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Vanillagorilla
Intermediate Member
Username: Vanillagorilla
Post Number: 203
Registered: 4-2005
| | Posted on Saturday, September 10, 2005 - 7:13 pm: | 
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Shootin a little skip this afternoon and after about 1/2hr or so with Palomar on "med" I noticed I'm only doing about 1/2 the power I was when I started.
I shut her down and checked radio output and all was well (full power thoughout VR power range).
Felt the amp and was cool to the touch. Speculating possibly burnt one of the two MJF455's?
How might I test these AND what can I replace them with if needed?
Was pushing it with the Galaxy Pluto at 3DK swinging around 10 with the VR power down.
With AMP on usually DK45 swing 100+ now DK 30 PEP to 60 or so...even after shutting down for an hour.
Just so you all know....set up in shack is as follows.
ANT--MFJ tuner--Dosy wattmeter--switchbox -- leads to Galaxy / Grant / upstairs Cobra.
Not ruling out a bad coax patchcord but doesn't seem likely as I have switched to the Grant and have the same low output from the Palomar...
FIRE AWAY!
Hank '905
CEF 559 |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 1437
Registered: 7-2004
| | Posted on Saturday, September 10, 2005 - 11:50 pm: |
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45 key on med may be a bit too much(too high input), though 100 swing is OK. that amp should not be doing 45 key on HIGH, at least not expecting long life expectancy. radio's input to amp should be adjusted for 15 watts carrier for each 455-therefore 30 watts dead key & 120 watts swing is what the amp should do, safely, to prolong life.
if swrs stayed the same, quite possibly a bad transistor. was amp 'cooler' then usual(no heat=no output)? did you check all power positions to be 'weak' on transmit?
the simplest thing to replace 455's with is...a texas star. oops, sorry, another matched pair of 455's
i have a 1x455 that was hammered with 5 watts carrier & 15 watts swing, that produced nearly 30 watts carrier & 75 watts swing. OUCH!!! it still lives. but i wouldn't suggest that type of abuse to anybody who doesn't want to kill their amp.
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Vanillagorilla
Intermediate Member
Username: Vanillagorilla
Post Number: 204
Registered: 4-2005
| | Posted on Sunday, September 11, 2005 - 11:01 am: |
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Thanks Pat ..point taken..must recheck input wattage...and yes...power is down across the 3 pos range....SWR stayed same as well.
TO the best of my knowledge it was being fed with 3DK from the Pluto OR 2.5 from the Grant.
From what I understand the 455's are no longer available? I thought I'd need a direct replacement in another manufacturer?
Anyone know a supplier who may still have them? Copper is out of stock as far as I know.
Thanks again~ |
Vanillagorilla
Intermediate Member
Username: Vanillagorilla
Post Number: 205
Registered: 4-2005
| | Posted on Sunday, September 11, 2005 - 11:59 am: |
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....furthermore.. ...
Decided to dive inside since there is NO SKIP today anyway for a few simple tests and checks. Not knowing exactly how to test either one of the transistors I simply ohm'ed them out..3 legs to ground and one on each to power...all ohmed out but told me nothing really other than the connections are good and niether are burnt COMPLETELY as far as I can tell (?)
Stupid question...shouldn't I see continuity between both center pins on the PL-259's? Even without the Amp on (which is how it was being tested of course!). Seems to me if I can use the radio without the amp powered then I should see SOME continuity between these? Hmmmmm.
Amp see's OK DK but swing is NOTHING like it was...will not get over 80w without a whistle.
Any more ideas? Hate to toss the amp when it COULD be something stupid...ya know...that and its the ONLY heat I have right now!
Hank CEF559 |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 1444
Registered: 7-2004
| | Posted on Sunday, September 11, 2005 - 12:36 pm: |
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RFparts lists a matched pair for...GULP! $65!!! $65 for a transistor that was 10 bucks not long ago! buying that texas star is sounding better already!
search the web, if you can't find any, let me know, i don't have any, but... |
Therealporkchop
Intermediate Member
Username: Therealporkchop
Post Number: 398
Registered: 11-2002
| | Posted on Sunday, September 11, 2005 - 2:16 pm: |
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Pat, I do believe Texas Star is owned by Galaxy isn't it? Seems like I read that somewhere, but I can't remember where.
