B&W 5100 AC bypass caps..

[K1ZJH]

Are these normally found to be leaky or failure prone?

Pete

[WBear2GCR]

A case could be made for putting in a modern "Corcom" type RFI filter in place of the old style bypass and/or wire choke. Of course that makes it not "authentic", in case you are interested in that, or if it is a pristine unit.

Imho, any and all old caps are potentially suspect and can leak (electrically) or fail.

            _-_-bear

[Jim, W5JO]

The ones in the B&W are not prone to leakage.  Last I looked (a long time ago) Surplus Sales of Neb. had them should they be missing or have problems.  I have never seen that type have problems.

[W2WDX]

I wasn't sure myself. They (AC filters) seem to test fine, but was wondering for my 5100B, which by the way is nearly pristine. Slightest bit of corrosion under the final tubes on the chassis, and that's it. I would like to replace them just for good measure. Righto on the Surplus Sales, I'll check that out.

I thought I had a problem with the iron but that checked out ok, and turned out to be a big gob of solder that must have creeped along the plate choke connection nearest the chassis. Seems there was quite a bit of arcing going on by the previous owner from the bottom of the choke to the chassis, where the B+ feeds into the choke thru a doorknob cap. It is only about a quarter inch away from the chassis and the arcing must have heated up the solder and it ran across the ceramic shorting the feedpoint of the choke to the chassis. Strange.

And yeah BEAR, I was looking at the CORCOM's as a possibility. Thanks.

[K6JEK]

I never leave old AC bypass caps.  There is a school of thought that says eliminate them altogether.  When I replace them, I replace them with AC rated caps, X1/Y2 caps. 

http://www.mouser.com/Search/Refine.aspx?Keyword=X1%2fY2

[JGLONG3]

Hello ALL ,,,,   

I am a newbie.

And, HELLO JOHN W2WDX.

John, I found this forum after I sent you some direct email.

A freind of mine bought a vintage BW 5100 and the shipper dropped it (!!!!!) (?),,,,,
 
I am helping him fix it. The drop sheared off all the external connections on the back of the chassis to include: The fuse connector/holder, the two Sprague caps to filter the 110 v AC line inputs, and the strip where signals/power are made available on the back of the chassis was broken. Also, the drop broke 2 of the 6146's, 2 of the 5R4GY's, and the 5V4. I have found these at a place in Florida. Even dropped, the chassis, the front panel, and the casing are in amazing condition.
 
I have repaired the strip for signals/power and replaced the fuse connector/holder.
 
We are looking to try and replace the Sprague .1 MF capacitors (Part Number 80P3) with original capacitors----If possible.

Could you please let me know of a link on the Internet or a place that I can find the Sprague Caps that filter the 110 v AC line in.?

Or, are the AC bypass  caps dicussed here the same?

Thank you for your  time, help, and advice!!!   

Jerry


 
P.S.  A JPEG file of mine is attached.

[KM1H]

Id replace the originals as a .1uF will allow a substantial current to the chassis, that much C is not allowed under current NEC rules either if that really bothers you. Unless everything on the bench is bonded together and to ground you can get a rather decent tingle. Use .0047 safety caps and add an external filter if you have RFI/TVI.

Carl

[JGLONG3]

Hello Carl ---  KM1H,,,,,,,   

OK,,,THANKS for the reply,,,,,

Not only am I a newbie in this forum but after a long exit from Amateur radio I have recently restarted.
 
In 1955 I became a Novice and one year later a General. I started Auburn University in 1960 and found I had to study----A LOT. As a result my General expired. I finished Auburn and worked in the Software and Hardware industry over the next 50 years or so. About 4 months ago I started over again as Technition. Next is General.
 
Also, a little bit at a time, I am relearning the stuff that was vacated between my ears over this time.
I can remember building my Novice CW rig and later building a HeathKit DX100B. Using a NC 125, when both were touched a little tingle was felt. That went away when these chassis where connected and then earth grounded.

I am thinking these Sprague HYPASS CAPS (.1 - 600 D.C. at 20 amps Part No. 80P3) are referred to as FEED THROUGH (and/or TERMINAL FILTERS). I am also finding many parts (vintage, etc.)  can be found on the Internet.

If you have the time could you please provide any links to the caps you referred?

Thank you for your time, help, and advice!!!! 

Jerry (KJ4YAP)

[WA1GFZ]

I would just yank them out. There is no point in pumping AC current into your ground system unless the rig is getting into some other equipment from conducted RF on the AC lead. Good chance they will cause a GFI breaker to trip.

[W2PFY]

I have had them explode in the BC-614 BC-610 s speech amp. I just yank them out.

[KM1H]

Mouser has them as the Vishay WYO series at .38 for the 4700pf. Those are universal X1/Y2 caps for 120/240V AC.

I also got my Novice in 55 but have pretty much stayed with radio ever since altho I do drift at times and have competing interests.

Carl

[ke7trp]

Let me guess, UPS?

Rememeber,  UPS has a 14 ft drop from the 30mph belts to the bins.  After having a radio destroyed, They told me this.  If the thing cant take a 14 ft drop at 30 mph, Dont send it ups.  If the bin is empty, its 14 ft. If its full, It will land on other boxes and can me only 5 ft drop.

We have had much better luck with fedex,  However, Fedex seems to lose a box once in a while. They always find it but sometimes the box takes a vacation to the islands or some far off land.
C

[JGLONG3]

Hello WA1GFZ, W2PFY, KM1H, KE7TRP,,,,,    

OK,,,THANKS for the advice!!!!

And, If I remember the owner comments correctly, I think he did say UPS (but ??).

