Page 3 of 5 FirstFirst 12345 LastLast
Results 31 to 45 of 64

Thread: JBL/UREI 6290 and 6260 Amps

  1. #31
    Senior Member Russellc's Avatar
    Join Date
    Jul 2007
    Location
    midwest
    Posts
    239
    Quote Originally Posted by speakerdave View Post
    I agree on all counts. A musical amp.

    Though this thread is six years old, the amps are older and still providing good value for money, and they still show up on the used market, although I like to advise caution when buying used pro power amps on ebay.
    Unless something is really burned up, they are quite "fixable". subwoof walked me through the repairs to my 6230 ebay amp, and as dumb as I am, it is and has been working fine. Basically there needs to be a lot of solder reflowing, and replacement of a few small electrolitics. Then its good for another 20+ years.

    Thanks again subwoof!

    Russellc

  2. #32
    Senior Member Russellc's Avatar
    Join Date
    Jul 2007
    Location
    midwest
    Posts
    239
    Quote Originally Posted by westend View Post
    I use a 6290, driving low end in a biamped Altec set. More than enough power, of course. I have a replacement fan sitting on a shelf as the older stock fans are a bit loud. I'm thinking the newer fan will be much quieter.

    JBL's own product literature states that the 62xx series are underrated as to the amount of actual power available. I've never tested mine but with that long row of Sanken's in there I don't doubt it has a lot of power to spare.
    You might ask subwoof about this, he once told me that the fan could be quited down considerable if need be. Lower the voltage to it maybe? I didnt inquire B/C I dont have the 6290.

    Russellc

  3. #33
    RE: Member when? subwoof's Avatar
    Join Date
    Aug 2003
    Location
    fingerlakes region, NY
    Posts
    1,898

    my fan club

    2 things would help the 6290 fan situation.

    First thing is that the amp was designed to be stacked and racked and left on for a bazillion hours SO airflow through it's chassis was designed not to interfere with other rack components ( at least too much ).

    If you removed the top and bottom covers, and cut out ALL the metal over *and under* the heatsink fins, and gave this a rack space above and below it would run a lot cooler and the need for high speed might never present itself.

    If it did it would be the LEAST noticeable volume in that room...

    Second is the value of the low speed resistor. The fan is a standard 120V bearing type and it needs to see 120V at start up then drop to the low speed otherwise it won't engage ( esp if worn ).

    The stock value can be increased to make the fan spin slower OR not unless the "magic" temp is obtained ( rewiring required ) for home use.

    I have 9 of them here from an install and later this month will be doing my analysis on this issue and will post a DIY thread.

    There is also the issue of bias voltage but that is a little more advanced BUT easily checked / adjusted. This amp series tends to drift up with age and that WILL cause heat buildup and early fan engaging.

    sub

  4. #34
    Senior Member Fred Sanford's Avatar
    Join Date
    Jun 2005
    Location
    Shenandoah Valley
    Posts
    1,608
    I remember also a small resistor that you said was a chronic problem in these amps, and should be upgraded...do you have detail on that?

    Thanks,

    je (6260)

  5. #35
    Senior Member
    Join Date
    Apr 2003
    Location
    Winnipeg Manitoba Canada
    Posts
    2,301
    I thought the 6290 fan was always on???

  6. #36
    RE: Member when? subwoof's Avatar
    Join Date
    Aug 2003
    Location
    fingerlakes region, NY
    Posts
    1,898

    schematic 101

    Look at the schematic and you will see a thermal switch wired across the dropping resistor. When the switch closes the resistor is shorted and the fan gets full voltage.

    If you actually REMOVED the resistor the fan would stay off until that temp is achieved, then go full speed.

    If you simply put the thermal switch in SERIES with the resistor ( and fan ) then the fan would go to low speed only when the temp is achieved...

    secrets out.



    http://www.jblproservice.com/pdf/Vin...0%20manual.pdf

  7. #37
    Senior Member Russellc's Avatar
    Join Date
    Jul 2007
    Location
    midwest
    Posts
    239

    Bias voltage

    Quote Originally Posted by subwoof View Post
    2 things would help the 6290 fan situation.

    First thing is that the amp was designed to be stacked and racked and left on for a bazillion hours SO airflow through it's chassis was designed not to interfere with other rack components ( at least too much ).

    If you removed the top and bottom covers, and cut out ALL the metal over *and under* the heatsink fins, and gave this a rack space above and below it would run a lot cooler and the need for high speed might never present itself.

    If it did it would be the LEAST noticeable volume in that room...

    Second is the value of the low speed resistor. The fan is a standard 120V bearing type and it needs to see 120V at start up then drop to the low speed otherwise it won't engage ( esp if worn ).

    The stock value can be increased to make the fan spin slower OR not unless the "magic" temp is obtained ( rewiring required ) for home use.

    I have 9 of them here from an install and later this month will be doing my analysis on this issue and will post a DIY thread.

