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New to Tubes...800c score...help restore.

Sounds like your 800C is in need of some new voltage doubler caps as I suspected. If you don't want to tackle the whole power supply, just replacing those caps underneath is a pretty straightforward undertaking. Personally I'd do the whole power supply and never have to worry for another few decades but that gets a little more complex. Honestly with how quick you've come with the metalbone kit I see no reason we couldn't walk you through it here. Especially with those great pictures you take. It can get a little tedious and will delay your gratification for awhile but I feel it really does make a big difference in the sound quality.

I'm far from the resident Fisher expert so I'd like to elicit other opinions as well, sound like I'm on the right track guys or is it possibly something else.

Kory
 
The cardboard covered can that's 200uf @250V which is insulated from the chassis and it is wired in a series with the other can which has a 200uf @ 250V section. I use 220uf@350V replacements in the recent rig's I've done.

Kory
 
The power supply are the three can caps?
Are we talking about restuffing or an SDS board.

The whole reason we venture into this madness is sound quality.
martin
 
I'm not a fan of the sds board but to each their own. I've personally just bought 2 brand new cans from tubesandmore.com and used 3 individual caps underneath.

I'd elaborate more but I'm at work and have to go out on a call.

Kory
 
You've done an excellent job so far. If it was my receiver I'd complete the job by replacing/restuffing the multi secton caps in the power supply. It would be a shame after the nice work that you've shown us to have something go south because of a failed $30 part. All the caps are available from Tom at hayseedhamfest.com, or you can search previous threads on restuffing multi section caps. You will find tons of info. I replaced all the multi section caps in all my Fisher gear just to be safe. I opened all cans after removal, about 10 total, all but one were dry and shot.
 
Thanks dsndblm
Considering my options.
Iv'e never restuffed a can. Do you know a good site with diagrams, pictures and arrows?
If I were to just order new replacements, what would I need to know to order the correct valued replacements?
By the way, you just made the "info" hit list
martin
 
I do remember reading a thread about cuttig open the cans, installing the new caps and epoxying it all back together. maybe it was at an antiques radio site.
It's all a blur at this point.
martin
 
Martin

If you do a search in the Tube Audio section I'm sure you can find pictures and detailed instrustions on restuffing. I restuffed some cans a few years ago when repairing antique radios. I went the new can route with my Fishers because of time issues. I was single with no kids when the radios were fixed :) Maybe someone can help out with the antique radio website with instructions and pictures. I've seen a very well put together site but can't recall the name. I think it might be justradios.com


All the cap cans are marked with the capacitance in uf (microfarads) along with voltages for each capacitor section.

There are a number of places that you can buy the new multi section caps. I've bought from AK member Jim McShane. Jim is a great guy and a wealth of information. Tom at hayseedhamfest.com should a have a "cap kit" with all the cans you need. tubesandmore.com is right down the street from my work. They are great people, I buy from them often. I bought my 500C multi section caps from Tom at hayseedhamfest.com because he was the only vendor that offered the correct schematic value caps. Toms were actually a few bucks cheaper each than the other vendors even with shipping charges.

Feel free to ask if you have questions. I don't know everything, just started with the audio stuff 4 years ago but will help when I can. I've learned a lot from the nice guys here at AK along with two very bright guys from our local antique radio club.

Again, great job on your 800
 
Hi Martin,

I'm a big fan of re-stuffing the old cans... particularly in receivers where 'sometimes' placing power caps below can interfere with the radio frequency signal - had it happen. It's not easy at first but after you've done a few it gets to be old hat. Of course, getting them already made up from Tom is easy-peasy, but doing them yourself gives a sense of pride of accomplishment if you know what I mean.

Here's my method... take a lot of pics of the cans - top and bottom. Top b/c you want to orient them the same as before. I even draw diagrams. Desolder everything - I use a cheap 100 watt Chinese solder iron to get the ones where the tabs are solder to the chassis - you want the tabs in good shape so you can lock them down as before. Then I mark lines before I cut them so I can place the cans exactly on the marks so they're as they were before.

I use a small hack saw just making small passes turning the can as I go. It's aluminum and easy to cut. Before you know it you've cut the can away.

Now, here's the hard nasty part. Not always but most are pretty hard and really stuck to the can. I start a dry wall screw in the center of the chemical dielectric stuff. Pull with a pair of vice grips and if you're lucky it might just come out. If it's subborn, I use a hot air gun and heat that rascal while holding with the vice grips and a welder's mitt. Then the'll glide out like melted butter.

Clean the can with some kind of solvent - I use WD40 - careful not to erase your marks. Get your caps together - here's where size matters. Beforehand, measure your can and make sure your new caps will fit. Most places give the size of the caps so you can figure it out. I use a lot of shrink wrap and sleeving so as not to short the pos side to each other.

I drill holes besides the old caps terminals to hook the leads of the new caps. Test with your DMM to make sure there's no shorts. Then dab some JB weld around the cut making sure you have the marks align. Let it dry overnight and you're done. I know it seems like a lot of work but after a few it goes pretty easy.
 
Last edited:
Inquired at hayseed and this is Tom's reply



"Hi, Martin:

Yes, we have sold quite a few pairs of can-caps for Fisher receivers. I know we've sold them for the 500C. I believe the cans for the 800C are the same. We would want to check to make sure, of course.

We say "pairs" because in the past, our customers have opted to replace the one section can by installing an axial lead capacitor under the chassis.

