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Revox PR99...plays....but no recording!?

Discussion in 'd.i.y.' started by Tonewheelkev, Nov 27, 2021.

  1. Tonewheelkev

    Tonewheelkev ...I can dream!!

    A couple of observations here!

    With mic input selected...signal creates bounce at VU meter...so a good sign.
    Using Line-in...via XLR...no such luck....no bounce at meters.
    (Signal IS getting to the Line Input PCB)

    Attempting to 'record' via mikes....appears to work (LEDs lit).....but replay show that previous recording hasn't been erased.

    Any thoughts as to what I might look at first here!!?
     
    Last edited: Nov 27, 2021
  2. david ellwood

    david ellwood Kirabosi Kognoscente

    Does it work with a blank tape?
     
  3. Tonewheelkev

    Tonewheelkev ...I can dream!!

    Hmmmnnn!!...
    It's a NOS tape...made recordings with B77....which play back on the PR99....but can't be recorded 'over'...
     
  4. 337alant

    337alant Negatively Biased

    Are you selecting Line for XLR input ?, if it works on mic it should also work on Line as its just a selector switch
    the switch could need cleaning ?
    No record or erase could be the sync or Oscillator relays try prising the lid off them and squirting contact cleaner in there
    It could also be just the duff capacitors
    Alan
     
  5. Tonewheelkev

    Tonewheelkev ...I can dream!!

    Yes...selecting Line....selector bounces VU's in the MIC positions....dead in Line position.
    All rotary/switch contacts are newly cleaned...so hopefully not them!

    So..I can safely (carefully) remove plastic covers from relays without killing them.... :)

    Capacitor-wise....is it a good idea to remove tants in general...?

    Occurs to me that I I should check that I've correctly wired my XLR cables!
    Don't have any balanced devices...so wired phono to XLR.....Hot side to XLR pin 2, and Sleeve to pins 1 and 3.......correct????
     
    Last edited: Nov 27, 2021
  6. 337alant

    337alant Negatively Biased

    yes carefully remove the covers and spray with a contact cleaner I use deoxit fader lube

    Its best to replace all electrolytics and tants in revox machines but don't do that yet.
    Does it make any difference when you press the cal / uncal switches, in cal the levels are set automatically but in uncal they are set by the pots
    Which model do you have Mk1,2,3?
    Alan
     
  7. Tonewheelkev

    Tonewheelkev ...I can dream!!

    It's a MK2....2 track....7.5/15ips
    Occurs to me that I should check that I've correctly wired my XLR cables!
    Don't have any balanced devices...so wired phono to XLR.....Hot side to XLR pin 2, and Sleeve to pins 1 and 3.......correct????
     
  8. 337alant

    337alant Negatively Biased

    That will work but I personally don't connect pin 3 to 1 as it can create a hum
    I connect RCA signal hot to pin 2 RCA ground cold to pin 3
    Alan
     
    Tonewheelkev likes this.
  9. david ellwood

    david ellwood Kirabosi Kognoscente

    Does changing speed make any difference?
     
  10. 337alant

    337alant Negatively Biased

    Have you just got this machine or have you been doing some work to it.
    Has it always had this fault
    You said the switches have been cleaned, to do that you will have had to strip the whole of the bottom panel down to the main audio interconnection board
    If so have you connected all wiring correctly ?.
    Alan
     
  11. Tonewheelkev

    Tonewheelkev ...I can dream!!

    Haven't tried that David!
    The machine has been with me for over 15 years now....and is an unknown commodity.
    When stripping down....took lots of pics...and everything is believed to have gone back together correctly.
    ...certainly fails to record from Line in the same way.
    Will be taking a look at those relays....just find myself wondering if both of them (2 channels) would be down at the same time.
     
  12. david ellwood

    david ellwood Kirabosi Kognoscente

    It’s likely an issue with the bias oscillator and it switches between frequencies when you change speed. So if it works at one speed but not the other then it’s a dodgy cap or switch contact.

    Check the connections to the bias oscillator card and give the speed switch a good wiggle.

    If all else fails check the transistors and voltages on the card and see if anything looks dodge.
     
    Tonewheelkev likes this.
  13. 337alant

    337alant Negatively Biased

    The speed rail and plug in boars can be problematic but I would have expected that you cleaned them thoroughly when you had the main audio interface board out ?.
    I clean the speed rail pins with a fibre pen and deoxit, you can see the difference it makes in the picture below
    Its also important that the audio and oscillator boards are seated correctly and they fit into the notches on the retaining bar
    Did you remove all of the switches and clean the gold contacts on the main audio interface board?
    Did you remember to reconnect the ground connection on this board as well

    [​IMG]20200923_120429 by Alan Towell, on Flickr
    [​IMG]20200923_115853 by Alan Towell, on Flickr

    Alan
     
    Tonewheelkev likes this.
  14. Tonewheelkev

    Tonewheelkev ...I can dream!!

    Didn't get the board into such a nude state as in 2nd pic...but yes...got to all the gold contacts shown...did this with the board still loosely attached...felt safer!!
    Haven't acquired any Caig products yet...and used IPA/Servisol Super 10...contacts were left clean/dry.
    TBH...didn't pay too much attention to the slider 7.5 to 15 (Speed Rail) arrangement:oops:...so will revisit that:)
     
    Last edited: Nov 28, 2021
  15. Tonewheelkev

    Tonewheelkev ...I can dream!!

    OK....went back inside....found a molex type connector that I'd managed to leave dis-connected....:(
    All back together now...and have recording...both from Line In and Mic...so far only tried 7.5ips:)

    Now noticing that record level controls aren't having desired effect...they do nothing, and it's as if the level was fixed!
    Also...Output level dual conc. pot does nothing too....Hhhmmnnn!!!

    Aaaaggghhh.....UNCAL switch needs to be selected...BINGO
     
  16. 337alant

    337alant Negatively Biased

    Ah great news, you got there in the end, well done :cool::D
    Enjoy it for a while but keep in mind the age of the caps.
    You can just leave as is and only replace what goes wrong in the future
    Or think about a systematic approach, but at each stage put the machine back together and test all functions so you can pick up if you made a mistake on 1 board
    1st step, replace any RIFA X2 film caps as the go up in smoke ASAP
    Next consider the power supply replace all caps and bridge rectifiers.
    Next start recapping the Capstan motor control board
    Next start recapping the tape deck control board, this ones tricky and the tracks are easy to lift so be careful, test all Triacs and transistors.
    Next recap the Oscillator board, test the transistor's and check the value of each resistor and replace with metal film if they are out of spec, clean the trim pots with deoxit, if they are ok leave them as they are better quality than the other trim pots in the machine
    Next replace the caps and trim pots on the Audio boards, do them one by one and keep checking
    Good luck

    Alan
     
  17. Tonewheelkev

    Tonewheelkev ...I can dream!!

    Thanks Alan. While inside the PR99, noticed that some work has already been done in removing Tants...must have been prior to 2005 when that was done!

    Last week, I did caps/triacs and BD135s on the tape deck control board on my other deck...a B77
    Can certainly vouch for it being a tricky job....with track wanting to lift...but got there too! :)
     

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