Results 1 to 32 of 32

Thread: Weird Capacitors! Need help determining replacement value

  1. #1
    Senior Member
    Join Date
    Aug 2011
    Posts
    163
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0

    Weird Capacitors! Need help determining replacement value

    So I've never seen capacitors like this before, in fact I'm not even 100% sure they ARE caps. They're referenced as C on the circuit board along with some other known capacitors though, so I'm to believe they are capacitors. Unfortunately none of them measure any capacitance on my multimeter and I can't understand the markings to determine replacement values. I also can't find a schematic for this amp (Carlsboro solid state amp).

    Here's a picture:

    Click image for larger version. 

Name:	DSC01186.JPG 
Views:	106 
Size:	1.31 MB 
ID:	44745

    The values written on the capacitors are like "100 MN". Any ideas?

    0 Not allowed! Not allowed!

  2. #2
    Supporting Member mozz's Avatar
    Join Date
    Oct 2015
    Location
    NEPA
    Posts
    512
    Thumbs Up/Down
    Received: 6/0
    Given: 5/0
    Do they measure any resistance? Model number? Problem you are encountering? If they are caps, I can't believe that many would be open, test known good caps with your meter, start at 100pf.

    0 Not allowed! Not allowed!

  3. #3
    Senior Member
    Join Date
    Aug 2011
    Posts
    163
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Quote Originally Posted by mozz View Post
    Do they measure any resistance? Model number? Problem you are encountering? If they are caps, I can't believe that many would be open, test known good caps with your meter, start at 100pf.
    Known good caps measure accurately. These mystery "Caps" all measure OPEN for resistance. This amplifier was making a lot of noise (windy, popping, etc..) and I replaced all of the electrolytic capacitors - it's quieted down but I'm still getting some Popping. The popping isn't affected by the channel volumes or tone controls, but it does go away when the Master vol is turned down.

    0 Not allowed! Not allowed!

  4. #4
    Supporting Member Jazz P Bass's Avatar
    Join Date
    Dec 2008
    Location
    Wernersville, PA
    Posts
    12,207
    Thumbs Up/Down
    Received: 5/0
    Given: 4/0
    Measuring a small value capacitor with your meter set to read resistance is pointless.

    Most caps will read open circuit.
    Electrolytic caps will show a reading as the meter voltage charges them up but this is not a valid test of the cap.

    If nothing else, go out and purchase a cheap meter that has a capacitance tester.

    0 Not allowed! Not allowed!

  5. #5
    Supporting Member
    Join Date
    May 2006
    Location
    Staffordshire UK
    Posts
    3,360
    Thumbs Up/Down
    Received: 7/0
    Given: 12/0
    I recognise those as caps, though can't recall the technology.
    The numbers are probably their value in pF

    0 Not allowed! Not allowed!

  6. #6
    Lifetime Member Enzo's Avatar
    Join Date
    May 2006
    Location
    Lansing, Michigan, USA
    Posts
    29,876
    Thumbs Up/Down
    Received: 77/1
    Given: 0/0
    They look like common ceramic caps to me. Common in a previous era, yes, but tube TV sets would be full of them. Numbers ought to be cap value in picofards.

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

  7. #7
    Senior Member
    Join Date
    Aug 2011
    Posts
    163
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Quote Originally Posted by Jazz P Bass View Post
    Measuring a small value capacitor with your meter set to read resistance is pointless.

    Most caps will read open circuit.
    Electrolytic caps will show a reading as the meter voltage charges them up but this is not a valid test of the cap.

    If nothing else, go out and purchase a cheap meter that has a capacitance tester.
    Hey JPB, I was measuring them in the capacitance setting but was responding to mozz who asked what they measured in resistance (presumably to see if they're something other than capacitors).

    0 Not allowed! Not allowed!

  8. #8
    Supporting Member mozz's Avatar
    Join Date
    Oct 2015
    Location
    NEPA
    Posts
    512
    Thumbs Up/Down
    Received: 6/0
    Given: 5/0
    I just mentioned resistance because he wasn't 100% sure they were actually a cap. If they are pf caps, why no meter reading? M could be tolerance 20% and then N stands for nano? Still doesn't answer why would they all be open. How old of a solid state amp? 1965? 1985?

    Here are some tube schematics, other page shows some of those caps even on the tube amp models, schematics call them 3kpf, 47kpf.

    Carlsbro Amplifier Vintage Wiring Diagrams
    Servicing a Carlsbro CS100 Reverb PA Amplifier

    Click image for larger version. 

