000 and doing a swing mod to it is butchering to me. Swing mods don't do anything useful. It's all show and no go. Sure your signal will look cool on the meter, but you won't be able to communicate further, you won't be louder, you won't get more power, and you won't have the high fidelity audio you said you were looking for.
Tweak it so it's capable of 100% modulation and you'll have a great sounding radio with the highest fidelity possible.
If you want to be louder use a speech processor or a compression microphone - both of which actually decrease the fidelity of your audio in order to increase the average modulation level. |
Patzerozero
Advanced Member
Username: Patzerozero
Post Number: 525
Registered: 7-2004
| | Posted on Friday, March 04, 2005 - 5:17 pm: |
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kidvicious, i'd clip the limiter & turn the AM & SSB power pots all the way up & put 12volts to a turner +2 & then...
just kidding.
"Taking a nice radio like a Cobra 2000 and doing a swing mod to it is butchering to me."
OK. because of the radio in particular, agreed.
go look for a used cobra 148 or grant xl & experiment with that. put your mods on switches whenever possible. & WHEN you find a mod you like, you may feel it is acceptable to be placed in the 2000, on a switch.
since the %$#@& grant xl owners group website is gone, several mods i cannot locate, your 3rd choice sounds familiar, but what i have written down is different part #'s & values.
now if you had that sacrificial 148, you could try those mods in combination with each other, partially or fully, etc, etc. |
Racer_x
Member
Username: Racer_x
Post Number: 95
Registered: 2-2005
| | Posted on Friday, March 04, 2005 - 10:28 pm: |
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" i'd clip the limiter & turn the AM & SSB power pots all the way up & put 12volts to a turner +2 & then..."
What? No D014?!?!!! You can't clip the limiter, turn all of the pots up and NOT use a D104 on it! How are you going to splatter all 40 channels without a D104?
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Patzerozero
Advanced Member
Username: Patzerozero
Post Number: 533
Registered: 7-2004
| | Posted on Saturday, March 05, 2005 - 8:48 am: |
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i don't run d104's on my equipt. have 5 of 'em though.
original turner +2 ssb something or another, the 1 that needs to be rewired for electronic switching bleeds over really good if you force feed 12v from the power supply into it. shure 526t super punch does a good job on bleedover, too. :-)
c'mon now, racer. there are some radios even i wouldn't butcher. at least not right away. had i purchased it new in the '80's & it wasn't yet a classic... |
Racer_x
Intermediate Member
Username: Racer_x
Post Number: 103
Registered: 2-2005
| | Posted on Saturday, March 05, 2005 - 4:24 pm: |
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Cool deal Patzerozero. It's good to know that we all have limits - even you.
Aside from their looks, I'm not a big fan of Astatics either. How do you like the 526T? I've never used one and I don't believe I've ever heard one on the air. I understand they have a very effective compressor and a good dynamic element.
I hope if you ever buy a CPI CP2000, ARF2001, Stoner Pro40 or GE Superbase you resist the temptation and let them stock too. There are some radios that really deserve respect because they are made so well. |
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 257
Registered: 9-2004
| | Posted on Saturday, March 05, 2005 - 8:11 pm: |
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thanks for the help guys, thats what i wanted to know. you can rest assured that i wont be doing any of the mods listed to this radio.
i need a new mic anyway. i havent looked at what's available in speech processors in years, anyone have any advice about choosing one?
this radio will never have a foil trace cut. i swear it!
matt |
Patzerozero
Advanced Member
Username: Patzerozero
Post Number: 541
Registered: 7-2004
| | Posted on Saturday, March 05, 2005 - 9:37 pm: |
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i commemted on bc's 'do you know where your mic is' thread because i did exactly that with 1 of my 2 526t's. & now i have no clue what happened to the other! it's killing me since shure discontinued it. i used it on my ic735, ft101e & ar3500, & it was GREAT on both AM & SSB. people who know my 'sound' knew when i wasn't using a handheld, which i do 90% of the time on the base. been looking for my other 1 for a while, to try it on my S9. i'm just going to have to look for another.
i'd love to have my d201a, golden eagle mkIVa & dak X back. never had a stoner or cpi, but have been keeping my eye open for things. can get the tram & browning, probably better then new, from a gent in mich, but i'll buy a brand new ic706mkIIg for nearly the same $ 1st.
