Vintage Synth Repair

Just let it sit still plugged in (grounded) for 30 seconds, or a minute if you're nervous, and you're ready to go.

There's nothing big enough in a power supply to hold a charge for very long.

  ----- Original Message -----
  From: f115@...
  To: vintagesynthrepair@yahoogroups.com
  Sent: Tuesday, April 08, 2014 9:23 AM
  Subject: [vintagesynthrepair] Discharging capacitors in your synths



  Hey everyone!

  I'm just wondering what methods you use to properly dicharge the capacitance in a synth before you work on it. Thanks!

With the exception of memory caps, I can not think of one model that had a cap without a bleeder of one kind or another.  If you must, I would use a 100K ohm, or a older meter like the once state of art Simpson 240, then you could watch it bleed out. 

On Tuesday, April 8, 2014 3:45 PM, "f115@..." <f115@...> wrote:

 
>Hey everyone!
>
>I'm just wondering what methods you use to properly dicharge the capacitance in a synth before you work on it. Thanks!
>
>
>

Do you mean big capacitors used for filtering in PSU? There's no high  
voltage, and no danger of electric shock - at least in my experience.

Tube amplifiers, Hammond organ or old TV set are something different :-)

Daniel Forro


On 8 Apr, 2014, at 10:23 PM, <f115@...>  
<f115@...> wrote:

>
>
> Hey everyone!
>
> I'm just wondering what methods you use to properly dicharge the  
> capacitance in a synth before you work on it. Thanks!

A screw driver! If you want to avoid creating an arc, then just use a resistor of two hundred ohms or so.

The lethality of an electric shock is dependent on several variables:

• Current. The higher the current, the more likely it is lethal. Since current is proportional to voltage when resistance is fixed (ohm's law), high voltage is an indirect risk for producing higher currents.
• Duration. The longer the duration, the more likely it is lethal—safety switches may limit time of current flow
• Pathway. If current flows through the heart muscle, it is more likely to be lethal.
• High voltage (over about 600 volts). In addition to greater current flow, high voltage may cause dielectric breakdown at the skin, thus lowering skin resistance and allowing further increased current flow."

All correctly designed tube amps/Hammonds/TVs have a BLEEDER resistor, typically a 100K ohm across the B+ or high voltage power supply.  It BLEEDS off any stored charges in the filter caps.  This is standard design practice. 

The exceptions that I can think of would be a photographic strobe light charge capacitor or sram memory capacitor.  If you are unsure of design, you can always do a quick voltage measurement. 



On Saturday, April 12, 2014 3:30 AM, "megaOhm1@..." <megaOhm1@...> wrote:

 
>Discharge with a bleed resistor as advised by others.
>You got some replies stating that low voltage is not dangerous.
>That is stupid advice and you should ignore it completely.
>
>below is quoted from:
>http://en.wikipedia.org/wiki/Electric_shock
>
>"
>
>The lethality of an electric shock is dependent on several variables:
>	* Current. The higher the current, the more likely it is lethal. Since current is proportional to voltage when resistance is fixed (ohm's
law), high voltage is an indirect risk for producing higher currents.
>	* Duration. The longer the duration, the more likely it is lethal—safety switches may limit time of current flow
>	* Pathway. If current flows through the heart muscle, it is more likely to be lethal.
>	* High voltage (over about 600 volts). In addition to greater current flow, high
voltage may cause dielectric breakdown at the skin, thus lowering skin
resistance and allowing further increased current flow."

>
>
>
>
>