Page 2 of 2 FirstFirst 12
Results 36 to 57 of 57

Thread: Zener diode

  1. #36
    Member
    Join Date
    Apr 2015
    Location
    Minneapolis, MN
    Posts
    333
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    5
    Quote Originally Posted by J M Fahey View Post
    If you want to play it real safe and easy to check, let transformer/diodes/capacitors rectify unimpeded, so ypu´ll get 1,41X the RMS voltage, and then sehd 10/30/50/whatever V **DC** from whatever +B you got.

    Absolutely no problem measuring continuous/average/RMS/peak voltage drop ... because all are the same if e are talking DC

    So if your supply is, say, 60VDC high, a 60V Zener will drop *exactly* 60V .
    Just to clarify things Juan, since he has already ordered those 10W 30V zeners as stated in post #29, could this work? Is this what you were getting at, at least in theory? Put the zeners in the B+ rail? Just install the zeners he has instead of the 12V 5W zeners as shown. Or if not, this could be an alternative at least instead of putting them in the PT CT.

    Click image for larger version. 

Name:	Zeners in B+ rail.jpg 
Views:	138 
Size:	64.4 KB 
ID:	43018

    0 Not allowed! Not allowed!
    Turn it up so that everything is louder than everything else.

  2. #37
    Senior Member SoulFetish's Avatar
    Join Date
    Jan 2016
    Location
    Massachusetts
    Posts
    1,160
    Thumbs Up/Down
    Received: 357/1
    Given: 316/0
    Rep Power
    6
    Quote Originally Posted by DRH1958 View Post
    Just to clarify things Juan, since he has already ordered those 10W 30V zeners as stated in post #29, could this work? Is this what you were getting at, at least in theory? Put the zeners in the B+ rail? Just install the zeners he has instead of the 12V 5W zeners as shown. Or if not, this could be an alternative at least instead of putting them in the PT CT.

    Click image for larger version. 

Name:	Zeners in B+ rail.jpg 
Views:	138 
Size:	64.4 KB 
ID:	43018
    Just curious, but is that a schematic for an old Ampeg?

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

  3. #38
    Lifetime Member Enzo's Avatar
    Join Date
    May 2006
    Location
    Lansing, Michigan, USA
    Posts
    31,779
    Thumbs Up/Down
    Received: 1,653/7
    Given: 0/0
    Rep Power
    54
    Quite a few of us are familiar with field coil speakers. BAck in the old days, before ceramic magnets were common, a field coil was a good way to make a strong magnetic field instead of a permanent magnet. All it means is there is a large coil of wire that is enegized - an electromagnet - to form the magnetic field in the speaker. Google "field coil speaker" for more.

    There are several threads around here discussing them, and their replacement.

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

  4. #39
    Member
    Join Date
    Mar 2017
    Location
    Belgium near Antwerp
    Posts
    23
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    0
    Hey Leo Gnardo, you're welcome man to come and see the old stuff lying around in fact I nearly fall over that junk here while finding a safe place to work on the oldies . The Kriek is plenty and the Duvel is next to it , I'll buy you some , together with the choclats and the original Belgien Fries ( you call it French fries , France has nothing to see with the original fries ) )
    Now just for the sake of it .. anyone can walk to Rome by all ways ..even by going via the moon and back ..
    I suggested a simple , fast , original and cheap solution in proposing a choke after the rectifier.. if You all guys prefer to look up first in your bloody smartphones to find an app to see where they sell computers you need to find out there exist some complicated modern technical ways to lower a DC ripled voltage .. go your way , I won't stop you .. progress is invented to make life easier .... or more difficult .....and certainly more complicated .. that's modern life now ..
    And since some of you seem to know a stranger immediately as a nono .. without knowing his backgrounds ( I own a muzeum with at least some 40 tubeFenders all kinds , nearly all the Klemt Echolette amps that where once available ,the old Dynacord amps from the 50's-60's , the Isophon golden speakers , all the models of Hammonds since 1935 till 60 , a big lot of the leslies and cabs of that time , I should apparently never have seen a tube amp inside and certainly never worked on a guitar amp .
    By the way the 'Fieldcoils' Jensens are still swerving around in my workshop .. need some ?? as are the JBL's D130F , the D110f's even some you probably never have seen in your life the ones with the orange aluminium Dustcap .. even, some later JBL's like the K140F and some E130 s out of JBL horncabs .
    Why is it that you should turn against an intruder with a simple and correct idea ? is it because I am stepping into your private teritorium , this forum ? or is it because I hate destroying old stuff or upgrading it with inaproporiate parts ?? ; I should say .. the hint was there , take it or leave .. not my problem , I hold on to my antic electronics point of view .
    I like the Legal Notice of Mr Fahey especially the use of that muriatic acid and water with some zinc clippings dissolved , pure proof he is up to my own technical level and a pure skilled electronics man ,almost a dinosaur .
    But in fact I think we should go for a donation so the proper transformer can be bought as a gift to Mr Stokes ,to solve this heavy problem and so we can close this discution .. but then we should really miss the fun of the whole discussion isn'it ??

