zx475ti repair questions.

[audiophyle_247]

Recently picked up a pair of zx475ti's and both need a little work. Mostly just cap replacement, but one has a little more wrong with it.

1. I need to find replacement rail caps, and will replace the PS caps while Im in there. I found a few options on newark's site, but I figured the repair guru's on here would have a part number for the ideal replacement of each. (possibly an upgraded option as well?)

2. The fan circuit has an issue, and previously had a switch wired in to interrupt the fan signal. The fan wont turn off without doing so via the switch, but the amp wont turn on again unless the fan is switched back on. I cannot see any damaged components, so Im hoping for a little insight on how this circuit works, possibly find a schematic if available. Searching found no similar threads.

Pic for reference.


All help will be much appreciated.

[dvnt88]

Recently picked up a pair of zx475ti's and both need a little work. Mostly just cap replacement, but one has a little more wrong with it.

1. I need to find replacement rail caps, and will replace the PS caps while Im in there. I found a few options on newark's site, but I figured the repair guru's on here would have a part number for the ideal replacement of each. (possibly an upgraded option as well?)

2. The fan circuit has an issue, and previously had a switch wired in to interrupt the fan signal. The fan wont turn off without doing so via the switch, but the amp wont turn on again unless the fan is switched back on. I cannot see any damaged components, so Im hoping for a little insight on how this circuit works, possibly find a schematic if available. Searching found no similar threads.

Pic for reference.


PM Valeks1 or email him. He's the local PG repair guru in town and can point ya in the right direction. His website is http://www.altser.com and is very good about gettin' back to people ...at least he is with me since I've done quite a bit of business with him, hope this helps.

All help will be much appreciated.

[ttocs]

wow............. wow.......

[tonym]

lol.......thats what I said when I seen the hack...

[ttocs]

when I look back now I am still afraid they will pop at any second...

[audiophyle_247]

Need advice on rail caps guys.

Panasonic
http://www.newark.com/panasonic/eca1hhg ... dp/96K9167

Rubycon
http://www.newark.com/rubycon/50px2200m ... dp/39T8996#

Im not a pro when it comes to component selection, but I think Ive got it narrowed down a little.
Both are the same physical size, and about identical to the OE cap sizes in the amp.
The Panasonic is rated @85*c (like OE caps), and the Rubycon is rated at 105*c.
Should I just go with the Panasonic? Or give Rubycon a shot with the higher temp rating?

[Thumper88]

eh....prefer Mouser...Newark is incorrect on the 85C rating for the Panasonic.
http://www.mouser.com/ProductDetail/Pan ... bxHSS2Y%3d
Check the datasheet out.

Just noticed it even shows it in the picture....lol

[stipud]

I personally use Panasonic caps, despite the price premium, as they have always been reliable for me. But the 105*C rating is also a must for any hot power amplifier, otherwise the caps will degrade much faster.

[audiophyle_247]

Damn its even $1.20 cheaper on Mouser too, lol. I figured the picture was a generic anyway, since the actual cap is as wide as it is tall & the image clearly isnt. I did download the datasheet, dont know how I missed the 105* rating in the chart.

The OE caps are 85*c, and I completely agree about using 105*c caps instead. I am happy to see the Panasonic is 105*c, makes the decision easy.


For the PS caps it seems I can fit larger caps without issue, is this something I should look into?
The OE is 2200uf 16v, and I found a Panasonic with 10,000uf 16v with the same diameter, just taller.
That would make a sizable difference in PS capacitance (8,800uf vs 40,000uf), and would fit inside the case easily.

Cap in question
http://www.mouser.com/ProductDetail/Pan ... wPqPqdU%3d

[stipud]

If it fits in there, there's no reason not to do it.

Hmmm I suppose the OEM caps being 85*C has to do with the fan cooling. I am used to swapping M and MS series amps which are passively cooled, so tend to get a lot hotter. With an 85*C rated cap you might get a bit more capacitance, but you still get more peace of mind with 105*C. Considering your factory caps are bulging as they are, it looks like the amp was driven very hard and they may have failed for thermal reasons.

[audiophyle_247]

Interestingly enough the PS caps in the amp are 105*, but the rail caps are 85*. The Panasonic caps fit the bill perfectly for size & spec, and offer a higher temp rating too, so win win.

Fan cooled or not, I will most def be putting 105* caps in instead of the oe spec 85* anyway. I may look deeper for possible capacitance increases, but I'm happy to have found a solid replacement.


The PS caps are directly connected to the +/- power terminals, so theoretically putting much higher capacitance caps would be no different than having a 1/2 farad cap placed outside of the amp, assuming all else remains constant. Right?

[stipud]

The PS caps are directly connected to the +/- power terminals, so theoretically putting much higher capacitance caps would be no different than having a 1/2 farad cap placed outside of the amp, assuming all else remains constant. Right?

Bingo. Same deal on the rail caps pretty much, as they are directly on the +/- of the high voltage power rails. So if you can fit bigger rail caps as well, then by all means, go nuts!

[audiophyle_247]

Good to know!

1 quick question, which I noticed after using Mouser to search parts & have had zero luck finding an answer.

Can I use a leaded cap to replace a snap in cap?
Mouser has these as different categories, and there is very little that fits my search criteria for snap-in, but leaded offers lots of options.

[stipud]

While it's possible as long as the size and lead spacing is identical, I'd definitely stick to snap in, if only because that's how the amplifier was designed. Snap in should be a more reliable mount for such big heavy caps anyways, especially on an amp that will see a lot of vibration, etc.

[audiophyle_247]

Gotcha, then I have a dilemna.

If I go snap-in, I can only find a suitable cap in an 85*c rating.
If I go leaded, I can get the cap in 105*c rating.

[stipud]

It will be hard to match the capacitance of an 85*C cap with a 105*C cap of the same size. If you want the same capacitance you will probably have to go taller. If I had to give up capacitance or temperature rating, only since the stock is 85*C rated, I would stick with the 85*C instead.

[tonym]

I have a LNIB with all paper work and crap if your intrested.....was mounted on a amp rack but never seen power (well it had to..to see if it worked)

[audiophyle_247]

Tempting Tonym, but I just picked up 2 rusty 475's & a 600.2 that I plan on custom finishing & having them all match.
Figure after a full cap replacement they should be good as new.



So far I think these are the caps Im going to try.

Rail Caps, with a bump from 2200uf to 2700uf each, voltage & temp remain unchanged. (50v & 85*c)
http://www.mouser.com/ProductDetail/Pan ... nvBovWY%3d

PS Caps, with a bump from 2200uf to 10,000uf each, voltage & temp remain unchanged. (16v & 105*c)
http://www.mouser.com/ProductDetail/Pan ... wPqPqdU%3d


Still gotta figure out this fan circuit though, nothing looks burnt or out of place anywhere on the amp or daughter board.

[ReneBMW]

Hello guys!

Any luck on the fan issue?!
I've got a zx475ti from wich the fan also won't stop.
It arrived to me with e small relay wich cuts the fan feed, it does the job,
But I want it to work propperly.
Any ideas on where to check??
When I opend it I fount 4 2.5 ohm resistors wich where bridged by 2 5 ohm resistors, after checking with my dmm I found out why, all of the 4 2.5 resistors showed infinite resistance.
The amp had a problem with thermal wich turned out to be a loose connector on one of the sensors.
I want to get this amp in tiptop condition with a zx600ti to put in afresh housing.
Any ideas?
Btw, nice forum!