    There is also the issue of bias voltage but that is a little more advanced BUT easily checked / adjusted. This amp series tends to drift up with age and that WILL cause heat buildup and early fan engaging.

    sub
    Does the bias voltage drift on the 6230 as well? If so. I'd like to know how to measure and adjust it if possible. Thanks in advance,

    Russellc

  8. #38
    RE: Member when? subwoof's Avatar
    Join Date
    Aug 2003
    Location
    fingerlakes region, NY
    Posts
    1,898

    drift away

    Nearly all AB output amplifiers drift with age. Some up, some down. Look at the schematic and you will see a trim pot for each channel on the output stage on ALL of the urei/jbl amps.

    Connect a voltmeter ( set to 2VDC ) across any output transistor's base to emitter junction for that channel.

    What you should see after the amp has been powered up ( no load / signal ) for 10 min or so is the actual bias voltage.

    If it is below .200 volts the amp will have a VERY SLIGHT crossover distortion. If it goes over .500 you will have a new toaster as the output stage will go into thermal runaway..

    The goal here is to give it enough bias ( like the idle on a car ) to keep the distortion low ( not stall ) while not allowing excessive heat to build up ( radiator fan on ) and cause problems.

    I usually aim for .250 to .300

    NOTE 1: This is a general adjustment for bipolar output stages ( no matter WHO makes it ) and is not a substitute for the manufacturers recommendation.

    NOTE 2: Some "fancy" makes and models, to get that magical itty bitty low distortion level, will recommend a "high" bias. This is not a very good idea unless you are sure that it can be tolerated...heat is heat and the laws of physics cannot be changed no matter how good a companies marketing dept can write.

    The difference in distortion between .01 and .001 is about the level of a mouse fart in the closet down the hall when you are at "11"


    If the amp is used for sub only use, the crossover distortion is inaudible so it can be tweaked much lower however the circuit can only go down to a fixed point.

    sub

  9. #39
    Junior Member
    Join Date
    Sep 2016
    Location
    Bangor ME
    Posts
    5

    6260 went from bad to worse

    Quote Originally Posted by Russellc View Post
    Does the bias voltage drift on the 6230 as well? If so. I'd like to know how to measure and adjust it if possible. Thanks in advance,

    Russellc
    I am working on a defective 6260 (non fan type).
    Here is the scoop, I probed around the drivers and outputs to discover CHA was glitching and relay dropping out at random due to DC fluctuation on that channel. Taking my meter probe to various points in the driver stages would cause it to suddenly become stable. So I did reflow solder on all the outputs and driver stages. I noticed someone had taken a sharpie and marked around the relay and one of the transistors. Probably in the past those had been replaced. After the reflow nothing changed. Ok so now it is looking like prior stages were causing DC offsets at random, perhaps a stage breaking into oscillation? Well no, it turns out IC2 is the culprit. Ok so since IC1 and IC2 are identical and socketed, I decided to swap them around. This puts the flaky chip into CHB. This caused CHA to stabilize but now CHB is jumping around. I should have stopped here with the conclusion that the ICs will need to be replaced.
    However....
    Still probing around to see if it was some other component resistor etc around IC2 or a bad cap maybe? Nothing changing it still randomly jumping DC to 3 volts bios and then sometimes back to the normal bias. After being on a while POP big spark and it now has blown R19

    So of course as are with most high power amps I suspect I will need to look at the schematic and replace everything connected to R19, which means the chip which was failing has now failed totally and over voltage CHB. I now also think there may be a weaker link in the chain as well.

    Mostly wondering if anyone else has seen this problem, and did changing out the chips solve the problem? Is it worth the effort to repair this amp? Are their other problems being the problem and not IC2
    Now of course am facing more problems that will have to be resolved before it lives and breathes right again. It looks I will be replacing that 27 ohm? R19 resistor along with the associated driver transistor to be on the safe side it would seem it popped when the IC2 finally has failed, and caused a huge voltage swing. I will be diode checking that transistor, and also shows a diode that is off the emitter that if bad will get replaced too. I am hoping it did not blow any of the output transistors.

    I would love to get ahold of a parts listing to locate proper parts. The manual I found online has very little technical information to help in repair especially to have a parts list to reference.
    Last edited by kb50; 09-26-2016 at 07:43 PM. Reason: Additional information added.

  10. #40
    Junior Member
    Join Date
    Sep 2016
    Location
    Bangor ME
    Posts
    5

    Fan controller

    Quote Originally Posted by Russellc View Post
    Does the bias voltage drift on the 6230 as well? If so. I'd like to know how to measure and adjust it if possible. Thanks in advance,

    Russellc
    It would seem to be the same design as that of Desktop Computer Power Supplies. However those use 12 volt fans with hall effect speed sensors to control the fan speed based on temperature.

    I think the environment and use of the amp, will dictate noise levels, and how long it takes to get to top speed. If its in an open enclosure, and used at normal levels then cooling should not be a problem.
    I am not seeing the familiar beads or thermistors, that when heat builds up on the unit, adjusts bias voltage slightly to keep things in perspective.

