Author Topic: I think I might've killed my astro sonic. :(  (Read 4893 times)

kyuubethe3rd

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Re: I think I might've killed my astro sonic. :(
« Reply #15 on: July 27, 2015, 10:21:02 PM »
:(

I disconnected the balance potentiometer, no change.

I flipped the newly installed caps on the speaker couplings around, made it semi-worse. :(

I really hope this doesn't mean abandon ship, I guess I'll see after getting some new caps. I don't wanna declare this over yet!

Hate to get emo on you all, but I'm starting to give up hope.

Alan Maier

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Re: I think I might've killed my astro sonic. :(
« Reply #16 on: July 27, 2015, 10:55:11 PM »
Well there you go! Compare the two part by part. Pay special attention to capacitor polarity and I bet you find your problem.


Be sure to check those connections Duce67US pointed out.

As for the other chassis having 200uf speaker coupling caps, likely a variation for that cabinet and woofer used. With an 8 ohn load, that would start a roll-off up around 100 Hz - so it may have come from a console with smaller woofers or due to some cabinet reason, had a resonance issue. So a variation of the chassis was made for it.  I see that with certain cabinet styles where due to various reasons, a smaller woofer is used in cabinet style than other models of the series and other cabinets.

The biggest shocker I ever saw was a post Astro-Sonic, high-end model to the point it had a separate power amp. Normally that series had a 10" three-way air suspension speaker system using cone midrange and tweeters along with a really robust high compliance woofer. But this one, in French Provencal  had the 8" free air woofer and no tweeter, just the 5" midrange Magnavox used forever - basically the speakers of those little space saver economy consoles. Funny thing was, it actually sounded pretty good! I bought it at an estate auction of a Magnavox engineer (I am in Fort Wayne) and guessed  he had a special order done knowing those speakers would sound better.

kyuubethe3rd

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Re: I think I might've killed my astro sonic. :(
« Reply #17 on: July 28, 2015, 12:00:00 AM »
Well there you go! Compare the two part by part. Pay special attention to capacitor polarity and I bet you find your problem.


Be sure to check those connections Duce67US pointed out.

As for the other chassis having 200uf speaker coupling caps, likely a variation for that cabinet and woofer used. With an 8 ohn load, that would start a roll-off up around 100 Hz - so it may have come from a console with smaller woofers or due to some cabinet reason, had a resonance issue. So a variation of the chassis was made for it.  I see that with certain cabinet styles where due to various reasons, a smaller woofer is used in cabinet style than other models of the series and other cabinets.

The biggest shocker I ever saw was a post Astro-Sonic, high-end model to the point it had a separate power amp. Normally that series had a 10" three-way air suspension speaker system using cone midrange and tweeters along with a really robust high compliance woofer. But this one, in French Provencal  had the 8" free air woofer and no tweeter, just the 5" midrange Magnavox used forever - basically the speakers of those little space saver economy consoles. Funny thing was, it actually sounded pretty good! I bought it at an estate auction of a Magnavox engineer (I am in Fort Wayne) and guessed  he had a special order done knowing those speakers would sound better.


Ah, I see. I guess I should have figured as much. I have bigger side woofers, so I guess ordering those 200uf caps was a bit foolish of me(?). I just replaced the crossover network caps to great success a few days ago. Those are easy since they're bipolar.

I guess if the 200uf caps don't work out and I have to go back the same 250 UF ones I got, I got a question, which side is negative and positive (there's an arrow, but I don't know where its pointing to)?
here's a pic of the cap I was working with: https://dl.dropboxusercontent.com/u/62158991/2015-07-28%2000.44.50.jpg

Also interesting story about that post astro sonic, I'm sure it looked nicer than the one I have!

I'm hoping I can get this worked out without sending this to someone! I guess speaker couplings are just not for me! (either that, or I just need to get a solder vacuum like a hakko FR-300).


Pat L

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Re: I think I might've killed my astro sonic. :(
« Reply #18 on: July 28, 2015, 08:32:27 AM »
The arrows always point to the ground. The positive side will be the side that's insulated. Typically the positive lead is longer.

kyuubethe3rd

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Re: I think I might've killed my astro sonic. :(
« Reply #19 on: July 28, 2015, 08:02:52 PM »
I thought Axials had equally long leads...? I guess I thought wrong. Hm.

So the black side is the positive side and the metal-ish side is negative, correct?

I just thought of something today, do those resistors fail after you put so much heat on them? I feel like I might have burned them out, but maybe I'm just over thinking it - those speaker couplings are a pain to desolder and resolder. :x I bought some alligator testing wires, so I should be able to get better readings with my fluke.

Can I leave the balance potentiometer unplugged? I feel its useless if I can't use it normally.

Also, dumb question, can I put bipolar caps in the speaker couplings or no?

Alan Maier

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Re: I think I might've killed my astro sonic. :(
« Reply #20 on: July 28, 2015, 10:48:14 PM »
Axials often are equal, radials always have a longer positive lead to aid in assembly. As for the black side, you really need to follow the markings just to be on the safe side.


