Cuda's SX-727 Refurb Thread
- Thread starter cuda440
- Start date
Since I had some in stock, I replaced the point to point bypass caps (this shot only shows 2 of the 3).
And here's the underside after the refurb.
And the top.
Note that the relay guts were replaced, but the original Omron shell was reused. I also recapped and retrans (is that a word?) the control amp (treble/bass/etc.), as well as deoxit of every switch and pot therein.
Once I get the old girl completed, I'll post the final beauty shots, hopefully by the end of the week. It will then be time to find her a good home.
Thanks for watching.
And here's the underside after the refurb.
And the top.
Note that the relay guts were replaced, but the original Omron shell was reused. I also recapped and retrans (is that a word?) the control amp (treble/bass/etc.), as well as deoxit of every switch and pot therein.
Once I get the old girl completed, I'll post the final beauty shots, hopefully by the end of the week. It will then be time to find her a good home.
Thanks for watching.
Do you have any plans to solder-over the wire wrapped leads arriving at each board? I've encountered a hard-to-locate problem in a similarly-laid-out SX-850 that ended up being a broken wire right at the wrapped point.
I have not seen that to be common practice here on AK (no?), so I was not planning to. Now I've only refurbed a handful of receivers/amps and only encountered one broken wire in the process, and that break occurred (as I suspect most do) right at the base of the post where soldering probably wouldn't have helped.
Plus it's pretty much done now and just needs the case and the knobs put back on so I can take some photos before going up for sale. I'll probably be doing that this weekend.
Plus it's pretty much done now and just needs the case and the knobs put back on so I can take some photos before going up for sale. I'll probably be doing that this weekend.
Hey Cuda440 how did your 727 turn out? I just purchased a nice looking champagne 727. Unfortunately the sound doesn't match the looks. I overhauled a 1010 with help from others on this site. It is used every day and sounds great. I hope to do the same work on the 727 but finding a complete bom has not been easy. Did you ever compile a complete BOM from your rebuild? If so could you please post it Thanks
I did not. This tuner didn't seem to need it, however I do have the parts listed in the bom. Conventional wisdom here says that recapping the tuner does not warrant a realignment, but changing out transistors might, depending on who you ask. I did recap the tuner in a 737 and it didn't have an adverse affect.
Oldsansui441
Super Member
Might be worth checking/cleaning the variable tuning capacitor where the main pivot shaft passes through the pivot points which are also the earth points.
Yes, very good advice about the tuning capacitor. A friend gave me a Mitsu RA-20 when I was just getting started in the hobby and it had a very noisy tuner. A quick query to AK pointed me to the tuner cap and the spring contacts that are found in each "gang". Upon inspection I found that the contacts were gummed up with some green gunk, old grease I suppose. I whittled down the end of a wooden handled q-tip into a flat point (like a screwdriver) and dipped it into deoxit. The wooden tool didn't scratch or bend the metal and the deoxit helped to loosen the gunk, restoring the connections. [You do not want to spray deoxit directly into the tuner cap as it can go places you don't want and adversely affect the cap performance.]
As part of my refurb process I now give every tuner cap this same treatment, whether it was noisy or not.
As part of my refurb process I now give every tuner cap this same treatment, whether it was noisy or not.
Oldsansui441
Super Member
I reviewed the SX-727 BOM spreadsheet I had and I believe it's ready to be published. It includes both the AWM-011 and AWM-027 versions of the protection board (mine was the 027). It includes the tuner board caps (though I didn't change mine), but not the transistors since replacing may require a realignment. The power transistors are also listed, but it's recommended to leave them alone unless they are known to be bad (or if any one of them is bad, then replace them all). Mine were good so I only did a lift, clean, and regrease.
The protection relay is at the end of the list. You can find instructions on how to replace it here on AK (it's pretty easy to reuse the clear plastic cover of the original, required to maintain the original appearance).
I don't know the proper devices to replace the 4.7k and 2.2k variable resistors on the power amp board, so those entries are blank. The service manual doesn't describe how to adjust them.
Lastly, when replacing 1uf and smaller caps, you can/should use film caps. Film caps are a bit more expensive, but there aren't that many of them to be cost prohibitive.
The protection relay is at the end of the list. You can find instructions on how to replace it here on AK (it's pretty easy to reuse the clear plastic cover of the original, required to maintain the original appearance).
I don't know the proper devices to replace the 4.7k and 2.2k variable resistors on the power amp board, so those entries are blank. The service manual doesn't describe how to adjust them.
Lastly, when replacing 1uf and smaller caps, you can/should use film caps. Film caps are a bit more expensive, but there aren't that many of them to be cost prohibitive.
OK, gave that a try today, but it did not clear up the static. Actually, I think it is more like distortion at lower frequencies in the bass range. When there is just talking the sound seems fine. Also, when there are brief silent parts to the broadcast, it is quiet - no static. So, I think this is more an issue where sounds in some frequency ranges distort, and it sounds like static.
The signal strength meter is not going as high as I think it should, but I have not tried various antennae or locations.
Oldsansui441
Super Member
Aah well , it was worth a try 
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