Replacing caps in Threshold S/200

Jump to Latest
S

sapek

Member
Joined 2007
#1
I have a Threshold S/200 amplifier. I don't have any problems with it but since it is 20 years old I'm thinking about replacing the PS capacitors.

The original capacitors are Mallory 15,000 uF, 80V. I found following capacitors in Mallory catalog that fit size-wise and have similar specs:

Code: 
Cap (uF) ESR     Ripple   Catalog#       Voltage
17,000   0.033    8.8     CGS173U075W4C   75V
25,000   0.024   11.7     CGS253U075W5L   75V
15,000   0.043    8.6     CGS153U100W5L  100V
30,000   0.011   15.2     CGS303U100W4C  100V

Would any of these work? Should I consider any other brands?

While I'm at it, are there other parts that would be worth replacing? I read somewhere about updating rectifier diod in Threshold amps.

Thanks,
Adam
 
#4
If you are bold and observe that it's only a 40v ac secondary 63V will be fully sufficient, it is then possible to fit 150.000uF x2, but you will then have to pay attention to the peak inrush current, adding a slow start is advisable anyway. I replaced the transformer (with a larger one) and cleaned the power switch while doing the upgrade.
After the upgrade it drives the older B&W 801's like nothing else...really punches through when called for.

The easy refurbish path for sure is to get a decent large can capacitor that will fit the original clamps and go for the lowest ESR highest ripple version you are willing to pay for 🙂
 
#6
Norgaard said:
...it's only a 40v ac secondary 63V will be fully sufficient....
Click to expand...

If you sell with more than 30-day warranty (or do your own warranty and hate it), you want to up-rate the cap more than 11%. The rated voltage may be for 1,000 hour life, not much. Working 11% under may make that 1,210 hours, still not much.

But if space is really tight and a soldering iron is near, you do what you must.
 
#7
You have to be careful, with rules of thumb here - as always it very much depends on the total application stress, and there are other factors which has far greater impact on (large can) electrolytic capacitor life than voltage.

There are good tools available for calculating the actual life some of these also taking differences of capacitor design into account.

In my example with a proper quality, but still standard long life large electrolytic can capacitor, we are well beyond 100.000hrs

Would I go that close to the 63V rating (taking 253v input into account) in a commercial product? - probably not 😉

Some of the maths:
http://www.rubycon.co.jp/en/products/alumi/pdf/Life.pdf

A calculator
CDE Screw-Terminal Life / Temperature Calculator

I also had a quick check on the illinoiscapacitor calculator available online - and that has errors or limitations which means it does not work outside certain values for size - so take care if using this, maybe you are better of doing your own calc. by hand....

PRR said:
If you sell with more than 30-day warranty (or do your own warranty and hate it), you want to up-rate the cap more than 11%. The rated voltage may be for 1,000 hour life, not much. Working 11% under may make that 1,210 hours, still not much.

But if space is really tight and a soldering iron is near, you do what you must.
Click to expand...
 
#8
What about the rectifier bridge - originally it's a 35amp/200 volt single bridge.

My caps have been changes to Nippon Chem 80volts/25000uF - but I don't think the additional 20000 uF puts a lot of strain on the bridge. But, would it be a noticable upgrade to change the bridge - maybe to two bridges, and soft recovery?
 
#18
LOL. They have a similar one with minimum quantity of 1...Ill give them a try and report back.



Any other caps in this bad boy? My eyes are getting old and I would need to disassemble it to see. Looks like there may be one in each side between the sandwich PCB's
 
#19
I fear you'll need to dissasemble it and make a list, by values and size

if there is any Tantal (brain on reserve now), you know the drill - decent elco of today is better than potential popcorn, even when new

I made a habit of using Pana in my builds, cheapest drek in prototypes, but there is plenty of decent productions ..... usual list - Elna, Rubycon, CDR .... rumor sez that current Samwha are good in all things
 
You must log in or register to reply here.
Top Bottom