Another ZX350 BBQ Help thread, blown input resistors?

[ajaye]

I've finally gotten the time and motivation to recap my ancient ZX350 that's been collecting dust since the 90s. I got everything disassembled to start cleaning and remove the old caps, and found several burnt resistors as shown in the pics. I have very little knowledge of the inner workings of circuits/components etc...My guess based purely on the location is that these are in the audio signal path? Is this from being over-driven? My little brother definitely drove my car a bit for the better part of 1998 while I was away at college and Im sure punished my system for every moment he did , that's the only thing I can think of.

If anyone could confirm what these are for me I would greatly appreciate it, and if its not too much trouble give me an idea of how to fix it? I'm confident in my soldering skills...what I don't know is how exactly to check to see what needs replaced, how far down the path to check for damage, etc. My meter is at work but I'll bring it home tomorrow to test whatever needs checked. If its as simple as replacing the burnt components that's awesome but things never seem to be that easy. Thanks in advance guys.

PS the other side of the board looks fine to me, I can post a pic of it if needed.

[zeropoint0.5]

the crossover pcb is the same as from the zx500.....

not sure about this, but since there close to the rca input, maybe there burned by receiving

a to high input voltage level ?? if you desolder them and tell the number i can check for you

in my shematics for the exact values......

[trickyricky]

High resolution pics (as the ones you provided) help a lot, both sides are better to actually determine the purpose of those resistors. Very likely damaged by high voltage input as zero started.

[ajaye]

Thank you my dudes. I remembered the meter today so I can check any values that would be helpful for advice. I'll grab more pics as well and show more of the real estate to show where exactly these are and how things are oriented. I really appreciate the assistance, I've been looking forward to getting this thing back in service since I found this site, kinda bummin over this.

[Eric D]

I am pretty sure those are damaged from too much input voltage as others have stated. I have seen them damaged in other ZX amps before.

If you email PG I am sure they would give you the values for them. I would, but I don't know what values they are supposed to be. Also, as stated above, that is the same PCB as in all other 2-channel ZX amps, so if you have access to another 2-channel ZX you can get the values from it.

[trickyricky]

I'll look at mine and give you values but as i mentioned i would need to see the bottom to make sure i give you the right ones.


Just by looking at the other resistors near by, I would say the one that is grounded is a 100k and the other that isn't is a 10k. But this would be a guess.

[jvj]

pictures of mine zx350. Hope it helps....

[trickyricky]

Just as i stated, those with the signal ground are 100k the others are 10k. Make sure you get 1% and correct size.

[ajaye]

@trickyricky Yeah considering these are taken with the flagship model point and shoot Cybershot...from 2002 ....the pics it takes aren't 1/2 bad. It doesn't cooperate with my Mac though or I would have gotten these up a lot sooner. So by "correct size" in your last post do you mean the physical dimensions of the resistors as well as the values? Just making sure I understood. I haven't priced the components yet but assuming they are cheap would it be better to just replace them all with new ones while I'm at it? Or just replace what has failed?


@jvj yeah man those will actually be very helpful to reference when I put things back together, big thanks.

Again thanks all of you who have responded, very grateful.

[trickyricky]

Yes, both correct value and dimensions. I believe those are 3.75-4.25mm in length but can't remember correct, they are smaller than most...Get a precision ruler and get the correct length and when ordering make sure they are similar size.

Not that it will matter if the new ones are a bit bigger in size but if you want it to look original get the same dimension. Don't worry about color as you will find out that most datasheets don't specify what color the coating is on the resistors just their properties (flame resistant).

[valeks1]

Replace burned two resistors with 100 ohm resistors. Also check for DC voltage between B-/B+ and speaker ground (two middle terminals). If you have more then 2Volts then you have problem with the amplifier.

[ajaye]

edit sorry meant to be PM