i'll keep modding the uniden, cobra & texas ranger mobiles til the supply is exhausted. but, kid vicious, i've got my S9, ar3500, 735 & 101 to get to my over & under freqs. if i ever re-
acquire 1 of those classics, a replacement 526t should do the trick when i go show off in front of the big boys, of course there will be a kilowatt or so to back up my bravado. the neighbors will survive-i don't do it often. |
Racer_x
Intermediate Member
Username: Racer_x
Post Number: 108
Registered: 2-2005
| | Posted on Saturday, March 05, 2005 - 11:16 pm: |
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The currently available speech processors I know about are the SP1, Lou Franklin's DSP kit, Ten Tec's kit, and the DF4ZS RF speech processor. There are also used speech processors on auction sites from time to time. |
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 259
Registered: 9-2004
| | Posted on Sunday, March 06, 2005 - 12:08 am: |
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thanks to both you guys, i have tried lou's processor before, but unless im going to buy a scope with it, i doubt i'll get it set right.
the one im most interested in is the VSB-1 that used to be sold by Selman Enterprises. maybe someone has a schematic on it.
matt |
Racer_x
Intermediate Member
Username: Racer_x
Post Number: 110
Registered: 2-2005
| | Posted on Sunday, March 06, 2005 - 7:50 am: |
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You don't really need an oscilloscope to install/adjust the Lou Franklin processor. If the limiter is set at 100% modulation you just adjust the output from the processor to the point where it doesn't get louder anymore. Back it down just a tad from the point where it gets the loudest and you should be at the right point.
I think the most important part is construction with the proper settings. I hear folks complain about squealing but there are instructions that make it simple to back down the audio gain and add RF filtering. For a Cobra 2000 there are specific instructions about eliminating excess audio gain. |
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 263
Registered: 9-2004
| | Posted on Monday, March 07, 2005 - 1:54 am: |
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i sure tried to get mine set right, but this was 14 years ago and i think i had already butchered the 142gtl i tried to install it on.
just out of curiosity, do you have a radio with one of these in it? if so, what do you think of the sound?
matt |
Racer_x
Intermediate Member
Username: Racer_x
Post Number: 117
Registered: 2-2005
| | Posted on Monday, March 07, 2005 - 9:44 am: |
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I've got one and it works great for what it is - a lot of bang for the buck - especially on SSB. It's much better than a compression processor. At higher levels of clipping there is quite a bit of noise added to the audio because clipping harmonics aren't totally filtered out in it's design.
I've got a multiband AF speech clipper that eliminates the noise problem by splitting the audio into 4 separate bands, amplifying, clipping, filtering, and then recombining the separate bands for output. It's outstanding.
All speech processors reduce the dynamic range of speech to increase the modulation level. As the level of processing increases, speech sounds less and less natural. But at moderate levels of processing it makes speech loud and strong. It also greatly increases the average modulation level which can make radios run much hotter than normal, so you've got to watch it and make sure the radio doesn't cook it's output transistors.
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Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 266
Registered: 9-2004
| | Posted on Monday, March 07, 2005 - 10:45 pm: |
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thanks for the input! do you think the VSB-1 is the same type of thing? if i remember right, it didnt have any VR's to adjust.
matt |
Racer_x
Intermediate Member
Username: Racer_x
Post Number: 122
Registered: 2-2005
| | Posted on Tuesday, March 08, 2005 - 5:48 pm: |
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It's been around a long time because I read a reference to it in a CB newsletter from 1986. I've never seen one. From what I've read I'd guess that it's a compression amp with mild levels of compression.
If that's what you're looking for, try the SP-1a speech processor. It's got variable compression and output level. |
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 271
Registered: 9-2004
| | Posted on Tuesday, March 08, 2005 - 6:34 pm: |
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the thing that i thought was most intruiging about the VSB-1 (its from the secret cb people), was that it had an "expandor" for the receiver, installed near the AM detector, and a "compressor" wired near the AMC circuit.
i had one but didnt know where to interface it with my radio, so i gave it away. DOH! now im on the search for another one or at least a schematic.
does anyone know if selman enterprises is still around in any way shape or form?
matt |
Racer_x
Intermediate Member
Username: Racer_x
Post Number: 124
Registered: 2-2005
| | Posted on Tuesday, March 08, 2005 - 7:15 pm: |
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Sounds interesting. If you ever find some information let us know about it.