Name:	carl17c.jpg 
Views:	46 
Size:	78.5 KB 
ID:	44748

    0 Not allowed! Not allowed!
    Last edited by mozz; 09-02-2017 at 10:43 PM.

  9. #9
    Senior Member
    Join Date
    Aug 2017
    Location
    Portland, OR
    Posts
    273
    Thumbs Up/Down
    Received: 7/1
    Given: 10/1
    Wonder if MN is milli-nano, which would be pico

    0 Not allowed! Not allowed!

  10. #10
    Old Timer
    Join Date
    Feb 2010
    Location
    Just south of Bawlmer, Merlin
    Posts
    2,315
    Thumbs Up/Down
    Received: 37/1
    Given: 28/0
    Quote Originally Posted by glebert View Post
    Wonder if MN is milli-nano, which would be pico
    Unless kpf is kilo-picofarad, which would be nanofarad.

    0 Not allowed! Not allowed!

  11. #11
    don't forget the joker g1's Avatar
    Join Date
    Feb 2010
    Location
    Canada, somewhere north of Fargo
    Posts
    9,838
    Thumbs Up/Down
    Received: 62/0
    Given: 102/0
    Does your meter cap setting normally measure down to small values like 50pF ?

    0 Not allowed! Not allowed!
    Certified Dotard

  12. #12
    Lifetime Member Enzo's Avatar
    Join Date
    May 2006
    Location
    Lansing, Michigan, USA
    Posts
    29,876
    Thumbs Up/Down
    Received: 77/1
    Given: 0/0
    milli-nano??? Now I have heard everything.

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

  13. #13
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Location
    Buenos Aires, Argentina
    Posts
    10,068
    Thumbs Up/Down
    Received: 82/1
    Given: 78/4
    Quote Originally Posted by Enzo View Post
    milli-nano??? Now I have heard everything.
    No Sir, you still need to listen to milli-vanilli

    enjoy specially from 0:52 on

    0 Not allowed! Not allowed!
    Juan Manuel Fahey

  14. #14
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    2,465
    Thumbs Up/Down
    Received: 18/0
    Given: 42/1
    MV... great, now my Master Volume knobs on my amps (built or bought) will be called the "Milli-Vanilli" knob. Because Milli-Vanilli and Master Volumes are equally criminal inventions foisted upon the world.

    Juan, that was as horrible as it was 30 years ago when I had to hear it on the school bus. A pox on you for posting that! T-Boy, where's that "HULK SMASH!" button?

    Justin

    0 Not allowed! Not allowed!
    "... If an older Boogie and classic Marshall had a (clearly illegitimate) child and you baked it in an oven set to clown shit crazy." - Chuck H. -
    "When receiving a shock I emit a strange loud high pitched girlish squeak." - Alex R -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  15. #15
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Location
    Buenos Aires, Argentina
    Posts
    10,068
    Thumbs Up/Down
    Received: 82/1
    Given: 78/4
    Ok, hereīs the antibiotics to cure that ear infection


    0 Not allowed! Not allowed!
    Juan Manuel Fahey

  16. #16
    Senior Member SoulFetish's Avatar
    Join Date
    Jan 2016
    Location
    Massachusetts
    Posts
    647
    Thumbs Up/Down
    Received: 8/0
    Given: 7/0
    Quote Originally Posted by waspclothes View Post
    Hey JPB, I was measuring them in the capacitance setting but was responding to mozz who asked what they measured in resistance (presumably to see if they're something other than capacitors).
    Most multimeters won't give you any accuracy at all under maybe a few hundred pf of capacitance. I think there are many techs who would argue that testing capacitance on almost all multimeters to be a convenient approximation at best, and any reliable reading should be done on a calibrated instrument (and probably at the high end of its voltage rating).

    edit: I think these are vintage "dogbone" temperature compensating type ceramic capacitors. "MN" might be the tolerance or something.

    0 Not allowed! Not allowed!
    Last edited by SoulFetish; 09-03-2017 at 06:02 AM.
    If I have a 50% chance of guessing the right answer, I guess wrong 80% of the time.

  17. #17
    Old Timer Tom Phillips's Avatar
    Join Date
    Jun 2006
    Location
    California, USA
    Posts
    3,468
    Thumbs Up/Down
    Received: 14/0
    Given: 13/0
    I'm wondering, during this whole thread, why all those parts were removed in the first place. I.e what troubleshooting pointed to them as "bad?"