    Have a nice day .. Stax

    Click image for larger version. 

Name:	DSCN0070.JPG 
Views:	160 
Size:	730.6 KB 
ID:	43020
    Click image for larger version. 

Name:	DSCN0071.JPG 
Views:	70 
Size:	601.3 KB 
ID:	43021
    Click image for larger version. 

Name:	DSCN0073.JPG 
Views:	69 
Size:	714.9 KB 
ID:	43022
    Click image for larger version. 

Name:	DSCN0075.JPG 
Views:	78 
Size:	590.0 KB 
ID:	43023
    Click image for larger version. 

Name:	DSCN0072.JPG 
Views:	77 
Size:	620.6 KB 
ID:	43024

    0 Not allowed! Not allowed!

  5. #40
    Senior Member
    Join Date
    May 2006
    Location
    Cheshire, UK
    Posts
    2,198
    Thumbs Up/Down
    Received: 503/4
    Given: 277/0
    Rep Power
    16
    Quote Originally Posted by stokes View Post
    Measured voltage drop across the zener.
    Right, that explains it. You should be measuring the B+ voltage not the zener voltage. A 60V zener in series with the transformer CT will reduce the B+ by 60V (as it would in series with the B+ rail). The meter won't measure the voltage across the zener as 60V because the waveform at that point looks like this -

    Click image for larger version. 

Name:	Zener 60V.png 
Views:	84 
Size:	10.2 KB 
ID:	43025

    0 Not allowed! Not allowed!

  6. #41
    Senior Member
    Join Date
    May 2006
    Location
    NYC
    Posts
    1,656
    Thumbs Up/Down
    Received: 7/0
    Given: 0/0
    Rep Power
    15
    Quote Originally Posted by Dave H View Post
    Right, that explains it. You should be measuring the B+ voltage not the zener voltage. A 60V zener in series with the transformer CT will reduce the B+ by 60V (as it would in series with the B+ rail). The meter won't measure the voltage across the zener as 60V because the waveform at that point looks like this -

    Click image for larger version. 

Name:	Zener 60V.png 
Views:	84 
Size:	10.2 KB 
ID:	43025
    I have measured both,the voltage across the zener is 29vdc and the drop in the B+ is 29vdc

    0 Not allowed! Not allowed!

  7. #42
    Member
    Join Date
    Apr 2015
    Location
    Minneapolis, MN
    Posts
    333
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    5
    Quote Originally Posted by SoulFetish View Post
    Just curious, but is that a schematic for an old Ampeg?
    Good eye. Pretty sure it's from the G-15. I found it in this thread on AX84's site. The first post refers to the "Ampeg G-15 B+ too high thing" and when you click on the second link, the new tab that opens on top says "G-15_ power_ supply_ zener": AX84.com - The Cooperative Tube Guitar Amp Project

    0 Not allowed! Not allowed!
    Turn it up so that everything is louder than everything else.

  8. #43
    Senior Member
    Join Date
    May 2006
    Location
    Cheshire, UK
    Posts
    2,198
    Thumbs Up/Down
    Received: 503/4
    Given: 277/0
    Rep Power
    16
    Quote Originally Posted by stokes View Post
    I have measured both,the voltage across the zener is 29vdc and the drop in the B+ is 29vdc
    I officially don't understand it then

    0 Not allowed! Not allowed!

  9. #44
    Senior Member
    Join Date
    May 2006
    Location
    NYC
    Posts
    1,656
    Thumbs Up/Down
    Received: 7/0
    Given: 0/0
    Rep Power
    15
    Quote Originally Posted by Dave H View Post
    I officially don't understand it then
    And that is exactly why I posted this here,I didnt understand.I think R.G. and Jazz hit the nail on the head.The 50watt zeners are just too big for this circuit.If you read back,I put a 18v 5 watter in there just to see and it dropped 18vdc in the B+ and the voltage across the zener was......18v's!If you read R.G.'s post,he explains it in detail as to why the 50 watter is too big.

    0 Not allowed! Not allowed!

  10. #45
    Senior Member SoulFetish's Avatar
    Join Date
    Jan 2016
    Location
    Massachusetts
    Posts
    1,160
    Thumbs Up/Down
    Received: 357/1
    Given: 316/0
    Rep Power
    6
    Quote Originally Posted by DRH1958 View Post
    Good eye. Pretty sure it's from the G-15.
    my eye's not that good, I was going to guess B-15

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

  11. #46
    Old Timer Tom Phillips's Avatar
    Join Date
    Jun 2006
    Location
    California, USA
    Posts
    3,559
    Thumbs Up/Down
    Received: 159/0
    Given: 92/1
    Rep Power
    17
    Quote Originally Posted by stokes View Post
    ...I think R.G. and Jazz hit the nail on the head.The 50watt zeners are just too big for this circuit.If you read back,I put a 18v 5 watter in there just to see and it dropped 18vdc in the B+ and the voltage across the zener was......18v's!If you read R.G.'s post,he explains it in detail as to why the 50 watter is too big.
    I concur. For additional supporting information one can look up the detailed specifications for a component. You didn't mention the part number of the 62V / 50 W Zener Diode that you used so I just used the data for the first one I could locate, a Microsemi 1N3335B. There is a parameter listed as "Zener Test Current (IZT)" and it is 200ma. I also looked up the specifications for a 1N4964 which is an 18V / 5W zener and the IZT for that component is 62 ma. The IZT is specified to insure that the part is operating over the knee of the curve when the voltage reading is taken. This data is the supporting evidence for the explanations previously posted by R.G. and Jazz and your actual fix confirmed it. In general, the high the power rating, the higher the current required to be flowing through the zener to achieve the rated zener voltage.
    Cheers,
    Tom

    0 Not allowed! Not allowed!

  12. #47
    Don't forget the joker g1's Avatar
    Join Date
    Feb 2010
    Location
    Canada, somewhere north of Fargo
    Posts
    11,601
    Thumbs Up/Down
    Received: 1,506/23
    Given: 3,819/11
    Rep Power
    22
    Thanks for the data Tom. I was always hesitant about using 'overkill' zeners in low voltage circuits for this reason, like a 5W in a 1/2W position for +/-15V etc. circuits. I'd suppose using 1W where 1/2W is spec'd is probably ok, but I guess you would really need to look close at the actual numbers when in use.

    0 Not allowed! Not allowed!
    Just because they don't have tubes doesn't mean they don't have feelings! - glebert

  13. #48
    Don't forget the joker g1's Avatar
    Join Date
    Feb 2010
    Location
    Canada, somewhere north of Fargo
    Posts
    11,601
    Thumbs Up/Down
    Received: 1,506/23
    Given: 3,819/11
    Rep Power
    22
    Quote Originally Posted by staxmotownjunkie View Post
    I suggested a simple , fast , original and cheap solution in proposing a choke after the rectifier..
    The criticisms of your posts is because you have completely ignored all the practical considerations that are required for the solution.
    Must use very little space
    Must not add much weight
    Must be cheap (1 or 2 dollars for new components)

    Using a new choke for the application requires that it can handle the full current from B+. These are large, heavy, and expensive. Subbing an OT instead of a choke is larger, heavier, and expensive.

    0 Not allowed! Not allowed!
    Just because they don't have tubes doesn't mean they don't have feelings! - glebert

  14. #49
    "Thermionic Apocalypse" -JT nickb's Avatar
    Join Date
    Dec 2009
    Location
    Devon, UK
    Posts
    3,508
    Thumbs Up/Down
    Received: 706/1
    Given: 578/1
    Rep Power
    13
    Quote Originally Posted by g1 View Post
    The criticisms of your posts is because you have completely ignored all the practical considerations that are required for the solution.