Is it covered in the "Secret CB" books? Long ago I read that they were full of errors and bad modifications so I never bothered with them. |
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 272
Registered: 9-2004
| | Posted on Tuesday, March 08, 2005 - 9:08 pm: |
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yep, they started putting the radio specific instrucitons in their books, so you had to buy the board, and then purchase the correct volume of secret cb.
yes, its true that the books have errors in them, but they printed corrections in later volumes. they're great to have if you have the whole set. (i dont). i find the volumes i do have to be great reading material while sandbagging on the local channel, and every once in a while, someone will key up with their latest "garage sale special", and i'll have a few mods for it.
i dont think they ever printed a schematic of the VSB-1 in them though. i sure hope im wrong on that one.
i think i'll start a "secret cb" post.
matt |
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 293
Registered: 9-2004
| | Posted on Monday, March 21, 2005 - 2:32 am: |
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well, im back. racer x and patzerozero, i took your advice and found a 148gtl to try my mods on.
i turned D54 around, this seemed to drop the deadkey while keeping the modulation peaks the same. didnt increase swing at all.
next, i tried replacing R194 with the 1N60 diode. this did about the same thing. less deadkey wattage, but same modulation peaks.
not liking this, i put R194 back in, but not before trying the radio with nothing in the R194 spot. this gave me absolutely NO deadkey wattage, but would swing to full mod. on the receiving end, i was told i was swinging from s2 to s10, but you can imagine what the audio sounded like.
so i put R194 back in, and turned D54 around the right way, putting the radio back to stock.
then i decided to volt the final, and remove R131.
im pretty happy with this; the radio keys at 5 watts and swings to about 16.
the audio reports i get are good, but who can trust a CB'er. J/K!
so my question is, what does R131 actually do?
and If this was your 148gtl, and you wanted to mod it a bit, what would be your preferred method?
thanks for all the help guys.
matt |
Patzerozero
Advanced Member
Username: Patzerozero
Post Number: 595
Registered: 7-2004
| | Posted on Monday, March 21, 2005 - 10:43 am: |
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r131 sets the limit for the limiter circuit, if i remember correctly. no matter where you turn the AM MOD VR (or ALC/AM) r131 limits it. that's the resistor i'd put on a switch, for local/distant use, AM/SSB use.
cut trace to middle leg of Q24, and bridge with 1.5k resistor.
replace r124 & r126 w/ 4.7k resistors.
tune L36 & 38 for AM peaks while adjusting VR 10 & 11 (i think) for AM & SSB.
remove c207
remove c232
lift r166 & check for correct operation
Q41(AM regulator) probably 2sc1419, change it to a NTE152
c18, change to 330uf 16volt or bigger
change c172 to 2200uf 50volt
place jumper across r180(it changes bias to q37 regulator & can cause signal to distort because it limits power output, when doing all the power mods)
change c163 to 3pf
change r114 to 10k for wider audio response(you can experiment to see how much lower you can go)
put a 10uf 25v elctrolyic cap positive leg to pin 9 of IC6, negative leg to r271/d63/r228 junction.
all of that should be performed prior to:
clip & separate TP8
solder jumper from c148/L39 junction to junction at d55/c188/red wire from input coil-should be 13.8 volts.
jump r196
and if you wire VR10 to external pot (into squelch, maybe) you can externally vary your wattage from about 1 watt or less up to maybe 6 or 7 & it should peak in the 20 range. on a bird. i've seen a dosy say 40, but....
i think that's most of the xmit mods
of course, you can add freqs thru the PLL mod or expo kit, open the clarifier on xmit, add a 10kc switch for 'a' channels, & more-
take a 10uf 25volt electrolytic cap & solder across spst switch, find c23 & run leads from + & - to same polarities of cap soldered to switch, fast & slow AGC for SSB.
replace q14 with a 2sc2999(that's the best choice, but i think NTE107 works also)for at least 3 db gain on weakly received signals!
take the q14 you removed & use it in place of q19(2sc945). that will be a major upgrade to SSB detector.
for even more increased AM sensitivity(& less noise), replace d1, d2, d21, & d22 with NTE583 schottky diodes, or sk9975 diodes.
i'm tellin' ya, KV, my grant xl with these mods & NO power mic SCREAMS. that radio is LOUD. a ham friend will scan & find me talking DX or LONG distance local from my mobile & he just laughs-'that has got to be the absolute loudest &*#%ing radio i have ever heard!!! so clear with no muffled cb sound at all!!!incredible!!!'
but to give racer his due, find another 148 or grant (!!!) & go the processor/compressor route & see which you prefer, which gets the best signal reports. then you decide how you'd like to live!