  11. #41
    Junior Member
    Join Date
    Sep 2016
    Location
    Bangor ME
    Posts
    5

    6290 fan

    Quote Originally Posted by John View Post
    I thought the 6290 fan was always on???
    Yes it is always on, when the amp is on. It just runs at low speed thru the current limiting resistor as shown in the schematic. Then the thermal switch when exceeded shorts the resistor giving full current to the fan. It runs on 120VAC or probably cut to 30VAC or some figure. So it stays on low speed unless the amp is driving hard, then jumps to full speed once a certain temp is reached. Most of these have a degree stamped on the side of the switch.

  12. #42
    Junior Member
    Join Date
    Sep 2016
    Location
    Bangor ME
    Posts
    5

    Fan worn

    Quote Originally Posted by subwoof View Post
    2 things would help the 6290 fan situation.

    First thing is that the amp was designed to be stacked and racked and left on for a bazillion hours SO airflow through it's chassis was designed not to interfere with other rack components ( at least too much ).

    If you removed the top and bottom covers, and cut out ALL the metal over *and under* the heatsink fins, and gave this a rack space above and below it would run a lot cooler and the need for high speed might never present itself.

    If it did it would be the LEAST noticeable volume in that room...

    Second is the value of the low speed resistor. The fan is a standard 120V bearing type and it needs to see 120V at start up then drop to the low speed otherwise it won't engage ( esp if worn ).

    The stock value can be increased to make the fan spin slower OR not unless the "magic" temp is obtained ( rewiring required ) for home use.

    I have 9 of them here from an install and later this month will be doing my analysis on this issue and will post a DIY thread.

    There is also the issue of bias voltage but that is a little more advanced BUT easily checked / adjusted. This amp series tends to drift up with age and that WILL cause heat buildup and early fan engaging.

    sub
    No it does not need 120 to start, and it would make no difference. If the fan did not start and then slow down, the amp will just warm up faster, and then the thermal switch will put the full 120 so then it would jump up in speed as it is intended. If the fan being ball bearing is the much worn out, or full of dust and dirt, then you should just replace it.

    Touchtunes jukeboxes use a 120 fan to provide airflow, and often they wear out, and the result is the amp either shuts down, or blows something out. But they did do 1 smart thing and that was to put in an air filter to limit the dust sucked into the fan over time. But still again the operators neglect to change the filter and so it still causes early fan failure, and/or poor airflow. Its usually a no win situation.
    The same problems exist in older desktop and laptop computers, the dust eventually causing overheating conditions. Annual or more cleaning will keep your equipment running for many years with proper maintenance. This is why electrolytic caps fail, because of excess heat over time.

  13. #43
    Senior Member BMWCCA's Avatar
    Join Date
    Feb 2006
    Location
    Virginia
    Posts
    6,960
    Quote Originally Posted by subwoof View Post
    Did you realize that this thread is SIX YEARS OLD????
    . . . and now THIRTEEN-YEARS-OLD!

    Now I have a 6260 I didn't own back then. Seems to work fine, but I've made no measurements. I do normally push decades-old Crown D and PS series amps, some of which have been returned to Crown for check-ups and most returned with minor tweaks but actually not enough out-of-spec to be a concern.

    Cheap Thrills!
    ". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers

  14. #44
    Senior Member 1audiohack's Avatar
    Join Date
    Jul 2007
    Location
    Las Vegas Nevada
    Posts
    2,692
    I have a bunch of these and have found as subwoof said, they are biased very low. I have heard that is because they are permanent install products and that a low bias value is both energy efficient and thermally efficient as well.

    They sound better the warmer they get (to me) and take 20 minutes to a couple of hours to sound their best. Biased up a bit, they come right around.

    My 2 cents 13 years later.

    Barry.
    If we knew what the hell we were doing, we wouldn't call it research would we.

  15. #45
    Member
    Join Date
    Sep 2015
    Location
    Los Angeles CA
    Posts
    89
    Hope this is the correct place to ask this question. I have a 6260 that I used for a time in my music room, fed via an RCA to 1/4" jack cable by a McIntosh C24 which was fed by an RCA wire to my laptop streaming Tidal. The problem was that there was always a background hum, almost like a faint static, audible through the speakers, increasing as the volume knob on the C24 turned to the right. The DC offset of channel A is 24mV and channel B is 14mV which seems acceptable. But the buzz got to me and I switched back to my MC502 which is quiet as a mouse.

    I'm trying to figure out whether the hum from the 6260 is due to the ungrounded RCA to 1/4" cable, or because of a problem internal to the amp, or whether that's normal. Any ideas? Thanks in advance.
    Currently: L300, L200B, C40 Harkness (030), DIY Altec A7, XPL140

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. 6290 amp questions
    By Jakob in forum Lansing Product Technical Help
    Replies: 7
    Last Post: 12-21-2004, 07:02 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •