Cuda's SX-737 Refurb Thread

I could understand the volume being nonlinear, but 20° of pot rotation with no change in volume, that I don't get.
 
I completed all the other board renovations except for the tuner, hoping something along the way might address the odd volume behavior. No luck.

I made a series of measurements from snout to tail and confirmed (again) the problem is on the Switch and Volume board (AWX-071), specifically the volume variable resistor.

I then pulled the volume pot and made some resistance measurements to see what I could find and despite repeated cleanings, I measured what I consider to be out of spec discrepancies. Example: at about a 12 o'clock position, one side 49k, the other 39k.

Is it just me, or does that seem out of whack?

So I am now in the market for a replacement volume variable resistor, described in the service manual as 250k-B1, part no. ACV-134-0. Before I go looking in Barter Town (or flea-bay), anyone listening have one they would like to sell me?

Thanks.
 
There's one on ebay, but it's $40. That's too much for what I already have invested and the overall value of the unit.
 
Try Danny @ Yesterdays Audio. email him at "yesterdaysaudio AT aol DOT com". He may have one. I wrote the email that way due to bots sniffing them out.
 
I did try his website yesterday and it was no longer in service. I'll try the email.

Thanks!
 
Danny replied - no part in stock, suggested I look at the one on ebay.

Scoured ebay one more time and found the whole SX-1010 volume control board for a little less than the other listing, so I grabbed it. It also includes the balance pot and 5 switches.
 
Man that sucks about the volume pot, at least you managed to find a replacement for fairly cheap and like Oldsansui said, you can sell the other pot's and such of the board and recoup some cash, or just keep them, never know when you might need a balance or tone control pot. I got a 737 waiting for it's re-cap and refresh.
 
I hope the "new" old part does the trick. I've done the rest of the recap/refresh so this 737 is otherwise ready to button up and find a new home.

I have a BOM for the SX-737 that is current if you would like me to send it to you. I'm planning to post it for all of AK, but I like to get it vetted one more time first.
 
I hope the "new" old part does the trick. I've done the rest of the recap/refresh so this 737 is otherwise ready to button up and find a new home.

I have a BOM for the SX-737 that is current if you would like me to send it to you. I'm planning to post it for all of AK, but I like to get it vetted one more time first.

I'm certain that the new volume will do the trick, don't forget to post some pic's when it's all buttoned up and lookin' perty! Thank you for the offer but I already have the parts, minus a few trannies I need to get around to ordering.
 
I hope the "new" old part does the trick. I've done the rest of the recap/refresh so this 737 is otherwise ready to button up and find a new home.

Can't see why it wouldn't as you proved it as problematic with your resistance checks. Hope you can get her all buttoned up soon.
 
Thanks for the thread Cuda, one followed me home yesterday and it's been on the bench playing all day.

Not sure what my plans are for it, it really sounds nice so it'll probably find a home here somewhere.

Would you consider your rehab 'varsity level" or could a schmuck with a soldering iron and an atrophied 30 year old elec. tech. degree do it?

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Probably JV level. Good soldering skills are important of course as are good desoldering skills since it's easy to damage the boards if you manhandle them.

As a high school and college student (late 70's), I did quite a bit of soldering and board rework as summer jobs and kept my skills up with car stereo installs and whatever household needs came along, so I have confidence in my skills in this area. That said, I knew that a bulb solder sucker and some solder-wick was going to make it more difficult to do well and take longer, so I invested in a Hakko soldering iron and desoldering gun last year and used them both on a refurb of my SA-9500ii. Since I plan to refurb units as a hobby, I thought the investment was warranted and after the 9500, was glad I did.

As for your 30 year old degree, well this gear is older still so you're probably okay. I have an electrical engineering degree, but spent my career in software so never really used it, though my being able to read and (largely) understand a schematic really helps when the inevitable troubleshooting is needed.

The SX-737 board with the volume control is tricky to get out without disconnecting some wiring, but it can be done. Based on the advice on AK, I only touched the caps on the tuner board since you may throw the tuner out of alignment when transistors are changed. Everything else was pretty straightforward.

Let me just parrot what you will find all over AK - take your time, read all the posts you can, get the service manual, build and use a DBT, and if you're not absolutely sure about something, ask.
 
The part came and was installed without any trouble, but I just noticed that the dial pointer lamp is out so it's not quite ready after all. I'll definitely take some picts when done.
 
Well, she's done and here are some shots of her.
 

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And a few more
 

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Thanks!

Only two ingredients required to get them that shiny - Blue Magic and elbow grease.
 
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