1. Rest in Peace Paul (Kegger) If you would like to help the family in this time of great sorrow and need, you may donate on their GoFundme page: https://www.gofundme.com/mckechnie-medical-and-funeral-fund?
    Dismiss Notice

Accidental Sound, Can Someone Explain Why....

Discussion in 'Tube Audio' started by racfan9, Jun 18, 2017.

  1. racfan9

    racfan9 AK Subscriber Subscriber

    Messages:
    711
    Location:
    SW Missouri
    Hey Everyone...

    Ok I've been troubleshooting a Telefunken 5216WK receiver/amp out of a Hymus Console. It has not been re-capped yet but will be once I figure out why there is no sound at all, it's actually been in this condition for almost 3 years. Ok here's what happened this evening. I had been taking some voltage readings along with checking resistors, well I accidentally left my Simpson 260 analog meter in the resistance setting and probed the 50uf leg of one of the electrolytic cans. When I did this I had music through one channel. You can see in the pic that I'm posting the can and the tab I probed, it has the 2 red wires along with a 390 ohm resistor attached to it. So my question is why would this cause it to produce sound? Oh by the way I did have a cd player hooked up to it, so it wasn't just music out of the blue coming through the speakers.lol! The pics will show the Simpson meter and the settings it was on. I don't have a schematic for this thing and for anyone who has worked on these German receivers know how tight things are underneath the chassis. I'll start a whole new thread in the next week or so when I really start digging in to this.

    Thanks,
    racfan9
     

    Attached Files:

  2. knockbill

    knockbill Addicted Member

    Messages:
    6,094
    Location:
    SE PA
    Maybe the meter in R mode jumped a shorted cap out of the circuit? hope it didn't kill the meter....
     
  3. triode17

    triode17 Active Member

    Messages:
    199
    Rac-Is it possible that the 390 is open and you connected the circuit through the meter?
     
  4. racfan9

    racfan9 AK Subscriber Subscriber

    Messages:
    711
    Location:
    SW Missouri
    Meter is Ok, and the 390 ohm resistor measures about 381, there is another electrolytic can that has two 50uf legs but I'm not getting any voltage to either leg of which one of those connects to the can in question via the 390 ohm resistor.
     
  5. primosounds

    primosounds AK Subscriber Subscriber

    Messages:
    1,020
    Maybe the leg of that condensor is loose and when you probed it there was a connection made again. That or some other component made contact while you were poking around.
     
  6. 6DZ7

    6DZ7 Super Member

    Messages:
    1,086
    Is one end of the 390R resistor grounded and the other attached to the cap (+)?
     
  7. racfan9

    racfan9 AK Subscriber Subscriber

    Messages:
    711
    Location:
    SW Missouri
    No, the resistor bridges the two cans. 50uf tab from one to the other 50uf tab on the second can. Also from a previous post, I resoldered the two wires to the tab just in case they were not making contact.
     
  8. cademan

    cademan Addicted Member

    Messages:
    8,157
    Sure sounds like an open resistor somewhere in the power supply. :idea:

    You are measuring DC voltages with the black meter probe on the chassis right?
     
  9. 6DZ7

    6DZ7 Super Member

    Messages:
    1,086
    Is it supposed to be a cathode resistor that is miswired? What is it's place in the circuit? The purpose of those 50uF caps and their voltage rating? When you touched it it only restored music through one channel... any clue to why that could happen if it is a PS resistor common to both channels?
     
  10. racfan9

    racfan9 AK Subscriber Subscriber

    Messages:
    711
    Location:
    SW Missouri
    Caveman, I kinda thought the same thing about maybe being a open resistor, also I am grounding the black lead to chassis.

    6DZ7... I don't believe it's a miswired resistor
    I've got the exact same receiver right next to it and it's wired the same way.. I've been looking for a schematic but no luck.
     
  11. gadget73

    gadget73 AK Subscriber Subscriber

    Messages:
    30,846
    Location:
    Southern NJ
    Taking a guess at it, what you have is the first filter stage right off the rectifier then a 390 ohm drop resistor to the second stage. If neither terminal has voltage, check output direct at the rectifier. Possible its bad, or the wire between the rectifier and cap is broken. I suspect the meter setting has nothing to do with anything, and you simply jarred a broken connection to life.
     
  12. racfan9

    racfan9 AK Subscriber Subscriber

    Messages:
    711
    Location:
    SW Missouri
    gadget73...I don't think it was a matter of jarring a bad connection, once I discovered this I did it 3 or 4 more times to try to figure it out. I would leave the probe on the connection for up to 5 or so seconds then take it off and it would continue to produce sound for a few seconds.

