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Im4jc
Intermediate Member
Username: Im4jc
Post Number: 230
Registered: 11-2005
| | Posted on Monday, March 26, 2007 - 9:05 pm: | 
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I just picked up a used 667V. With my Uniden Grant LT set at a 2 watt deadkey and about 14 or 15 PEP, it keys the amp at 200 watts. Youch! This is with the dial-a-watt switch off and variable fully clockwise. Just to see what would happen, I turned the Grant (VR10) as low as it would go which is about 1 watt. I keyed it up and am still getting over a 200 watt deadkey. I am shooting for about a 125 watt deadkey, but I just can't get it low enough.
This is driving me crazy. The only way this amp is usable is if I turn on the dial-a-watt and turn the variable down to about 11 o'clock. This produces a 100 watt deadkey and about 450 watt PEP. I don't want to continue running this amp with the variable on because it will eventually burn it out.
If I turn the variable beyond 11 o'clock to achieve a 125 watt deadkey, it begins to squeal. What's weird is that if I touch the radio bezel or the mic jack with my left hand while keying up with my right hand the squeal goes away.
I have 25' 8 gauge wire running directly from a bank of 4 batteries to the amp, and I have a shorter 5' 8 gauge wire that runs from a bolt in the metal floor straight to the ground wire on the amp. I have a 160 amp alternator.
I do not have the amp chassis or the radio chassis grounded. My SWR with the amp off is 1.1 to 1. With the amp on and keyed at 100 watts, the SWR is 1.2 to 1.
Also, I can make it squeal by taking my bunched-up coax and moving it around. I have to find the right place for the leftover coax and all is well...kinda.
Any help would be greatly appreciated. |
Romstar
Junior Member
Username: Romstar
Post Number: 35
Registered: 3-2007
| | Posted on Tuesday, March 27, 2007 - 3:21 pm: |
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If you have extra coax, get rid of it. There are very, very few applications where you need a specific length of line. In most cases, you want the shortest length that will do the job.
Certain rare antennas require a specific coax length, but again these are rare.
If you can't get rid of the coax, coil it up. Not too tight, and not too loose. Use two or three zip ties to hold it in a coil. Find a convenient out of the way part of the length to do this with.
Next, get grounded. There are all kinds of tech tips and articles on the forum about proper grounding, and you should read as many as you can.
When you can cause squeals with your body, or by moving coax, you have an issue there.
Start with those two items and work outward from there.
Romstar |
Hotwire
Senior Member
Username: Hotwire
Post Number: 2195
Registered: 1-2005
| | Posted on Tuesday, March 27, 2007 - 1:33 pm: |
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I would check to make sure everything is rf grounded well. Ground the radio and amp chasiss. I like to run both positive and negative power wires directly to the battery, radio and amp. Check your pl259's to be sure that the braids are soldered correctly. If the braids solder connection is broken in the pl259 then that can cause trouble like what your having. Also where is your antenna mounted? Is it grounded and up above the vehicle away from other antennas or anything that can cause rf to get inside the radio?
One more ideal and this just might be the problem.Unhook all that wire you have connecting all those batteries to the amp. A 160 amp alternator with the amp connected directly to the vehicles starting battery is plenty of power for a Texas Star 667.
I run my Texas Star 500V, ( pretty much the same wattage as the 667) with a 100 amp alternator and Optima red top with no troubles at all!
good luck
Kenny
cef491(27.115lsb)
2sf491(27.555usb)
Indiana
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Patzerozero
Senior Member
Username: Patzerozero
Post Number: 3570
Registered: 7-2004
| | Posted on Saturday, March 31, 2007 - 3:35 pm: |
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erik, was there an amp before the 667 was in? how did IT work? have you looked inside the 667? bad pot, or resistor, or did somebody try to modify it for higher input capacity? or something else going on inside it? anyway, sounds like bad ground/stray rf issues, based on the fact that the 'squeal goes away when you touch it'. have you checked with a 'reverse' reading wattmeter, to see how much forward power, then how much reflect? better yet, an analyzer could help. i have seen plenty of 1.1:1 swr readings show 50-75% reflect, and antenna resonance nowhere near the intended frequency.
romstar is correct in saying 'In most cases, you want the shortest length that will do the job'. if you don't look at a wattmeter, things are just fine. but since you want to be as near optimum as possible (like me  ), start at 'A', make sure radio is good, then check ALL coax & antenna, check amp, then, yes, try different jumper lengths, amp/meter locations, check/shorten grounds, leave hammer at home, etc |
Im4jc
Intermediate Member
Username: Im4jc
Post Number: 231
Registered: 11-2005
| | Posted on Monday, April 02, 2007 - 2:46 am: |
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Thanks all, I just got back from being on the road again.
