Assessment/advice on a sx-727

[33&athird]

Hey all, I recently bought a sx-727 from e-pray (I know, I know), and surprisingly, it arrived safely. I paid somewhere around what I belive to be fair-market value (including shipping), and that's not a big deal, I never get scores or whatever to brag about. The problem comes from the unit itself.

Cosmetically its around at least 9.5/10, everything is mint (minus some dust), and everything is original...hasn't been touched in 37 years...and thats the problem. The left channel appears to be working (as far as amplifing), since when switched to mono, both play through the speakers...but in normal mode, the left channel is absent. I had some luck moving buttons and switchs around to get the left working, but even then it was intermittant. I assume that deoxit would fix this, but being new to actually repairing units (my 525 was fine from the get-go), I want to be sure I get the right stuff.

The other concern is also over the 37-year old thing, the capacitors. I would like to recap it, and I downloaded the service manual to get the values. My father does not see the point of recapping, since "hes never replaced a cap for anything", But from what i've read, this could greatly improve sound. My 525 may need it to, but that can wait. The reason the re-cap came up is because the sx-727, from my inital listening (one channel out, bear in mind) was not a great improvement on the 525, maybe it shouldn't be...I did not know what to expect.

Now, as not to post a standard recap-deoxit thread, a different question; This was advertised as working/sounding great...So, this is false advertisment, and since I just now got it, I could potentially deal with it and get a different unit later. My dad belives this to be the correct course, although I think I wouldn't run across one in this overall condition for a long time. From what i've read, a re-cap is easy, once you sit down and work on it, and de-oxit is not too hard, but you have to remove some boards.

So, what do you guys think? any advise or opinions on this receiver?

I could explain things better, if need be, since I generally write in stream-of-consious, and it can be difficult to get the point across.

Thanks in advance for any information, or insight into what to do next.

 

[mjennens]

Now, as not to post a standard recap-deoxit thread, a different question; This was advertised as working/sounding great...So, this is false advertisment, and since I just now got it, I could potentially deal with it and get a different unit later. My dad belives this to be the correct course, although I think I wouldn't run across one in this overall condition for a long time. From what i've read, a re-cap is easy, once you sit down and work on it, and de-oxit is not too hard, but you have to remove some boards.

So, what do you guys think? any advise or opinions on this receiver?

I could explain things better, if need be, since I generally write in stream-of-consious, and it can be difficult to get the point across.

Thanks in advance for any information, or insight into what to do next.

I'd contact the seller and see what he/she has to say. Other than that, I'd go the de-oxit & recap route; any older receiver has a good chance of needing both. The 727 seems to be a highly regarded receiver. As great of shape as it's in, if de-oxit will bring it back to life, you can't go wrong. If a recap helps, it's even that much better.
Mike

 

[markthefixer]

In a unit that old, to get something that is "better sounding", you will have paid for someone else to replace the capacitors before you bought it.

The fact that "moving buttons and switches around" got something out of the other channel proves a major cleaning is needed.

Also remember that a capacitor does not work "perfectly" until suddenly one day it dies and fails to pass sound.... it steadily gets worse.... then multiply that by an entire receiver's worth of caps.

The costs of the (good ones even) caps is rather low - and if you supply the labor for deoxiting (and recapping at the same time - it's just a bit more work at that point) yourself, it's a sweet deal.

 

[33&athird]

I'd contact the seller and see what he/she has to say. Other than that, I'd go the de-oxit & recap route; any older receiver has a good chance of needing both. The 727 seems to be a highly regarded receiver. As great of shape as it's in, if de-oxit will bring it back to life, you can't go wrong. If a recap helps, it's even that much better.
Mike

A good point, even some re-embursment (like for the cost of deoxit) would probably be enough for my dad to be satisfied with it. Honestly, if not for the shipping, it was a pretty cheap receiver. then again, shipping 31pounds is alot

In a unit that old, to get something that is "better sounding", you will have paid for someone else to replace the capacitors before you bought it.

The fact that "moving buttons and switches around" got something out of the other channel proves a major cleaning is needed.

