CX-600 Thread. My bucket of mistakes and learning experiences.

Bratwurst7s

Bratwurst7s

In The Frying Pan
Subscriber
I was cruising the 'bay last night and came across a CX-600 just a couple minutes before it closed. It apparently has a problem with the power switch and possibly/probably a problem with the transformer. It's a General model, with switchable power 110/120v & 220/240v, and has a power cord with a US plug. My first thought is that someone brought it to Germany from the US and turned it on without switching the voltage to 240v and burned the transformer.

For the German readers I believe this thread on HiFi Forum Germany that I found today is the exact unit in question...
http://www.hifi-forum.de/viewthread-185-12998.html

Anyway, I jumped on it and bought it for ca €70. I figured that the risk wasn't too high at that price and if I can fix it I'll be on the path back to separates (where I want to be). It should be here in a few days and I'll start looking into it and most likely start asking questions looking for help.

Cheers,
James
 
Hi Avionic, thanks for stepping in. The pre arrived this afternoon. I've opened it up and so far have only checked the to see that the power switch doesn't hold in the on position, but I haven't checked it with a meter yet. If I'm at all understanding things correctly the power switch isn't switching directly to the primary at all, seems to be going through front panel board nr 2 to the relay on the main pcb. So the relay is actually connecting the primary transformer windings to the mains. Is that correct? Which would mean that the primary windings are always live when the unit is plugged in? I see no fuse anywhere.

edit: No, my mistake. The relay turns off the secondary windings? Or what?

I also put my meter on the primary trafo wires where they are connected to the main pcb and the AC outlet board. I get open any way that I measure. Grey/blue, grey/brown and blue/brown all measure infinity regardless if I let my meter auto-range or select down to 1.0 ohms range. So it would look like the primary windings are open, or the thermal fuse (if it has one) has blown. I get continuity on the secondaries any way that I measure them. Red/red, blue/blue, red/blue, black/red, each to ground, etc, all continuity (less than 1 ohm).

It's relatively clean inside, no signs of nicotine and no massive amounts of dust, and has the white glue rather than the nasty brown stuff, but smells musty and has some signs of rust here and there, so looks like it has been in a cellar or attic for a while.

I do have the SM and schematics thanks to the AK database but an original is available on the 'bay so I'll probably go ahead and buy it this weekend just to have it. That's as far as I have gotten. After that I got side tracked by some Friday night ZZ-Top and bier. :)

Do you know if the RS-CX-1000 remote will work with the CX-600? I'll eventually need a remote and there's a RS-CX-1000 available for a reasonable price. If it will work I'll buy it.

Cheers,
James
 
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After a very long time I've finally gotten some other projects out of the way and started taking a closer look at this unit. I wanted to take the transformer completely out of circuit to check it and couldn't see any way to do that without removing the main PCB so in the end I have basicly completely disassembled the pre-amp to do that. It's not as clean inside as I had first thought, I have to guess that it's been stored somewhere damp for a good while.

And it seems that the transformer isn't bad! If I'm reading the schematic correctly the grey primary wire is neutral, the brown one is for 120v and the blue one is for 240v. And I get 26 ohms between grey and brown, and 106 ohms between grey and blue. So that gives enormous hope that the pre can be fixed. I resoldered the switched/unswitched plug block and the transformer connection to it as well as replacing the power cord with one with a Euro-plug. I also pulled and disassembled the voltage selector. It had continuity but was oxidized black inside and it's solder connections didn't look very good. Theres a lot of signs of corrosion through the entire pre-amp.

Someone has taken the power switch apart and all of the small parts to make it latch are now missing, so I need to find a new switch. C417 is starting to bulge. Q407 and R414 have dis-colorization around them. Smoke? Q403 & 406 have oxidized leads and their solder connections don't look good, everything in that area looks a bit corroded/oxidized. That's just an initial survey. Next step will be to clean everything with an alcohol bath then start checking components working from the PS out. And make a list of components to buy. I'm thinking that I really don't want to re-install any old parts, just check them for damage, mark a copy of the schematic and set them aside.