    0 Not allowed! Not allowed!

  18. #18
    Senior Member Pedro Vecino's Avatar
    Join Date
    Jul 2006
    Location
    Spain
    Posts
    485
    Thumbs Up/Down
    Received: 1/0
    Given: 1/0
    Ceramic tubular capacitors. Measurements are usually in picofarads, from a few to 5000. Itīs very difficult to find them damaged.

    0 Not allowed! Not allowed!

  19. #19
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Location
    Buenos Aires, Argentina
    Posts
    10,068
    Thumbs Up/Down
    Received: 82/1
    Given: 78/4
    Yes, they very much look like old style (say the 50`s, 60īs) ceramic caps.
    If some factory was already set up to make them that way, they would keep doing so until dies or machines broke or wore off, they would be well amortized anyway.
    Any new production line would be set up to make them the modern way, of course.

    I read them as small value ceramics, visible value being from 33pF to 100pF, *very* hard to read on a multimeter since probably cable and test leads would already show more than 100pF.
    And if user is holding probes with his hands, forget about it.

    A proper LCR meter would have them attached to some terminals, no human hands nearby, and even so might show "parasitic" 10 to 50 pF, which would have to be substracted from displayed measurement

    I have this very same model, faithfully working since the late 70īs:


    I think the caps shown are ceramics, value in pF is the printed number, and MN either shows voltage and tolerance or temperature coefficient or is plain brand indicator (Minnesota Capacitors anybody? )
    Click image for larger version. 

Name:	MysteryCaps.jpg 
Views:	23 
Size:	582.6 KB 
ID:	44753

    0 Not allowed! Not allowed!
    Juan Manuel Fahey

  20. #20
    "Thermionic Apocalypse" -JT nickb's Avatar
    Join Date
    Dec 2009
    Location
    Devon, UK
    Posts
    2,755
    Thumbs Up/Down
    Received: 16/0
    Given: 6/0
    Quote Originally Posted by Tom Phillips View Post
    I'm wondering, during this whole thread, why all those parts were removed in the first place. I.e what troubleshooting pointed to them as "bad?"
    Me too! I would list bad semiconductors, electrolytics, then resistors as noise suspects in that order for a SS amp. Little caps like those would be last.

    0 Not allowed! Not allowed!
    Experience is something you get, just after you really needed it.

  21. #21
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Location
    Buenos Aires, Argentina
    Posts
    10,068
    Thumbs Up/Down
    Received: 82/1
    Given: 78/4
    Agree.
    Ceramic tubular capacitors, number is capacitance in pF, no need to stablish units, MN may be voltage and tolerance or temperature coefficient code, donīt expect any mystery data.
    Or even plain Brand label.
    They should never have been pulled, shotgunning is a terrible repair technique and in any case they would never cause noise as described, which is way more possible coming from bad active components, in general ICs or transistors.

    0 Not allowed! Not allowed!
    Juan Manuel Fahey

  22. #22
    Senior Member SoulFetish's Avatar
    Join Date
    Jan 2016
    Location
    Massachusetts
    Posts
    647
    Thumbs Up/Down
    Received: 8/0
    Given: 7/0
    Quote Originally Posted by J M Fahey View Post
    Yes, they very much look like old style (say the 50`s, 60īs) ceramic caps.
    If some factory was already set up to make them that way, they would keep doing so until dies or machines broke or wore off, they would be well amortized anyway.
    Any new production line would be set up to make them the modern way, of course.

    I read them as small value ceramics, visible value being from 33pF to 100pF, *very* hard to read on a multimeter since probably cable and test leads would already show more than 100pF.
    And if user is holding probes with his hands, forget about it.

    A proper LCR meter would have them attached to some terminals, no human hands nearby, and even so might show "parasitic" 10 to 50 pF, which would have to be substracted from displayed measurement

    I have this very same model, faithfully working since the late 70īs:
    That LCR meter is a sweet unit, Fahey! I want one of those. I admit, I have a little bit of gear envy.
    (But how obnoxious is it the i look over and see the "range multiplier" switches and think "Ew! I would have to do it?" #spoiledbyautorange)

    0 Not allowed! Not allowed!
    If I have a 50% chance of guessing the right answer, I guess wrong 80% of the time.

  23. #23
    Better Tone thru Mathematics bob p's Avatar
    Join Date
    May 2006
    Location
    Chicago, USA
    Posts
    4,908
    Thumbs Up/Down
    Received: 37/0
    Given: 0/0
    I have one of these. current production, easy to find.



