[sdiy] Siel OR400 power supply busted

Sat Aug 3 13:17:31 CEST 2013

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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