• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Hi guys, Tube newbie with a project here.

John Burt

John Burt

New Member
So I recently bought an Allied 935 (Pioneer SA-400) from that auction site. It was advertised as working well, so I hooked it up and plugged it in.

Darned if it doesn't sound great! I used it for a week or two, then after reading the horror stories about bad capacitors, I set it aside. I opened it up today to take a look, and everything seems pretty straightforward in the cap replacement department except one can cap.

It's not a twist-lock type, the can is held by a clamp that is screwed to the chassis.

Any advice?

16096122674732660661491971436323

16096122674732660661491971436323

  • Media owner John Burt
  • Date added
Elna can capacitor
16096122674732660661491971436323

16096122674732660661491971436323

  • Media owner John Burt
  • Date added
Elna can capacitor
PXL_20210102_172046931.jpg
 
Register to hide this ad
Any other electrolytic caps, like that black axial cap in the picture should be replaced also. Multi cap cans are available. Some people pull the guts out of the old cap and restuff them with individual new caps. You can go up in voltage also. Like 400v, or 450v. It may be easier to find the multi cap you need at these higher voltages.
 
John Burt said:
So I recently bought an Allied 935 (Pioneer SA-400) from that auction site. It was advertised as working well, so I hooked it up and plugged it in.

Darned if it doesn't sound great! I used it for a week or two, then after reading the horror stories about bad capacitors, I set it aside. I opened it up today to take a look, and everything seems pretty straightforward in the cap replacement department except one can cap.

It's not a twist-lock type, the can is held by a clamp that is screwed to the chassis.

Any advice?
Click to expand...
While clamp mount cans are available, and you could even clamp in a twist-loc if the diameter is correct, I'd suggest using individual caps mounted underneath and just leave the old can in place for looks.

Replacement cans are convenient, but pricey. Most seem to run ~$40 plus shipping. Also, if you check the hour and temp ratings, you'll see that their specs are are not particularly good.

These amps seem to have enough space under the chassis that using individual caps should not be a problem. Just mount a terminal strip and put the caps on it.

I normally suggest caps rated for 10,000 hours at 105 degrees. A 47uf (which is the standard modern value) 350v will be under $1.80 for a quality Nichicon or Panasonic. For the others use 22uf, or go up to 33uf, 350v. Those will be about $1 each.

If you like you can use 450v caps, just don't use anything lower than the stock voltage.

As you are apparently aware, all the gray caps in these Japanese amps need to be replaced as well as any out of spec resistors.

Has this had any work done on it previously? Pics of the entire under-chassis area would be helpful.

Digi-Key offers a free shipping option. See details here:

http://www.audiokarma.org/forums/in...hipping-on-parts-orders.739513/#post-10018562
 
Thanks Charlie. Good info there. I might be able to get three individual caps underneath.
From what I can tell, nobody has touched this thing before me. It's even got the original tubes. Yes, all electrolytic capacitors are on the chopping block, as well as a polarized power cord.
 
Also, thank you Lavane.

If I do go with individual caps is it safe to assume that number one terminal is the first value 40 number 2 terminal is 20 etc?

They have a common negative in that can.
 
John Burt said:
Also, thank you Lavane.

If I do go with individual caps is it safe to assume that number one terminal is the first value 40 number 2 terminal is 20 etc?

They have a common negative in that can.
Click to expand...
Cans have symbols next to the terminals, typically a triangle, a square and a half circle. The schematic will have those on it. The highest value (40uf) would be the first cap after the rectifier.
 
I was looking for the symbols on the can cap, but all I see on the terminals are 1, 2, 3, and one painted black. The side of the can is stamped "black neg" so I guess we know what that one is.

I'm going to assume 40-20-20 corresponds with 1-2-3.
 
John Burt said:
From what I can tell, nobody has touched this thing before me. It's even got the original tubes. Yes, all electrolytic capacitors are on the chopping block, as well as a polarized power cord.
Click to expand...
Please post pics of the entire amp including one showing all the parts underneath.