    https://www.bkprecision.com/products...-with-esr.html
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	880_front_lrg.jpg 
Views:	181 
Size:	82.3 KB 
ID:	44755  

    0 Not allowed! Not allowed!
    "Stand back, I'm holding a calculator." - chinrest

    "I happen to have an original 1955 Stratocaster! The neck and body have been replaced with top quality Warmoth parts, I upgraded the hardware and put in custom, hand wound pickups. It's fabulous. There's nothing like that vintage tone or owning an original." - Chuck H

  24. #24
    Senior Member
    Join Date
    Aug 2011
    Posts
    163
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Quote Originally Posted by J M Fahey View Post
    Agree.
    Ceramic tubular capacitors, number is capacitance in pF, no need to stablish units, MN may be voltage and tolerance or temperature coefficient code, donīt expect any mystery data.
    Or even plain Brand label.
    They should never have been pulled, shotgunning is a terrible repair technique and in any case they would never cause noise as described, which is way more possible coming from bad active components, in general ICs or transistors.
    Hi JMF, point taken. I thought the shotgun replacing of the mystery capacitors would be a quick experiment before I go to replacing transistors and then IC's. I thought I was onto something when they wouldn't measure any capacitance with my multimeter (and a known .1uF cap measured fine). The transistors in this are unlabelled and I can't find a schematic, so I'm not sure how to approach that problem.

    0 Not allowed! Not allowed!

  25. #25
    Old Timer Tom Phillips's Avatar
    Join Date
    Jun 2006
    Location
    California, USA
    Posts
    3,468
    Thumbs Up/Down
    Received: 14/0
    Given: 13/0
    Quote Originally Posted by waspclothes View Post
    Hi JMF, point taken. I thought the shotgun replacing of the mystery capacitors would be a quick experiment before I go to replacing transistors and then IC's...
    The usual troubleshooting technique is to isolate the problem to a certain area of the circuit. Granted, that is hard to do if you don't have a schematic and are not familiar with the circuit in your amp. In post number 1 you said the equipment was a Carlsboro solid state amp. I suggest that we start by getting the complete model number and photos of the amp so the group can try to find a schematic.

    Once we know more about the circuit then we can do troubleshooting to determining if various controls affect the noises. In addition, we can do various simple things to interrupt the signal path and/or dump the signal to ground with a temporary capacitor in certain places in the circuit and observe how that affects the noises. (Caution: Don't try this until you really understand the technique) Other things are thumping, poking & prodding, freeze spray, heat gun, pot, switch & connection cleaning and detailed visual inspection. The goal is to narrow down the section of the circuit where the noise is originating and all this comes before shotgun parts replacement.

    Cheers,
    Tom

    0 Not allowed! Not allowed!
    Last edited by Tom Phillips; 09-04-2017 at 05:00 AM.

  26. #26
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Location
    Buenos Aires, Argentina
    Posts
    10,068
    Thumbs Up/Down
    Received: 82/1
    Given: 78/4
    Excellent advice and the way to go.

    So far we know nothing, "Carlsbro SS amplifier" covers way too much, we need some focusing.
    Post model, whatever is written on the backpanel, plus some pictures:
    front and back panels, then pull chassis out and post preamp and poweramp pictures ... weīll then ask for more

    After we get some idea of what you have, weīll suggest some tests.

    I seem to have read no controls affect noise except Master Volume?

    If so, you need to detect which is the last active section , based maybe on an Op Amp or perhaps a couple transistors, which feeds/drives that MV, I guess we wonīt be far from the suspect.

    Problem is Carlsbro was actually a very popular, widely sold and available British brand (I saw them all over the place in UK in ī86, way more than Laney, Marshall or Vox, go figure) , but since "nobody famous" used them, they are ignored today.
    HH was more famous, but also disappeared, was absorbed by Laney; another popular but obscure brand was Torque.

    Sadly Music pages, IF they remember them somewhat, that applies only to Tube circuits, but never SS.