I believe the easiest way to test a transistor would be to go to the Shack and get a cheap tester. I bought mine for about 10 bucks. OR you can use an Ohm meter. I believe the correct way is to connect one probe to base and the other to the emitter. If you don't get anything, reverse the leads cause some meters use reverse bias when ohming.
If you still don't get anything, then you have an open emitter.
You could have a weak transistor and not a burned one. That could cause that or a resistor somewhere that is burnt open could cause such problem as well (or choke for that reason).
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Vanillagorilla
Intermediate Member
Username: Vanillagorilla
Post Number: 208
Registered: 4-2005
| | Posted on Sunday, September 11, 2005 - 2:46 pm: |
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Thanks for the input on my output.
I'm pretty good at troubleshooting electrical but only when I know the device I'm trying to repair. Little power goes in and a lot comes out is all I really know here. I'll keep investigating till something makes sense.
If I drop it off at my local "Tech" (and I use that term loosely) it'll cost a minimum $65...so yes Pat....TS is looking good from here.
I wanted to put the big "New" amp in the mobile and leave the lil guy in the base...ahhh whatever. Back to troubleshooting!
Thanks again~ '905
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Patzerozero
Senior Member
Username: Patzerozero
Post Number: 1448
Registered: 7-2004
| | Posted on Sunday, September 11, 2005 - 3:43 pm: |
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hanks 11:59 post wasn't up when i wrote mine....yes, chop, texas star & galaxy, & rci &...everybody (almost) is related 1 way or another .
any signs of blackened resistor or choke or melted solder/foil inside amp?
you know what else you could check, hank, is the wattmeter ITSELF. don't remember what you said it was, BUT, if it reads peak/pep the problem could be there. REAL pep reading meters require voltage to HELP follow the swing semi-accurately. such as a wall wart or other 12 volt connection. the NON-powered types use a capacitor to help 'store' the 'wattage swings' so they read 'higher' on the meter then rms/avg/so-called bird watts. problem could be wattmeter, no matter how it reads peak, if it indeed is considered a peak reading wattmeter. (have an OLD maco peak reading wattmeter. NON-powered of course. the cap LONG since burned out. it reads dead key FINE, but now only reads rms swings. my XL shows about 8 watts rms swing on maco, but 12-14 pep on my diamond. perfectly fine. the maco used to show 15+).
the reason i say meter, is because you say dead key is good. if either transistor was bad, you would NOT see more then half the dead key as before. check your radios, if you know what the swing was. you should see SOME decrease in their swing as well.
lastly, ask others at a fair distance how you sound. if they say it doesn't sound as loud as usual, or carrier is lower, THEN you have a problem. if it's the same, i wouldn't worry about it.
is your 'tech' a shop, or someone private? not a shop in farmingville, is it? |
Vanillagorilla
Intermediate Member
Username: Vanillagorilla
Post Number: 209
Registered: 4-2005
| | Posted on Sunday, September 11, 2005 - 5:29 pm: |
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Tech Shop is in Holtsville...I think you may know them.
NO signs of wear or burning melting or otherwise abuse inside kicker.(WAS hoping to see SOMETHING!)
I'm running my stuff through 2 meters at once. A Dosy 4001 and the MFJ tuner (cross needle).
Both showed me reduced power with amp on "only". I still sound clean from what I hear but somethings wrong. This afternoon I bypassed all (see first post) and put the Ant. to Dosy to Amp to Radio...direct. This way I had a handful of coax jumpers to switch around....to no avail. Think I may have just weakend something..a transistor or otherwise as Porkchop said. Whatever helps my "swang" is weak.
Tried different radios, different mics and different meters. Will NOT peak over 60ish.
Sounding more like a blown 455 or at least near dead. I myself can't test any further without knowing more about the workings/components of the amp....outta luck in other words!