Here's the schematic. There is no Sams, so no parts list with specs, just the schematic. It can be enlarged to show detail.

I'm not sure if this is the same as your amp. But the SA-400 uses a voltage doubler supply so the 40uf in the can cap is not the first cap after the rectifier.

Also, it is not just the electrolytic caps that need to be replaced. ALL the caps, except any ceramics, need to go.
 

Attachments

or for 16 bucks, one of these

https://www.amplifiedparts.com/products/capacitor-jj-electronics-500v-40202020-f-electrolytic

and just ignore one section, or jumper a pair of 20s to make it a 40/40/20 depending on what makes sense.

confirm the dimensions of course.

I'm not opposed to individual caps underneath and have done it lots of times but for the price vs effort involved a replacement can makes a lot of sense IMO.

The rest of the caps would also deserve an inspection. Japanese gear usually has a lot of coupling caps of a type that are not very reliable. I also see an axial electrolytic in the first pic, its just as old as everything else.
 
gadget73 said:
or for 16 bucks, one of these

https://www.amplifiedparts.com/products/capacitor-jj-electronics-500v-40202020-f-electrolytic

and just ignore one section, or jumper a pair of 20s to make it a 40/40/20 depending on what makes sense.

confirm the dimensions of course.

I'm not opposed to individual caps underneath and have done it lots of times but for the price vs effort involved a replacement can makes a lot of sense IMO.

The rest of the caps would also deserve an inspection. Japanese gear usually has a lot of coupling caps of a type that are not very reliable. I also see an axial electrolytic in the first pic, its just as old as everything else.
Click to expand...
I've used the JJs on a couple of projects. One when I didn't know any better (my first DIY build, a Bugle 45 SET) and the other because they fit and there wasn't really any more room under the chassis (Sherwood).

They are considerably more affordable than other replacement cans. And I can't say I've had any issues with them, although they don't have huge numbers of hours on them. I even have a 100uf/100uf 500v in stock, just in case I can't get anything else to fit.

But their specs are pretty dismal. Almost all of their caps are rated for only 1000 hrs at 70 degrees. They have one line that's a bit better, 2000 hours at 85 degrees.

https://www.jj-electronic.com/en/capacitors

I'm not an engineer so I'm not capable on analyzing all the technical nuances. And I'm not usually too concerned about relatively minor differences in specs. But the hour/temp rating affects reliability. So, when I can get individual caps rated for 10,000 hours at 105 degrees that cost much less, and with free shipping, the JJs are pretty much my cap of last resort.

I don't mind having to expend a bit more effort if it allows me to use much better parts.

From the pics I've seen of these amps there is plenty of room underneath and lots of holes already in the chassis so mounting a terminal strip would not be a problem.

There are also a pair of 100uf caps used in the voltage doubler. And who knows how many of the smaller gray caps that are so failure prone.
 
I've used a few of the JJ multi caps and no problems yet. You can always get a clamp to fit it if its a different diameter from the original. I have used a rubber strap wrapped around a cap to fit a larger clamp before. Some will use something like straps of foam insulation, but I don't like that method.
 
Check out Hayseed Hamfest. They will make a can to the required specs and already have a number of standard offerings.
 
JohnT123 said:
Check out Hayseed Hamfest. They will make a can to the required specs and already have a number of standard offerings.
Click to expand...
They are definitely high quality. Still much more expensive than putting individual caps underneath but, if you're going to use a can they're the best ones by far.
 
I'd also recommend F&T (Fischer & Tausche) can capacitors from Germany. My Japanese-built Realistic tube amp had the same type of can caps as yours and I replaced them with F&T's. In my opinion they're a step above the JJ can caps and only cost slightly more!
 
I've used both, haven't had issue with either. Only trick is finding a 3 (or more) section. 2 sections in a clamp-in is the usual option.
 
You must log in or register to reply here.
Back
Top Bottom