amp questions???????no output

thedeal7235 · Post by **thedeal7235** » Tue Jul 22, 2008 5:37 pm

I found a website that talked about finding problems with your amp; my dilemma is this, i have an old school zx450 and an extra ti 600.2( both have no output)- long story short, i read to check the outputs u can switch your multimeter to ohm, then read each channel, if its good then you should read 0.00, or go back to ol., if it does not read 2 of the later does that mean that channel is gone? and if so, what is the fix, is what im actually asking- thanx, just trying to get a better understanding of how amps do work- and are fixable, vs. not

Thumper88 · Post by **Thumper88** » Tue Jul 22, 2008 5:52 pm

Is it Perry Babin's site?

He has a great DVD tutorial available...if you really want to learn about the inner workings of car audio amplifiers and how to fix them...not for the faint of heart, takes some dedication to learn (not to mention money for equipment/tools to fix them).

Not sure what you mean by "read each channel"...if you mean put one lead on the ground terminal and the other terminal on one of the speaker output terminals...it should not read 0 ohms...that would be a shorted audio output, more often than not blowing the power supply along with it....unless that's what your multimeter shows with a high load. I just performed the test mentioned on a JBL GTS50...since I had it handy....around 2k ohms on each channel, not 0 ohms, but not OL either (Open Loop - Extremely High Resistance).

A JL e6450 that I also have on hand, which I know is blown, shows around 0 ohms on most of the outputs....yea, it's got shorted output transistors...haven't checked into the amp much other than that.

thedeal7235 · Post by **thedeal7235** » Tue Jul 22, 2008 5:59 pm

i thought i understood to put the neg lead on the left neg, the posi lead on the left posi ( left front speaker outputs) for this; figure i cant hurt them anymore then they already are, since neither the 450 or 600.2 have any output????????

Thumper88 · Post by **Thumper88** » Tue Jul 22, 2008 6:03 pm

thedeal7235 wrote:i thought i understood to put the neg lead on the left neg, the posi lead on the left posi ( left front speaker outputs) for this; figure i cant hurt them anymore then they already are, since neither the 450 or 600.2 have any output????????

That won't tell you anything really...unless somehow the two rails (+-) were shorted together....

The blown amp (JL) shows around 1.5 megaohms for example with that test....the only real test that can be done without removing the cover is the one I mentioned above and checking the resistance between the power input terminals to see if the power supply is shorted.

Not a sure way to diagnose an amp of course....always end up taking the cover off.

Post by **Jacampb2** » Tue Jul 22, 2008 6:07 pm

I have seen the same test described, and while it can tell you if the output devices have failed shorted, it is by no means is a quantitative enough test to tell you what is wrong. Obviously, if it shows shorted condition, then the output devices have likely failed, but if it doesn't, then the problem can be anywhere. You are checking with the power disconnected, correct?

As thumper said though, if the output transistors fail shorted, then they typically will take most of the FETs in the power supply with them.

PG will fix them for a flat rate and IMO is pretty reasonable. If you decide to just unload them though, look me up, I am always looking for parts and fixer-uppers.

Later,
Jason

Post by **Jacampb2** » Tue Jul 22, 2008 6:30 pm

Thumper, what he described is correct and the same way I have seen the test described. The +/- rails have almost nothing to do with the results. While not bridged, the output signal only exists on one of the two conductors that you hook the speaker to. It is not necessarily the + terminal, because it depends on what channel is inverted for the ability to be bridged. It doesn't matter for this purpose though. The output is an AC waveform referenced to ground. One of the two wires for each channel has output and the other is already the output ground. The +/- rails are used to get that AC wave on the one conductor. In the case of BJT output pairs like in these amps, if they fail shorted emitter to collector then you will see the short at the outputs via the path of the shorted transistor, through one side of the PS xformer and to ground, both center taps on the secondary side of the PS transformer are tied directly to ground, the same as with one of the two speaker terminals for each channel.

In these amps, one channel has the AC speaker output on the + side, and the other of the channel pair has the INVERTED AC speaker output on the - side. So, if the left channel is has the in phase output, it has signal on the + and ground on the -. Then the Right channel would have the signal 180° out of phase on the - and ground on the positive. That is what allows the amplifier to be automatically bridged, and has absolutely nothing to do with the discussion at hand, except hopefully to clarify things.

Later,
Jason

thedeal7235 · Post by **thedeal7235** » Tue Jul 22, 2008 6:37 pm

yes, this has not been used in 2years, so it is disconnected, and yes i know cecil or pg will fix; it just drives me crazy when i cant fix equipment, i dont mind paying, its just a part of my personality, i guess-i undeerstand obviously enough to install, tune etc, just wish i could understand this end of it more-for example, how much ampersge does an amp actually pull( i know it depends on the watage size etc., but when i look at my ti 600.2 birth cert. it shows 4.93volts and produced 653 watts-so does that mean if i have 4 amps, of same power they all draw 20-25 amps at peak volume??? thanx for any and all respnses-i know what the crossovers looklike intrnally, caps, but not sure what piee is the actual power supply-thought it was the piece that has the wire wrapped around( shaped like a circle, inside of amp-however , after reading more, i believe that helps with the ac end of the amp??!! thanx again Christian

Post by **Jacampb2** » Tue Jul 22, 2008 7:32 pm

Christian, Take a look at page 2 of this:

http://download.phoenixphorum.com/Manua ... titech.pdf

The round thing in that picture is labeled. Yours is likely red. It is the transformer for the power supply. Directly above it in the 600.2 under the heat sink are the power supply FETs. The short card that stand perpendicular to the amp is the power supply controller. The output BJT pairs are under the two heat sinks on the top left hand side of the amp.

As for the specs on your birth sheet, it has been a long time since I looked at a birth sheet, but I think that the 4.93V must be referring to the signal level required to drive the amp to full output power. I think the 600.2 draws between 60 and 80 amps at full output depending on how it is configured.

Later,
Jason

thedeal7235 · Post by **thedeal7235** » Tue Jul 22, 2008 7:39 pm

yeaph, on my zx 450 it is red, but thanx man, i get it a little more now!!! im sure ill send it in 2 pg for repair, but i understand the caps and the pic does help!!!!