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 Post subject: Zx600 ti
PostPosted: Wed Oct 17, 2018 9:52 am 

Joined: Tue Nov 06, 2012 9:30 pm
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Hi, trying to fix a zx600 for my buddy. Its got some issues cap leaked and burned a hole in the board, it seems to not be shorted there, so that fix should be straightforward.

He sent it in for repair and got it back as not economical for that guy to do it. But id like to learn. I know these amps are mirrors left and right. And it looks like several resistors have been replaced as they are not blue.

Does anyone have some advice on where to start? I have noticed that all of the transistors on one side are marked 1xx and on the other 2xx which corresponds with the left and right channels marked on the board.

Some other observations are that both the 117 and 217 A1659 transistors have had their bases snipped. And the left sides Q111 has had its emitter clipped and the board terminal jumpered to C110 leg closest to the speaker terminals.. any thoughts on that?

Thanks for any advice/ schematic help. ImageImageImage

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 Post subject: Re: Zx600 ti
PostPosted: Wed Oct 17, 2018 2:40 pm 
the Floor Sweeping Hack with Golden Ears

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that isn't a big whole, sounds like your repair guy is either a MS/M pg dude or god help us he is more of an RF dude... I think Jacob has posted some how-to's on cb repair.



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 Post subject: Re: Zx600 ti
PostPosted: Wed Oct 17, 2018 2:56 pm 
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Well, you got yourself a mess right there. To be brutally honest, this might not be the best repair to learn on. Chasing down a botched repair, or series of repairs like in this case can be extremely difficult and frustrating.

Q111 controls bias current for that channel. No idea why they have it jumpers like that. It's emitter doesn't connect anywhere near C110. Some techs clip leads while troubleshooting. It's a singularly stupid thing to do because many of these parts are long obsoleted and clipping leads of working parts just screws you in the long run.

I have suitable substitutions for the driver and pre-driver transistors, I can look things up for you if need be. Almost all of the 1/4w resistors in the poweramp are supposed to be flame proof. Any that have been changed to standard resistors should be changed back. You also have to many times meter check part by part in the faulty amplifier until for find all the issues.

I haven't run into a PG amp yet that wasn't economical to repair. I've heard Mantz has condemned zx/ti/zpa amps to death for less than this, but the rest of the stuff doesn't really sounds like his work...

Good luck,
Jason



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M: M100, M44 for a custom amp project
Zx: Zx500, Zx450, Black Zx350
ZxTi: 4 Zx600Ti's, 1 Zx400Ti
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 Post subject: Re: Zx600 ti
PostPosted: Wed Oct 17, 2018 7:11 pm 

Joined: Tue Nov 06, 2012 9:30 pm
Posts: 162
I can fix the hole in the board. Thats not hard. I like a challenge, are the circuits in the 600 the same as any of the other zx amps?

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 Post subject: Re: Zx600 ti
PostPosted: Wed Oct 17, 2018 8:21 pm 

Joined: Tue Nov 06, 2012 9:30 pm
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Ok, I'd love some direction on replacement parts.
Q111 is 2SC1567 and the legs were cut, can't find too much information on that transistor apparently its NLA.
Q114 and Q115 are missing.
Q117 is a 2SA1659A which doesn't match any other transistor on the board so it's got to be a replacement.
Q116 has been changed but I didn't write down what transistor is there.
D101 was removed and replaced, probably to verify that the problem is not a dead LED.
The jumper wire with the resistor is odd.

There are no burned traces other than one of the power supply caps, and none of the resistors look like they got hot, other than what was replaced in front of Q121.

Any suggestions on test points and their values?


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 Post subject: Re: Zx600 ti
PostPosted: Thu Oct 18, 2018 11:18 am 
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Flame proof resistors never look like they got hot, that's kind of the point. That's why I said you have to go through and meter check everything in the dead amp. I'll get you part numbers and substitutes tomorrow, if you use substitute parts you really should do both channels of the amp will ever be run bridged. I'm away from the shop today, but I should have time to get back to you tomorrow.

Good luck,
Jason



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M: M100, M44 for a custom amp project
Zx: Zx500, Zx450, Black Zx350
ZxTi: 4 Zx600Ti's, 1 Zx400Ti
Ti: 5 800.1's & 900.7 for a custom amp project. 1 1200.1, 1 1000.2
Tantrum: 2 1200.1's, 1 600.4, 1 500.2
XS: XS6600
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 Post subject: Re: Zx600 ti
PostPosted: Thu Oct 18, 2018 11:25 am 

Joined: Tue Nov 06, 2012 9:30 pm
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Thanks!

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 Post subject: Re: Zx600 ti
PostPosted: Sun Oct 21, 2018 7:28 am 
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lilviper wrote:
Ok, I'd love some direction on replacement parts.
Q111 is 2SC1567 and the legs were cut, can't find too much information on that transistor apparently its NLA.
Q114 and Q115 are missing.
Q117 is a 2SA1659A which doesn't match any other transistor on the board so it's got to be a replacement.
Q116 has been changed but I didn't write down what transistor is there.
D101 was removed and replaced, probably to verify that the problem is not a dead LED.
The jumper wire with the resistor is odd.

