SX 1250 FROM SCRATCH
- Thread starter rhodus
- Start date
Spe@kerBox
Addicted Member
Thank you Sir. I enjoy restoring things, not just old radios.
Made a Mouser order today for the electronic components. Here are the other things I'll have to locate:
2 - tone controls # A166 and A167
Top metal cover
4 feet
power cord
tuning shaft and flywheel
tuning dial string and spring
knobs - tuning,volume, balance, 4 tone controls
7 lever caps
Probably some other things too but that's what I know for sure right now.
2 - tone controls # A166 and A167
Top metal cover
4 feet
power cord
tuning shaft and flywheel
tuning dial string and spring
knobs - tuning,volume, balance, 4 tone controls
7 lever caps
Probably some other things too but that's what I know for sure right now.
I do not usually use the popcorn, but for this thread I will, since it is an unusual challenge for an AK member. I too am wondering of your solutions for connections. You have wire wraps and those obsolete connectors to solve. Looks as if the original wires were chopped short, they did not leave much wire slack when they first wired them up, so I am thinking many wires may need to be extended, esp. if you plan to use the original hangers.
Might want to trade in that pin nailer for a pneumatic w/w tool
Good Luck
Rick
Thank you! I have all the molex connectors I need. Yes, I'm sure several wires will need extending and I will solder the ones that were previously wrapped, like I did on a recent Spec2 rebuild. I will also solder all the chassis ground connections. I think the biggest challenge coming for me is the tuner section. I'll have to locate the equipment needed to do the alignment or take it to a local shop when I get to that point.....
I do not usually use the popcorn, but for this thread I will, since it is an unusual challenge for an AK member. I too am wondering of your solutions for connections. You have wire wraps and those obsolete connectors to solve. Looks as if the original wires were chopped short, they did not leave much wire slack when they first wired them up, so I am thinking many wires may need to be extended, esp. if you plan to use the original hangers.
Might want to trade in that pin nailer for a pneumatic w/w tool
Good Luck
Rick
FYI those connectors are not mfg by Molex, I wish they were, but people like to call them that because they do not know who mfg them. The mfg logo is stamp is on them, I looked and looked, I can not find a second source for them. I think the company is out of business = to bad.
Once you get it running you will determine if it needs FM tuner adjustment. If the front end and the IF boards came from the same unit, chances are less that an alignment is necessary. On the ones I have done, it was meter centering and on another one a var cap trimmer on the front end was out of adjustment, it had poor sensitivity. Hopefully you are okay
That should be fun soldering all those wires to that function switch board with oxidized w/w posts, will make your spec2 challenge feel like a peice of cake. If that is the case, look at using some Teflon wire for extension vs pvc
Once you get it running you will determine if it needs FM tuner adjustment. If the front end and the IF boards came from the same unit, chances are less that an alignment is necessary. On the ones I have done, it was meter centering and on another one a var cap trimmer on the front end was out of adjustment, it had poor sensitivity. Hopefully you are okay
That should be fun soldering all those wires to that function switch board with oxidized w/w posts, will make your spec2 challenge feel like a peice of cake. If that is the case, look at using some Teflon wire for extension vs pvc
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Molex and JST / JS Terminals are the two I designed in most, ... and a lot of them were the same, just depeded on who Purchasing was working with at the time.
Even if those weren't Molex, I believe that Molex made a compatible connector at the time (I probably even have some stashed away where they will never be found).
Even if those weren't Molex, I believe that Molex made a compatible connector at the time (I probably even have some stashed away where they will never be found).
They are "SMK", unknown mfg to me, defunct, I know of nothing equivalent, form, fit, function, silver plated contacts, not used much these days.
My issue is, if I design a new AWR-106 what am I going to use to replace them with, I am thinking to extend the board to clear the chassis cutout, use terminal blocks and/or TE(Amp) MTA56/ Molex KK156, choices choices. Transferring over the old connector is an option I'd rather avoid. One way or the other, it is not going to be so easy to replace as it is with some of the other power supplies. Maybe take this discussion to a new thread, if you have other ideas.
