[sdiy] Siel OR400 power supply busted

Sat Aug 3 17:32:03 CEST 2013

A couple of other thoughts: 

1. check the polarity of the caps, make sure they're not backwards.  Polarized caps aren't always labeled consistently.

2. verify the bridge rectifier is in the circuit properly. Is it clearly marked so that you know the orientation of the internal diodes?  If not use your DVM in ohms mode to figure this out.

3. Were any of the regulators originally  attached with insulators separating them from the heat sinks?  You can't assume a component's metal case is always ground.

maeghan <synth.diy at pulsewidthmod.com> wrote:
>Dave,
>
>Thank you! It looks like I got some work  ahead of me. Before i got
>your email, last night, I found a cold solder joint but I went to bed.
>I'm gonna start there. I'll report back as soon as I know something.
>
>thank you ~ maeghan
>
>Sent from my iPhone
>
>On Aug 3, 2013, at 2:48 AM, Dave Manley <dlmanley at sonic.net> wrote:
>
>> Let's just step through the circuit starting from the secondary side
>of the
>> transformer. Read through the entire email first.  If you have any
>questions
>> resolve them before doing any power on testing.
>> 
>> Start with a visual inspection: are there any damaged components or
>traces
>> on either the top or bottom of the power supply PCB?  Cracked pcb
>traces
>> can some times be difficult to see. Are there any cracked solder
>joints?
>> Check for 'cold' or 'dry' solder joints as well.  Reflow/repair
>anything
>> that looks suspicious.  Inspect all point to point wiring and
>connectors.
>> 
>> For all measurements use the center tap of the transformer as
>> the ground reference (or equivalent point).
>> 
>> To start take the measurements without any load on the power supply.
>> 
>> OK, enough preliminaries.
>> 
>> 1. Remove the regulators. Replace the fuse. Turn the power on.
>> 
>> If the fuse blows again, stop and report back. If the fuse doesn't
>blow,
>> continue on.
>> 
>> 
>> 2. Using your scope and the center tap as the ground reference what
>is the
>> AC voltage put out by the transformer going into the bridge
>rectifier?  You
>> should see a sine wave on both outputs from the transformer to the
>bridge rectifier.
>> You can also measure these two points with your DVM set to AC VOLTS. 
>If you
>> have a dual trace scope you can measure both transformer outputs
>simultaneously -
>> they should be 180 degrees out of phase and the same amplitude.
>> 
>> 
>> 3. Using your DVM set to DC VOLTS what is voltage across the 1000uF
>capacitors
>> on the output of the bridge rectifier. This is the input voltage to
>the voltage
>> regulators, so this is a key measurement.
>> 
>> 
>> 4. Set the DVM to AC VOLTS and measure the same two points.  This AC
>measurement
>> will show the 'ripple'.  See 
>http://en.wikipedia.org/wiki/Ripple_(electrical)
>> for more details.  (Note there are some caveats here - when measuring
>AC the DVM
>> is expecting a sine wave, but the ripple won't be a sine wave so this
>measurement
>> isn't accurate.)  You can also look at this with your scope.  Set the
>scope input
>> to AC coupling (not DC! you're looking for a small AC voltage imposed
>on a large DC)
>> and see if you can get the scope to trigger on the ripple.  With no
>load on the power
>> supply you may not be able to measure any significant ripple.  If you
>do, it should
>> have a frequency of 120Hz (60Hz full-wave rectified has a 120Hz
>frequency).
>> 
>> -----
>> 
>> After these background checks are done if nothing looks out of whack,
>we can move
>> on to the regulators.
>> 
>> -----
>> 
>> Note, later it will be helpful to have some 1 to 5 watt, 100-500 ohm
>resistors
>> to use as power supply loads.
>> 
>> -----
>> 
>> You may find the following site useful:
>> 
>> http://www.wisc-online.com/Objects/ViewObject.aspx?ID=DCE8204.
>> 
>> Go up to the parent page and click around, there is a lot of good
>info there.
>> 
>> 
>> -Dave
>> 
>> 
>> 
>> On 8/2/2013 5:36 AM, M Maeghan Skala wrote:
>>> I retitled the thread because the transformer is fine.
>>> 
>>> In trying to save myself the work of rebuilding a new power supply,
>I tried installing a few new components …
>>> 
>>> I installed a new bridge rectifier and replaced the 1000uf 25V caps
>with new ones and it was still not giving off the proper power needed …
>the readings I am getting are -6, +5.9 and -10.2, +9.8 …
>>> 
>>> so i swapped the voltage regulators  that are supposed to give off
>-12, and +12 with the regulators that were on the board when the synth
>short-circuited (i had two power supply boards for this
>>> synth)… when I did that, the slow blow 1amp fuses blew …
>>> 
>>> any help would be appreciated. I am trying to learn this stuff
>because I hope to someday be a tech. I understand that I have a lot to
>learn …
>>> 
>>> thanks :) ~ maeghan
>>> 
>>> 
>>> On Jul 29, 2013, at 7:07 AM, M Maeghan Skala
><pulsewidthmod at gmail.com <mailto:pulsewidthmod at gmail.com>> wrote:
>>> 
>>>> Hey Dave,
>>>> 
>>>> I took a break from working on the Siel; (sorry for the delayed
>response.) I also posted most of this to the thread I created on
>muffwiggler, if you're a member you can view it here:
>>>> http://www.muffwiggler.com/forum/viewtopic.php?p=1242106#1242106
>>>> 
>>>> the shrink tubing was on the AC wiring before I turned it on,
>before it short-circuited.
>>>> 
>>>> I could possibly move the pcb forward and to the left.
>>>> 
>>>> Here's what I'm currently doing to solve the power supply issue:
>>>> 
>>>> I'm gonna build a new power supply. The voltage regulators that it
>has are no longer available so I'm gonna use LM317's and LM317's. I
>know these aren't the best but my local store had them.
>>>> Unfortunately, my local store didn't have everything so I'm gonna
>have to order and then wait.
>>>> 
>>>> Since I"m using LM317/LM337 .. and the voltages I need to supply to
>the circuits are +6, - 6 , +12, -12 ... the Siel Mono uses the
>LM317/LM337 regulators and supplies the same voltage's ... I'm
>>>> gonna follow the schematics for it when building the new supply.
>>>> 
>>>> I'm really hoping that the rest of the synth's circuits are fine,
>if there's still an issue with the synth after I get the power supply
>squared away, I won't give up.
>>>> 
>>>> The amount that I have learned as a result of this mishap has been
>substantial; in a way ... I'm glad that it happened.
>>>> 
>>>> 
>>>> 
>>>> Cheers ~ maeghan/pulsewidthmod
>>>> On Jul 28, 2013, at 3:54 PM, Dave Manley <dlmanley at sonic.net
><mailto:dlmanley at sonic.net>> wrote:
>>>> 
>>>>> On 7/27/2013 9:54 AM, M Maeghan Skala wrote:
>>>>>> Sorry it took me a minute, I uploaded a set to flickr … here it
>is http://www.flickr.com/photos/pulsewidthmod/sets/72157634811572365/
>>>>> 
>>>>> <<<resend - first didn't make it to the list>>>
>>>>> 
>>>>> 
>>>>> So when you close the synth the new AC socket hinges into contact
>with the heat sink? Was the heat shrink tubing on the AC wiring there
>when the problem occured or was it added afterwards?
>>>>> 
>>>>> I can't tell from these pics how bad the mechanical interference
>is, but any contact between the AC wiring and the heat sink is a safety
>issue. The insulation of the AC wiring must not touch the
>>>>> heat sink. You don't want any possibility of the insulation
>getting damaged due to vibration, friction, or heat. The wiring must be
>dressed so this can't happen.
>>>>> 
>>>>> Obviously the plug can't be easily moved. Can the power supply PCB
>move forward and to the left?
>>>>> 
>>>>> I'd be tempted to add a hard insulated covering over the back of
>the socket.
>>>>> 
>>>>> Or switch to this type of socket which has a low profile on the
>inside of the panel:
>>>>> 
>>>>> Switchcraft EAC323.
>>>>> 
>>>>> -Dave
>>>>> 
>>>>> 
>>>>> _______________________________________________
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>>>>> Synth-diy at dropmix.xs4all.nl <mailto:Synth-diy at dropmix.xs4all.nl>
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>> 