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Last November I asked for advice as to recapping a receiver, and appreciate the information given.
Life got in the way and progress slowed to a crawl - who says retired people can do whatever they want when they want? But now I have gathered the necessary equipment, watched YouTube videos, studied the service manual, disassembled the receiver, and made a list of capacitors to be replaced.
Despite reading everything I can find about capacitors there are a couple points that must be considered common knowledge as they are never mentioned, thus the following questions.
First: Many, if not most, of the capacitors in my receiver have a polarity symbol next to them on the board and in the wiring diagram. However, some do not. Is it assumed that those with no polarity indicated are non-polarized? There is nothing in the service manual to indicate that is the case, and I have not removed any so a close examination can be made.
Second: the wiring diagram uses two parallel bars as the symbol for capacitors. However, a few of them have slanted slash marks between the bars. The slash marks must mean something, it's doubtful they are there just for decoration, but nothing I've found indicates what they mean.
Thanks in advance enlightening a rank amateur.
Follow Ups:
As I know NOTHING about this, allow me to say that I admire your ambition.
My knowledge is very limited, and I am beginning to question my wisdom. But, onward and hopefully upward.
nt
The service manual has examples of 1, 2 and 4. Thanks.
Slanted slash marks can also mean optional. Meaning the capacitor may or may not be present/needed in the circuit. This occurs for example with crystal oscillator capacitors.
I may be way off on this, but reading between the lines, you may be considering replacing more capacitors than you need to. Typically what people replace when updating audio equipment are the power supply electrolytics and coupling capacitors to improve/change the sound and/or they are or may become leaky. There are also some capacitor types that from experience, are knows to have high failure rates. For example Hunts PIO's, and I wish I could recall the name of the silver coloured foil type capacitors they used in the 60's that had a high failure rate. And any electrolytic cardboard exterior or that are bulging.
Several capacitors indicated on the schematic and block diagrams are not present in the receiver.
As for replacing more than needed, I was going on advice to replace all electrolytic capacitors. If that isn't necessary - well, what a time and work saver.
I was thinking you were changing a lot more caps than just electrolytics. Some equipment it does make sense to change all of them, but that is usually when there aren't that many of them. What is the receiver you are working on?
It is a Denon DRA-1025-R receiver, a late seventies surround sound item. Only electrolytics are being considered for replacement. There are 56 caps in the amp / phono input / power sections. I'm not messing with the tuner section.
Change the 4 large capacitors in the power supply. On the amplifier board you could change the 5 physically larger electrolytics, and any larger electrolytics in the phono section and then see how it sounds.
I did something similar with a Sony surround that was about 10 years younger, but it was left on for all that time. I changed the large electrolytics in the power supply and one that had failed in the amplifier, and it has been fine.
The large power capacitors are #1 on the list. Coupling caps are also a prime target. I suspect one or more are not good as my tweeters keep frying. If my skills were good enough I could pinpoint the high frequency area of the circuit, but about all I can do is figure out which are coupling caps that might be letting DC into the circuit.
Thanks for your advice. The number to be replaced has been dramatically reduced.
I have come across a few instances where the + symbol silk screened on the board was not the + pin on the cap that was installed. I did not have a schematic, so I dont know which was in error. Since the unit worked fine for years before I got it, I installed the replacement the same as the one I took out, even though the board showed otherwise. So far so good, no problems. I always take a marker and make a mark on top of the old caps before I remove them. I make it on the side toward the front of the unit, so after removal, I know what orientation it was in. It has come in handy a few times.
Once again, use a marking pen and mark the BOARD!!!! BEFORE !!!! you take that cap out. If there is a discrepancy between the board and schematic - go with what's already in there.
I got into the habit of marking the negative leg.
The cap with the arrow sign is a variable capacitor. Don't touch it.
nt
Second: the wiring diagram uses two parallel bars as the symbol for capacitors. However, a few of them have slanted slash marks between the bars. The slash marks must mean something, it's doubtful they are there just for decoration, but nothing I've found indicates what they mean.
Often the slash mark also has an arrow head on it also. At any rate these are the station tuning capacitors, and the trimmer capacitors used for aligning the tuner. the trimmer capacitors will have a screw head or some other way to insert a tool to adjust the capacitor by changing the distance between the capacitor plates.
The tuner is off limits. I haven't the knowledge or equipment to adjust it properly, and it works quite well anyway.
There are several types of capacitors (mica, ceramic, poly..., and
the electrolytic). this last one comes in polarized and non-polarized
form. it is the polarized e-cap that must be installed in the same
orientation. inspect each e-cap (these are almost always cylindrical
with a wrapper with printing of value, ratings, and polarity) to
match the stenciling and the schematic to ensure you replace with
the correct one.
In general, you can buy the non-polarized version to avoid the
possibility of installing the e-cap in the wrong orientation.
the value and voltage rating is the same - just make sure they fit
since they are larger than their polarized cousins.
And, if so, would using a non-polarized cap defeat whatever purpose the polarized cap was to perform?
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