    0 Not allowed! Not allowed!
    Juan Manuel Fahey

  27. #27
    don't forget the joker g1's Avatar
    Join Date
    Feb 2010
    Location
    Canada, somewhere north of Fargo
    Posts
    9,838
    Thumbs Up/Down
    Received: 62/0
    Given: 102/0
    Quote Originally Posted by waspclothes View Post
    I thought I was onto something when they wouldn't measure any capacitance with my multimeter (and a known .1uF cap measured fine).
    This is what I was getting at. A .1uF is 100,000pF. You are trying to measure caps in the vicinity of what we think is 50pF. A lot of multi-meters with capacitance functions will not measure caps of such a low value.
    I would guess that when you measure them, you get the same reading as when the probes are open and not touching anything.
    If you were comparing to a known good 50pF cap, and the meter measured one but not the other, then you could suspect the cap.
    Out of curiosity, what is the make and model of your meter?

    0 Not allowed! Not allowed!
    Certified Dotard

  28. #28
    Senior Member
    Join Date
    Jul 2017
    Location
    British Columbia
    Posts
    357
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Quote Originally Posted by Pedro Vecino View Post
    Ceramic tubular capacitors.
    I remember those! Thin-walled, hollow, ceramic tubes, metallized on the inside and outside of the tube.

    This thread is giving me flashbacks to my childhood. I started tinkering with electronics when I was about 8 years old, and saw a few of these ceramic tubular capacitors (pulled from dead electronics that was already old then) during my first few years in the hobby. I haven't seen any of them in a very long time, though.

    -Gnobuddy

    0 Not allowed! Not allowed!

  29. #29
    Senior Member
    Join Date
    Aug 2011
    Posts
    163
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Quote Originally Posted by J M Fahey View Post
    Agree.
    Ceramic tubular capacitors, number is capacitance in pF, no need to stablish units, MN may be voltage and tolerance or temperature coefficient code, donīt expect any mystery data.
    Or even plain Brand label.
    They should never have been pulled, shotgunning is a terrible repair technique and in any case they would never cause noise as described, which is way more possible coming from bad active components, in general ICs or transistors.
    Just a quick update. I replaced all of the LM741 and CA741 op-amps and the noise is gone. Thanks everyone for their patience on this.

    0 Not allowed! Not allowed!

  30. #30
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Location
    Buenos Aires, Argentina
    Posts
    10,068
    Thumbs Up/Down
    Received: 82/1
    Given: 78/4
    Glad to know

    0 Not allowed! Not allowed!
    Juan Manuel Fahey

  31. #31
    Senior Member
    Join Date
    Aug 2011
    Posts
    163
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Quote Originally Posted by J M Fahey View Post
    Glad to know
    It's news to me that opamps can become noisy like that. Intermittent crackly noise, but still functioning. Anyone know why that happens to them and what causes it?

    0 Not allowed! Not allowed!

  32. #32
    Lifetime Member Enzo's Avatar
    Join Date
    May 2006
    Location
    Lansing, Michigan, USA
    Posts
    29,876
    Thumbs Up/Down
    Received: 77/1
    Given: 0/0
    Semiconductors are way more likely to go noisy than caps or resistors.

    If you are looking for a "cause", you likely will never find it. If you think it will be a "I did this, so that happened...", you will be disappointed. It rarely will be anything you "did". Playing real loud into it, or turning up your fuzz pedal will not affect the amp.

    On the other hand, even when you cannot feel it, there is static electric charge on everything. it is possible at some point you plugged a guitar into the amp and a static discharge went through things and damaged a semi junction. Didn't kill it, just damaged it. Like stepping on a ladder rung and cracking it, but not all the way through. The six months later, it finally goes. Now you have no way to know what happened.

    But within the IC, a defect or weak spot in the silicon could result in noise.

    Failures elsewhere could afffect them. If for example you are running 15v rails, and a power supply fault puts 25v on the op amp, that can damage it. And again, it might not show up immediately.

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

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Fender Red Kbob twin replacement capacitors and upgrades
    By jalexquijano in forum Maintenance, Troubleshooting & Repair
    Replies: 7
    Last Post: 08-29-2017, 07:21 PM
  2. Weird, Weird stuff with the PT of a Twin, Secondary Voltage.
    By wizard333 in forum Maintenance, Troubleshooting & Repair
    Replies: 11
    Last Post: 07-11-2013, 07:58 AM
  3. determining wattage
    By blueguitar in forum Theory & Design
    Replies: 18
    Last Post: 06-24-2012, 03:31 AM
  4. Help determining output impedance.
    By DLNB in forum Maintenance, Troubleshooting & Repair
    Replies: 13
    Last Post: 08-06-2011, 06:46 PM
  5. Can anyone please reccommend replacement capacitors?
    By jakobsongs in forum Music Electronics
    Replies: 1
    Last Post: 05-18-2010, 07:37 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
  •