#31
|
|||
|
|||
Quote:
One in particular looked kind of out of place (it looked a little newer than the rest of the capacitors in the unit and also it was a higher capacitance rating than what's called out in the Sam's), which is C30 (C2530) which is supposed to be a 100 µF 16V but instead had a 470 µF 16V capacitor in that spot, which unless there was some sort of design change made to the unit that wasn't reflected in the Sam's (or that was reflected in the Sam's) I think someone installed the wrong size capacitor in there, which I'm apted to think that someone put the wrong size capacitor in there because as I said the capacitor was a completely different style of capacitor than the rest of the capacitors in there. |
#32
|
||||
|
||||
Quote:
If I had that machine first thing I would be doing is checking every electrolytic in it with my ESR meter. I actually have two, one I used at the shop and the other for home use, it's that important and useful. Last edited by Ed in Tx; 05-21-2022 at 10:39 AM. |
#33
|
||||
|
||||
Won't let be attach two files! What the ...??!
OK I see what's going on. I already attached that one in another thread a while back. Another pic (right side) testing the Hi-fi audio board from an old JVC VCR. Those old surface mount caps were notorious for failing. Last edited by Ed in Tx; 05-21-2022 at 10:38 AM. |
#34
|
|||
|
|||
Quote:
The Sam's for this VCR is from 1987 and my VCR is from 1984... |
#35
|
||||
|
||||
You need to get another one then. I wouldn't even attempt to fix this old stuff without an ESR tester. Can save hours of work, and the old equipment you're trying to fix.
|
Audiokarma |
#36
|
|||
|
|||
Quote:
I have posted a screenshot of the section of the schematic with the capacitors in question including the 470 uF 16V Capacitor and its overall circuit context. Last edited by vortalexfan; 05-21-2022 at 12:19 PM. |
#37
|
||||
|
||||
First ESR meter I ever used was an analog one, Capacitor Wizard I think it was called. The shop owner bought it in the mid-80s for us technicians to share. I got tired of having to track it down every time I wanted to use it and found the black digital one, a kit from Dick Smith Electronics in Australia, so I could have my own. Still works great! |
#38
|
|||
|
|||
Quote:
I ended up getting a MAT Electronics Analog ESR Meter model MUL3333 that can test capacitors in-circuit and it was only $45 (I will have to use the cables from my old ESR Meter as the original cables didn't come with this unit but they were basically just your standard mini-banana plug style cables. so what do you think of the circuit diagram I uploaded showing the capacitors in question? |
#39
|
||||
|
||||
Quote:
Quote:
Quote:
|
#40
|
|||
|
|||
Quote:
|
Audiokarma |
#41
|
||||
|
||||
That's no problem being larger value, it's on the 12V B+. Might have been a production change to fix some ripple or interference when the motors were loaded down. In that diagram they show 2 100 uF's in parallel for total 200 uF.
Last edited by Ed in Tx; 05-21-2022 at 02:28 PM. |
#42
|
|||
|
|||
Ok, I wasn't sure, I knew in old tube equipment, capacitor values weren't too critical but I wasn't sure about solid state stuff ( I know some solid state stuff like this capacitor value is more critical, than in tube circuits, which is why I asked.)
|
#43
|
||||
|
||||
And I would think tube equipment would be more critical than solid-state...
|
#44
|
||||
|
||||
How critical a capacitor value is depends on its function, and has relatively little to do with tube vs. solid state. Power supply filter caps need to be a certain minimum size. Signal-handling cap tolerance depends on function. Stage-coupling caps need medium-tight tolerances to assure low-frequency response. Caps for functions like tuned circuits require the tightest tolerance.
Tube and transistor circuits are similar in their sensitivity to passive component values. Tube amplifiers generally may be sensitive to individual tube parameters, while most transistor circuits are generally insensitive to transistor parameters above a certain minimum, for example if current gain (beta) >=100. There are exceptions, for example where matched transistors and/or diodes are required to maintain proper bias in push-pull power stages. |
#45
|
||||
|
||||
Quote:
I've always avoided working on anything with vacuum tubes including CRT TVs. Reason why is, back in the '70s my Aunt and Uncle up in Connecticut came home to find my cousin dead on the living room floor. He had been working on a tube-type guitar amplifier. So I've been a bit wary ever since. Although one of these can nail 'ya too, about 80V + and - on the finals... one of my Pioneer SPEC-4 power amplifiers that decided to let the smoke out one day. Last edited by Ed in Tx; 05-21-2022 at 06:39 PM. |
Audiokarma |
|
|