Thanks for all the help guys! |
Kb9umt_don_123
Member
Username: Kb9umt_don_123
Post Number: 50
Registered: 3-2004
| | Posted on Sunday, September 11, 2005 - 8:01 pm: |
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Vanillagorilla-Hank,
The small wattage increase you are talking about is less then 3db or on most s-meters a whole 1/2 s-unit, I would betcha money hardly noticeable at all to someone on what you like to work..DX. Unless you are working 'weak signal' work and need all you can get if you were to do a test from the wattage you are stating there will be very little difference to the DX station on the other end if any at all if the conditions or polarity is in/out. I think a good choice if at all possible is not putting money into the amp at that wattage difference and put that $65 or maybe more tech bill into a simple yagi/beam..even the Maco 3 element beam at only $100 will give you much more value for your buck than the fixing the wattage difference you are talking about on the amp..the 3 element Maco beam will give you easy the extra 1/2 s-unit gain....it will also give you added interference/rejection if needed...it also adds something the amp can never add to your station, better receive and signal BOTH not just one end of the equation.
de kb9umt Don/123
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Patzerozero
Senior Member
Username: Patzerozero
Post Number: 1456
Registered: 7-2004
| | Posted on Sunday, September 11, 2005 - 9:14 pm: |
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Did you check to see if wattage DIFFERS when you are in peak mode vs rms mode? my ar3500 will go from 160pep to 100rms on diamond if i don't hit switch. if peak's not working, rms will show less out & everything is as it's supposed to be.
also, i meant check RADIO only, & see if THEIR output(swing) dropped as well. that would be a meter problem.
i don't see the amp as being broken-yet, don. as for a beam, hank lives 30 miles east of me-way out in the country! a 3 element beam would encroach my neighbors' property, if it didn't hit his house! (not quite, but you get the picture). hank, living out in farmland, may be able to go laser 500(40'boom, 18bdi) & forego the amp altogether. but you know us CBers, if 50 times 4 watts is GOOD, 50 times 500 watts is better |
Tech291
Moderator
Username: Tech291
Post Number: 230
Registered: 11-2004
| | Posted on Monday, September 12, 2005 - 8:31 pm: |
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I was gonna put a 4 element up horizontal in next couple weeks but now have changed my mind.Instead ,now gonna put up 33'boom 6 element!
tech291
cef#291
kc8zpj
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Patzerozero
Senior Member
Username: Patzerozero
Post Number: 1477
Registered: 7-2004
| | Posted on Tuesday, September 13, 2005 - 4:33 pm: |
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when your at 33', what's a few more? go ALL the way with 8 elements or a laser 500! 40'boom....that WOULD hit my neighbors house |
Vanillagorilla
Intermediate Member
Username: Vanillagorilla
Post Number: 212
Registered: 4-2005
| | Posted on Tuesday, September 13, 2005 - 5:06 pm: |
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Thanks for the input once again guys..still sorting this one out when there's time to do so. Still get the same reports out there although a local does notice less swing in my signal with the amp.
I found another supplier for the 455's @ $14 a pop...not TOO bad! May be worth replacing at that price. Peak and RMS readings are different. Peak does peak on Dosy ..just not like it did. MJF tuner although not advertised as peak reading did give a "heavy" peak reading...both are down respectivly.
As per my first post which maybe I wasn't clear...radio (radios...two were used for testing) test fine and as they were before lower amp readings.
Don...I hear you on the antenna thing. Unfortunitly I'm only equipped with a single mast right now and would rather just keep it simple with a verticle...less to break in the wind around here AND even though its up 40 ft I can lower it in a pinch IF needed. I will look further into those options as my career developes
Pat...you nailed it..the kid? The Gal? I know no gal but I think your talking about Dave. Think he's older than me?! (Kid? )
They have moved from there to Holtsville some time ago. They do Ok and I'll visit when I need a part or supplies. No more repair work there unless I'm really stumped!
Pat..email headed your way~
Thanks all...I'll let ya'll know if I find something..