Also remember that a capacitor does not work "perfectly" until suddenly one day it dies and fails to pass sound.... it steadily gets worse.... then multiply that by an entire receiver's worth of caps.

The costs of the (good ones even) caps is rather low - and if you supply the labor for deoxiting (and recapping at the same time - it's just a bit more work at that point) yourself, it's a sweet deal.

I figured that was the case, I think I got lucky with the 525 not needing to be cleaned (I think it still has the old caps, but sounds fine). I assume that what i'm looking for is De-oxit and Fader-lube?, I will check on the topics concerning that. As for the capacitors, should I do every capacitor, or just the power section, amp boards, etc.? On that note, would the service manual have the correct ones?, From reading other topics (like the sx-780 repair , I think?) It seems the only way to be 100% sure about the caps is to manual go through and write down the values:scratch2:.

I'm not too concerned with replacement, but getting to the boards seems stressful, since I don't want to misplace or break anything digging around, But it seems like just about anyone can do it, so I should be able to. I'm majoring in electronics, but yet, on certain projects I still get nervous with the soldering iron. Actually the thing im most concerned about is getting to the potentiometers, they seem really nestled into the faceplate:sigh:

On the note of the sound, I don't know what I expected, especially since the 727 is just 2 steps up from the 525, although they use parts, the amplifier section is actually very similar. If nothing else, it sounds very very good (to my ears at least...so far), and the build quality is astounding.

thanks for the input, I feared it was a cleaning thing, but I assume that's better than some weird transistor going bad...

 

[Mark W.]

You might get your purchase price back from the seller but you will pay the shipping both ways and that will more then likely be a BUNCH of money.

I have had a number of my Pioneer units recapped and other maintainace work done and the return is amazing.

Think of your 727 as a 1972 Nova or Mustang that no one has changed the plugs or oil for 35+ years. While it's still limping around. think what it will be clean and firing on all cylinders

 

[33&athird]

You might get your purchase price back from the seller but you will pay the shipping both ways and that will more then likely be a BUNCH of money.

I have had a number of my Pioneer units recapped and other maintainace work done and the return is amazing.

Think of your 727 as a 1972 Nova or Mustang that no one has changed the plugs or oil for 35+ years. While it's still limping around. think what it will be clean and firing on all cylinders

Good analogy, but i'm freaked out. ara: We happen to have a 1968 mustang that hasn't had new plugs, since probably around the late 70s, so that statement hit amazingly close to home :yes:.

I don't really think this warrants sending it back, since shipping this way was $30, and even with a refund, i'd only come out $20 ahead, unless he covered shipping (don't think so), for $81 (total), which is pretty fair market value, I think it's not bad, especially if the repair material can be used for other projects.

I am looking forward to hearing this in its prime:yes: From what I can gather from the sellers listing the estate sale, the owner had a sx-727, pioneer cs-99a's and a garrard zero 100, so the guy who bought them really lucked out.

 

[markthefixer]

Just the electrolytic caps, 1 microfarad and up with a few exceptions in the 0.1uf to 1uf range.

They are water based, and water escapes over 30 years. And like a car battery drying out, they get worse and worse and finally conk out.

We aren't throwing you to the wolves here, get the service manual, use it to make a starting list, then visually verify that those values are actually used.

THEN post the list here, in the format:
aaa-999 cx xxuf xxv cxxxxx
and I'll inhale it into a spreadsheet, get parts numbers for them, and post the results. Since it's easy - I'll also massage the parts numbers so that they can be lifted in bulk with mouser's bom entry tool and save you a lot of typing.

aaa-999 is the board number like awf-072 etc
cx is the pat designation like c1, c34 etc
xxuF microfarads of cap
xxv voltage of cap
cxxxx is a code (cea, ceanl, etc ) that describes "flavors" of electroltyics.

 

[33&athird]

Just the electrolytic caps, 1 microfarad and up with a few exceptions in the 0.1uf to 1uf range.

They are water based, and water escapes over 30 years. And like a car battery drying out, they get worse and worse and finally conk out.

