As I'm restoring my Fisher 500-C, I noticed the two silver multi-section caps on the chasis top were too high by about an inch for the wooden case to slide on. In the process of replacing them, I found the following strange substitutions:

Capacitor 91 - the original 20/40/40/40 uF cap was actually a 20/20/40/50 uF (my replacement is to be 22/47/47/47 uF).

Not too bad, but here's the strange one:

Capacitor 92 - the spec. 50/50/50/200 uF cap was actually a 60/90/125 uF (yep, just three sections) (my replacement is be 47/47/47/200 uF).

Anyone know of a reason to vary so much and use a 3-section cap for C92 instead of 4-section? Maybe that's why my left channel is weak.

Sure sounds wrong to me. Are there any caps under the chassis that would have taken the place of the missing section? Did you find new cans or are you building under the deck?
John

You can use stacked caps to build multisection unit. Tomorrow I can post a picture if you wish.

Sounds like someone has done some tinkering on that one. I wouldn't think Avery would have sent it out like that.:no:

You can use stacked caps to build multisection unit. Tomorrow I can post a picture if you wish.

Please post pics! I'm very interested.
Thanks

I used the SDS labs board in my first 800c. Easy to assemble and also has rectifier on board. On my second 800c, I used individual caps. I put a new 220uF in the old 200uF can, and built board for the other multi caps.

I wouldn't think Avery would have sent it out like that.:no:

In 60th electrolytic caps were much larger, multi-section caps were used to save space on chassis. Today highest-graded Epcos 560 uf/450V takes exactly the same space as old 100 uf/300V. You can build much better supply these days.

I've got this idea is from Jim McShane. He used 2 metal cap clamps with 2 distancers to stack caps (see photo 1). I used his kit with my Fisher 400. However, I found this construction too complex and combersome for the task. Additionally, metal clamps manufactured today are not perfectly round, they are oval and may damage caps.

So I found nylon clamps which are round, flexible, and perfectly fit for this purpose (see 2 another photos of my Pioneer SM-83). Clamps are available in different dimensions, so you can stack any radial electrolytic can caps. And you need only 1 clamp per couple of caps !

PS. Another tip: you can disassemble old can cap, remove all internals, clean the can, solder several 20 - 50 uf units inside, and close it again. Thus, you can preserve old (original) look :thmbsp:

Only thing that I might mention is that with the terminals of the caps on the top, high voltage is present and someone who is nosy, may touch them. They would be in for a big surprise. Most times, all leads and terminals are "below deck".

Just my 2¢...

Funny thing is that the 500-C seems to work OK, except for the weak left channel. Anyway, my new 4-section caps were custom made by Tom Hayseed Hamfest Co.(tom@hayseedhamfest.com) in a factory he has access to. They look original and are the proper height. I have C91 installed already but am having trouble understanding how C92 is wired. I have the schematic but could sure use a photo or layout sketch of the chasis underside showing the wiring of C92. Anyone?

Only thing that I might mention is that with the terminals of the caps on the top, high voltage is present and someone who is nosy, may touch them. They would be in for a big surprise. Most times, all leads and terminals are "below deck". Just my 2¢...

The amp on photo have top cover off. With top cover, no one can touch them :thmbsp:. Additionally, after restoration is finished completely, top of can caps will be wrapped with insulation tape. I see virtually no advantages of using obscure and expensive multi-section caps today, it may make sense only for amps without top cover at all for aesthetic purposes.

I also worry about the inverted cans. Cover with tape or wood case, but I'd rather leave the old cans for looks and put caps under the deck. If possible I'd rather restuff the old caps. I will post a photo of the connections when I get home. I doubt this would account for sound imballance. John

I have C91 installed already but am having trouble understanding how C92 is wired. I have the schematic but could sure use a photo or layout sketch of the chasis underside showing the wiring of C92. Anyone?

Ooh! I just dealt with this... unfortunately, the unit is no longer here.

Here's the way I remember it looking... maybe this will help:

http://www.audiokarma.org/forums/attachment.php?attachmentid=131212&stc=1&d=1232805643

There may also be a ground wire (or wires), from the other side of the "barrier/divider" thing, from the rectifier area... this should be connected to one of the ground lug (or lugs) of the new cap.

EDIT: For your new cap, think "47uf" wherever my diagram says "50uf"...

EDIT^2: I don't think this cap would have anything to do with just ONE channel being weak. If the 200uf section of C92 is bad, BOTH channels will sound wimpy. The smaller sections power the tuner... so, they would affect both channels equally, too.

One channel weak is probably either a bad tube (phase inverter or output), a bad cap or resistor (MOST likely- plate or cathode resistors on the phase inverter are probably most suspect) or god forbid, a bad output transformer...

Regards,
Gordon.

I also worry about the inverted cans.


What exactly make you worried ? Radial can cap does not have a gyroscope to be sensitive to its positioning. You can find a lot of devices where radial can caps mounted horizontally, upside down, etc.


