Clarion DPX11500 #2 Repair

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You had to fight to remove a jumper? nevermind.. I don't wanna know.

I feel like I failed ya some how on this. It's just not how I chase after things when I have them here. I'm spoiled with a signal injector, scope, all the toys. it's fairly cut and dry for 99% of the cases using those tools and a personally established troubleshooting routine.

Can I safely assume you've taken the initiative to test all the sub 100 ohm value resistors in the pre-drive, differential, and drive sections? There are things you can proactively check between posts. It'll save time if you can catch it in something simple. Resistors fail UP, not down. So if you're directly across one, it should read within 5% of it's value or LESS depending on what might be parallel with it in circuit, If in doubt you can lift a leg to check. There are 11 transistors in the block I'd like you to focus on, any resistor from 1 - 100 ohms. You're just gonna have to start beasting it out on this one, There is a bad part in there somewhere.


I have gone through the board and tested many diodes to ensure they were not leaking. I have tested some resistors as well, and replaced where I wasn't confident in their integrity.

One resistor that comes to mind, is R166, it is discoloured, and quite a bit moreso than when I started. I have a replacement I can put here after I test it tonight.
 
Well, I feel a little bit of progress was made tonight.

I took your advice Matthew and went over some resistors in the sub 100ohm range. I found R1 to be reading almost 600 ohms, when it should have been 36.2 or so. I swapped a good resistor from my parts amp over and temporarily reconnect j2. My DC voltage now measures around +18VDC rapidly dropping to around 15VDC. Not good, but an improvement over +38.
 
Sorry, I got unsubscribed to replies on this thread somehow. r1 feeds q2 and bringing it into spec helped level the drive down some. I would suspect q2 *could* be degraded. Remeasure r1 and swap q2 with your q2 in the parts amp.

Also r161 & r6 are paralelled with an inductor and 1.1 ohm resistor. So if you want proper reading for those, you'll want to lift a leg of each r161 & r6 and then test the 4 resistors in that loop.

Why can I not find 'r166' ? Do you have that number right? Am I in the wrong block?
 
R166 is near the pwm ic. If you are looking at the diagram, it is right near the edge of the board.

It is definitely darker than it was before I started my initial work a couple of weeks ago.

I swapped q2, no change. Checked R6 with one pine lifted, it was ok, so I reinstalled.

I don't understand. The voltage starts out really high at about +38VDC and rapidly drops. Hitting below 10 VDC in less than 30 seconds or so,
 
1) ok, r166 is part of the fan circuit and is clearly isolated as such in the schematic.

2) Just keep an eye on that r1 if things start to go backwards again.

3) I also said you should check r161 and it's paralell resistor counterpart. I think you skipped it.

4) I want to say this without coming off as insulting, but I can't figure out how. I don't think these were good amplifiers to learn on, And you clearly need to learn a lot. You're having trouble understanding how this all comes together and it's not helping you. What is your experience level and have you considered a tutorial? A lot of these questions would answer themselves if you understood some of this stuff which is why I ask/suggest it.

I would venture a suspect guess that r1 may have been your initial issue (the 2 volts on the output due to drive imbalance, which would also affect your ability to adjust bias where it sits). So it kinda explains it being not completely dead, but part of a balanced circuit and a few hundred ohms out of tolerance. It also explains the white noise effect, at least to me. Whatever you shorted on the board while working is probably whats left and the current issue. You said you had some idea of where the short occured but never actually said where?
 
Hi Matthew,

I respect your opinion of my skill level as accurate and I am not insulted.

My skill level is limited. I have no problem using a DMM to test parts. When it comes to circuit tracing my skill is quite limited as to how everything works together. I can trace a circuit but do not really understand a lot. This amp was definitely the wrong choice to learn on. To be honest; when I got into the first one, it was way more work than I was expecting. Now I've got too much invested really to just give up all together. However, I am at the point where it is being considered.

As for where the short occurred, I am not 100% sure.
 
Well, i'm glad I didn't offend you. Political correctness doesn't seem to be my forte even when I try. I tend to be blunt and that's refreshing for some, and aggravating for others. It seems a shame after 10 pages that we can't get this one right just for the sake of getting it done. Perry is significantly better at walking people through things like this over the internet and I admire that. For all his patience he should probably be teaching somewhere.

Do you have a capacitor checker? There are at least 2 I think i'd like you to check, unless you just want to do some swapping from your parts amp. What about your friend earlier in this thread with the scope and proper test bench? Paul was it?
 
Hi, pot is still turned all the way counter clockwise.

I replaced Q38 with a new MPSA06. Was faster than swapping or testing.

Tested, same results as prior tests.

Swapped C78 same results
Swapped C85 same results.

I timed the test. After thirty seconds or so voltage dropped to 10. After about 45 seconds voltage finally settled right around +8.91VDC

There is a TL074 in close proximity (right next to) and a TL072 as well.

The TL072 is at U1, and the TL074 is U3. Would these be useful to test due to their proximity to the caps? (Because of the accidental short)
 
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voltage finally settled right around +8.91VDC

There is a TL074 in close proximity (right next to) and a TL072 as well.

The TL072 is at U1, and the TL074 is U3. Would these be useful to test due to their proximity to the caps? (Because of the accidental short)

That's a really interesting voltage measurement it settled on.. in the schematic that's VEE +/- for the differential. I think Perry just got a shove in the right direction for ya. Hopefully he'll pick that up because i'm burnt for now.
 
Was hoping i'd get a pinch hitter on this, but 10 pages and 1,000+ views in I feel like we should push forward some how.

Please post the following voltages, powered up, unloaded, no signal, and once the dc offset has settled to that lowest reading of 8-9v.

U2:

Pin 1
Pin 7

Banded end of D18
Non-Banded end of D19

The schematic doesn't show me proximity, but since you mention it you can try decoupling those parts from the drive by lifting one leg of c13 to see if it rectify's your issue, but ONLY once you've got me those voltages. If you lift it, take a measurment on either side of r37 then for me.
 
It's difficult to have multiple people helping. When someone else is helping, I try not to interfere unless I see something that may have been missed. If a brick wall is finally hit with the current thread, a new thread would need to be started with a description of the original problem, the current problem and what happened that resulted in the secondary problem.
 
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