So I have to start finding transistor and diode replacements. Vishay metal film for resistors. And find a replacement relay. And of course caps. This will take a while, I can only afford a little bit each month. I can use the time to clean switches and potis, replace corroded jumpers and resolder things. All of this is going to be good practice and I need that. Because when this is finished I can start on the M-70 that I found. I haven't even opened that up yet and for sure not even plugged it in. One thing at a time.

Cheers,
James

DSC02518.jpg DSC02524.jpg DSC02529.jpg DSC02532.jpg DSC02535.jpg
 
Q407 solder connections look "cold" in the photo. I'll bet if you wiggle Q407 the leads will wiggle in the solder pads.
 
avionic said:
Q407 solder connections look "cold" in the photo. I'll bet if you wiggle Q407 the leads will wiggle in the solder pads.
Click to expand...

You called that right. :thumbsup: Wiggler. It'll get pulled and checked. I'm sure that there are more, a lot of questionable looking solder points. I assume that I'll have to touch up the entire board(s).

Cheers,
James
 
Nashou66 said:
Do you have a close up of the power switch? Does it mount via two screws?
If so I used this one in my A-1 :
https://www.e-switch.com/system/asset/product_data_sheet/pdf/49/P197.pdf
http://www.digikey.com/product-search/en?mpart=P197EESB&v=141
Digikey shows it as a 125AC but the data sheet shows it as 250 also @ 5 amps
Been working flawlessly for me.
Nashou
Click to expand...

Mine mounts with 2 screws but the pin-out is completely different. 2 rows of 3 pins. About 6mm spacing between the rows with 4mm spacing along the row. Unless I'm looking at this wrong the switch doesn't carry any current to speak of but rather just controls the relay. Looking at the parts list the subsonic filter and stereo/mono switch are the same ones. So if worst comes to worse I could swap it the subsonic filter switch and leave the subsonic permanently off since I never use that anyway. I'll try writing Clinic-Audio/Patrice and ask if he has one. Also ebay-USA has a used power switch out of a CX-830 that looks the same. But I'd rather not go that route because it would end up being a pretty darned expensive used switch by the time it got through German customs.

Nonetheless, thank you for taking the time to look and write. :):thumbsup:

Cheers,
James
 
Today I marked the leads of all of the cabled switches, boards etc and took more photos of where everything is connected to the main pcb. It doesn't help that most of the wire connections aren't numbered but instead are marked in Japanese. After that I de-soldered all of the connector blocks to everything external to the main pcb. So now I have an unentangled pcb to work with. Also, as it shows in the earlier photo, I left the transformer wire wrap connections and de-soldered the complete lead block from the pcb when I removed it. Tomorrow I'll start cleaning things.

Project for the weekend is to make a list of caps, transistors, diodes etc and start looking for cross references/replacements. Some transistors I will have as I ordered a lot of extras when I was working on an A-1020. I should also have a good number of the caps. In general I have some Panasonic FCs, UCC KYBs, Nichicon KZ, ES & FG, and Wima and Panasonic film caps, MKS-2 & ECQ. I'll order more as needed. Any cap 6.8µF and under will be replaced with a film cap.

I'm still working on understanding where some specific types of elcos are needed. I've caught on to using 105° high ripple current caps in power supplies for instance, and have using KYBs and or FCs everywhere outside of the signal path or where an NPE is needed, but I see people talking about "low leakage caps" and don't understand yet where such a cap is best used (and why) and what specific product lines are low leakage.

Anyway I also have printed a number of sheets of the schematic and board layouts and will be using Avionics suggestion of marking any bad components in red on a schematic and layout.

The end of the month is coming up and so I'll be able to afford to make a parts order then. I'll normally be limited to making one Mouser OR Digi-Key order per month, min of €65 to get free shipping, and a max of about €100. And that adds up pretty fast, especially as I still need to buy some op-amps and resistors to finish a CD player.