Assuming that the component numbers are the same as for the 500C, we, supply a 47/47/47/22 uF @ 450V (500V surge) can-cap for C-91. The one section of C-91 that came from the factory at a 500V rating is replaced with a 450V with 500V surge. We have had no problems with this spec, as the capacitor sees only about 375 volts. And more importantly, our temperature rating is up-graded to 105C degrees.

C-92 is replaced with a 47/47/47/200 uF @ 250V unit, also 105C.

We have these units scheduled for production. Unfortunately we are out of stock at this time. Normally we keep a good supply on hand, but recently we had to reject 600+ base discs because the water-jetting did not meet our spec for taper tolerance.

This has pushed us back and I'm guessing we're about 3-4 weeks out on production. We just received another batch of discs from the engraver yesterday, but have a large backlog of orders to work through.

Would this create a problem for you?

This pair of can-capacitors sells for $62.95 (total for 2 cans) + S&H.

They are roughly 1.5" in diameter by 2.9" tall.

Please let us know if you have any questions on the above. We would like very much to be of service to you.

Thanks,
Tom Farland
Hayseed Hamfest Co."


Nice email...seems like a nice guy. I like service oriented companies.


The values on 800c and 500c are the same, just the cap # is different.

800c C87 (C91 on 500c) A-20uf B-40uf C-40uf D-40uf
Tom @ HS C87 22uf 47uf 47uf 47uf

800c C91 (C92 on 500c) A-50uf B-50uf C-50uf D-200uf
Tom @ HS C91 47uf 47uf 47uf 200uf

Are these values too far apart?

Perhaps C98 (black wrapped) can cap could be stuffed with the single 200uf 250V cap.

My cans are 1 3/8" x 3".

Guess I have 3 to 4 weeks to decide.

Martin

P.s. I have been rereading alot of older post dealing with biasing and some are running 370 - 390V from their PS andseem to have no problem getting the proper ma's to their tubes.
I really think I'm measuring something wrong and its due to my lack of understanding.
I'm really not sure of the right questions to ask.
So I'll keep reading and studying in the meantime.
 
Martin, Tom makes great can caps. I used them for my Fisher TA-600 seen HERE that really has no space for extra caps underneath. If you're willing to wait his prices are great and the product is also great.

In the 500C I most recently worked on for specialidiot here's how I re-did the power supply with parts available immediately.

From tubesandmore.com I ordered 2 cans.

50/50/50/50uf@350V

40/40/40@525V

Then from mouser I ordered the remaining individual lytics':

Radial lead 22uf@350V
(2) 220uf@350V

I installed the two new cans, used new metal-film and wirewound resistors in the power supply also purchased at mouser. While the original wirewound resistors are most likely fine, they're 50 cents and you can uprate the wattage for cooler running. Also I find some of these old parts get brittle after you bend em' around a bunch of times.

All I had to do was wire in the 22uf@350V cap with the 40/40/40 can, and then install the (2) 220uf@350V caps underneath as well which there is tons of room for.

Waiting for Tom to make you up a can is definitely cheaper and a bit more tidy so to speak, just explaining another option to consider.

Kory
 
As far as re-stuffing can caps goes...It just seems like more work than it's worth to me. But this is coming from a guy who works 70 hours/week and plays with tubes whenever I have the time. If I had more free time I may just try it for the hell of it sometime. They always say don't knock it until you try it! :dunno:
 
Okay...
Before I make a decision on buying new cans or restuffing. I would like to make sure that this is the problem. I realize that the power supply is weak and should be replaced. But it would be nice to rule out the usual suspects.
The metalbones kit delt mainly with caps and a few resistors.
I would like to know if there are any particular resistors that are prone to being troublesome and should be check.
Of course I'll lift a leg. :D
martin
 
marloubow said:
Okay...
Before I make a decision on buying new cans or restuffing. I would like to make sure that this is the problem. I realize that the power supply is weak and should be replaced. But it would be nice to rule out the usual suspects.
The metalbones kit delt mainly with caps and a few resistors.
I would like to know if there are any particular resistors that are prone to being troublesome and should be check.
Of course I'll lift a leg. :D
martin
Click to expand...

Martin, I'm pretty sure your voltage doubler caps are shot. They are a common failure in these Fishers mainly due to that solid state power supply that slams them when you first turn on the receiver each time.

You could definitely just replace those two caps underneath and it would only set you back like 8 bucks plus shipping. Listen to it for awhile and decide on the rest of the power supply later, or replace them while waiting for hayseed's cans.

Kory

Edit: As far as testing resistors, I honestly never do this unless there's problems. If I have to go to the trouble of heating it up multiple times to remove a leg for testing, I mine as well drop a new one in regardless since they're so cheap. Just my opinion on that, many people do test.
 
If I remember right I've replaced less than a dozen resistors during all my Fisher rebuilds. We are lucky, Fisher used quality resistors that don't drift. My X-101-B had a couple of crusty resistors in the power supply, my FM-100 tuner had a couple of problems that were traced to out of spec resistors. I always check resistors that are removed when placing other components, otherwise I leave them unless the set has an issue.

If it was my 800 and I had potentional issues the power supply caps I'd wait until I had the new caps installed. Why take a chance?
 
I have always read that Jim McShane uses much higher quality parts and also includes the multi caps needed but does not include detailed instructions such as the Metalbone kits.

In an ideal world I think it would be best to get the McShane kit and see if you could figure most out and have those here help with anything you cannot figure out yourself (or maybe someone could get you some instructions).

McShane's Kit is more expensive but only by about $40 over what you would be paying out for the Metalbone plus Hayseed parts.
 
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