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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Sun 10, 2017 7:47 pm 
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Thanks for the help about the 8 mfd cap but the other question about the cap with all the wire description has anyone been able to figure out thanks.


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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Mon 11, 2017 12:13 am 
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Im still a novice , and my hard drive is not very fast or has much memory . Lol. I would have to have the radio to help. It looks like the values are on the cans?

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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Mon 11, 2017 12:31 am 
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Yes I posted what was written on all the cans earlier but no one commented on it. It is on top of page 3.


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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Mon 11, 2017 2:02 am 
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Any help in regards to listing of markings on capacitor cans on top of page 3 would be great thanks. Are these the actual cap values or something else . Also if you count lugs used you get 15 but schematic on page 2 with the caps circled there is 14 caps.


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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Mon 11, 2017 2:44 am 
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Rogers had 4 multi capacitor blocks in the 841 (besides the filter blocks)...You can see them on the bottom right of the page below....Part numbers R10374 to R10377....That`s just a guide since they may of been changed....

https://app.box.com/s/tl4bo4xh9dp63r0az1w0p2b6uq7cmea1

Ken


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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Mon 11, 2017 4:11 am 
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Here's a snip from what Tarpawns posted:
Attachment:
cap-modules.jpg
cap-modules.jpg [ 12.46 KiB | Viewed 737 times ]

If all four of those modules is used, you have:
6 ea 0.1 uF
3 ea 2.0 uF
2 ea 0.5 uF
1 ea 1.0 uF
total 12

compare to what I circled on the schematic:
8 ea 0.1 uF
2 ea 2.0 uF
1 ea 0.5 uF
1 ea unknown
total 12

Neither one of these lists includes the two 8 uF caps, which I assume are in some kind of different package.

Here is how to sort all this out:
--First, identify the circuit node associated with each capacitor**
--Second, look at the actual capacitors and get the capacitance from the label on the can, or by looking at the size (assuming the same voltage ratings, a 2uF part will have roughly twice the volume of a 1uF. reconcile this with the list of nodes.
--If necessary, measure the capacitance of the old part

**the node identification needs to be simple and unambiguous--eg a particular element on a tube. Here is a start, based on the schematic provided by Tarpawns.
Rogers 841 bypass caps by node
Format: Node, Value

(Working from top left)
1. RF amp (51) cathode, from the volume control wiper, 0.1uF

2. volume control wiper through 1kohm resistor (goes to mixer cathode through the oscillator coupling coil), 0.1uF

3. Local oscillator cathode, 0.1uF

My next step would be to finish this list.

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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Mon 11, 2017 11:43 pm 
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How does one measure the capacitance of a old capacitor.


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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Tue 12, 2017 2:17 am 
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Ive heard you can reconstitute old caps , but not sure how thats done. At any rate if you do reform them they wont last long.

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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Tue 12, 2017 2:57 am 
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devildog63 wrote:
Ive heard you can reconstitute old caps , but not sure how thats done. At any rate if you do reform them they wont last long.

I don't think we are dealing with electrolytics here....

sp; measure the old cap the same way as a new one. With a paper cap, if it is not shorted, it should read somewhere close to the spec value. BUT--I suggested this only as a last resort. You should be able to reconcile everything by the other steps i recommended

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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Tue 12, 2017 11:17 pm 
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Nope, i didnt know if you could reform either. Those caps you have squires look like a old block of chewing gum. I guess those are old type paper?

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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Wed 13, 2017 2:07 am 
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Somebody say something . Lol

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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Mon 18, 2017 12:03 am 
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Time to put it back on the bench so any help will be great thanks. Has anyone on line already rebuilt one of these.


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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Mon 18, 2017 12:39 am 
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spsquires wrote:
Time to put it back on the bench so any help will be great thanks. Has anyone on line already rebuilt one of these.

Do what I already suggested a few posts ago: trace out all the wiring so you know which cap is which.
I started the list for you with 3 items......

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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Mon 18, 2017 10:23 am 
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Just wondering where those two 8 mfd capacitors could be , I do not see a can or cap separate from the four I listed earlier.


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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Mon 18, 2017 11:09 am 
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Mark could you trace off the three caps you have already identified on a schematic and post please and thanks. Also the part number on my cap block go 36/8713 and 36/8714 that I can see so far.


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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Mon 18, 2017 11:43 am 
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Also could someone tell me if it is possible for these to be the to 8 mfd caps.


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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Mon 18, 2017 2:50 pm 
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I don't see any capacitors in that picture. The two objects at the top are small transformers or chokes.

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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Mon 18, 2017 3:46 pm 
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spsquires wrote:
Just wondering where those two 8 mfd capacitors could be , I do not see a can or cap separate from the four I listed earlier.

Start at the cathode (filament) of the rectifier tube (type 280). This connects to an 8uF cap and a filter choke. At the other side of the filter choke is another 8uF cap. From there, the path goes to the speaker connector and from there to the field coil.

Take this one step at a time. If you can't find any of these points on the schematic, ask for more help.

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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Mon 18, 2017 3:53 pm 
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spsquires wrote:
Mark could you trace off the three caps you have already identified on a schematic and post please and thanks. .

Go back to the picture I posted that shows all of the larger capacitors.
Start with the one that connects to the cathode of of the RF amplifier (type 51). Can you find this point on the schematic?

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 Post subject: Re: rogers majestic r-841
PostPosted: Dec Mon 18, 2017 10:29 pm 
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It is the .1 mfd cap you have circled in the top left corner of schematic.


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