Identifying replacement capacitors from old part numbers

[huston55]

I have acquired a Bradford WGEC-95190A and am getting ready to recap the amp. This is my first foray into refurbing an old tube amp. This one looks to be in nice shape (see pics) and I have purchased the Sams Photofact for it (well worth the price). But, I am having a heck of a time finding replacement capacitors and have searched here on the forums and gone to many of the recommended sites. I can find no cross references to the many parts numbers listed in the SAMS. Even using the capacitor values for the electrolytics, I haven't found any matches. Surely, there are cross references out there.

The parts numbers available are:
Bradford
Aerovox
Cornell Dublier
General Electric
General Instrument
Mallory
Sprague

Can anyone point me in the right direction?
Thanks

 

[cademan]

Um, the brown disc capacitors don't need replaced. They last forever. It looks like you might only need to replace the can capacitor and a couple of electrolytics I see under the chassis.

The can cap will have its values engraved on the side. The one's underneath also have the values printed on them.

I see 5 which are called bumblebee capacitors. They look like oversized resistors. There are charts for these online. I don't have one off hand. Let's see a scan of your schematic.

 

[huston55]

I know what the values are, I just can't find them with the part numbers given on the SAMS or searching for values. The biggest issue is the multi-cap electrolytics. One of them is 60/40/20/10 at 350/blank/350/350 volts. Maybe I don't know how to search for these. Part numbers are given for each from multiple manufacturers, but I am getting results that are anything but what I am looking for with google search and parts sites like tubesandmore.com. I did find a 80/40/30/20uF 525VDC. I am thinking I just don't know how to search for these properly. Thanks for responding,

 

[Big Harry]

I see 10 small caps that should be replaced along with both of the can caps. There are several of the dreaded bumblebee caps that are guaranteed to be electrically leaking. Antique Electronic Supply in Arizona has a good selection of the can type electrolytic caps along with all of the smaller caps needed to restore the amp. You can also restuff the electrolytic cans or mount discreet components under the chassis on terminal strips to replace the electrolytic caps.

 

[gadget73]

Mostly those old part numbers are not going to be all that useful. What you need is the value and voltage of the capacitor. From there, you can replace with any cap that matches the value within about 10% and meets or exceeds the voltage. The individual caps are widely available in film types that will out last all of us. Honestly I don't buy into fancy capacitors, so I usually stick with more basic caps from the likes of Illinois, Cornell-Dublier, or whatever Mouser or Digikey can provide in a suitable package for prices that don't make me cringe.

The multi-section caps you can actually get replacements made for. Hayseed Hamfest will custom make whatever you need if you give them voltages and values, or you can mount individual caps underneath, or re-stuff the old cans.

 

[cademan]

I see 10 small caps that should be replaced along with both of the can caps.

There are actually only 8 including the can but I was just pointing out the bumblebee caps as the other electrolytics were obvious. There are only 5 bumblebee's, two coupling, and one small black electrolytic.

This ain't my first trip around the block!

 

[huston55]

I have been looking at Antique Electronic Supply, best site I have seen so far. Thanks for all the responses.

 

[cademan]

I know what the values are, I just can't find them with the part numbers given on the SAMS or searching for values.

Nowadays, the part numbers are useless. You go by the actual values. If not available (and most are not), you can always go up in value but never down. Example: a 40uF @ 350 volts can be sub'd by a 47 uF @ 450 volts.

Gadget says 10% and that is acceptable but 20% seems to be the norm around here.

 

[gadget73]

20% is generally fine for most things, but if you can keep it within 10%, so much the better. I've definitely gone outside of that window but sometimes its not well advised.

 

[cademan]

I also like to be as close as possible.

 

[danrclem]

Were you wanting to replace the can cap as a whole, restuff the cans or just put individual caps under the chassis? You probably already know this but just in case you don't most people just put individual caps underneath as long as there is room and your not concerned with everything looking original.

 

[huston55]

Were you wanting to replace the can cap as a whole, restuff the cans or just put individual caps under the chassis? You probably already know this but just in case you don't most people just put individual caps underneath as long as there is room and your not concerned with everything looking original.

I didn't know this, so thank you. I have no problem with putting caps underneath. That sounds like a good option.

 

[primosounds]

I didn't know this, so thank you. I have no problem with putting caps underneath. That sounds like a good option.

Your chassis is quite roomy and replacing the can caps with individual units below the chassis is sometimes simpler and cheaper. You may have to install some solder lugs to attach the caps. Since you know the value of each section of the can cap you can just get the individual caps of correct value. Whether you want to do it this way or replace the cans it makes no difference to the circuit.