    I just finished taking some voltage reading from both receivers. Both use a selerium rectifier, (the large black can type with 4 legs.) The readings at the rectifier on the receiver in question clockwise from ground,
    2nd receiver.......... 129 vdc. / 114 acv.
    147.7 vdc / 118.6 vac. ( I took readings in ac and dc setting since I wasn't sure) 265 vac.
    4.71 vac. couldn't get a reading in dc volts. 128 vdc. / 115 vac.
    147.7 vdc / 118.6 vac
    2nd receiver
    1st Electrolytic can:
    100uf 317 vdc. 100uf 262 vdc
    50uf .741 vdc. 50uf 250 vdc
    2nd Can 2nd can
    50uf .733 vdc 50uf 205 vdc
    50uf .733 vdc 50uf 243 vdc

    Well looks like the rectifier is bad, now whether or not that will correct to voltages to both the cans, which will be replaced anyway.

    Anyone out there have a schematic for this unit? WK 5216 is the number or probably anything in the early 60's say 61 or 62 that uses four ECL-86's for the outputs.
     
  13. 6DZ7

    6DZ7 Super Member

    Messages:
    1,086
    The twist tabs on those caps need to be soldered to the chassis or have a ground line run to them if the can says it is common ground. You might just have a poor ground connection to the filter/s.
     
  14. gadget73

    gadget73 AK Subscriber Subscriber

    Messages:
    30,846
    Location:
    Southern NJ
    well, something I might suggest is making sure your meter still works. I've repaired several 260's with roasted resistors caused by checking high voltage when set in resistance mode. I want to say its a 95.3K ohm resistor, at least on the Series 7. One of them I fried myself, which is why I knew what had happened to the others :) It also makes me appreciate my 7P with the protection circuit. It has become my primary bench analog meter, and I've popped that breaker several times.

    Possible you gave it a tiny bit of voltage and the tubes were actually working with a couple volts off the plate. The x10K scale I think uses 9 volts out, the other two are 1.5 volts.

    The two rectifier terminals with a ~ are the AC input. Measure across those to see what it has to say. The + will be positive DC out, the - is negative. Usually the - is grounded, but it might just be the actual body of the thing where it mounts to the chassis.

    If you have AC in and no DC out, thats what ails it. Looks like the filter caps are telling the tale, one has 243v, the other has effectively nothing. I presume the one with 243v is working, since the other one cannot function with no plate supply.
     
  15. racfan9

    racfan9 AK Subscriber Subscriber

    Messages:
    711
    Location:
    SW Missouri
    Gadget73...remember the tab I was probing on the 50uf can has no voltage, I think it read .731 on my digital meter. The Simpson is still working, although I have a hard time reading it. Never used a analog meter before.

    I measured between the AC terminals the rectifier and got 234 vac.
     
    Last edited: Jun 19, 2017
  16. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    22,447
    Location:
    uk.. the middle bit
    continuing to play for a few seconds suggests a capacitor draining . so you may have inadvertently charged up a capacitor with your meter . at a guess there is a bad ground connection somewhere .
    analogue meters can do things like this .
     
  17. gadget73

    gadget73 AK Subscriber Subscriber

    Messages:
    30,846
    Location:
    Southern NJ
    ok if you get 234 vac in and no volts DC out, the rectifier is open. Confirm the + and - terminals are connected but it sounds like you're due for a new one.

    Analog meters take a little getting used to, but with a little practice you can read them fairly quickly and accurately. I've been back to using mine more lately, my good digital is on the blink and my portable isn't all that good. I've been sort of needing a meter upgrade for years, but I'm still soldiering on with the same entry level basic meter that I've had since 1999.
     
  18. racfan9

    racfan9 AK Subscriber Subscriber

    Messages:
    711
    Location:
    SW Missouri
    Suggestions for a replacement ?
     
  19. gadget73

    gadget73 AK Subscriber Subscriber

    Messages:
    30,846
    Location:
    Southern NJ
    Any bridge rectifier rated for an amp or more. I like the 3-5 amp ones with the center hole for mounting. They're fairly easy to bolt in place of the original.
     
  20. racfan9

    racfan9 AK Subscriber Subscriber

    Messages:
    711
    Location:
    SW Missouri
    I've got a bridge rectifier with the center hole but it's 25 amps, I know it's overkill got it for.25 at rat shack during their going out of business sale, it was the only one left.
     

Share This Page