Onkyo TX-8500 filter cap replacement
- Thread starter z-adamson
- Start date
century tek
Addicted Member
I think if the old one's aren't bad, leave 'em!
z-adamson
Addicted Member
They are long enough past there expected service life to where I would rather replace them than leave them.
century tek
Addicted Member
Be sure to mark the wires on the old ones and just take one out so you can read the side to show which is negative and which are the two positives.
Last edited:
Binkman
Lunatic Member
You have another posting asking about bias and offset. So I'm answering it here as best to leave all on one thread.
SM shows the test point on adjacent left schema. My advice is don't mess with adjustments as if you missed the notes that unless you replaced any transistors. Basically no need to. Nothing wrong with putting dmm on mv (NOT ma) and I highly recommend you assure that you don't short them by using probe clamp shielded or shielded test cable. Quality of adjustment pots is important but usually set and you get a good reading, playing with the pot to see what happens may risk blowing a driver transistor.
I'm saying its best to get an overall picture of health before screwing around. Those mains caps may be perfectly good and how do you know they're 'past' their life expectancy when you don't even know what the ct test points are? Or own a cap tester? What you should do is be checking the 'BASIC' voltages noted for the various transistors. On the schema they are bited in the rectangular boxes. + this - that. 0v etc. If all those are within even a mv it's good to go. even if a couple mv's isn't necessarily a concern if the other side +/- transistor is close, too. You can have variance at idle it's when the transistors start kicking what counts and circuit v's can vary.
Now the mains caps my be fine but you may have lower v caps that need replacing or reforming. You can post close up pics and we can usually identify shrink. 15v rated caps ought to go. again post pics. Be surprised how many caps can reform.
bink
SM shows the test point on adjacent left schema. My advice is don't mess with adjustments as if you missed the notes that unless you replaced any transistors. Basically no need to. Nothing wrong with putting dmm on mv (NOT ma) and I highly recommend you assure that you don't short them by using probe clamp shielded or shielded test cable. Quality of adjustment pots is important but usually set and you get a good reading, playing with the pot to see what happens may risk blowing a driver transistor.
I'm saying its best to get an overall picture of health before screwing around. Those mains caps may be perfectly good and how do you know they're 'past' their life expectancy when you don't even know what the ct test points are? Or own a cap tester? What you should do is be checking the 'BASIC' voltages noted for the various transistors. On the schema they are bited in the rectangular boxes. + this - that. 0v etc. If all those are within even a mv it's good to go. even if a couple mv's isn't necessarily a concern if the other side +/- transistor is close, too. You can have variance at idle it's when the transistors start kicking what counts and circuit v's can vary.
Now the mains caps my be fine but you may have lower v caps that need replacing or reforming. You can post close up pics and we can usually identify shrink. 15v rated caps ought to go. again post pics. Be surprised how many caps can reform.
bink
z-adamson
Addicted Member
z-adamson
Addicted Member
I am ok with running the risk that they may still have some life left in them.
z-adamson
Addicted Member
Thanks for the well thought out reply.
My thoughts in response to your thoughts....
I am replacing the trim pots (amongst other things) as part of the restoration of this receiver, so adjustments will be made. I just need to find the test points and I will be good to go. I understand the importance of insulating the tooling that is used to minimize the chance of shorting something out.
I have never heard the term "CT-E" nor have I ever heard the term "ID-CT". What do they stand for? What do they mean?
I am no pro at this. It is a hobby. And I have no idea at this point what "ID-CT" and "CT-E" are, what the letters stand for etc. Yes I own a cap tester, but I don't use it very much. My main cap tester is a measurement of the cap's age. If it is 40+ years old, it gets replaced even though they may still have some life left. I am OK with that.
If my biggest problem in life is that I have things to learn about this then that means I am doing quite well.
So, could you explain ID-CT and CT-E for me and help me find them?
Thanks,
Z
z-adamson
Addicted Member
century tek
Addicted Member
Well sure it is. Just take one out and have a look at it. The specs should be printed right on the side.
What I meant was to just take one out so you can see the printing on the side and to make sure you remember where the original connections go to.
You're taking them out to replace them anyways. The replacements you want will work and I know what I am doing but I (we) need to see the originals. The thing that throws me is the clear (no black or red dot) connection. Is it negative or the other positive?
Black is always negative when you have just a single capacitor in one can. You have two in one can showing a red, black, and clear dot on each capacitor so I was just wanting to know which is negative and which is the other two positives.
Then I or we can show you how to connect the four in their place. It's very simple to me anyway.
What I meant was to just take one out so you can see the printing on the side and to make sure you remember where the original connections go to.
You're taking them out to replace them anyways. The replacements you want will work and I know what I am doing but I (we) need to see the originals. The thing that throws me is the clear (no black or red dot) connection. Is it negative or the other positive?
Black is always negative when you have just a single capacitor in one can. You have two in one can showing a red, black, and clear dot on each capacitor so I was just wanting to know which is negative and which is the other two positives.
Then I or we can show you how to connect the four in their place. It's very simple to me anyway.
Binkman
Lunatic Member
They really don't stand for anything just the pcb id of the two noted test points that other SM's would typically note as 'TP1, TP2 etc. Note the diagram left ID E CT. Noted ID and CT being the bias test points.
z-adamson
Addicted Member
My schematic reading abilities are not such that I can look at the schematic then look at the components and determine which wires need to go where. As I indicated, I am no pro.
Binkman
Lunatic Member
You're looking for pins or soldered points labeled on the top of the board not the soldered side. You need to get used to identifying what parts are where or you'll get nowhere. Get a good magnifying glass and small flash light if dust bunny deep that you can't read the pcb.. then cleaning needed.
z-adamson
Addicted Member
Thanks!
From the looks of this the middle post of the dual cap needs to be connected to NEG of replacement cap #1 and POS of replacement cap #2.
Some kind of "bridge" with ring terminals needs to be made to join the these two points together. This looks like what has been bone by other folks.