There are no burned traces other than one of the power supply caps, and none of the resistors look like they got hot, other than what was replaced in front of Q121.

Any suggestions on test points and their values?


Q111- I use KSC2690A as a sub, KSC3503 will also work, but I typically save those for the amps with higer rail voltages. Both parts are currently backordered at the major US suppliers. Mouser shows they should be getting about 5,000 in November, I would get on the list if you want them. They go quickly.

Q114- is supposed to be 2SC5248E; You should be able to use 2SC4883A-- I have not tried these, but they are a good match on paper. I still have a fair supply of the stock drivers and another driver that I use to sub, but both are obsolete now.

Q115- is supposed to be 2SA1964A; You should be able to use 2SA1859A, same caveat as above. Both of these particular transistors are available at digikey. Mouser had nothing suitable is the TO-220FP package.

Q116-is supposed to be 2SC5248E; Same as above for Q114

The 2SA1659A/2SC4370A pair are suitable replacements although their bandwidth is only 2/3rds of the stock parts. They are also long obsolete, and the Sanken transistors I recommend above are much closer to the stock parts.

Q117-is supposed to be 2SA1964A; Same as above for Q115

The red LEDs are used to provide a specific voltage drop for the bias of each channel. If it needs replaced, you need to measure the voltage dropped across one of the LEDs which are working and buy a red LED with a published spec that matches that voltage for it's forward voltage. Alternatively I believe there are two unpopulated diode locations near the LED, you can remove the red LEDs entirely and use two 1N4148 diodes in series in their place. As long as the voltage drop across the pair of LEDs per channel are close to the same, it will function properly. The same goes for a pair of diodes if you go that route, the drop across each set in a channel should be as close to the same as possible. Do not try to use a resistor in this location to provide the current source, a resistor will shift to much with heat. It has to be an LED or pair of diodes. Also, the color was chosen for it's particular forward voltage. If you get the notion to change them to a prettier color-- don't ;).

Good Luck,
Jason



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M: M100, M44 for a custom amp project
Zx: Zx500, Zx450, Black Zx350
ZxTi: 4 Zx600Ti's, 1 Zx400Ti
Ti: 5 800.1's & 900.7 for a custom amp project. 1 1200.1, 1 1000.2
Tantrum: 2 1200.1's, 1 600.4, 1 500.2
XS: XS6600
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 Post subject: Re: Zx600 ti
PostPosted: Thu May 09, 2019 1:45 pm 

Joined: Tue Nov 06, 2012 9:30 pm
Posts: 162
Ok, got the board fixed. Whoever worked on this before screwed a bunch of the pads and traces up, so ill fix those too.

I dont have a second 600 handy. But are these supposed to be here? They are 1N4752AImageImage

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 Post subject: Re: Zx600 ti
PostPosted: Wed Aug 14, 2019 5:23 am 

Joined: Thu Aug 01, 2019 7:25 am
Posts: 6
The one I have on my bench does not have those, if that is helpful.


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 Post subject: Re: Zx600 ti
PostPosted: Wed Aug 14, 2019 5:40 am 

Joined: Tue Nov 06, 2012 9:30 pm
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Thanks! I figured they were added after the fact.

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 Post subject: Re: Zx600 ti
PostPosted: Mon Aug 19, 2019 4:33 am 
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The diodes on the bottom were stock. Later revisions had a location for them on the top of the board.



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M: M100, M44 for a custom amp project
Zx: Zx500, Zx450, Black Zx350
ZxTi: 4 Zx600Ti's, 1 Zx400Ti
Ti: 5 800.1's & 900.7 for a custom amp project. 1 1200.1, 1 1000.2
Tantrum: 2 1200.1's, 1 600.4, 1 500.2
XS: XS6600
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 Post subject: Re: Zx600 ti
PostPosted: Mon Aug 19, 2019 4:04 pm 

Joined: Tue Nov 06, 2012 9:30 pm
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Interesting. What do they do?

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 Post subject: Re: Zx600 ti
PostPosted: Wed Aug 28, 2019 8:15 am 
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Sorry, I missed this question. The two diodes are part of the ±15v supply. There is a second parallel zener on the top of the board. The zeners clamp the rail voltage at ±33v to take a little bit of load off of the linear ±15v regulators this amp uses. In later revisions of the board, both parallel diodes are on the top of the board.

Good luck!
Jason



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M: M100, M44 for a custom amp project
Zx: Zx500, Zx450, Black Zx350
ZxTi: 4 Zx600Ti's, 1 Zx400Ti
Ti: 5 800.1's & 900.7 for a custom amp project. 1 1200.1, 1 1000.2
Tantrum: 2 1200.1's, 1 600.4, 1 500.2
XS: XS6600
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 Post subject: Re: Zx600 ti
PostPosted: Wed Aug 28, 2019 8:17 am 
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I should add, the 4 channel versions of this amp did not use the same regulation scheme for the ±15v rails.



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M: M100, M44 for a custom amp project
Zx: Zx500, Zx450, Black Zx350
ZxTi: 4 Zx600Ti's, 1 Zx400Ti
Ti: 5 800.1's & 900.7 for a custom amp project. 1 1200.1, 1 1000.2
Tantrum: 2 1200.1's, 1 600.4, 1 500.2
XS: XS6600
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