I ended up grounding the chassis of the amp and radio, and the squeal went away.
Man this thing rocks with my Grant, lol. What a prefect combo!
I talked with a few people who run a 667v, and they all run it with dial-a-watt on and the variable all the way clockwise. At this setting, I get a 150 watt deadkey and 600+ watts PEP. This is with the radio set at 1.25 watts dk and about 13 to 14 watts PEP (TR26 removed, R131 intact). With dial-a-watt off, I get 250 watts deadkey with 1.25 watts in. This is way too much, so I'm just running it with dial-a-watt on and everything is great.
I have read here that the variable will burn out if you run with dial-a-watt on all the time, but others say they have been running it like that for a long time with no troubles. One guy says that he's been running with dial-a-watt on and a 250 watt deadkey for over a year now with no troubles. He uses it every day like this.
On the 667V, the variable works whether the dial-a-watt is on or off, not like the 500V where the variable only works with dial-a-watt on. On the 667V, it makes me wonder what the heck the dial-a-watt is even on there for if the variable works at all times anyway.
So, is this abnormal for me to be getting a 250 watt deadkey with 1.25 watts in and dial-a-watt off?
I tell 'ya, if it's not hurting anything, it's working just perfect the way it is with dial-a-watt on, the variable fully clockwise, a 150 watt deadkey, and 600 watts PEP.
One thing bothers me though. I have a 1.1 to 1 SWR with the amp off both at the radio and after the amp. But with the amp on and keyed up at 150 watts deadkey, the SWR after the amp is 1.1 to 1, but the radio is reading 3 to 1. Should I worry about this? If so, is it something that can be repaired inside the amp, or is it as simple as trying different jumper lengths until the SWR between the radio and amp is in the safe zone when the amp is keyed at 150 watts? If it's not going to damage anything, then I'm not really worried about it for awhile.
Pat, no, I don't have a reverse reading watt meter. What the heck is that? Also, I don't have a clue how to calculate percentage of reflect or antenna resonance. I sure wish I could get my hands on one of those Aries digital meters that they don't make anymore.
Hotwire. I have the amp in a big rig, and it requires 4 batteries. The batteries are all connected to each other with 1 gauge, then they are grounded straight to the frame with a 1 foot run of 1 gauge.
I'm still a bit worried about getting a 250 watt deadkey with 1.25 watts in with dial-a-watt off, even though I never run it at that. |
Dale
Advanced Member
Username: Dale
Post Number: 707
Registered: 12-2002
| | Posted on Monday, April 02, 2007 - 9:48 pm: |
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dont understand about the dial-a-watt not working
push button in then dial-a-watt should lower that
250 watt carrier.howerver this amp should be
fine at 250watt dk because its not a little 100
watter.imho anyway.the texasstar amps are nortourious for that kinda swr reading.with
amp off/not inline go with that swr and forget it
dale/a.k.a.hotrod
cef426
cvc#64
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Im4jc
Intermediate Member
Username: Im4jc
Post Number: 232
Registered: 11-2005
| | Posted on Tuesday, April 03, 2007 - 1:32 am: |
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Dale...the dial-a-watt does work. It lowers my numbers like it should. What I am saying is that the variable works whether or not dial-a-watt is on or off. I have found that this is how it's supposed to work on the 667V.
With dial-a-watt in, like I said above, it lowers the carrier from 250 watts to 150 watts.
Someone else told me that I need to adjust the input tuning on the amp, that a 1.25 watt input should not be producing a 250 watt deadkey with dial-a-watt off.
Oh well, as it is, I'm happy with the 150 watt dk and 600 watt PEP with the dial-a-watt on and the variable fully clockwise. I am going to play with jumper lengths to get the right readings between the radio and amp. |
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