the receiver transistor & diode mods i would make no matter what. no effect at all on transmit, but they make those incredible receivers even BETTER!!! |
Usa2112
Junior Member
Username: Usa2112
Post Number: 41
Registered: 2-2005
| | Posted on Monday, March 21, 2005 - 8:37 pm: |
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I would do the power and modulation mods and leave the freqs alone.That radio is an audio monster opened up. |
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 296
Registered: 9-2004
| | Posted on Monday, March 21, 2005 - 10:35 pm: |
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patzerozero, you probably wont believe this but i am grinning from ear to ear after rading your post. thank you so much for the info! i have been scouring the net trying to find exactly what you gave me.
youre right that i should give racer x his say before i do the TX mods, but think this is what im going to do. i'll do the RX mods no matter what! the mod sounds similar to the RCI2950 RX mods ive done. is Q14 a 2SC1674? ive seen these on the parts list and wonderedif i should cahnge them to 2SC2999's.
thanks again for the GREAT info. i'll bet im not the only one that you've helped. think about all the future searchers who will come across your post. if you could, would you check the part #'s that you posted? id hate to burn a radio because of a typo. hope i get to hear you on the net on sunday. thanks a million!
matt |
Racer_x
Intermediate Member
Username: Racer_x
Post Number: 197
Registered: 2-2005
| | Posted on Tuesday, March 22, 2005 - 6:12 am: |
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Kid_vicious - It's your radio so please do as you like to it.
If it were MY radio, I'd install a 7.8MHz Channel Guard, give it a good alignment, and possibly do the receiver modifications.
For big modulation with mobile CBs, I use a small RF speech processor. When I want to have a nice clean sound, I just switch off the processor. No swing mods, no audio mods, no transmit mods of any kind. |
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 299
Registered: 9-2004
| | Posted on Tuesday, March 22, 2005 - 10:30 pm: |
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thanks for the response racer x, you dont know what it means to me to have people that actually know what theyre talking about take time to answer my questions.
im going to do the mods pat00 suggested to my 148, except cutting the foil trace, i'll remove the TR and solder on the resistor and then replace. i always keep good notes on my mods and save all the old parts, so if i choose, i can put the radio back to stock. however, if i find that i like the sound of that radio after the mods, there's a good chance that the 2000 will get the same treatment. i will be getting a channel guard for these radios. i realize that some people reading this will consider me a "butcher" for modding these classics, but that's the draw of the hobby to me. thats why i love these old uniden chassis so much. if i wanted a radio that was kept completely stock then i would buy a TS940S. rest assured that i consider the radios that i have to be classics, and i wont be hacking them apart trying to get 2 more watts or 20khz of slide.
thanks for all the input guys, you both have taught me a lot.
matt |
Patzerozero
Advanced Member
Username: Patzerozero
Post Number: 605
Registered: 7-2004
| | Posted on Wednesday, March 23, 2005 - 5:21 pm: |
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double checked 2x as i did it,KV. these mods work in grant xl & lt, 148, texas ranger 296. the only differences i have found so far are labeling transistors Q or TR in different radios, some parts seem to be in different spots on xl & lt, & 296. 148 & xl seem to all be in same place. also noticed different resistor & cap values , wattages & voltages from radio to radio, guess either 'factory improvements', parts availability or whatever.
how the heck did i forget the channel guard???
some mods go hand in hand with each other, some can be used separately. like i said, experiment with 'em & see which ones results' impress you. & i always put the limiter on a switch. close SSB qso's & local 'amp-on' talking SOMETIMES benefit from the limiter being inline. & of course the external wattage variable control...
yes that's the 2sc1674 that's being replaced with a 2sc2999, for improved receive sensitivity, & that used 1674 is going into the SSB detector circuit. be careful, there are several 1674's in the radio, don't know what happens if you change the wrong 1 though...
i picked up a lot of that info through the years, & i know some(maybe most?) was available on the now defunct uniden grant xl owners club website.
i've tried all the mods over the years, piecemeal & together & other then stupid mistakes that had to be retraced & repaired, they all work. did most of those mods to a recently acquired 296, & sold it to someone who was so impressed with it's rcv as well as xmit the 1st time i used it, this week, he offered me a price i couldn't refuse!!! i have to order a channel guard for him, as i didn't have 1 in it, but he is already shopping his AM galaxy & connex's around! everybody is telling him how much better he sounds!
GOOD LUCK!!! |
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 304
Registered: 9-2004
| | Posted on Wednesday, March 23, 2005 - 6:30 pm: |
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right on, thanks again pat.
looks like ive got to wait a bit to the mods. my dad just brought over his PRO-538w to have me lower the deadkey on it. it also has a motorboating sound to it. so, i gave him my 148 to use until i get this one fixed. (sure hope he lets me have the 148 back!)
matt |
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