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Old 05-09-2019, 12:18 PM   #1
TheDragon
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Default Car amp, headunit and crossovers

Hi all, I would greatly appreciate some technical advice.

I have acquired an old Pioneer car cassette HU - KEH-P8600R , which I plan to install (from around late 90's). It works fine, but my question is, due to its age, is it worth replacing the caps, even though its functioning fine?

Secondly, I have a JBL amp, GTO75.4. Sonically, not the greatest but has served me well for more than a decade to run a sub and front component speakers. Again, it's working ok but is it worth replacing some caps. Would I gain anything?

And thirdly, I have some component speakers, brought at same time as amp and used in two cars.
These use passive crossovers. Would the caps in these be worth upgrading too?

Thank you.
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Old 05-09-2019, 02:22 PM   #2
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Default Re: Car amp, headunit and crossovers

Hmm.. Do you have an ESR meter by chance? If it were me, I'd probably do an esr test on the electrolytic caps and, if they seemed ok, would put it back into service. (I'm a bit unprofessional though. lol) Past that, I probably wouldn't worry too much.

-----------
Other than just testing the caps for a poor ESR and to see if they have the right capacitance, you could also use a spectrum analyzer (if you have one) and see if you have any distortion on the output. (using FFT) You could also just use an oscilloscope and do a basic sweep of the audible spectrum and see if you have any noise on the output. (If you don't have a signal generator then you could download sample tones/with pilot from the internet and play it from a music player.) This would let you know if you have any harmonic distortion or similar.

One thing that may give us a better idea of if the caps need replaced is what brand the capacitors are. For instance, if they were a really cheap/well known for being bad brand we may recommend just replacing them because they are likely to fail anyways.
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Old 05-09-2019, 03:19 PM   #3
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Default Re: Car amp, headunit and crossovers

Quote:
Originally Posted by Retro-Hipster View Post
Hmm.. Do you have an ESR meter by chance? If it were me, I'd probably do an esr test on the electrolytic caps and, if they seemed ok, would put it back into service. (I'm a bit unprofessional though. lol) Past that, I probably wouldn't worry too much.

-----------
Other than just testing the caps for a poor ESR and to see if they have the right capacitance, you could also use a spectrum analyzer (if you have one) and see if you have any distortion on the output. (using FFT) You could also just use an oscilloscope and do a basic sweep of the audible spectrum and see if you have any noise on the output. (If you don't have a signal generator then you could download sample tones/with pilot from the internet and play it from a music player.) This would let you know if you have any harmonic distortion or similar.

One thing that may give us a better idea of if the caps need replaced is what brand the capacitors are. For instance, if they were a really cheap/well known for being bad brand we may recommend just replacing them because they are likely to fail anyways.
Hi Retro-Hipster, thanks fro chiming in.

I don't have either, esr meter or oscilloscope unfortunately. Just a standard multimeter, that does read capacitance.

Thats good advice, I will investigate the capacitor brands used.
My guess is that the JBL amp will have middle to low quality caps,whilst the pioneer has some decent ones as they were top of the range units in their hay day. Then again I could be totally wrong.
As the pioneer is 20+ years old, used in variable climate conditions,
I wonder how much they deteriorate even if good brand caps?
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Old 05-10-2019, 02:05 PM   #4
Andrew F. Ali
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Default Re: Car amp, headunit and crossovers

My guess is. If everything is working fine why go looking for trouble. I'll do any/all corrective maintenance when a problem arise.
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Old 05-10-2019, 02:59 PM   #5
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Default Re: Car amp, headunit and crossovers

Quote:
Originally Posted by Andrew F. Ali View Post
My guess is. If everything is working fine why go looking for trouble. I'll do any/all corrective maintenance when a problem arise.
Yeah, I'm kind of of that mentality too. If I have an attachment/really like something then I tend to do "checkups" before putting it back into service, but they tend to be pretty brief.

Oh, this is barring old tech though.. If it's older tech I tend to give it a pretty good once over/don't plug it in until I've checked the power components and such.
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Old 05-10-2019, 06:26 PM   #6
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Default Re: Car amp, headunit and crossovers

Quote:
Originally Posted by Andrew F. Ali View Post
My guess is. If everything is working fine why go looking for trouble. I'll do any/all corrective maintenance when a problem arise.
I generally agree to that too. It's just that, as I'm setting up a fresh, and the age of the equipment, I thought a good service would be useful after putting in the effort of installing.

Quote:
Originally Posted by Retro-Hipster View Post
Yeah, I'm kind of of that mentality too. If I have an attachment/really like something then I tend to do "checkups" before putting it back into service, but they tend to be pretty brief.

Oh, this is barring old tech though.. If it's older tech I tend to give it a pretty good once over/don't plug it in until I've checked the power components and such.
I looked into the pioneer unit, there are no bulging caps and most are panasonic m series, with 2 being elna branded. I couldn't say if they have deteriorated, but I'd say some would have, whether it effects the sound. I'm not an expert on that.
Haven't had chance to disassemble the amp yet.
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Old 05-11-2019, 05:27 PM   #7
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Default Re: Car amp, headunit and crossovers

Just learnt that the High pass filter on the amp isn't working. It's sending all the frequencies through. I'll have to check why.
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Old 05-12-2019, 04:21 AM   #8
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Default Re: Car amp, headunit and crossovers

forget the caps if they arent leaking/bulged.

but a warning - dont try to play any tapes without replacing the pinchroller(s) and any belts it may have.
it will unspool your tape into the mechanism and be a right bastard to untangle.
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Old 05-12-2019, 06:47 AM   #9
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Default Re: Car amp, headunit and crossovers

Well, all the caps seem ok.
Just tested all the frequencies coming through with test tones.
Apparently my MM can read frequency 0-20khz
Whether the character of the sound has changed, I suppose so, but thats subjective.

Just looking at an external crossover now.

Though Ive seen this too
https://www.ebay.co.uk/itm/NAKAMICHI...AAAOSwuytcSXgb

Of course, not the nakamichi of old, and cannot find any reviews.

STJ, I have indeed changed them. Always to point out.
It's electroluminescent display was dim, so I've replaced it and looks much brighter now. I did try to figure an LED alternative, but gave up.

A ribbon cable for the display is on order too, as the original is intermittent

I've acquired two more pioneers of the same decade (older), similar display/ribbon issues though. Will see whats more suited.
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Old 05-12-2019, 09:12 AM   #10
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Default Re: Car amp, headunit and crossovers

ribbon?
so these are the ones where the front folds down to access the tape slot?
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Old 05-12-2019, 11:03 AM   #11
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Default Re: Car amp, headunit and crossovers

Yes, Stj. Apparently, it's a common repair.
My later model pioneer (got stolen), was motorised, used a different connection
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