[trickyricky]

Someone or anyone correct me if am wrong, but don't the fan's on these amps always stay on? I mean when I turned on mine to test after repairing they cut one immediately, don't get me wrong they have thermasistors so the speed of the fan will vary with the actual output power. Also its required because the amplifier runs pretty warm/hot at idle (voltage regulators get pretty hot, which those rail caps are near by hence the question that's why the top looks like their about to burst but I have a feeling they're perfectly okay...just cosmetics if you ask me.

I've seen plenty of amps (even JL slash) that have the same issue with the plastic top on the caps....they are by some hot components and their wrap actually shrinks. Also when I try looking for replacement for the rail caps on certain ZX amps I notice that the value they had was pretty much the limit (couldn't find any higher capacitance with a 105c rating....and you probably wont either, that's why they are 85c instead of 105c).

just my two cents.

[audiophyle_247]

The fans on Ti amps are always on, and the speed is controlled by temp (has a high & low setting I think).
The issue is in the small vertical board, and with mine when you cut power on the remote wire the amp would not shut off until you interrupted the fan wire (switch hack-jobbed into the setup).
If the fan is not turning off with the amp the problem is probably related to mine.

The fan control system is also on that small board, and you will most likely need to desolder & remove it from the main board to gain access to the parts you need to replace. I replaced a handful of transistors on mine that tested bad (small black half circle pieces with 3 legs) and it now works fine. The actual part number I have no idea, but there were only 2 different part numbers between all of them on the board. Best bet would be to just remove the board & start testing everything on it to find inconsistencies. There really isn't that much going on on that board, just looks confusing.

The resistors, if I'm not mistaken, are special in that they are designed to fail open like a fuse which is to protect the amp from melting down. You would be wise to replace the hack repair fuses with the correct resistors (fusible resistor?) so in the event of another failure your amp doesn't catch fire.

[ReneBMW]

Hey guys, thanx for thinking with me.
But i meant that the fan is on without power on the remote, sonwhen everything switches of, that one fan stays on.
Also on start-up it doesnt start withe the red overload led, followed by the 8 or so leds on the left Side in the output stage.
For the rest this amp works great!
It has 27 mv Dc offset on 1 channel , the rest is between -5 an 17mv.
All resistors and mosfets checked while it was openend
I stil have another zx475 and a 500.4 so it doesnt realy need to be repaired, but if it can be fixed cause its a known problem i would be glad to get the housing in my girlfriends Car colour, cos since she heard my install for the first time she also wants one of those old f#ckers.

[ReneBMW]

@audiophyle, now i think of it...
The parts you talk about are transistors, and i think tha fan is switched on and of with a transistor, couldnt it?!
I Will get a soldering iron and all stuf needed tomorow and take that board out.
Its my first time doing something like this.
If i get it fixed i Will post the solution here.

Thx for the tip btw!!

[audiophyle_247]

I fixed mine a long time ago, but the board uses multiple transistors paralleled with resistors, and that's how it controls the fan speed by how many transistors are letting power through. It could be a failed transistor not opening the circuit to kill the fan, but it could also be a lot of things that won't get figured out until you physically test all the parts.

[ReneBMW]

Hey!

I found out something!
On the motorboard, (if you look from the front) at the back you have 4 2.5 ohm resistors wich are connected to 4 of the 5 small transistors.
On mine they where damaged so the Guy soldered 2 times 5 ohm transistor over them, connecting two 2.5 ohm resistors, so now you have one 5 ohm resistor for 2 transistors.
As i took those 5 ohm resistors of the fan wouldnt do anyting.
Soldered the daughterboard of, measured and compared it with the dauchterboard from my 600.2, with the only difference being those four 2.5 ohm resistors.
Looking on your picture i think i can see atleast one of those bigger 5 ohm resistors.
My gues is if you take those two 5 ohm and the four broken 2.5 ohm out, replace them with new 2.5 ohms (four pieces) your problem is solved (if you stil have it...)
I can not power mine up to check because may railcaps havent arrived and i need to solder those 4 resistors back in, but im pretty sure thats the problem.