Cheers,
James

DSC02539.jpg DSC02542.jpg
 
I believe that I've found the right switch now. The original is an Alps SUN2-2ns which is of course no longer made. But Alps has a current production SPUN series and the SPUN191400 looks to be a drop in fit. Looking at the specs it looks really good. And even though it doesn't have a mounting plate that's OK. I took a look at the other 2 switches (mute, stereo) and they have a blue snap on front frame that isn't installed on the power switch. And if one removes that little plastic frame the steel mounting plate removed from the old switch pops right on. I'm thinking very strongly that this will work. So I'm going to order 3 of them from Mouser when I make my order. At a price of only €1.40 each I'll take the risk.

And the SPUN 194700 looks like a drop in fit for the Source Direct switch so I'm going to order one of them also (€1.20). At these prices I'd much rather buy new switches than clean the old ones.

http://www.mouser.de/ProductDetail/...ha2pyFadujyvPJY0%2bUWPSOEaReGfezUDuWLT7zzZmA=
http://www.mouser.de/ProductDetail/ALPS/SPUN194700/?qs=WAEtoynyCxJ6AjQ6qdTvuQ==

Cheers,
James
 
I'm trying to decide on the main filter capacitor. I'd like to go with 105° and a bit more capacity so 2700µF 50v. These 2 are on my short list with the KYB probably the one that I'll order unless anyone has a warning or better suggestion.

http://www.mouser.de/ProductDetail/...n0r9vR22UhSjrTM10DE9rjLiWmnBz%2bLFvYENmmpyg==
http://www.mouser.de/ProductDetail/...=sGAEpiMZZMtZ1n0r9vR22V0yJaboBTX6TgkLmRF2wFU=

I realize that caps have gotten smaller but the size difference over the original Elna 2200µF 42v makes me wonder if I'm not making a mistake. 30mm dia x 40mm H vs 18mm dia x 35.5/40mm with the UCC & Nichicon. Lead spacing on the Elna appears to be 11mm vs 7.5mm on the new ones. 11mm seemed such an odd spacing that I've measured several times and that looks like the spacing. The new ones are so much smaller that it looks like I should be able to shift them around to stay in the traces without a problem. But 10mm lead spacing sure would be easier.

Cheers,
James
 
Today I dismounted all of the switches and potis after marking them for their position. And then removed the old 2200µF/42v filter caps. After that the board got washed in hot water and citrus cleaner, blow dried and then washed again in alcohol. It cleaned up very nicely including getting all of the old flux off. Once I got it back on the bench I removed the old glue from the filter cap area.

After that I replaced all of the small value elcos with film caps. The .0.22, 0.47 and 1.0µF 50v were replaced with 63v, the 3.3µF/50v and 4.7µF/25v with 50v, all 5% Wima MKS-2. The 0.33µF/50v were replaced with Panasonic ECQ as I have a huge amount of them. Lastly I got perhaps 20% of the boards solder connections re-flowed, all along the front edge and the microcontroller area. I'm being damn careful never to be on a connection longer than a second or 2. I'm checking the old caps as I replace them. They haven't drifted to speak of in capacitance but some are showing what seems to me to be high ESR, such as 9.5 ohms on the 0.22µF caps. The old filter caps however still looked pretty good @ 2247µF/0.5 ohm and 2190µF/0.5 ohm. I sorted through my supply and measured and installed L&R pairs that matched as closely as I could find.

The photos are after washing but before any other work. I've never gone this far into dismantling a unit so it's both interesting and a little bit scarey. I hope that I don't screw the pooch on this one. Tomorrows plan is to finish the solder reflow on the rest of the board except for the power supply area. That area the plan is to systematicly dismount components and check them.

Cheers,
James

DSC02564.jpg DSC02567.jpg
 
That white glue is a bitch to completely remove without scuffing the PCB.
 
What is your plan for the RCA jacks ? OEM or after market ?
 
What are you using for that memory back up cap. C227-- 4.7 millifarad / 5.5volt ?
 
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A while back. I did a CX preamp. Mouser had 9 or 10 left of a discontinued model , Nichicon I think, 47mf/5.5volt e-caps. I snagged all of them. Now if I could just remember where the hell I put them ???
 
BTW - There is a typo in the schematic for C227. Its not 47000µf. 4700µf:thumbsup:
 
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