Cover with tape or wood case, but I'd rather leave the old cans for looks and put caps under the deck. If possible I'd rather restuff the old caps. I will post a photo of the connections when I get home. I doubt this would account for sound imballance. John

There may be not very much space under the deck, like in SM-83 on my photo. Additionally, with stacked caps you can build much better power supply. In PS filters capacitance does matter!

Just don't like the look of wires and tape on the top of a chassis. I like to keep things looking stock or as close as possible. If there is room inside then good to put them there. If not then you have to do what you need to to get it done.

I used the SDS labs board in my first 800c. Easy to assemble and also has rectifier on board. On my second 800c, I used individual caps. I put a new 220uF in the old 200uF can, and built board for the other multi caps.

That's pretty slick.:thmbsp: I try to keep comercial stuff looking fairly stock too, but homebrew, now that's where you can have some fun.:yes:

What exactly make you worried ? Radial can cap does not have a gyroscope to be sensitive to its positioning. You can find a lot of devices where radial can caps mounted horizontally, upside down, etc.



There may be not very much space under the deck, like in SM-83 on my photo. Additionally, with stacked caps you can build much better power supply. In PS filters capacitance does matter!I stack Jim's doubler caps in much the same way, except I dont use both metal clamps and stand-offs. First I glue them together "top-to-top" (making sure to properly orientate the +/- terminals opposite to each other) then I cut apart an gut an old cardboard covered can (I save them all) and stuff em up in there.
I agree it is somewhat of a safety issue to leave them exposed, and who needs the liability. :no:
WOT

http://www.audiokarma.org/forums/attachment.php?attachmentid=112988&d=1224039166
http://www.audiokarma.org/forums/attachment.php?attachmentid=112996&d=1224040917
http://www.audiokarma.org/forums/attachment.php?attachmentid=112995&d=1224040865
http://www.audiokarma.org/forums/attachment.php?attachmentid=131232&d=1232818401

I stack Jim's doubler caps in much the same way, except I dont use the 2 metal clamps and risers. First I glue them together "top to top" then I cut apart an gut an old cardboard covered can and stuff em up in there.
I agree it is somewhat of a safety issue to leave them exposed, and who needs the liability. :no:
WOT

http://www.audiokarma.org/forums/attachment.php?attachmentid=112988&d=1224039166
http://www.audiokarma.org/forums/attachment.php?attachmentid=112996&d=1224040917
http://www.audiokarma.org/forums/attachment.php?attachmentid=112995&d=1224040865

Very nice.:thmbsp:

Nice job wop. Like the idea. I too keep all the old stuff I pull, never know when it will come in handy. Here are a couple photos of the original cans in the 800c I did. Same as the 500c. Sorry they are not the best, but it may help some.
John

I stack Jim's doubler caps in much the same way, except I dont use the 2 metal clamps and stand-offs. First I glue them together "top-to-top" (making sure to properly orientate the +/- terminals) then I cut apart an gut an old cardboard covered can (I save them all) and stuff em up in there.


Very cool indeed, new stuff, but old look preserved :thmbsp: BTW, amp pictured in your avatar, is it Bob Carver's stuff ?

Very cool indeed, new stuff, but old look preserved :thmbsp: BTW, amp pictured in your avatar, is it Bob Carver's stuff ?Thanks u guys. As far as the amp in my avatar, nope- that's my 1960 Citation II (fully Mcshane'd of course) ;)
It's currently sporting a hard-to-find quad of Ei KT-90s Type III (not those 6550 as shown in the pic)
WOT

Sloober and Gordon, I'm trying to reconcile your diagram and photo with what I have. Sloober, your photo and my original wiring did not have the 470 ohm resistor between the 50 and 200 uF terminals though it shows on the schematic. Here's my diagram with a few questions on it. Appreciate both your comments.

I kept all my notes and drawings and had one for that cap. Looks like you are on target. The 470 ohm resistor you show as missing is mounted on the 200uF black can. Hope this helps. John

Thanks u guys. As far as the amp in my avatar, nope- that's my 1960 Citation II (fully Mcshane'd of course) ;)
It's currently sporting a hard-to-find quad of Ei KT-90s Type III (not those 6550 as shown in the pic)
WOT


I've got a new old quad of EI KT 90s. How can you tell if they are type 3 etc.?

I've got a new old quad of EI KT 90s. How can you tell if they are type 3 etc.?EveAnna Manley used to have a nice set of photos posted showing all the Ei KT-90 versions. I can't seem to find it any more, but I saved it somewhere- possibly on my laptop (which isnt with me right now). Let me find it for you.
WOT

<EDIT> nm I found the link http://www.manleylabs.com/galleria/KT90.html
I only use the Ei-90s when I'm in the mood (or musical selection) for triode mode on the Deuce. Normally for rock'n it out a max-powa I use the reissue Genelex in pentode UL. What do you plan to run them in?? (with apologies to the OP for the temporary thread jack) :D

Thanks, looks like I have a quad of version 3, and a pair of version 4. Do you know what the "sacrificial thingy" is all about?:scratch2: