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Anyone have a Pioneer SK-550?


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#1 Superduper

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Posted 23 October 2009 - 02:14 AM

I need to find out how the cassette door latches. If someone can describe or even better, snap a photo of how the door latches, it would be appreciated. I have one with broken belts and head mechanism up, preventing door from opening, which prevents splitting the case -- the catch 22. :sadno: Can't open case unless door is open: Can't open door unless case is open to spin down the heads. :hmmm: Sheesh, why do engineers design products like that? Surely these big companies must have someone smart enough on their payroll who can foresee such problems?

Hopefully, someone here owns one of these and can help show me how to "slim-jim" the door open.

#2 Gluecifer

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Posted 23 October 2009 - 05:41 AM

I'll take a look at mine tomorrow, Norm. Mine has a tape mech that keeps locking itself up.. which is apparently a common fault. But one I've never seen a soloution to.

Will get some pix for you and post here within the next 24 hours.



Rock On.

#3 Superduper

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Posted 23 October 2009 - 08:57 AM

Thanks Glucifer. The tape mech locking is a problem, but one I want to work on. The problem is that the tape deck door won't open which prevents me from taking it apart in the first place. If I can see what the actual latch looks like and the actual location, then I can try to fish something in there and maybe get it open. Right now, I'm flying blind. I can actually slip a flat piece of metal rod in there, just can't seem to get it.

#4 blah blah

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Posted 23 October 2009 - 12:11 PM

norm- i had the same problem, i think i actually used a thin butter knife from the top to flip up lock, once i respun the flywheel, it took it off perma lock and no more problems since then.

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#5 Superduper

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Posted 23 October 2009 - 07:57 PM

norm- i had the same problem, i think i actually used a thin butter knife from the top to flip up lock, once i respun the flywheel, it took it off perma lock and no more problems since then.

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whoa...... I was thinking this was gonna be hard to photograph because I expected the latch to be at the top left corner, which was where I was concentrating my efforts. Couldn't do much better blind. Now I think I stand a much better chance getting it opened! Thanks a bunch blahblah, THAT is much helpful.

Unfortunately, the latch looks deeply recessed so I don't think this is gonna be easy by any stretch of the imagination. I can't see how you would get a butter knife into that location with the door closed though.

#6 blah blah

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Posted 23 October 2009 - 08:01 PM

:-D i remember it being easier than i thought...sure you'll have it in no time.

#7 Gluecifer

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Posted 23 October 2009 - 09:33 PM

Ahh! Beaten to the punch!
Thanks for saving me taking mine apart Blah. Good luck Norm, I hope you can work it all out
and we all get our tape mech's working properly. I know with mine it only happenedwhen it
was put into record mode, if that's any help.

Hope the mystery can be solved as this is a really great radio that deserves to be put into full rotation.



Rock On.

#8 Superduper

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Posted 24 October 2009 - 01:36 AM

Hey guys. No joy. Spent almost 3 hours tonight tying to get this unhooked and just couldn't do it.

The image was a little too small for print (I printed it out to have it next to me as I tried to rig something up but no success.) While it looks fine on screen, when printed, the resolution was really poor.

Could either of you guys get me a larger photo or other angles? The problem is from the angle of the shots, it's really hard to tell and estimate the measurements for me to bend my jig. Photos can be deceptive. Is the latch about reel disk height? Also, how deep from the front of the cassette door would you estimate I would need to bend my rig to catch the latch? Maybe I'm missing it entirely (too shallow) or maybe I'm too deep -- it's really hard to tell since the spring wire I'm using is really stiff and rubbing all over the place. This thing has been bugging me like forever and I really hate to snap that door since I'm pretty sure there is no parts units available. I hardly see any of this model at all, as it is, in any condition.

Blah Blah, you must've had great luck. The thin butter knife thing from the top just doesn't seem possible unless the knife is like razor blade thin and can zig and zag too. Also, it seems like from the top, you would be pressing the hook down and not hooking it up. Oh well, gonna take a break now before I get too tempted to smash it apart.