I think you can leave the balance pot out of the circuit, but once you are fixed and running, it won't hurt a thing.


Indeed you can roast those carbon resistors. So it's worth a check with the meter just in case.


Naa - don't use bipolars for speaker coupling. A bi-polar is actually 2 capacitors in one - one in each polarity direction. For speaker coupling, you are really blocking DC from the amp. If you measure voltage ahead of those speaker caps, you'll have half of the B+ voltage present there. It's just that the value is set to also provide a suitable roll-off. On component audio from that era that is designed to be flat to 20Hz, 1000uf to 2000uf is common. Magnavox (and others) just took advantage of the need for a coupling cap and also rolled off the amp to compliment the speakers. I was once restoring a beautiful Fisher that had a variant of a component receiver installed - but they installed low value caps to kill the low bass. Very nice detailed sound, but they killed the bass to prevent feedback to the Dual changer with a magnetic cartridge.

kyuubethe3rd

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Re: I think I might've killed my astro sonic. :(
« Reply #21 on: July 29, 2015, 01:14:52 AM »
Ah, I guess that explains it.

Anyway, some discoveries I made. I was playing around with the spare amp i got for parts, cleaned its pots, and it worked great, but I discovered something interesting, when I reverse the plug, that hum comes! (I still think its because my house was improperly wired - long story) of course, its the same level of hum.

So I guess that amp has the same "problem" too. I'll have to record the hum and see what y'all think.

I think I blew out those new caps, I shouldn't be surprised (one measured at 210, and the other at 225), oh well. I'll have to downgrade them to 200uf due to cost reasons.

I guess I'll ask some questions since I'm thinking about it:

Why do the old caps I have pulled out the amp measure higher than they're rated? Does this mean they're still good or does that mean they are unusable?
(Example: https://dl.dropboxusercontent.com/u/62158991/2015-07-29%2000.40.40.jpg - this is the best picture I took, and if you can't read what it indicates its 453.07UF)
This is something that's always bothered me for the longest since I started this journey.

I broke this component, and I don't know what its called, its on the radio part of the chassis
Pic: https://dl.dropboxusercontent.com/u/62158991/2015-07-29%2000.34.56.jpg
Pic2: https://dl.dropboxusercontent.com/u/62158991/2015-07-29%2000.35.26.jpg
is this part still being made?

Also, there's a lamp issue I have, the stereo lamp is dim to the point where I can't see it light up. What bulb do I use instead or is the socket dirty...?

Sorry for the barage of questions, I do appreciate the help sincerly!

I'll update again when I get the caps and when I install them.

Duce67US

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Re: I think I might've killed my astro sonic. :(
« Reply #22 on: July 29, 2015, 05:57:24 AM »
I think I blew out those new caps, I shouldn't be surprised (one measured at 210, and the other at 225), oh well. I'll have to downgrade them to 200uf due to cost reasons.

Cap tolerance is generally +/- 20%      250uf @ +/- 20%  is 200uf to 300uf.    Personally, I like 10% or less tolerance.

I guess I'll ask some questions since I'm thinking about it:

Why do the old caps I have pulled out the amp measure higher than they're rated? Does this mean they're still good or does that mean they are unusable?  This is something that's always bothered me for the longest since I started this journey.

No, IMHO they should be replaced.
My theory is that older caps often shift higher due to the different dielectric used.    Over the years, the formula changed.   Some cheap modern formulas have worked their way into the market, and quite often they fail in the other direction.   Often times they will show themselves by swelling up and leaking dielectric out. 

I broke this component, and I don't know what its called, its on the radio part of the chassis
Pic: https://dl.dropboxusercontent.com/u/62158991/2015-07-29%2000.34.56.jpg
Pic2: https://dl.dropboxusercontent.com/u/62158991/2015-07-29%2000.35.26.jpg
is this part still being made?

You are going to need another radio chassis.  You might get away with robbing one out to replace that part.  Even better would be to just use the 2nd radio chassis.  It is most likely a tuning component in the RF circuit, and after you replace the original, you would need an alignment.   It may prevent AM, FM or both from being properly tuned, depending on the location of the bad part.   
Check the SAMS for the section "Alignment Instructions"   

Also, there's a lamp issue I have, the stereo lamp is dim to the point where I can't see it light up. What bulb do I use instead or is the socket dirty...?

Lamp values should be listed on the bulb base.    If you have the SAMS, it is also listed in the parts section.

Alan Maier

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Re: I think I might've killed my astro sonic. :(
« Reply #23 on: July 29, 2015, 11:26:59 PM »
Indeed this might be the time to swap to the second chassis and restore it, using the knowledge you've picked up with the one that isn't so healthy anymore.  I recommend changing a cap at a time to ensure correct polarity. For as many as I have done (Astro-Sonics and receivers in general) I still limit myself to how many caps I pull before I insert the replacement. I usually do it one-by-one or pair-by-pair when dealing with a stereo board like the audio driver board.