Hank CEF559 |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 1479
Registered: 7-2004
| | Posted on Friday, September 16, 2005 - 4:33 pm: |
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yeah, dave, that's right. they were on N ocean in center behind BK/TGI friday YEARS AGO(like EARLY 80's), then in building on north side of parking lot they're in now. they used to rent videos before the day of bbuster. IN FACT, was in traffic on nicolls rd overpass around 1PM yeaterday & heard you guys talking about 'em...wife was on cell & couldn't key up, by time you were past wm floyd, bleedover from big trucks there was killing me |
Vanillagorilla
Intermediate Member
Username: Vanillagorilla
Post Number: 224
Registered: 4-2005
| | Posted on Thursday, September 22, 2005 - 4:10 am: |
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Been behind over here! Never did find the problem yet but my money is on at least one transistor..speaking of which..
SRF3775....70w ea. matched set?
Was told these are direct replacement transistors for the 60w MRF455's? Sound right?
Stupid question time : What is meant by "matched set"? |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 1520
Registered: 7-2004
| | Posted on Friday, September 23, 2005 - 5:57 pm: |
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when used in a 'matched configuration', gain/output of both transistors is THE SAME and not just 'within a tolerance rating'. that way you don't have 1 transistor fighting the other. |
Vanillagorilla
Intermediate Member
Username: Vanillagorilla
Post Number: 231
Registered: 4-2005
| | Posted on Saturday, September 24, 2005 - 10:32 am: |
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Solid...once again Pat..thanks.
Bought a matched set of the above mentioned for $25 new in envelope.
As always I'll keep this thread posted for future generations to learn from |
Vanillagorilla
Intermediate Member
Username: Vanillagorilla
Post Number: 240
Registered: 4-2005
| | Posted on Tuesday, September 27, 2005 - 1:54 pm: |
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Dropped in those transistors last night and...NO MORE problem .
If I DK3 on Low power the amp will DK 25 and swing to 120....all is well. I will have to lower the radios power a little though. If I run HI power I'm told I have a slight backward swing...verified by my RMS reading.
Thanks again for all the input~
'905..out of the Mud-duck soup. |
Mudducksoup
Junior Member
Username: Mudducksoup
Post Number: 14
Registered: 6-2005
| | Posted on Friday, November 18, 2005 - 7:23 am: |
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i have a cobra 29 thats tweaked and peaked and a shooting star 225.how much power do in need from the cobra to properly drive this amp,and what kind of power does it out uot low/hi/med.Also whats the dif between the 225 and the 225 plus i have both and i am driving them with 18 watts swing (not at same time lol) but i think this is too much and watts the power ratings on the 225 plus aswell.( i know a million ?'s) any and all ansers and help is mucho apreciated! |
Mudducksoup
Junior Member
Username: Mudducksoup
Post Number: 16
Registered: 6-2005
| | Posted on Friday, November 18, 2005 - 7:54 am: |
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18 watts out of the cobra dint look at dead key,thot i might need to clear that up. |
Mudducksoup
Junior Member
Username: Mudducksoup
Post Number: 17
Registered: 6-2005
| | Posted on Friday, November 18, 2005 - 7:54 am: |
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18 watts out of the cobra dint look at dead key,thot i might need to clear that up. |
Vanillagorilla
Intermediate Member
Username: Vanillagorilla
Post Number: 324
Registered: 4-2005
| | Posted on Friday, November 18, 2005 - 4:36 pm: |
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Currently I'm running mine with the GrantXL (same as 148GTL) at 2.5DK swing to 16-18...on "Lo" it Dks 27 swing to 130..Med pwr Dk50 swing 150+ and "Hi" DK60 swing to 180+....all PEAK readings are saying "Auuuuuudio" NOT WHISTELING .
For the record I'm sure a lot of this is Harmonics as my Grant has been neutered and am using an Astatic 575 or Chicken choker D104.
Peak readings are about 10-15% less with stock mic.
These readings are a bit better than the MFR455 were giving me originally and the Amp does not get as warm. Either way aim for 2.5DK and see how your kicker likes it. Check RMS readings for backward swing..adjust DK so there is NONE.
I do believe the MRF455s are rated at 60w @ 3w input..don't push your luck Stay below 3dk and your swing is fine....I can swing my 225 with 23w from the Galaxy Pluto just getting a bit warmer than average but that would be pushing it I suppose. As Pat likes to say "put a fan on it"
Hank |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 1903
Registered: 7-2004
| | Posted on Friday, November 18, 2005 - 5:51 pm: |
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