Observations of a newly acquired zpa0.5

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vwdude
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Observations of a newly acquired zpa0.5

Post by vwdude »

I know hat I have a thread already about the actual purchase, here are some observations of this amp.

It appears to be a v2 amp because of the 7 fan blades:
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But then I noticed few traits that my other 0.5s don't have.
1) burns on the fan board by the resistor:
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2) strange angle to the rectifiers:
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3) the side blades (not sure what they are called) came off when I removed the end plates. On this amp they are cut into 3 pieces each and are screwed onto the heat sink plates.
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4) this s/n seems a bit on the low side. Must have been early in the production run
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I also recall seeing printing on my other boards saying ZPA0.5v2. Don't see that on here.

So as I took the covers off I felt that the gold traces are shinier than my other amps (maybe I am crazy).

I knew that the caps were replaced as they weren't original values, but not sure what to think of this...I know that the m series had caps hot glued together, never seen it on a ZPA.
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And then when I looked under I made some entirely new observations:
2 bad cap vias:
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Fets were replaced (probably upgraded, I will verify later) but no damaged vias:
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Not a huge fan of the soldering job done to the caps:
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And looking closer at the repair job when the fan resistors were replaced, not a huge fan of the job done here either:
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I powered the amp up and it works. I checked the cd offset and it was less than 1mv on the right side but about 7-8 mv on the left. I adjusted it down to less than 1mv.

On this amp I plan to replace the caps again, but with 8200 uf caps. I also plan to remove each heat sink and replace the thermal paste with the Antec formula 6 stuff that I used on the other ZPA. This way I can further check the fets to see which ones are in there and inspect for any burned parts.

Any feedback? Anything that I'm missing that I should look for.
Last edited by vwdude on Thu Jan 23, 2014 11:18 pm, edited 1 time in total.
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vwdude
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Re: Observations of a newly acquired zpa0.5

Post by vwdude »

So in the auction description he stated that the outside was a little scraped up. I took care of that with some satin black paint.
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Don't mind the amp in the background. It's just my McIntosh that I'm replacing the fans on.

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Kirghiz
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Re: Observations of a newly acquired zpa0.5

Post by Kirghiz »

In before someone says that is a board out of a Jensen amp mounted inside of a ZPA chassis. :lol:

I'm kidding, don't get mad.
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vwdude
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Re: Observations of a newly acquired zpa0.5

Post by vwdude »

Haha why would I get mad?

That was funny.
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zeropoint0.5
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Re: Observations of a newly acquired zpa0.5

Post by zeropoint0.5 »

the angle of the rectifier is totally normal.... almost all of my zpa's have it mounted this way.....

there has been done a terrible desoldering job of the the ps caps....

if i received this amp i would take all the shit out first and replace them.....

seeing the 7blade is not a certainty there full V2....looking at one pic at some resistors it probably will be....

but i never seen discoloring on a V2 amp, only on V1's.....

it's not because the serial doesn't say V2 that it's not a V2...............

seeing these pics is the reason why i prefer to buy amps with the original caps in.....you never have to clean up

the mess other people did before......

i would resolder those resistors on the daughter board and replace R35 and R36 with a 5W model also 330 ohm and

half an inch away from the board.......

the best thing on this amp is probably a plexi in good condition......

if you want to send it back it's you're choice.... then i would not start to work on it you'rself probably......
vwdude
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Re: Observations of a newly acquired zpa0.5

Post by vwdude »

Thanks for the info. I was going to ask what resistors to use there. Yes I plan to replace all caps, fets, gate resistors, and those fan resistors.

I think he PWM is good as the amp seems to be working ok, but I can change that as well if you think it's worth doing as I have a spare.

Yes I know that most people would prefer to buy unmolested amps, but then what would happen to all of these poor amps? Someone needs to save them.
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Re: Observations of a newly acquired zpa0.5

Post by vwdude »

zeropoint0.5 wrote:
i would resolder those resistors on the daughter board and replace R35 and R36 with a 5W model also 330 ohm and

half an inch away from ....
5w? That would be huge. Aren't those the big white ceramic cube resistors?

Are those crappy resistors r35 and r36?
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zeropoint0.5
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Re: Observations of a newly acquired zpa0.5

Post by zeropoint0.5 »

vwdude wrote:
zeropoint0.5 wrote:
i would resolder those resistors on the daughter board and replace R35 and R36 with a 5W model also 330 ohm and

half an inch away from ....
5w? That would be huge. Aren't those the big white ceramic cube resistors?

Are those crappy resistors r35 and r36?
http://www.phoenixphorum.com/viewtopic. ... 8&start=25

take a look in this topic on page 2..... this is what i mean and it is done on all of my zpa amps.......
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MW3
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Re: Observations of a newly acquired zpa0.5

Post by MW3 »

VWDude pm or email me.

I will send you the info how to check/mod it to V2.

