Results 1 to 11 of 11

Thread: Xr500 compression kicks in when any signal is put thru

  1. #1
    New Member
    Join Date
    Dec 2018
    Posts
    3
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    0

    Xr500 compression kicks in when any signal is put thru

    I have an old xr-500 series 260c. When ever i put audio thru any channel the compressor light imeadiatly lights up and the signal is very distorted and sounds real bad. I have cleaned all the pots,jacks connectors etc. I have done a visual inspection as well as used a chopstick to check for any loose connections or bad solder joints and found no issues. Any guidance would be appreciated. I am a guitar guy but try to do basic repair on my amps when possible. Thanks in advance.

    0 Not allowed! Not allowed!

  2. #2
    Lifetime Member Enzo's Avatar
    Join Date
    May 2006
    Location
    Lansing, Michigan, USA
    Posts
    31,535
    Thumbs Up/Down
    Received: 1,421/7
    Given: 0/0
    Rep Power
    54
    The light is on the front, but the circuit is in back on the 260C board.

    Are both polarity main power supplies present, roughly 42v each? Scope the output, what does the distortion look like? Missing half waveform? CLipping severely? Other?

    Your main IC on the 260C board is a TL074. There are several of those on the preamp board (mixer, front panel). Swap the TL074 in your power amp for one of the ones up front. Any change?

    0 Not allowed! Not allowed!
    Education is what you're left with after you have forgotten what you have learned.

  3. #3
    New Member
    Join Date
    Dec 2018
    Posts
    3
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    0
    No scope available. I can swap the IC and check pwr supply voltage. Thanks for the info. Will let you know what i find.

    0 Not allowed! Not allowed!

  4. #4
    Lifetime Member Enzo's Avatar
    Join Date
    May 2006
    Location
    Lansing, Michigan, USA
    Posts
    31,535
    Thumbs Up/Down
    Received: 1,421/7
    Given: 0/0
    Rep Power
    54
    I used to have an XR500.

    WHile at it, make sure the two 15v supplies are OK as well.


    Use the patch jacks on front. Plug a signal into the GRAPHIC IN jack to bypass the preamp, sound OK? Run a cord from MAIN output jack to some other amp and speaker, does the preamp sound OK? We want to narrow it down to power amp or preamp.

    0 Not allowed! Not allowed!
    Education is what you're left with after you have forgotten what you have learned.

  5. #5
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Location
    Buenos Aires, Argentina
    Posts
    11,208
    Thumbs Up/Down
    Received: 1,388/18
    Given: 1,056/27
    Rep Power
    26
    Please somebody post the schematic.

    Youīll have to troubleshoot, which means making some tests, evaluating results and making decisions accordingly.

    Random/Blind parts replacement will not help you and probably increase/cause damage.

    In principle you will have to take some voltage readings, starting, as Enzo suggested, with +/-V supply rails, +/-15V ones, presence of DC on speaker output, and transistor voltage between pins, but for any concrete suggestion we must both refer to same schematic.

    Later Iīll suggest how to use a software oscilloscope and signal generator , plus making the necessary cables and signal attenuators so PC/Notebook can be used for both functions.

    0 Not allowed! Not allowed!
    Juan Manuel Fahey

  6. #6
    New Member
    Join Date
    Dec 2018
    Posts
    3
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    0
    Problem appears to be in power amp section. I bypassed the pwr amp and ran from main out on front of unit to a different amp and signal was good sounded perfect. No compression happening. I ran signal directly to the graphic in to bypass the preamp section and the amp imeadiatly started compressing and breaking up. Think we are narrowing it down. I did not have time to open it back up.

    0 Not allowed! Not allowed!

  7. #7
    Lifetime Member Enzo's Avatar
    Join Date
    May 2006
    Location
    Lansing, Michigan, USA
    Posts
    31,535
    Thumbs Up/Down
    Received: 1,421/7
    Given: 0/0
    Rep Power
    54
    260C power amp
    Attached Files Attached Files

    0 Not allowed! Not allowed!
    Education is what you're left with after you have forgotten what you have learned.

  8. #8
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Location
    Buenos Aires, Argentina
    Posts
    11,208
    Thumbs Up/Down
    Received: 1,388/18
    Given: 1,056/27
    Rep Power
    26
    Oh, it comes out (for us) as a single white dot "clear.gif"

    Maybe you can zip it, give it another name, whatever

    0 Not allowed! Not allowed!
    Juan Manuel Fahey

  9. #9
    Supporting Member Jazz P Bass's Avatar
    Join Date
    Dec 2008
    Location
    Wernersville, PA
    Posts
    12,692
    Thumbs Up/Down
    Received: 363/2
    Given: 190/0
    Rep Power
    25

    1 Not allowed! Not allowed!

  10. #10
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Location
    Buenos Aires, Argentina
    Posts
    11,208
    Thumbs Up/Down
    Received: 1,388/18
    Given: 1,056/27
    Rep Power
    26
    Thanks JPB

    So we have:

    Click image for larger version. 

Name:	Peavey 260C sch.png 
Views:	19 
Size:	217.6 KB 
ID:	51547

    and, just in case:

    Click image for larger version. 

Name:	Peavey 260C layout.png 
Views:	16 
Size:	603.5 KB 
ID:	51548

    0 Not allowed! Not allowed!
    Juan Manuel Fahey

  11. #11
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Location
    Buenos Aires, Argentina
    Posts
    11,208
    Thumbs Up/Down
    Received: 1,388/18
    Given: 1,056/27
    Rep Power
    26
    1) in principle, *excellent* DDT Compression used by Peavey works by comparing power amp output and signalinput.
    So if output can not track input (damage/overload/short circuited load) and we feed signal in, it will trigger (itīs its duty) and as a side job light the Limiting Led.

    2) check that all main voltages are present: +/-42V rails.+/-15V ... also check these reach T074 power pins 4 and 11, that you have 0V at speaker out rail, at TL074 pins 1 and 14, all this withpout speaker connected, without signal in.

    IF TL074 has different voltages than shown in schematic, you can replace it with a fresh one as suggested and recheck.

    Although I personally suspect some power or driver transistor is damaged, and amplifier can not drive a proper load.

    But letīs go step by step.

    0 Not allowed! Not allowed!
    Juan Manuel Fahey

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. SVT 4 PRO Compression circuit no working
    By cerrem in forum Maintenance, Troubleshooting & Repair
    Replies: 6
    Last Post: 06-02-2018, 09:16 AM
  2. peavey xr-700 compression stays on!!
    By divebag2000 in forum Music Electronics
    Replies: 1
    Last Post: 05-18-2011, 04:14 AM
  3. Unwanted compression
    By skynyrd in forum Mods & Tweaks
    Replies: 4
    Last Post: 10-03-2010, 11:59 AM
  4. compression
    By frosty55 in forum Music Electronics
    Replies: 2
    Last Post: 10-14-2008, 07:29 PM
  5. maxtone-compression sustainer
    By jcs in forum Guitar Effects
    Replies: 0
    Last Post: 10-08-2008, 09:42 PM

Bookmarks

Posting Permissions

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