    Using a new choke for the application requires that it can handle the full current from B+. These are large, heavy, and expensive. Subbing an OT instead of a choke is larger, heavier, and expensive.
    And the OT solution requires a big gapped core designed for class A operation i.e that can handle DC. A push-pull OT cannot take much DC.

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

  15. #50
    Member
    Join Date
    Apr 2015
    Location
    Minneapolis, MN
    Posts
    333
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    5
    Quote Originally Posted by staxmotownjunkie View Post
    And since some of you seem to know a stranger immediately as a nono .. without knowing his backgrounds
    or is it because I hate destroying old stuff
    .. Stax
    As a matter of fact, we WELCOME newcomers as a general rule. But we also are looking for people who can read the posts, interpret them and THEN offer solutions within the guidelines of the Original Poster (see g1's post #48). And since I see that you like to save old useful parts like so many of us do, I would think you would commend stokes on re-using old iron. Instead, you wonder why he used the "wrong" Power Tranny in lines 3-6 of your post #24 and add fuel to the fire at the end of your post #39 suggesting that we take up donations to get him the "proper" PT.

    0 Not allowed! Not allowed!
    Turn it up so that everything is louder than everything else.

  16. #51
    Senior Member
    Join Date
    May 2006
    Location
    NYC
    Posts
    1,656
    Thumbs Up/Down
    Received: 7/0
    Given: 0/0
    Rep Power
    15
    Quote Originally Posted by g1 View Post
    The criticisms of your posts is because you have completely ignored all the practical considerations that are required for the solution.
    Must use very little space
    Must not add much weight
    Must be cheap (1 or 2 dollars for new components)

    Using a new choke for the application requires that it can handle the full current from B+. These are large, heavy, and expensive. Subbing an OT instead of a choke is larger, heavier, and expensive.
    +1,only thing is I'm not so concerned about "Must be cheap",actually cost me $25 for the two zeners,but much cheaper than an OT big enough to handle the job.

    0 Not allowed! Not allowed!

  17. #52
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Location
    Buenos Aires, Argentina
    Posts
    11,720
    Thumbs Up/Down
    Received: 1,850/22
    Given: 1,449/35
    Rep Power
    26
    Quote Originally Posted by SoulFetish View Post
    Anyone else have to look up what a field coil speaker was?? Just me?
    Just you ...... youngster !!!!!!!!!!






    0 Not allowed! Not allowed!
    Juan Manuel Fahey

  18. #53
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Location
    Buenos Aires, Argentina
    Posts
    11,720
    Thumbs Up/Down
    Received: 1,850/22
    Given: 1,449/35
    Rep Power
    26
    Quote Originally Posted by DRH1958 View Post
    Just to clarify things Juan, since he has already ordered those 10W 30V zeners as stated in post #29, could this work? Is this what you were getting at, at least in theory? Put the zeners in the B+ rail? Just install the zeners he has instead of the 12V 5W zeners as shown. Or if not, this could be an alternative at least instead of putting them in the PT CT.

    Click image for larger version. 

Name:	Zeners in B+ rail.jpg 
Views:	138 
Size:	64.4 KB 
ID:	43018
    Almost
    You are not passing DC through them (yet) but full wave rectified AC, not the same thing.
    It may work, and the 5W ones can just float in the air, on terminal strips or something, but you know I am a minimalist and want to reduce problems to their minimal expression if possible.

    IF I have , say, 450VDC and add ,say, 60V worth of zeners in series, I *know* I will end up with 390V (450-60) ... period.
    No Ifs or Buts or Whens or Whys DC is DC.

    If I add them at a non sinusoidal waveform point I have to start thinking RMS/Peak voltage, Duty cycle, dynamic Impedance, etc.

    Not saying they will not work, just not sure what exact voltage will I get at the end.

    Hope this clarifies my simplistic ways

    0 Not allowed! Not allowed!
    Juan Manuel Fahey

  19. #54
    Senior Member
    Join Date
    May 2006
    Location
    NYC
    Posts
    1,656
    Thumbs Up/Down
    Received: 7/0
    Given: 0/0
    Rep Power
    15
    Ok,I put the 2-30v 10 watters in.I got the plate voltage down to an acceptable 360v when I biased it up using a 5Y3 rect.Only problem is the zeners are getting so hot I'm afraid the solder holding the 2 in series is going to melt.I had it running about 10 mins while I djusted the bias and took measuremnets and then about 5 mins or so looking at the oscope with a signal running thru the amp.I have a smaller PT I'm thinking about using,I'm just not sure the current rating on the HT is enough.I dont know for sure but I guesstimate it to be 70 to 90ma's.Its an old Thordarson,I emailed them to see if they have any info.

    0 Not allowed! Not allowed!

  20. #55
    "Thermionic Apocalypse" -JT nickb's Avatar
    Join Date
    Dec 2009
    Location
    Devon, UK
    Posts
    3,508
    Thumbs Up/Down
    Received: 706/1
    Given: 578/1
    Rep Power
    13
    Quote Originally Posted by stokes View Post
    Ok,I put the 2-30v 10 watters in.I got the plate voltage down to an acceptable 360v when I biased it up using a 5Y3 rect.Only problem is the zeners are getting so hot I'm afraid the solder holding the 2 in series is going to melt.I had it running about 10 mins while I djusted the bias and took measuremnets and then about 5 mins or so looking at the oscope with a signal running thru the amp.I have a smaller PT I'm thinking about using,I'm just not sure the current rating on the HT is enough.I dont know for sure but I guesstimate it to be 70 to 90ma's.Its an old Thordarson,I emailed them to see if they have any info.
    The two diodes are thermally as well as electrically coupled and in total dissipating something like 5W at idle. You are going to need a small heatsink to bring the temperature down. It should take too much, just a few sq in of aluminum will probably be enough. If these are stud types don't forget about isolation of the heatsink from other parts.

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

  21. #56
    Senior Member
    Join Date
    May 2006
    Location
    NYC
    Posts
    1,656
    Thumbs Up/Down
    Received: 7/0
    Given: 0/0
    Rep Power
    15
    The problem is that I have one zener mounted to the chassis with a heat sink,the second is soldered to the first just "floating",this one got so hot I couldnt touch it.Got a response from Thordarson about the other PT,said he had to go into the archives to find the ratings,will get back to me tomorrow.

    0 Not allowed! Not allowed!

  22. #57
    Senior Member
    Join Date
    May 2006
    Location
    NYC
    Posts
    1,656
    Thumbs Up/Down
    Received: 7/0
    Given: 0/0
    Rep Power
    15
    Ok,just to let you youngsters who contributed here know,I went and ordered a Hammond 200 series PT and put the vintage one back on the shelf for some future project.The only other time I've used a zener was a singled ended dual 7581a output I built about ten yrs ago.The PT I had was some Canadian brand,forget the label,but it looked to be a re-labeled Hammond.Was putting a little over 500v's on the plates.I used a 50 watt 62v zener and it worked fine.In this case R.G. and Jazz pointed out the fact that if there isnt enough current the zener wont work,to put it simply.That was the problem here.The next lower current value was 10 watt,and stringing 2 of them caused them to get too hot for my comfort zone so I bit the bullet and bought a suitable tranny.Probly what I should have done to begin with but I've held onto these vintage trannies for a reason and I will use it some time.Thanks to all involved here.

    0 Not allowed! Not allowed!

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. zener diode as grid bias/clipper
    By Guitarist in forum Theory & Design
    Replies: 1
    Last Post: 01-14-2016, 07:38 PM
  2. lowering B+ with Zener diode
    By paulj in forum Tweed Builders
    Replies: 13
    Last Post: 05-25-2012, 09:03 PM
  3. Zener diode question
    By elmo in forum Mods & Tweaks
    Replies: 8
    Last Post: 10-01-2008, 12:39 AM
  4. Lowering B+ with zener diode
    By zhyla in forum Build Your Amp
    Replies: 3
    Last Post: 09-30-2008, 04:41 AM
  5. zener diode
    By studioit in forum Mods & Tweaks
    Replies: 15
    Last Post: 04-05-2007, 03:19 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
  •