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Author Topic: Drake R4C capacitor question  (Read 2106 times)
K8BUX
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Posts: 10




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« on: June 07, 2017, 05:38:27 PM »

I've recently unshelved a very late serial number Drake twins set and started to use them a bit.  They are absolute stock, as far as I can tell, and I'm making up a list of logical upgrades to old capacitors.  In doing so, I've noticed that the label on my HV can three section on the R4C doesn't seem to match the schematic in the manual.  The schematic shows a cap with sections of 100 mfd, 200 mfd., and then a 20 mfd section.  The can in my rig, which appears to be absolutely original, is 100,100,20.  I haven't found any references to this in an internet search.  All available info seems to suggest a 200 mfd section, yet mine is clearly original and doesn't have it.  I do have a very very late serial number....29000+.

I can't figure out why this is so.  Anyone have any explanation?  The issue is whether to replace the existing one with the 100 mfd. cap, or go with the schematic indication at 200 mfd.  The section is c164 on the schematic, in the power supply section.

After cleaning up the switches, and getting the cables connected, everything seems to work very well as it is.  I'm just wondering about that discrepancy.
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KB7TT
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Posts: 16




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« Reply #1 on: June 08, 2017, 01:52:48 PM »

There were three generations of the R4C, likely your schematic doesn't match your radio...Thats all it is...

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K8BUX
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Posts: 10




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« Reply #2 on: June 08, 2017, 02:52:20 PM »

Possibly.

My manual (original, and thought to be the one with the radio) shows a date on the schematic of 11017625900.

Maybe its just an oversight, or they decided not to change the manual printing for a 100 mfd change in the cap.   
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WA4JQS
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Posts: 70




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« Reply #3 on: June 08, 2017, 03:55:33 PM »

Heyseed sells a direct replacement cap for the R4 series in case you want to change it out. at 20+ years old it is something you may want to consider  might save you some problems down the road.. also there is a youtube video on that cap.
73 Tony WA4JQS

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K3STX
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Posts: 1580




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« Reply #4 on: June 08, 2017, 07:30:32 PM »

Why not join the Yahoo Drake group and buy the Drake R4 DVD's that tell you ALL about repair of the station?

paul
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KD0REQ
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Posts: 2018




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« Reply #5 on: June 09, 2017, 10:38:58 AM »

in the old days, a common cap section could be +100% -50%. so get what you can, a 100.100.20 would be within the original spec.
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KI4WCQ
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Posts: 2




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« Reply #6 on: July 14, 2017, 11:54:32 AM »

Here is what the power supply instructions from Sherwood Engineering says about the confusion on the capacitors.

"The following is the nomenclature on the can capacitors on the R4C. Different schematics show them differently.
Back Electrolytic 1000uf 20V (Triangle) C167*
3000uf 20V (D) C166*
* Both of these capacitors could be called C166 on some schematics.
Front Electrolytic 100uf 200V (D) C164**
100uf 200V (Square) C163**
20uf 200V (Triangle) C202**
**All three of these capacitors could be called C163 on some schematics. Also the 100uf 200V (Square) C163 is labeled 200uf 200V in the schematic, but the cans have 2 100uf caps and a 20uf labeled on the outside of the can. Very confusing.
C202 the 20uf 200V cap is located in the audio section of the schematic if it is shown."
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AC7CW
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Posts: 967




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« Reply #7 on: July 15, 2017, 09:49:58 AM »

Gadz... takes me back to the days working in electronics. We had one self-assessed superior introvert guy that turned out schematics with only the theoretical values for all the parts. He left it to others to select the actual parts and produce the final docs. Another one simply would never update his schematics. I guess he upped his "power" in that people had to kiss up to get the right info from him. Another would hand somebody all sorts of changed drawings and ask somebody to get it in shape so that the "docs department would accept it..." The upshot is that it's sort of up to the rig owner to check and see if his documents are all that correct.

As a junior high teenager I started off my electronics life by buying a homebrewed modulator for an ARC5 that 1)had never worked 2)had no schematic. It was my baptism by fire. After scratching my head for days I realized that I needed to draw the schematic. After that I had to figure out what they were trying to do. I wish I had a picture of the seller's face when I told him I had gotten it working and made a contact!!
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Novice 1958, 20WPM Extra now... (and get off my lawn)
W9GB
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Posts: 3148




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« Reply #8 on: July 17, 2017, 11:49:10 AM »

Quote from: K8BUX
All available info seems to suggest a 200 mfd section, yet mine is clearly original and doesn't have it.  I do have a very very late serial number....29000+.
There were 2 different schematics, and I believe 4 production changes for Drake R-4C receiver.
http://www.wb4hfn.com/DRAKE/DrakeManuals.htm

Garey Barrell, K4OAH detailed Drake photos/schematics show these changes.

Hayseed Hamfest shows one set of can capacitors.
https://hayseedhamfest.com/collections/drake/products/r-4c-re-cap-kit
« Last Edit: July 17, 2017, 11:55:18 AM by W9GB » Logged
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