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 Post subject: RBO repair
PostPosted: Feb Thu 15, 2018 1:20 am 
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Joined: May Thu 06, 2010 10:12 pm
Posts: 246
Location: Albany, OR
I have an RBO I'm going restore, but before I get to deep into the restoration I have a few questons.
Mine is just a plain RBO, not a 1,2 or 3.
I have found several manuals out there and even was able to turn up a plain RBO.
All in the parts lists in all the manuals I've found have the filter (C101 thru C104) caps listed as 4mf @ 600v. However the caps are stamped as 40mf @600v. The caps seem to be original. According to the manual, these don't seem to be Electrolytic.

I have no way to test these other than with one of those Chinese all in one testers. Does anyone have any experience with the failure rate of filter caps and bypass caps in this type of unit. I know they were military grade, but after +70 yrs I wonder.

Usually with older stuff (+40 yrs) I'll just replace the caps to be on the safe side.

Thanks,
Stan


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 Post subject: Re: RBO repair
PostPosted: Feb Thu 15, 2018 1:31 am 
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Joined: Nov Sun 04, 2007 6:01 am
Posts: 2951
Location: Redding, CA
The original filter capacitors in the RBO were 4.0-mfd, 600-volt threaded base oil capacitors. Most are still good and reliable today. Are you sure they are marked 40-600 rather than 4.0-600?

Norman

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"No home is complete without music" - Capehart Sound Amplifying and Distributing Systems


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 Post subject: Re: RBO repair
PostPosted: Feb Thu 15, 2018 2:15 am 
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Joined: May Thu 06, 2010 10:12 pm
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Location: Albany, OR
Thanks,
I will double check.
I don't see a dot between the 4&0
Although they may have leaked as there is a bunch of oily stuff on the top, around the caps.


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 Post subject: Re: RBO repair
PostPosted: Feb Fri 16, 2018 3:03 am 
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Joined: Feb Tue 12, 2008 4:24 pm
Posts: 448
Location: Manassas, Virginia
A little bit of 'weeping' isn't unusual in these old rigs over time. Quite often you'll see fuzz stuck to the chassis around the caps.

A puddle or visible liquid is another matter.

I have an RBO-2 as a garage radio, still working great on its original caps. The dial cover is gone, but the caps are fine.


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 Post subject: Re: RBO repair
PostPosted: Feb Fri 16, 2018 3:08 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1337
Location: Morris Plains, N.J. 07950
Besides, for most of us, an RBO is probably the only E.H. Scott receiver we'll ever get to own.


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 Post subject: Re: RBO repair
PostPosted: Feb Fri 16, 2018 3:14 am 
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Joined: Feb Tue 12, 2008 4:24 pm
Posts: 448
Location: Manassas, Virginia
That or the RCH. Quite a few of the SLRM, H, and others out there, too.


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 Post subject: Re: RBO repair
PostPosted: Feb Fri 16, 2018 3:36 am 
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Joined: May Thu 06, 2010 10:12 pm
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Location: Albany, OR
There was a huge puddle that dried up all over the area surrounding the caps. The oil even leaked thru the "O" ring where the power switch and headphone wires pass and got all over the bottom of the unit.
Yep this is as close as I'm going to get in owning EH Scott.


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 Post subject: Re: RBO repair
PostPosted: Feb Wed 21, 2018 5:50 pm 
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Joined: Sep Sun 08, 2013 11:53 pm
Posts: 42
Question : didnt these oil caps have PCB's in them ?
Just wondering.


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 Post subject: Re: RBO repair
PostPosted: Feb Wed 21, 2018 6:11 pm 
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Joined: Jun Sun 19, 2011 2:31 pm
Posts: 5615
Some but certainly not all oil impregnated caps contain PCB. One of the better known is the "pyranol" line made by GE. PCB added to the oil stabilizes it and lowers the flammability and as long as it isn't leaking it isn't anything I would worry about. Quite frankly with the poor quality control of the global food processing industry PCB from a vintage cap is very low on the list of concerns.

If the cap (or oil impregnated transformer) is leaking, put on gloves and clean it up putting everything into a sealed bag and send it out with your community's next hazardous waste drive. If you get it on you wash your hands thoroughly and dispose of any clothes that get contaminated (rather than cross contaminating other stuff in the wash).

You don't want to be careless with old oil impregnated/filled caps and transformers but handled carefully they are no more dangerous than many of the substances found in vintage radios. Your chances of getting Hantavirus from a barn stored radio are far greater than a fairly careful collector being exposed in a harmful way to PCB compounds.

It is not unlike the fear that some have when seeing the nuclear warning symbol on some of the miniature voltage regulator tubes. They are "doped" with a trace element to ensure reliable starting in cold/dark conditions and are completely safe if not broken and if broken then cleanup should focus upon not stirring up the tube contents and not breathing or ingesting the remains. A plastic food storage bag, a pair of disposable gloves, and some damp paper towels (and a bit of common sense and caution) will render harmless a broken "radioactive" VR tube.

Rodger WQ9E


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 Post subject: Re: RBO repair
PostPosted: Feb Wed 21, 2018 6:57 pm 
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Joined: Nov Sun 04, 2007 6:01 am
Posts: 2951
Location: Redding, CA
Several types of oil were used in capacitors. PCBs were primarily used in larger capacitors for transmitters and industrial equipment but they may have been used in some later receivers. Almost all small capacitors used some version of mineral or vegetable oil. I have seen a lot of the 4-mfd, 600-volt threaded base capacitors but none with PCBs. The PCB oil is thick, smelly (some say like pine), and is the only oil that sinks in water. Other trade names for PCB oil include Chlorinol and Dykanol.

Norman

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"No home is complete without music" - Capehart Sound Amplifying and Distributing Systems


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 Post subject: Re: RBO repair
PostPosted: Mar Mon 05, 2018 12:52 am 
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Joined: May Thu 06, 2010 10:12 pm
Posts: 246
Location: Albany, OR
Just as an update. I did manage to get this working. I used 4 4mf caps (yes there was a dot there, I looked really hard as it's quite small).
I was lucky as one of the inductors was open and found a replacement on ebay at a reasonable price. Replaced all the paper caps that were in the metal containers. That was a chore! It does work though.
Stan


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