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    Fried rectifier solution

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    baddog1946

    Posts : 304
    Join date : 2010-02-03
    Location : Costa Rica

    Fried rectifier solution

    Post by baddog1946 on Sun Nov 28, 2010 9:18 am


    Hi:
    I have been having trouble it turns out with poor power regulation and voltage clipping from the utility company frying my Weber WZ-68 rectifiers.
    It seems that here in Costa Rica the power supply is poorly regulated for several reasons and we have a lot of voltage spikes and brown outs occuring which have caused my Weber WZ-68 to burn out several times.
    At $22 bucks a pop I needed to find a solution quick. This no doubt applies everywhere else from time to time.
    I am sending this in as a possible preventitive solution for those people who were on the mysteriously burnt out rectifier thread recently.

    Both the resistors and the diodes in my Weeber WZ-68 have burnt out at various times. I tried re-building them changing just the resistors, then with just the diodes as well with both always using the stock parts. no luck!
    I was still having issues with the rectifier getting fried during these times when the voltage was too high. I have measured as much as 138.6 volts for a few seconds!

    The last time I fried one in desperation I contacted Bob and with few suggestions from him I was able to discover the likely cause and solution.
    I then tried rebuilding a Weber with(IN5408)diodes and the stock resistors ((18 0hm-10 watt). The diodes are bigger but I got them to fit neatly on the little board in the weber.

    I had to install the resistors a hair higher to clear the diodes.
    i also took the time to swaet the solder out of the pins and put the wires in as the same way as they camefrom weber. All the wires I spliced on were part of a failed rectifier. It may have been a contributing factor i am not sure but it would seem to be worth the effort to do it this.
    I also put a piece of heat shrink on all the leads of the resistors to make sure they don't short out with the diodes and the top of the cap which is very close to the leads on the resistors. So far they are bulletproof.

    We had a terrible storm two days ago when I was listening to my ST-120 and I put my meter on there and measured two spikes of 127 volts and one of 129.3 volts both only for a few seconds in less than half an hour. The weber was fine.

    My point of all this is that the more robust diodes seem to do the trick fit well and work fine.

    if anyone else has a similar problem with webers it could be the power fluxes and tougher diodes might be the answer for them as well. Although the stock diodes are 100 volts they are only 1 watt and the bigger ones carry 3 watts a safety margin may be what's missing.
    Hope this is of some help to someone.
    Cheers
    Baddog1946

    baddog1946

    Posts : 304
    Join date : 2010-02-03
    Location : Costa Rica

    Fried rectifier solution

    Post by baddog1946 on Sun Nov 28, 2010 9:21 am

    Sorry about the typo thats 1000 volts!
    BD1946

    dynacophil

    Posts : 33
    Join date : 2010-10-26
    Age : 59
    Location : Berlin/Germany

    Re: Fried rectifier solution

    Post by dynacophil on Sun Nov 28, 2010 1:51 pm

    you can edit a post...

    mantha3

    Posts : 298
    Join date : 2010-11-10

    Re: Fried rectifier solution

    Post by mantha3 on Sun Nov 28, 2010 5:29 pm

    Pretty cool. just buy the parts in bulk.

    Do you worry that by building with the higer spec parts that some other component may go out during the spike?

    You may want to look for some 120 volt power line conditioner. Maintains regulated 120V nominal output over an input range of 89 to 147V. Power Conditioners are built for this exact problem.

    Toss a photo on here next time you have to rebuild






    baddog1946

    Posts : 304
    Join date : 2010-02-03
    Location : Costa Rica

    Re: Fried rectifier solution

    Post by baddog1946 on Sun Nov 28, 2010 7:56 pm

    The problem may also have been the quick on off usually accompanying these spikes. Although it may be a risk (unknown) at this time the IN4007's were dying like flies so the tougher diodes will do until I have another problem. I will post a photo of the rebuilt Weber later tonight.It has to cool off first.

    baddog1946

    Posts : 304
    Join date : 2010-02-03
    Location : Costa Rica

    Re: Fried rectifier solution

    Post by baddog1946 on Sun Nov 28, 2010 9:44 pm

    Picture of WZ-68 copper cap with IN5408 diodes. Working fine!

    http://s1212.photobucket.com/albums/cc446/baddog1946/

    mantha3

    Posts : 298
    Join date : 2010-11-10

    Re: Fried rectifier solution

    Post by mantha3 on Mon Nov 29, 2010 10:20 am

    Nice, Not much to those things really when you crack the cap open. Interesting.

    baddog1946

    Posts : 304
    Join date : 2010-02-03
    Location : Costa Rica

    Re: Fried rectifier solution

    Post by baddog1946 on Mon Nov 29, 2010 12:54 pm

    BTW
    Weber sells kits to make solid state rectifiers yourself and they use the 3 amp diodes in there. Check it out at: https://taweber.powweb.com/store/modkits.htm#SSR

    baddog1946

    Posts : 304
    Join date : 2010-02-03
    Location : Costa Rica

    Re: Fried rectifier solution

    Post by baddog1946 on Tue Nov 30, 2010 8:21 pm

    another update for the DIY crowd: You can get the exact same sockets that Weber uses on their copper caps from:http://www.surplussales.com/Tube-Sockets/TubeSkts-2.html. Lots of other good stuff at fair prices too.

    Corona

    Posts : 32
    Join date : 2010-03-11

    Re: Fried rectifier solution

    Post by Corona on Tue Nov 30, 2010 9:32 pm

    Get a power conditioner or UPS like people use for computers. It costs a lot, but it will save you many rectifiers in the long term.

    tubes4hifi
    Admin

    Posts : 1261
    Join date : 2008-11-30

    Re: Fried rectifier solution

    Post by tubes4hifi on Sat Dec 04, 2010 2:58 pm

    I kind of suspected all along that there was $2 worth of parts inside a $5 copper tube with a socket on it.
    I prefer to make my own and while I'm at it use CL90 current limiters

    baddog1946

    Posts : 304
    Join date : 2010-02-03
    Location : Costa Rica

    Re: Fried rectifier solution

    Post by baddog1946 on Sat Dec 04, 2010 3:17 pm

    They already have a Digikey CL current limiter in them it does show in the pic.
    What are the specs for the CL90? The copper cap is a very good heat sink. I made one out of a used KT-88 tube base as well. Cheaper for sure but I already had some dead Webers lying around.

    KT88

    Posts : 10
    Join date : 2011-08-12
    Location : Dubrovnik,Croatia

    Re: Fried rectifier solution

    Post by KT88 on Fri Aug 12, 2011 9:51 am

    baddog1946 wrote:
    Hi:
    I have been having trouble it turns out with poor power regulation and voltage clipping from the utility company frying my Weber WZ-68 rectifiers.
    It seems that here in Costa Rica the power supply is poorly regulated for several reasons and we have a lot of voltage spikes and brown outs occuring which have caused my Weber WZ-68 to burn out several times.
    At $22 bucks a pop I needed to find a solution quick. This no doubt applies everywhere else from time to time.
    I am sending this in as a possible preventitive solution for those people who were on the mysteriously burnt out rectifier thread recently.

    Both the resistors and the diodes in my Weeber WZ-68 have burnt out at various times. I tried re-building them changing just the resistors, then with just the diodes as well with both always using the stock parts. no luck!
    I was still having issues with the rectifier getting fried during these times when the voltage was too high. I have measured as much as 138.6 volts for a few seconds!

    The last time I fried one in desperation I contacted Bob and with few suggestions from him I was able to discover the likely cause and solution.
    I then tried rebuilding a Weber with(IN5408)diodes and the stock resistors ((18 0hm-10 watt). The diodes are bigger but I got them to fit neatly on the little board in the weber.

    I had to install the resistors a hair higher to clear the diodes.
    i also took the time to swaet the solder out of the pins and put the wires in as the same way as they camefrom weber. All the wires I spliced on were part of a failed rectifier. It may have been a contributing factor i am not sure but it would seem to be worth the effort to do it this.
    I also put a piece of heat shrink on all the leads of the resistors to make sure they don't short out with the diodes and the top of the cap which is very close to the leads on the resistors. So far they are bulletproof.

    We had a terrible storm two days ago when I was listening to my ST-120 and I put my meter on there and measured two spikes of 127 volts and one of 129.3 volts both only for a few seconds in less than half an hour. The weber was fine.

    My point of all this is that the more robust diodes seem to do the trick fit well and work fine.

    if anyone else has a similar problem with webers it could be the power fluxes and tougher diodes might be the answer for them as well. Although the stock diodes are 100 volts they are only 1 watt and the bigger ones carry 3 watts a safety margin may be what's missing.
    Hope this is of some help to someone.
    Cheers
    Baddog1946

    I think I have problems with diodes as well...in my amp there are 8 IN5408 diodes and output from the trafo is 330 V,800mA...so what happened...Black out occurs while the amp was on.The result - the picture lost the
    tightness and deepness.The instruments have not this strong structure as
    they normaly have.All other is there - no distortions but both chanels have
    the same deffect...voltages are ok but it seems that curent (mA) is not ok...diagnosis - a switch transient overload hit the amp. I think the most sensitive parts are semicondactors and in this amp only diodes are...The IN5408 can work till 1000v and I was told that tranzient overload is very short but can reach 2000 - 3000 v...obviosly it's HT issue and the suspects are diodes...please your opinions

    Bob Latino
    Admin

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    Join date : 2008-11-26
    Location : Massachusetts

    Re: Fried rectifier solution

    Post by Bob Latino on Fri Aug 12, 2011 11:40 am

    I believe that the Weber's do use two of the 1N4007 diodes. These are 1000 volt rated but only at 1 amp. The 1N5408 diodes are also 1000 volt rated but at 3 amps. The 1N4007 won't stand up as well to the severe power spikes that Baddog has mentioned in his post. If you have power spikes up to 138 volts (!) as Baddog does at times in Costa Rica you can expect issues with your rectifiers either tube or solid state. Personally, I have used the same Weber WZ68 in my own ST-120 here for over 2 years with no issues. My voltage is always in the 119 - 120 volt range and I don't ever remember any voltage spikes. IMHO Weber should probably make the Copper caps with 1N5408 diodes. The cost difference is very little. Diodes are very inexpensive. In quantity you can get the 1N4007 for 2 or 3 cents each and the 1N5408 for maybe 7 cents each. It would cost pennies for Weber to make the Copper caps a little more resistant to severe voltage spikes.

    Bob

    KT88

    Posts : 10
    Join date : 2011-08-12
    Location : Dubrovnik,Croatia

    Re: Fried rectifier solution

    Post by KT88 on Fri Aug 12, 2011 12:46 pm

    Bob Latino wrote:I believe that the Weber's do use two of the 1N4007 diodes. These are 1000 volt rated but only at 1 amp. The 1N5408 diodes are also 1000 volt rated but at 3 amps. The 1N4007 won't stand up as well to the severe power spikes that Baddog has mentioned in his post. If you have power spikes up to 138 volts (!) as Baddog does at times in Costa Rica you can expect issues with your rectifiers either tube or solid state. Personally, I have used the same Weber WZ68 in my own ST-120 here for over 2 years with no issues. My voltage is always in the 119 - 120 volt range and I don't ever remember any voltage spikes. IMHO Weber should probably make the Copper caps with 1N5408 diodes. The cost difference is very little. Diodes are very inexpensive. In quantity you can get the 1N4007 for 2 or 3 cents each and the 1N5408 for maybe 7 cents each. It would cost pennies for Weber to make the Copper caps a little more resistant to severe voltage spikes.

    Bob


    Thanks for your promt answer...I have as well very stabil power of 220 v...I have no problem with instability of the mains..the issue here are so called switch transient spikes which are very short spikes but with huge voltage impact..more then 2000V....so I think I will swapp my diodes with new one or put even some stronger like HVR320 - 2000 v,3A...what is problem for diode are sparks of any kind...sparks produce this scwitch transients which are killers for sensitive circuits as silicon diodes are....but good idea is UPS...at least no bluck outs are possible...somebody mentioned UPS abowe...but I must warn the people...not any UPS...ONLY double conversion 100% on line machine with no switching moments as then you have again sparks and spikes..it's very sensitive thema...do You think diodes are more sensitive then resistors?

    merlot

    Posts : 22
    Join date : 2008-12-22

    Re: Fried rectifier solution

    Post by merlot on Sun Aug 14, 2011 11:47 am

    I too have a couple of WZ68s that I want to rebuild. I haven't seen any mention of the disc shaped component in the WZ68. Is it a thermistor? If so, does anyone know the specs? Where's the best place to get it? How do you test one?

    If it is not a thermistor, what is it?

    KT88

    Posts : 10
    Join date : 2011-08-12
    Location : Dubrovnik,Croatia

    Re: Fried rectifier solution

    Post by KT88 on Mon Aug 15, 2011 3:50 am

    I would like to put a queston do Baddog1946....were the diodes totaly out of use or sound was there but with defect?

    baddog1946

    Posts : 304
    Join date : 2010-02-03
    Location : Costa Rica

    Re: Fried rectifier solution

    Post by baddog1946 on Sat Aug 20, 2011 10:56 am

    Hi:
    Sorry to be so tardy with a reply but I was on vacation for a month fishing in Northern BC. To the answer the question, the diodes were totally out of use in all cases. The thermistors seemed to have survived in all cases as well. I never replaced any of them and they are still working fine.

    KT88

    Posts : 10
    Join date : 2011-08-12
    Location : Dubrovnik,Croatia

    Re: Fried rectifier solution

    Post by KT88 on Thu Aug 25, 2011 9:23 am

    baddog1946 wrote:Hi:
    Sorry to be so tardy with a reply but I was on vacation for a month fishing in Northern BC. To the answer the question, the diodes were totally out of use in all cases. The thermistors seemed to have survived in all cases as well. I never replaced any of them and they are still working fine.

    Yes but in my case voltages are ok only it seems the current is low.Some people think that 1-2 (there are all in all 4 diods in power stage) diodes are damaged by high transient sipke...so the sound has bad dinamic and lack of bas...what you think?

    baddog1946

    Posts : 304
    Join date : 2010-02-03
    Location : Costa Rica

    Re: Fried rectifier solution

    Post by baddog1946 on Fri Aug 26, 2011 9:24 am

    I replaced the diodes with 3 amp diodes and the same resistors as were in there and up to now this has been successful. You may not have the brutal voltage swings we have here in Costa Rica which may be the reason you only blew two of them. I rebuilt all my Webers with 3 amp diodes in anticipation of needing them at some point but so far this mod has performed flawlessly. If that proves otherwise I will be back on this forum for more feedback.
    BTW I got little help from Weber on the tech side they only suggested replacement but did not comment on my mod.
    I did notice however they sell rectifier kits with 3 amp diodes which may suggest it is a good idea or at least 3 amp is a viable diode replacement type.

    KT88

    Posts : 10
    Join date : 2011-08-12
    Location : Dubrovnik,Croatia

    Re: Fried rectifier solution

    Post by KT88 on Fri Aug 26, 2011 12:01 pm

    Thanks.Yes I will swap my IN5408 with UF5408 ...let see what impact has this fast diode on sound...I asked a profesor from university about how diode get damaged...here his answer..."
    Diodes get damaged when their reverse voltage or forward current ratings are exceeded. It is also possible that a high speed transient could exceed the forward voltage rating before the diode turns on


    sandy

    Posts : 36
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    Age : 54
    Location : Los Angeles, CA

    Re: Fried rectifier solution

    Post by sandy on Sun Aug 28, 2011 1:03 pm

    I was just looking at this thread after checking some simple circuits with the Duncan Amp power supply simulator for an amp I'm working on and it seems that with the simple full wave set up that it looks like a 360v Center tap rectifier with 1000v diode is at the very edge of PIV during the simulation if I am looking at it correctly. I don't know how closely this maps to the ST70's voltage at operation, but seems very close to the ratings of a 1KV diode. I found this formula for calculating the PIV ratings on one of the other audio sites for Full Wave Center Tap power supply -

    PIV = 2 * sqrt(2) * ACV or 2 * 1.414 * 360 = 1018

    Not sure if I am on track, and not sure how the circuit (resistors) in the WZ68 impact this rating, but I'll be looking to use a higher voltage rectifier to be safe.

    Sandy

    The simulator can be found here - http://www.duncanamps.com/psud2/index.html


    tubes4hifi
    Admin

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    Re: Fried rectifier solution

    Post by tubes4hifi on Sun Aug 28, 2011 3:04 pm

    without even looking at any complicated math you can figure the diodes need to be rated at 2.8x the maximum voltage.
    (that's the ratio of peak-to-peak VS rms voltage) which means that 1000v rated diodes are good for around 357v.
    The ST70 transformer is putting out 360v and the MK3 transformer is putting out 400v.
    That one more reason why doing the simple diode mod on a recitifier tube is a good idea (see other thread on this forum).
    And that's why you see HV solid state supplies usually are designed with two diodes in series, to give a 2000v peak rating.

    KT88

    Posts : 10
    Join date : 2011-08-12
    Location : Dubrovnik,Croatia

    Re: Fried rectifier solution

    Post by KT88 on Sun Aug 28, 2011 8:48 pm

    I personaly would never put rectifier diodes in power stage of a tube amp...this things are just to sensitive on transients but not the rectifier tube...you just need very short black out while amp is on and you get diode damaged..why?...The opening of the primary circuit of a transformer generates
    extreme voltage transients, especially if the transformer drives
    a high impedance load. Transients in excess of ten times
    normal voltage have been observed across power
    semiconductors when this type of switching occurs.
    Interrupting the transformer magnetizing current, and the
    resulting collapse of the magnetic ux in the core, couples a
    high voltage transient into the transformer secondary
    winding
    Unless a low-impedance discharge path is provided, this
    burst of transient energy appears across the load. If this load
    is a semiconductor device or capacitor with limited voltage
    capabilities, that component may fail....The amplitude of transient recordings covers the range from
    harmless values just above normal voltage to several
    kilovolts. For 120V AC lines, flashover of the typical wiring
    spacing produces an upper limit between 6kV and 8kV.

    baddog1946

    Posts : 304
    Join date : 2010-02-03
    Location : Costa Rica

    Re: Fried rectifier solution

    Post by baddog1946 on Mon Aug 29, 2011 9:44 am

    This thread is interesting in the way it continues to hold our interest. Makes me think there are a lot of people with issues related to the rectifier and power surges. They seem to be a universal problem and their frequency is the only variable. We will all experience it eventually no matter where we live.
    Somewhere along the line I put a GFI breaker on my power cord and it continues to cut the power regularly which tells me it works.
    There are and probably always will be a lot of issues with the grid and that a GFI breaker on your house panel or inline is cheap ($20)insurance for us all.
    Someone should design a nice compact unit that could be installed in any amp chassis. I am sure it would sell like hot dogs.


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