We aren't throwing you to the wolves here, get the service manual, use it to make a starting list, then visually verify that those values are actually used.

THEN post the list here, in the format:
aaa-999 cx xxuf xxv cxxxxx
and I'll inhale it into a spreadsheet, get parts numbers for them, and post the results. Since it's easy - I'll also massage the parts numbers so that they can be lifted in bulk with mouser's bom entry tool and save you a lot of typing.

aaa-999 is the board number like awf-072 etc
cx is the pat designation like c1, c34 etc
xxuF microfarads of cap
xxv voltage of cap
cxxxx is a code (cea, ceanl, etc ) that describes "flavors" of electroltyics.

I phrased that wrong, I knew not every cap would be replaced (otherwise it would take months), looks like instead of being a electronics major, I should go into english. I just finished digital today, and it's spoiled me, since everything is +5 or ground, I should go back into devices, or refresh my memory:yes:.

I'll start the cap list tomorrow, and visually verify...sounds like fun. I wouldn't mind being "trown to the wolves" a little, I can't imagine it being much fun compiling list for mouser/digikey for all these caps:scratch2:, I will be much in your debt.

With all the help and information on here, I think i'll try to be a subscriber by the end of the year. Textbooks are $100+, a subscription is $20, and i've gotten alot more information, and assistance here at ak. Thanks alot guys!

Edit: out of curiousity, while i'm in there, would increasing the power supply filter caps have any benefit, I imagine it would be easier to find the proper size with a larger uf cap, but am unsure of the inrush current that could result. I think the caps are 6800uf, which sounds like enough for whatever demand they have...or should I just leave it be:scratch2:

 

[markthefixer]

I inhale it into a spreadsheet, sort it by microfarads and voltage, and then split screen up MY parts lists (which are also in house) which are also sorted by microfarads and voltage - glom onto the part numbers and specs columns and paste them as needed onto the target list. I also grab a list of just the parts numbers.

Next I run on over to the mouser site and plug in the parts list to see if any end up back ordered, and correct as necessary.

Then I restore the old order of the parts list, and repost it with the corrected part numbers and spec additions and tack on that parts number list I grabbed that eventually worked 100%.

A LOT faster than the old ways... this is the result of years of refinement of technique and a dislike of spending unnecessarily long times on doing such.

You do a lot of the hard stuff, but HAVE to, to be sure of the correct initial values.

And I DO keep a copy.

 

[33&athird]

Alright, I'm about to start taking in all the notes and working stuff out, I would have started today, But a late math class and doing some work slowed me down. I wanted to double check some other things before getting all reved up;

For one, The standard de-oxit is what I need, correct? I went to the Caig site, and they have a ton of products, I assume I don't ned to account for abc plastic or anything like that. Also, I've heard of faderlube...do I need that as well, or will the de-oxit be alright on it's own.:scratch2:

When the unit starts up, the relay clicks after a couple of seconds...seems to be correct, right? my understanding is that the relay breaks contact when a problem arises. Also, I assume its in there to avoid some of the speaker pop from the startup, Am I correct in these assumptions?, I have read about relay protection a little, but not alot, since my 525 does not have one.

And one other technical detail...when the volume control is all the way down (counterclockwise) I can still hear sound, very little, but noticable...Is this normal, maybe connected to the potentiometers current state, or does it imply something different is wrong with the unit?

 

[markthefixer]

deoxit d5s-6 is what I use
faderlube f5s-6 is what I use on ANY pots afterwards - or the carbon element will be subject to unlubricated premature wear-out from the slider.

your protection assumptions are correct, and it uses the 7vac lighting power to determine the power's status. Thus if the light fuse goes, so does the protection. Protection does suppress pops - but it's main purpose is to eliminate house fires.

pull the back jumpers and see if you can still hear it.

 

[33&athird]

deoxit d5s-6 is what I use
faderlube f5s-6 is what I use on ANY pots afterwards - or the carbon element will be subject to unlubricated premature wear-out from the slider.

your protection assumptions are correct, and it uses the 7vac lighting power to determine the power's status. Thus if the light fuse goes, so does the protection. Protection does suppress pops - but it's main purpose is to eliminate house fires.

pull the back jumpers and see if you can still hear it.

Alright, still need to test the volume issue, but I started documenting the caps, and already ran across some oddities. Here's a couple of things I don't get:

The protection board is a AWM-027 (a later adaptation of the AWM-011), and it has these very small caps, and judging by the value/board symbol, they aren't electrolytics...I think, they look atlot like it though. On that board are 4 other caps, two are correct, and the 4.7uf one is correct, except for voltage. I'm guessing I should write down exactly what I see, since I think this is a factory-standard deviation from the manual, I belive the other caps are correct.:

And this one puzzles me, I looked in the manual, and it doesn't seem to list the cap, unless they count it as being tied to one of the boards. The bigger mystery is the fact that the manual doesn't even have the terminal strip being there...maybe they left it out of the image?...I also assume its original, since it has the same lead casing as some others...but I have no idea what its doing where it is. I belive its tied into the chassis ground from the power amp board, but am unsure.

Edit: I had written all of the electrolytics down, and this one is not in the list at all, maybe it has a higher voltage rating than what its supposed to be?, i'll try to sort it out with some research...

I'm going through the amp and checking all the others, as well...so far the power supply is fully "correct", but i'm going to have to move some stuff to check everything out. Needs a little dusting as well.

Out of curiousity, there is a metal perforated "cage" on top of the heatsink area...what is this for? it seems like maybe it helped dispell heat a little, but I don't know. I don't think it would keep out radio frequencys from the power amp board, but maybe it does .

I'm going to order the caig stuff tonight or tommorow, and ill test it with jumpers out later tonight. Hate to ask so many simple questions, But i'd perfer to get it right the first time...and while I know some of the stuff I always seem to second guess myself when I get into this kind of stuff.:scratch2:

Thanks for the assistance:yes:.

 

[markthefixer]

last in first out:
better questions than smoke

cage is for fingers/safety - dropped on later models, the cases of the transistors are at +50v or so and -50v or so (i didn't look it up), get between them and your body resistance isn't enough at times....

re: terminal strip cap, hmmmm, need to see where the wires go...

2 little blue caps in the boxes - could be "solid aluminum" caps - which are like tantalums - they DON'T like reverse polarity and don't fail gracefully. What are their values? 0.056 or 0.22 ? either way - a film cap will shrug off reversals etc.... and last forever.. which is what I am recommending EVEN though a reversal at that point is super unlikely - but for other reasons they fail shorted too.
They are "traditionally" considered part of the protect circuit, for "overcurent - and the only way a failure shows is when it amp DOESN'T protect out in extreme current circumstances.


oh, and electrolytics can be found down to and below 0.1uf - usually it's a space issue - they're small.

 

[33&athird]

last in first out:
better questions than smoke

cage is for fingers/safety - dropped on later models, the cases of the transistors are at +50v or so and -50v or so (i didn't look it up), get between them and your body resistance isn't enough at times....

Ah! that makes sense...though it's weird, I guess my model was made before they took the cage out, but after the protection circuit change...

re: terminal strip cap, hmmmm, need to see where the wires go...

I'll whip out the fluke and report back tomorrow, there are quite a few orange wires in that area, and its hard to differentiate between them.

2 little blue caps in the boxes - could be "solid aluminum" caps - which are like tantalums - they DON'T like reverse polarity and don't fail gracefully. What are their values? 0.056 or 0.22 ? either way - a film cap will shrug off reversals etc.... and last forever.. which is what I am recommending EVEN though a reversal at that point is super unlikely - but for other reasons they fail shorted too.
They are "traditionally" considered part of the protect circuit, for "overcurent - and the only way a failure shows is when it amp DOESN'T protect out in extreme current circumstances.

Yeah, there in the protection circuit, and I can see their use there...I belive they are .22...but i'll double check.

oh, and electrolytics can be found down to and below 0.1uf - usually it's a space issue - they're small.

Hmmm...must be unusual to run across one, I knew I was concerned when I was writing down .5uf caps...I think this unit has 3 or 4 of them, my dad was thinking that 1uf was about the lowest, or at least the lowest standard value.

Again, thanks...this unit is worth it just from what i'm learning on it, and the results should be great as well.:yes:

 

[markthefixer]

if this link works:
http://www.mouser.com/Passive-Compo...word=aluminum+electrolytic+capacitors&FS=True

you'll see values below 0.1uf.....

 

[33&athird]

if this link works:
http://www.mouser.com/Passive-Compo...word=aluminum+electrolytic+capacitors&FS=True

you'll see values below 0.1uf.....

wow, never relised they went that low. If the manual calls for a .5uf, I assume the .57, or next closest would be used? the manual seems to approximate/round off certain numbers (6 volts, rather then 6.3, for example).

I'll try to start wrapping up the capacitor stuff tomorrow...not looking forward to all the unscrewing to look at them all. as mentioned before, the build quality is outstanding, I can't belive it, the 525 is no slouch either. Would have been interesting to see the assembly line at the time, must have been a sight.

 

[fastbike]

Don't totally trust the manual

Manuals aren't always correct. If the unit is working, trust what is actually installed.

As for getting sound when the volume is down, that may be another sign of dirty pots. You should be able to get to everything you need without removing boards.

 

[markthefixer]

To get at the pots, you WILL have to "remove" boards MECHANICALLY - BUT they are MADE to stay electrically connected and slide out. The decorative front panel comes off, showing the chassis front panel where they are held by screws and threaded nuts on the pot shafts.

That will give you access (probably - unless additional plates come off) to the OPEN wafer connection area of the pot.

The X2X series were built like tanks.

I have an 828 open on the bench right now, thus I am SURE of what I say.

 

[33&athird]

To get at the pots, you WILL have to "remove" boards MECHANICALLY - BUT they are MADE to stay electrically connected and slide out. The decorative front panel comes off, showing the chassis front panel where they are held by screws and threaded nuts on the pot shafts.

That will give you access (probably - unless additional plates come off) to the OPEN wafer connection area of the pot.

The X2X series were built like tanks.

I have an 828 open on the bench right now, thus I am SURE of what I say.

woof, not looking forward to that...

Need to continue to go through the caps, I would/should have had it done by now, But i've had a rough couple of nights here...but I think later today i'll finish up the cap count. And order the de-oxit...which should have been done days ago, but hit some speed-bumps due to my fathers lack of acceptance that this qualifys as standard maintanance.

He pointed it out that E. caps have a minimum of 10yrs before degradation...I had to pint out that these caps are nearing 40years old, a heck of a time for any component.

 

[33&athird]

Alright, been working on the cap list, got the am/fm, power supply, head amp, and filter caps checked off, but i'm running into some trouble with the boards. So far, the service manual is quite correct, though alot of voltage ratings seem to have been increased. Odd collection of nippon chemi-con, elna, and sanyo caps...especially the sanyo, never seen markings like theirs.

The power amp board seems to be connected to a seperate chassis, which is then connected to the heatsinks. It seems like the thing to do is pull all of it together, but I don't know how to approch it. The screws holding it on the sides are very close to the inside edge of the main chassis, and I don't think I can get to them easily. If I want to pull just the board, I belive the transistor wire wouldn't allow it, and then there are the other components also attached to the heatsink.:scratch2:

The other board is the one nearest the faceplate. I think, as mentioned, that the entire front has to be pulled off to access the board. If that's true, I may wait till I have the deoxit, so I only have to make one trip, until the re-cap.

And news on the strange cap!, the one attached to the terminal strip goes to the power amp section, pin 3 I think (but i'll double check later). The weird thing is the "negative" (-) side of the cap goes twoards the board, and the "positive" side is coupled to the chassis ground. I asked my dad, and he thinks its for AC coupling, but I don't know, its an awfully high value for that:scratch2:.

When checking the power supply board, I noticed the diodes have some oxide on the leads, its very dark and tough. I don't think it could cause any issue, but if they need to be replaced, nows the time I figure. Very thick leads...so I don't think they are in immediate danger of failure.