I recommend gluing that coil on the multiplex decoder board you use as it really is fragile and very much in the way. Better to glue it around the base now to reinforce it than repair it. You won't need to adjust it as once you recap the MPX board you'll have good FM stereo, but you want to stiffen it as it's way too easy to bump it when installing the chassis back into the console.

Don't fret over the stereo lamp. Important tip - it is not the same voltage / amperage as the dial lamps. The stereo lamp isn't bright when fully aligned, so I just am sure to move it close to the white stereo indicator when I assemble the chassis into the cabinet.  Stereo lamps on Astro-Sonics nearly always last the life of the console even past a full rebuild. I've replaced countless dial and front pilot lamps, but I can't recall ever replacing a stereo lamp.


I'd definitely check your AC outlets!


You'll get through this, and enjoy the console for years and years to come.

kyuubethe3rd

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Re: I think I might've killed my astro sonic. :(
« Reply #24 on: August 01, 2015, 12:45:58 AM »
So, I got the new caps.

Eliminated my hum problems!

However, 2 new problems have come up! Its always something!

The volume knob is scratchy again! I didn't have this problem after drenching the controls in contact cleaner.

I seem to now have a distortion problem now, could this be caused by 200UF caps? I got rid of the hum, but now something isn't right!

I seemed to have lifted pads or traces, could this be my issue?

So much for meeting my deadline. This has been a whack-a-mole scenario fo sho. :|

kyuubethe3rd

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Re: I think I might've killed my astro sonic. :(
« Reply #25 on: August 01, 2015, 02:55:14 AM »
here is the burnt traces in question. Could this be my scratchy volume and distortion (its in one channel) issue?

PIC: http://gyazo.com/0c7190daef9bf846af04f4b3bbfdc590

If the traces are bad, which parts should I insert jumper wires to?

I was so close to making this thing sound right! Where did I go wrong?

Alan Maier

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Re: I think I might've killed my astro sonic. :(
« Reply #26 on: August 01, 2015, 03:22:18 PM »
Ahh  - key you are getting closer!


First thing is clean up the board. I use 91% alcohol and a Q-Tip. Once the solder work is clean, you can inspect much better for cracks and breaks in the traces.


If you have a damaged trace, simply solder in a wire lead, say some clipped off a resistor or capacitor, and try to loop it around a component for the best connection. I'd use some solder wick to pull off solder from the lead sticking through the board for the best connection - then reflow the trace.


As for the distortion problem, does it sound like clipping? You might have an issue with the speaker coupling caps reversed and passing half of the waveform.


Two things can cause a scratchy volume control. One is simply needing cleaned again. I use Caig DeOxit in 2 strengths (to save money - I use the 100% only when I really need it) as well as CRC QD for a really good flush. Sometimes the corrosion continues to flake off and a recleaning is needed. The other cause is DC present at the pot, which would be a cap problem. I'd definitely do a second cleaning. Running into the same thing with an Imperial I am restoring but is on hold. Cleaned the pots, then the volume pot picked up static again! Catch is, for the era I am working on, removal of the chassis was via screws in the changer area and below... and on an Imperial, the "blow" hex head screws are inside the sealed speaker enclosure. So it' about 20 hex head crews to remove the right channel plywood speaker cover to get to the 2 lower screws! UGH!

kyuubethe3rd

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Re: I think I might've killed my astro sonic. :(
« Reply #27 on: August 02, 2015, 01:39:13 PM »
Good news! I eliminated my hum problems and scratchy volume problems!
Bad news... I ended up scrapping the original chassis. I was bummed I had to do it, but the newly rebuilt chassis fits into the cabinet like a glove. Plus its the same chassis model number, so its not like it doesn't match the cabnet model numbers (I have a 1ST-622A)

I did something that is probably a bit ghetto, but what I did was I used the original leads that were on the original capacitors on the speaker couplings and I made a knot on the leads of the new caps and put a dab of solder on the leads, so yeah, this thing is almost ready to be shown off to the people I bought it from! Now to get the micromatic back (I sent it out because I couldn't fix it myself and it was making me all sorts of mad)

The hum is still there when I flip the plug but its very minute and I don't really hear it in quiet songs anymore.

Like I said, I'm glad I found this forum and I wish I found it when I was first starting out, I'm also really kicking myself for not getting a multimeter sooner, it would have saved me many headaches and guessing.

Now to just clean the radio part and it should be ready to rock for 20 more years!

Alan Maier

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Re: I think I might've killed my astro sonic. :(
« Reply #28 on: August 02, 2015, 07:18:14 PM »
Great! Don't feel bad about swapping chassis - especially when it's the same chassis. The original one just was so buggy that it was the right move.


Now go rock the house!!!

hermitcrab

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Re: I think I might've killed my astro sonic. :(
« Reply #29 on: May 11, 2016, 02:52:38 PM »
I maybe wrong, but the main 400 uf caps to the speaker outputs the positives should be to the speaker outputs.... looks like you have one right and one backwards? I could be wrong , but that is how mine is wired
Elton