One final question. If all else fails, I might consider cutting an access hole at the bottom, do you guys think the capstan flywheel will be visible so I can spin it if I cut a hole below the tape mechanism?

#9 Gluecifer

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Posted 24 October 2009 - 03:53 AM

Ok Norm, I'm on it!

Just got mine open. It was locked up entirely, heads were engaged and none of the buttons were doing anything.

This was my method.

Get something like a butter knife with a reasonable flex and run it under the left edge of the door and up. You need to make the door flex a bit so a bit of force is required. When you wiggle it right you'll catch it on the clip that holds the door front in place and you'll be able to slide it up and off.

I found that now I could get access to the reel spools I just got a flat tip screw driver wedged between the spool and reel so I can manually turn them. This eventually got it into neutral with the heads disengaged and everything opens and shuts as it should.

Mine's still rooted, however, and won't get any further.

Here's some pix:

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Posted Image

Hope this helps, Norm. If you need more of anything else specific let me know.



Rock On.

#10 Superduper

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Posted 24 October 2009 - 02:05 PM

HI Glucifer and Thanks a bunch. I think these pictures are much more helpful because the vertical positioning is much clearer now. I'll give it another try tonight.

A couple of questions: If I understand you correctly, the goal is to try to slide the door cover off the metal frame and not undo the spring latch, right? If so, what is the purpose of the butter knife? Is it to hook the door clips and if so, then why are we only working on the left side? It looks like there are 2 door clips (right and left)?

#11 Gluecifer

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Posted 24 October 2009 - 07:20 PM

You need the knife to lift the door up to give it enough clearance to slide up. It's a tricky little thing because it's recessed in a bit. The knife will life the door up and push the catch up. The catch goes deeper than the door frame so the knife will hit this as it moves up and slide it off.

It sounds more complicated than it really is though!

Good luck Norm!



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#12 monchito

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Posted 24 October 2009 - 07:36 PM

i belive that the conion c100 would have benefited from that as most had there cassette doors blown off just to get to the deck :lol: :lol: :lol: :lol: :yes: :yes:

#13 blah blah

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Posted 24 October 2009 - 09:37 PM

nice pics gluecifer, see i didn't steal you thunder bro! :-) much easier to see what is going on. your description is good too, seems harder than it is but very hard to explain.

hope norm gets it open...don't cut a hole norm :sadno: , it really will open, it is a very wiggy little area and the door has more flex than it seems, and don't smash it either!

i think i may have gotten luck by actually prying the door down far enough that the catch slipped up. it was impossible to see so indeed was probably luck...but can be done.

#14 Superduper

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Posted 24 October 2009 - 11:49 PM

:clap: :clap: Yippee, Hooray! :clap: :clap:

Got it open guys! Thanks a bundle. :bow: :bow: You guys are da bomb!

OK, I figured out that there is no way in hell of hooking and releasing the door latch -- it is firmly locked in place when the heads are up. That's why I wasted hours yesterday night trying to jimmy the latch -- that path is a no-deal. The only chance of getting the door off was to slide off the cover. Had this been a panasonic, the door clips would've been snapped off on the first try.

What I did was
(1) put a big wide flexible putty knife at the top and pried the door outward.
(2) put a stiff putty knife on the bottom edge and pried the door upwards.
It popped off successfully. I'm not 100% convinced however, that this would be an official recommended repair technique because I do think that if practiced regularly, some doors are gonna break. It's a little risk, no question.

Anyhow, I'm just glad this door opened successfully. Now, the fun begins.

#15 blah blah

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Posted 25 October 2009 - 12:56 PM

excellent. it is not a factory recommended technique indeed but at least you got. :thumbsup:

#16 Gluecifer

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Posted 18 November 2009 - 04:02 PM

Any updates on this yet Norm?
My SK-550's still in pieces, waiting for your intstructions!



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#17 monchito

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Posted 18 November 2009 - 04:11 PM

glue i think he already put his back together :yes: :yes: :yes: : :-)

#18 Superduper

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Posted 18 November 2009 - 04:38 PM

Hey guys, sorry about that -- didn't know anyone was waiting for a fix. Actually, mine is stil in pieces. I found the problem though -- there is a solenoid that keeps the FF and RW from releasing. The fix will actually take some troubleshooting and then waiting for parts. Without a service manual, it makes it a bit harder since I can't do any troubleshooting from the desktop. Rather, I have to actually look at the PCB and try to reverse engineer the intentions. The problem: Space. I need a workspace that will allow this guy to be disassembled for at least a week or two while I wait for parts. This guy doesn't have a internal chassis like other boomboxes so once apart, it will be all over the place.

My guess: There is a power transistor that powers the solenoid. I haven't found it yet. My guess is that it's shorted. This solenoid is for the AMSS search feature. During the search function, it actuates to hold the FF and RW in place. When it deactivates, the FF or RW will stop and allow the normal play function to resume. Since it's on all the time, the stop function does not work.

Other possibility: This one is more problematic but less likely since this circuit uses low signal levels instead of the power transistor circuitry which for obvious reasons, is more prone to failure. I'm talking about the AMSS search feature circuitry. Without a manual, there is no way to diagnose or fix this, if it indeed is the problem. But if it is constantly sending an activation status signal to the solenoid, then obviously, the solenoid will always be engaged and prevent the stop function from working correctly.

The WORK-AROUND: Good news. If your SK-550/SK-750 is having this problem, merely disconnecting the solenoid will permit normal tape functions. Obviously, the search feature will not work. But at least you can use your boombox normally otherwise.

Try the workaround Glucifer and let me know if this works. Someday, I will find out which transistor is causing the problem and if I find a solution, I'll let you know.

#19 monchito

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Posted 18 November 2009 - 06:10 PM

norm now that you mentioned that that might be probably the problem because i remember that my sk-95 deck stopped working one day and it turned out to be a transistor :yes: there was a small selenoid that was supposed to open it stopped so i desmantled the deck and there was 1 transistor on the deck board that was it ,, i know they are not the same deck but there might be a slight posibility that it may be that also :yes: :-)

#20 Superduper

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Posted 18 November 2009 - 09:03 PM

The deck itself has no electronics on the sk-550. There is a solenoid but that is connected to and powered by the mainboard. I see what looks like several larger power transistors in that vicinity so one of them probably powers the solenoid. The question is whether the transistor is shorted or whether it is switched on because the source signaling circuitry is not behaving normally.

The problem for me is that this pioneer is built kind of like a lot of panasonics. The case back serves as the chassis including the mounting place for the circuit board. You can't just unplug the mainboard. Lots of wires tethered by soldered connections. No problem except that once I get it apart completely and remove the transistors for testing, I'll probably not want to reassemble everything until I get the parts. Right now, I just don't have the space to have a boombox completely in bits for a week or more. BUT, I know that simply disabling the solenoid will allow the deck to work normally. I know this because with the deck removed from the boombox, I tested it with a 9v battery and all functions including STOP works normally. It' s only when it's hooked up to the boombox does the solenoid activate (I only powered the capstan motor on the bench) all the time. So, remove or disable the solenoid and 99% of the functions are restored.

#21 monchito

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Posted 18 November 2009 - 09:18 PM

well the seleniod has its use if not they would have not used it but on the sk-95 and the 61,71,31, and the 900 they all use the same deck so it does need the selenoid for the songfinder and autorepeat so the deck has a small board on the deck itself with has the transistors for the seleniod plus a couple of microswitches thats why i thought it might be simular even though i did not think it had the autorepeat or songfinder feature......