Based on the condition of the RF line from the final to the external connector it looks like RF will get into the AC line inputs and probably fill up the shack with RF. This is an RG68U line under the chassis but about 3 inches is not covered with a shield. The shield is there to provide connection to the chassis as ground, but has been cut and a length made to allow these to be soldered leaving about a 3 inch gap where the center RF line is not shielded. And, the shack has a good ribbon connection to an Earth burried ground.

Once all has been fixed (tubes and line filters) we are going to try and bring it up as it exists. But, we are prepared that some of the paper capacitors will need to be replaced and the RF line from the final to the external connector will need correcting.

Also, since I have been out of tube stuff for so long I have attached a JPG  file showing the shematic part of power supply of the 5100 area where the SPRAGUE .1  -  600D.C. line filters are attached.  I just want to make sure that I understand the advice mentioned.

Please take a look at that JPG  file,,,,,I have marked the line inputs and the two SPRAGUE filters with a question about these and added an additional schematic that I think is the suggested change to allow filtering.

THANKS for your time, help, and advice!!!!    

Jerry (KJ4YAP)

[KM1H]

That change will be OK for a 2 wire line cord but you really should go with 3 wire. Then run one cap from hot to chassis ground, another hot to neutral, and another neutral to ground.

Carl
KM1H

[WQ9E]

Follow Carl's advice and the only thing I can add is when possible I put the bypass cap on the "hot" or "load" lead after the fuse. 

My worst failure with original line bypass caps was a RME-45.  In this model the bypass caps are mounted directly on the transformer terminals snugged up against the transformer windings.  One of the bypass caps went up in smoke and burned the paper around the winding.  Although the transformer tested OK I didn't trust it so I replaced it with another from a parts unit.  Several of the RME units use this mounting scheme so check for them when you go through one.  The original owner said it was working and it probably did; I guess he just ignored the sound and smell of cooked cap.

[The Slab Bacon]

I have had them explode in the BC-614 BC-610 s speech amp. I just yank them out.

I had a cute line bypass cap failure about 15 years ago. I was repairing what I seem to remember was an "all american 5" for a friend of mine. I had partially recapped it and changed out a few resistors and it was sitting on the bench, playing pretty well.
It was around 2 in the morning and I was pretty well sleepy eyed. I figgered I'd finish it up the next day. (I hadn't replaced the line bypass capz yet)

Just as I was nodding off, one of the line bypass capz blew!! It went off lke a sizeable firecracker and the whole chassis jumped up on the bench. It startled the
szht out of me and I fell backwards over the chair. It definately woke me up the hard way when I hit the floor backwards!!   

Lesson learned: Always replace or remove the line bypass capz first!!

[The Slab Bacon]

 <snip> "Based on the condition of the RF line from the final to the external connector it looks like RF will get into the AC line inputs and probably fill up the shack with RF." <snip>

Jerry,
        I seriously doubt if not having "feed thru" caps on your incoming line will fill your shack with RF. Much of the heavy filtering, shielding, and bypassing was the accepted rule from many years back when OTA television was the norm, and crappy weak signals were pretty much all that you had to deal with. With the current advent of sattelite, cable, and other modes of digital broadcasting, the "Tenessee Valley Indians" have pretty much gone extinct.

A small amount of leakage is also not always a bad thing. It sometimes is a bog help trying to spot or zero beat another signal when it is extreemly noisy or you are trying to zero beat some very large signals.

I do not have any line bypass caps at all on my 4-1000A rig and have absolutely no "RF in the shack" problems. You just need a good, well planned out ground system. Just remember that a good DC (AC) ground is not an RF ground if the conductor is more than 1/4 wavelength long!!

[JGLONG3]

Hello KM1H, WQ9E, "The Slab BAcon",,,,,,  

OK,,,,,THANKS for the advice!!!!  

Sorry, I may not have mentioned that the RF line from the Final stage to the COAX connector on the back of the chassis has about 3-5 inches that is not shielded.  Please correct me, but with the smallest SWRs this looks like when the FINAL PLATES are keyed that this unshielded part of the RF line would expose an extra  amount of RF to the chassis and the shack because this 3-5 inches is not shielded.

And, I did not mention the AC Line is a three line cable.

Also, just made some modifications to the schematic relative to the AC Line inputs base on  the suggestions made. I have placed a circle around the changes. Please take a look and advise if I have drawn these changes correctly and/or any changes necessary relative to the .005 CAPS

OOOPPSS,,,Sorry for the two JPEG files, I had forgotten to put the circle in the SCHEMATIC,,,,,,     


THANKS for your time, help, and advice!!!!  

Jerry (KJ4YAP)

[KM1H]

Now you got it.

You can also increase the value of the cap in the middle H-N to whatever you want and still be in NEC code. I generally use a .047 there only if Im concerned about a dirty AC line spike damaging something in the PS. This is mostly the many wood cabinet table and console radios scatterered around the house. For regular ham use I built several of the line filters in the 12/86 QST and also in many HB's. I made mine 2 section and they certainly do the job for TX and RX and were part of making the station RFI/TVI proof back in my wild and crazy contesting days.

Carl

[JGLONG3]

Hello KM1H,,,,   

OK,,,thanks for your time, help, and advice!!!!   GREAT HELP and patience with an "OLD GUMMER".

And, as time goes on I am remembering stuff lost "between my ears" over those years.

For me this is a "DONE DEAL". But, since I am a newbie I have no idea how the Subjects are managed in these forums.

So, if there is a Moderator this is a DONE DEAL!!!!

THANKS FOLKS for your time help and advice!!!!!   

Jerry  (KJ4YAP)