Other Capacitors

[Stringster]

I'm the original owner of a 20 yr old red stripe Simul-class Mk III. The caps have never been changed and I'm getting all the symptoms from ghost notes to fizzy sounds to pops and blurry bass. I've been doing all the searches and have found alot of great information here. I know I've got 7 large filter caps to replace but there all also 7 on the board that look to be electrolytic, including 1 can that's standing up. I've found a schematic on-line but it's blurry and I'm not sure which of these caps do what. If I need to replace these caps where is the best place to get them. The large filter caps were easy to track down at the Tube Store or Tube Depot but the others are a bit more elusive. Any help is appreciated. Thanks.

 

[Boogiebabies]

I would not worry about the small low voltage electrolytics. I would replace the blue power supply 30uf/500V and the blue 220uf/285V and the two Nichicon bias supply caps at 47uf/100V.

 

[Restless Rocks]

If you have the Graphic EQ there is a pair of 220uf/63volt "lytics" that are like "might as well while you're at it". These filter the power supply to the EQ.

 

[Boogiebabies]

Good Luck getting the board off and Good Luck getting the board back on.
I would just snip the old leads and solder the new ones to them on the EQ board. On those small ones, if they are not bulging I leave them.

 

[Monsta-Tone]

Make sure that you change the filter cap for the DC portion of your filament supply, which feeds V1 filaments and the Relays. I can't quite make it out, but I think it's a 3300 micro farad, 10v.



Also, make sure that you change the Bias Supply caps, I have seen many amps with hum and ghost notes that were related to the Bias Supply caps.

I can't quite make them out, but it looks like there are 2 50 micro farad, 73v caps.


These values might not be accurate, I only have 1 Mark III drawing and it just says Mark III ver. 2.



I would also just leave the lower voltage caps that are attached to your preamp tubes. I haven't seen many of these fail.

It is really easy to snip the leads of the caps and solder a new one directly to the old leads, just make sure that you don't leave the iron on the leads too long or you could end up with cold solder connections.

If the cap sticks straight up and you can't get to the leads, you can disect the cap to get to them.

Make sure that you get the polarity right, + goes to the + side of the cap, etc. or you will have problems. I accidentally put one in backwards, looked like one of those confetti things that you get for the 4th of July.


Hope this helps.

 

[Restless Rocks]

http://forum.grailtone.com/viewtopic.php?t=84&highlight=markiii+mod

Everybody has their own technique but I prefer to heat the solder joint and use my needle nose pliers to pull the lead (carefully) out of the hole. Then using a vacuum solder sucker and or copper braid to clear the hole. After cutting the new leads to the proper length, I insert them into the holes and resolder. Removal of the board is not necessary to do this. The radial filament filter is the only one that is a total pain unless as suggested you cut the thing apart then remove the leads from the board as above. I then use an axial cap with insulation on the leads to replace the radial 3300uf/10V. One must use great care not to pull the traces up from the board. See the post above; that fellow did a real nice job recapping his amp.

 

[Boogiebabies]

http://forum.grailtone.com/viewtopic.php?t=84&highlight=markiii+mod

Everybody has their own technique but I prefer to heat the solder joint and use my needle nose pliers to pull the lead (carefully) out of the hole. Then using a vacuum solder sucker and or copper braid to clear the hole. After cutting the new leads to the proper length, I insert them into the holes and resolder. Removal of the board is not necessary to do this. The radial filament filter is the only one that is a total pain unless as suggested you cut the thing apart then remove the leads from the board as above. I then use an axial cap with insulation on the leads to replace the radial 3300uf/10V. One must use great care not to pull the traces up from the board. See the post above; that fellow did a real nice job recapping his amp.

You must have Russian acrobat genes.

The bias caps are impossible to find at 50uf anymore. I learned the cut and paste from the master. Mike Bendinelli. I personally do not use it, but for a DIY without the mad skillz of you guyz I would use it. I'm so retentive I have to put zip ties back in the same spot and all the pots have to align perfectly.

 

[Restless Rocks]

http://forum.grailtone.com/viewtopic.php?t=84&highlight=markiii+mod


You must have Russian acrobat genes.

The bias caps are impossible to find at 50uf anymore. I learned the cut and paste from the master. Mike Bendinelli. I personally do not use it, but for a DIY without the mad skillz of you guyz I would use it. I'm so retentive I have to put zip ties back in the same spot and all the pots have to align perfectly.

Rich D. can send you 50uf/100volts and you can get the nichicon's from www.digikey.com. I'm the compulsive type I guess; there's just something beautiful about a pristine circuit board. Many techs use the "cut and paste" method and it is perfectly acceptable, but like you I want my work to look good. I'm just weird like that. anywho while we're back on the subject of caps here's some stuff I found interesting you guys might want to checkout this thread on "reforming new caps" http://www.thegearpage.net/board/showthread.php?t=247850

 

[Boogiebabies]

The stock part is 50uf/75 volt mainly from Mallory and ITT. If you find these, you've got breakfast at the Danel Boone on me.

Mesa has the Nichicons if you order parts from them as well.

I don't think RD would send you the lint from between his toes.

 

[Restless Rocks]

They're using the 50uf @100 now/ Yup! the 75 volters are looking scarce, but I love a good challenge. and hearing the latest gossip from downtown Helius Prime over biscuits would be tons O fun.

 

[Stringster]

Thanks for all the great advice guys. It's exactly what I needed. I was an electronics tech twenty years ago but I'm a little anxious about working on my pride and joy. The only thing it's ever needed has been a power switch. I've always wondered if there was a deeper problem with internal currents because I went through 2 switches in a years time. So far the one I got from Boogie is doing fine but it would be interesting to know if the switch arcing was connected to the cap issues I have now. Thanks again for all the input.

 

[Boogiebabies]

You may have had the luck of two pre-siesta Carling switches.
Proudly made in Mexico. It's kind of like buying a car finished on Friday.

 

[jvk]

:lol:

 

[Stringster]

Thanks for all your help. I recapped the 7 large filter caps as well as the 2 bias caps and my she's got her sparkle back. No noise, no ghost notes and much improved response, especially in the bass. Feels much more dynamic and musical. Well worth it!