#22 Superduper

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Posted 18 November 2009 - 09:45 PM

Ramon. That is true. If you read my other post more clearly, you'll see that I mentioned that the solenoid is used for initiating autostop during the music search. But right now, it's probably more important that the deck does not lock up, which is what happens when the solenoid engages but won't release. So you are right, disconnecting the solenoid will result in the music search feature being not-operational but at least the deck won't lock up, and you can play, FF, RW and record normally. Of course ideally, fix the issue causing the driver transistor to switch on will fix the problem properly.

#23 monchito

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Posted 18 November 2009 - 09:52 PM

well once you get her up and running let us know how it goes for you those 550 are really nice and hard to come by :yes: :yes:

#24 Gluecifer

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Posted 19 November 2009 - 01:12 AM

Awesome Norm!! Your work is greatly appreciated!

I'll attempt to locate and disconnect the solenoid on the weekend then. I don't mind not having music search, like you say, it's the basic deck functionality that is the main thing!

Thanks again, really marvellous work on your behalf!



Rock On.

#25 monchito

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Posted 19 November 2009 - 06:34 AM

glue there you go man :yes: :yes: so now you know once you get her running let us know :yes: :yes: if not i will be waiting send it down this way :lol: :lol: :lol: :lol: :lol: :lol:

#26 Gluecifer

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Posted 21 November 2009 - 03:30 AM

Well, I took mine apart. Had a look around the mech, manually rotated the wheel a few times to get it into neutral, and then powered her up.

Much to sheer amazement everything started working. All the decks functions, including the music search, are going like clockwork. I let it run for a while, and apart from a bit of hum when the deck isn't going in the right channel (any ideas?) it's all rockin! I really have no idea what I did, apart from manually rotating the deck, but I'm very happy regardless.

How long this will last, I don't know however, and as I couldn't find the solenoid you mentioned, Norm, I'd reallllly appreciate a photo of it or instructions of where to find it, whenever you get around to doing yours.

Been a lucky day on the blasters today, I also slipped while adjusting the head azimuth on my C-126F and snapped a wire off the tape head a while back and I got that all resoldered and fixed up today.

So it's been a winning saturday!



Rock On.

#27 monchito

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Posted 21 November 2009 - 04:39 AM

you did good glue and the selenoid should not be hard to find in the deck mostly they sit on the outer corners of the deck plate and you will see 2 wires going to it it has a small coil shape a plunger or a plate :yes: :yes: :yes:

#28 Gluecifer

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Posted 21 November 2009 - 06:15 AM

Ohh I know that thing! I'm learning even more today then!

I thought that contraption was related to recording!

thanks heaps Ramon!



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#29 Superduper

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Posted 21 November 2009 - 06:58 AM

Hey Glue, that solenoid is in the rear of the deck mechanism. When activated, it locks the function slide levers and prevents manually stopping the FF or RW modes. When I had mine apart, I could get the solenoid to deactivate by touching or slighly tapping on the power transistor that is secured at the heatsink directly behind the tape mechanism on the left side. Touching the large capacitor and the transistor could cause sufficient change in capacitance to cause this to happen. I suspect that this is the transistor that is powering the solenoid but I don't want to guess. Anyhow, if it's all working, then congratulations. However, if it locks up again when it's all reassembled, will it present a problem disassembling it once more?

BTW, the hum you are experiencing is tyically a symptom of an ungrounded head cable shield. Since you broke the leads, maybe it's related. Also, you may want to clean the record bar (the long bar mounted on the PCB). If it has poor connection, it could manifest like an ungrounded cable. Of course hum could also be evidence of an issue in the amp or preamp. If that is the case, re-capping the box would usually take care of it.

#30 blu_fuz

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Posted 31 August 2010 - 06:19 PM

For such a simple looking box there is a lot going on in the cassette area. I hate that there aren't quick connectors on all wires, just makes working on these more frustrating.

You guys gave such great directions to open the door that I got mine in less than 5 minutes :thumbsup: .

But now I need to get the heads down on mine too and I don't understand the "wheel cranking" you guys talk about. Can any of you describe what I need to do? Thanks a lot for the help!