If you are going to do some work on that amp you might as well do it all.
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vwdude
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Re: Observations of a newly acquired zpa0.5

Post by vwdude »

Thank you Morgan for the info. I will have to read through it and make the full
V2 conversion.


So upon further inspection I see that the pa caps were hot glued down to the board. When I remove them will they damage the board? Had anyone dealt with kind of stupidity before? I guess I'll just have to be careful and slowly try to lift the glue without pulling up any gold.
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vwdude
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Re: Observations of a newly acquired zpa0.5

Post by vwdude »

So I got the caps off without damaging the board. Every one of the caps was hot glued down to the board. So much extra solder was used on them that my solder sucker couldn't get it all. I got enough that I can make it much cleaner when I install the new ones.

I also see that none of the FETs burned. Never seen a board this clean before. 2 vias were slightly damaged but I was able to touch them up so I won't have to run new leads.

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Sorry for the blurry pictures I was holding my kid when I took these and he was trying to play with the iPad while I snapped them.
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freshkryp69
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Re: Observations of a newly acquired zpa0.5

Post by freshkryp69 »

Are you upgrading the PS Fet's? IFRZ48's work great and the irf3205's have a super high amp rating on them so the duty cycle they will see will keep them from ever stressing..
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Re: Observations of a newly acquired zpa0.5

Post by LowandLoud »

I have seen the glue/silicone on caps before but only to each other, not down onto the board itself. I think it is meant to stave off vibration. (like when mounted to a sub box)

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vwdude
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Re: Observations of a newly acquired zpa0.5

Post by vwdude »

Yea I'm using ifrz48. I accidentally ordered 1/4 watt resistors so I am waiting on 1/2 watt ones to arrive. Apparently digikey no longer carried 330 ohm 1% 1/2 watt metal film resistors. I had to go through mouser, which also works.

Yes I have seen the hot glue before as well, but not on the ZPAs. I've seen them on M series and other older amps. Since I will never mount an amp to a sub box and I will never have an SPL vehicle I don't expect the amp to ever sustain enough vibrations to knock the caps loose.
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Re: Observations of a newly acquired zpa0.5

Post by vwdude »

So I got the new caps, fets, and resistors on. I'm discovering that on older amps the pads come off way too easy. Luckily I was still able to work with it, it just isn't as pretty as I would like (please don't judge my soldering skills in the bad areas).

I still need to remove the fan board to change the resistors, but I wanted to make sure it still powered up after all of this work, and yes it's all good.

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For the life of me I could not find anyone who still sells 330 ohm 1% metal film through hole 1/2 watt resistors that have the stripe coding. I usually use digikey but they apparently no longer carry them and the ones I ordered from mouser didn't have a picture, but they were not stripe. Maybe this is how they are doing resistors now.

Also, you can see that the person who previously changed the caps (and used hot glue to hold them down) used he leg to jump 2 of the caps that lost their pad. It was totally not necessary and once I soldered them all on I used my DMM and verified that they are all connected. On the flip side, 3 fets needed jumpers because without pads I couldn't get continuity rough the gate resistor.

Overall this is much cleaner than the original job, and I now have higher capacitance and better fets.

Now all I need to do is get that fan board squared away. I have removed the other board (on my other ZPA) to replace the PWM, but since I've had so much trouble with the pads I'm a bit nervous to do this one. Anyone have advise? I know I can cut the pins and replace them when I reinstall, but any other advise?
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trickyricky
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Re: Observations of a newly acquired zpa0.5

Post by trickyricky »

Moose should have it, trust me. As for the makings on the estuaries you'll have to go by what the datasheets specify not the reference pics.
vwdude
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Re: Observations of a newly acquired zpa0.5

Post by vwdude »

Yea I learned that. I know better but I guess it doesn't matter in the long run. These are the right resistors, they just look different, which doesn't matter since they are hidden under the heat sink.
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trickyricky
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Re: Observations of a newly acquired zpa0.5

Post by trickyricky »

Correct'o. But why the 1%, the originals are 5%? Lately everyone seems obsessed with 1% resistors, even in circuits where the signal isn't involved, what's the deal?


BTW the repairs LOOK much better than before. Good job, with the perfect solder tip and temperature as well as solder you should get better results, not saying you got a crappy solder station, but may be the wrong tip. If the tip is bigger than the pad then your transferring much more heat faster and can cause damage. A pad bigger than the tip will mean you will have to increase heat and keep tip longer on pad, which could also result in damage to the pads (pulling component and pulling the via through holes).


ONE BIG CONCERN OF MINE....would be the gate resistors you used. Why are they 330 instead of 33, also are those flameproof (fuse type)? If something bad happens to the power supply you want those resistors to OPEN right away before serious damage occurs. The originals where also 1/4watt so increasing them is only making them more likely to survive an accident causing more damage to the PBC than needed. Just a thought.

Here's a pic of a fuse type flameproof resistor.
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