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Old 25th October 2015, 11:33 PM   #1
asilker is offline asilker  United States
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Default Adcom PCB connectors

I'm trying to reflow some connections and possibly recap the smoothing capacitors in my Adcom Gfa 5300. However, I can't flip the psu pcb and see the underside because it's attached to the other boards and transformer with these wires connectors.
Click the image to open in full size.

I'm mostly not sure if they're supposed to clip off with a gentle tug or if they're soldered to the board. I sprayed one with deoxit and gave it a small pull and it didn't come off, so before I really lay into it, I'm asking for advice

Has anyone come into contact with these connectors? Can I just wiggle them off?
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Old 26th October 2015, 12:06 AM   #2
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Default Adcom PCB connectors

SOLVED:
The ones in the previous photo are soldered to the board. However the ones on the sides of the board slip off. They look like this:
Click the image to open in full size.

Which means that specifically for the 5300, the transformer is hard wired while the left and right channel connects slip on. Sweet.

Now here's a noob question:
I think this stuff points to some leaky caps. Anyone wanna confirm?
Click the image to open in full size.Click the image to open in full size.

Thoughts?
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Old 26th October 2015, 12:40 AM   #3
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Adcom glue - solvent base rubber cement as you can see on the sleeving of the caps lower down, next to the board. That's normal. If the caps have leaked too, you'd probably see signs of corrosion like someone spilled acid and bare metal surfaces turned to a crumbling mess.

It could be leakage but it's not obvious from your pic what the source of the discolouration is. If it appears to flow from under the cap then yes, if its not tough like rubber cement, that's leaky caps and not unusual for these amps.
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Last edited by Ian Finch; 26th October 2015 at 12:50 AM.
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Old 26th October 2015, 12:51 AM   #4
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Very cool. I think I'm just gonna go ahead and order new caps because there's only 4 in there and they'll need replaced eventually. Also I'm suspicious one or two could be a bit dried up.

Should I replace with the stock value or beef up the value or rating? (I know this has been asked a number of times)
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Old 26th October 2015, 01:04 AM   #5
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BTW, some of those lead clips will have a properly formed retaining clip which will be hard to remove, as you found. Mostly, a little wiggling while pulling will do it but you notice there is a hole in the fixed spade and this is where a "pip" formed in the clip fits and locks under its own spring force. You can push that clear with a small pointed tool from the open side, right through the sleeving and bingo!

You can up the values by 50% or more but it's really down to the fit on the board and pin spacings.
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Old 26th October 2015, 02:35 AM   #6
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Wowowow, Ian, are you saying that the capacitors clip off of the pcb? That they're snap-in?
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Old 26th October 2015, 02:58 AM   #7
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Regardless.. IF you replace those Electros, Do remember to replace the Diodes as well. Tired old ones don't do well with the revitalised current demands of Fresh Electros.
Just a heads up :-)
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Old 26th October 2015, 03:11 AM   #8
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Quote:
Originally Posted by Bare View Post
Regardless.. IF you replace those Electros, Do remember to replace the Diodes as well. Tired old ones don't do well with the revitalised current demands of Fresh Electros.
Just a heads up :-)

Oh I didn't know that. Is this a must-do?

Also I'm having trouble figuring out how to find a replacement
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Old 26th October 2015, 02:28 PM   #9
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Quote:
Originally Posted by asilker View Post
Wowowow, Ian, are you saying that the capacitors clip off of the pcb? That they're snap-in?
No, I referred to the spade connectors of the leads you show in your pics. Look at the connectors closely. Under that sleeving is a spade clip and some of those actually lock onto the spade terminal as described. That's why they're hard to remove

Different matter:
If those short capacitor leads are at 10mm spacing, the PCB will accept "snap- in" terminal style capacitor which is more sturdy than thin wire leads that can easily tear out of the cap if you aren't careful with handling the amp when it's in pieces. Order that "snap-in" style if they'll fit - just common sense really.

BTW, diodes don't get "old and tired" unless they are operated outside their Safe Operating Area, like power transistors. That sort of breakdown develops to inevitable failure which I doubt will be an issue with the GFA 5300 in our lifetimes. Smaller, more appropriate rated diode bridges are actually more expensive now than the metal clad monsters shown here so we usually find plenty of diode overkill. I'd wager the metal casing will probably corrode away before the diodes show any sign of quitting or hurting any musical electrons .
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Old 27th October 2015, 12:26 AM   #10
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Quote:
Originally Posted by asilker View Post
....I'm having trouble figuring out how to find a replacement
Note the capacitance in uF and voltage rating. These are you minimum values for a parts search. Measure the O.D. and pin (lead) spacing and perhaps length (height) if its close to the amplifier cover.

Go to Digi-Key, Mouser or Newark websites and search "Aluminium Capacitor" There will be tons of caps available there so select what fits from the many available brands. Don't go excessively high on ratings because price skyrockets as voltage goes from 80V upwards. I suggest Panasonic TSHA grade because its economical whilst being a reliable, top performer with one of the highest ripple current ratings. Nippon Chemicon types are also excellent and theres tons more from Rubycon, Nichicon, etc.
example: Aluminum Capacitors | Capacitors | DigiKey
There are "gold -plated" audiophile grade caps from high-end retailers too if you have plenty of lazy cash and believe in magic. These may indeed be better quality but not necessarily fresh stock. Whether they do anything more for your sound than simply fitting new caps is often debatable. Try partsconnexion.com for that stuff. Capacitors fill more forum thread topics than any other so you'll find lots of speculation, imagination and plain BS but few facts out there.
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