My issue is, if I design a new AWR-106 what am I going to use to replace them with, I am thinking to extend the board to clear the chassis cutout, use terminal blocks and/or TE(Amp) MTA56/ Molex KK156, choices choices. Transferring over the old connector is an option I'd rather avoid. One way or the other, it is not going to be so easy to replace as it is with some of the other power supplies. Maybe take this discussion to a new thread, if you have other ideas.
In a pinch, I have stuck a thin jewelers screw driver in the housings to detract the locking tabs to remove the contacts. Finding the correct diameter extraction tool might be an issue unless you have a wide selection of them to choose from. I guess I could try it out again on that one since I have a few of those old connectors in the parts bin. They are crap connectors as it is, no locking/retention means, silver contacts that oxidize and become high resistance, I see glue on many of them because the come loose. I had a 1250 in for service, it would not bias, it was those damn connectors oxidized, crap I say, another Achilles heal in that model, same goes for those damn switches too. The not so holy grail receiver imo.
I was going to mention those switches to the OP, you might want to take them all apart and clean all the crap out of them, it is a big job, a perfect COVID-19 project
I have an stock 950 with the same problem, deoxit is a band-aid fix.
I was going to mention those switches to the OP, you might want to take them all apart and clean all the crap out of them, it is a big job, a perfect COVID-19 project
I have an stock 950 with the same problem, deoxit is a band-aid fix.
I assume you are referring to the pushbutton switches. I have experimented with a couple of those and have not been successful. It is extremely difficult to not damage the contact plates during cleaning and reassembly. The slightest bend or kink and that's it, switch ruined. I've been carefully removing the top only, and saturating the inside with deoxit gold in a jar. So far so good.In a pinch, I have stuck a thin jewelers screw driver in the housings to detract the locking tabs to remove the contacts. Finding the correct diameter extraction tool might be an issue unless you have a wide selection of them to choose from. I guess I could try it out again on that one since I have a few of those old connectors in the parts bin. They are crap connectors as it is, no locking/retention means, silver contacts that oxidize and become high resistance, I see glue on many of them because the come loose. I had a 1250 in for service, it would not bias, it was those damn connectors oxidized, crap I say, another Achilles heal in that model, same goes for those damn switches too. The not so holy grail receiver imo.
I was going to mention those switches to the OP, you might want to take them all apart and clean all the crap out of them, it is a big job, a perfect COVID-19 project
I am referring to every switch in the signal chain use silver plated contacts which oxidize over time and make unreliable connections. It was a bad design choice. Silver contacts are fine for high power, low resistance contacts but for low current signals paths it was the wrong choice. I guess their thinking was, once the contacts oxidize, so badly to affect the signal paths, throw it out in the junk and buy a new one.
MTF reports that he uses his propitiatory chemical mix and ultra-sonic cleans them. Even then, I am sure there are times they are so bad that they need to be disassembled and cleaned properly. I have no experience doing this myself, but member zeb, aka Bob, and some others have mastered it from what they have shown. I know it is a royal PITA. I could probably design a new switch board using a gold plated contact relay faster The choice is yours alone, I am just here to follow along and eat my
MTF reports that he uses his propitiatory chemical mix and ultra-sonic cleans them. Even then, I am sure there are times they are so bad that they need to be disassembled and cleaned properly. I have no experience doing this myself, but member zeb, aka Bob, and some others have mastered it from what they have shown. I know it is a royal PITA. I could probably design a new switch board using a gold plated contact relay faster
The choice is yours alone, I am just here to follow along and eat my
petervv
Active Member
hi Rhodus,
Nice to see you're still into repairing SX-1250's!
I'm still enyoing the 1250 that I could finish thanks to the parts I got from you very much!
The making of it in this thread: https://audiokarma.org/forums/index.php?threads/i-finally-found-a-sx-1250-but.677841/
Seeing your list of parts you need for your project you gave away too much, I hope you will be able to find everything.
stay healthy!
kind regards, Peter
Nice to see you're still into repairing SX-1250's!
I'm still enyoing the 1250 that I could finish thanks to the parts I got from you very much!
The making of it in this thread: https://audiokarma.org/forums/index.php?threads/i-finally-found-a-sx-1250-but.677841/
Seeing your list of parts you need for your project you gave away too much, I hope you will be able to find everything.
stay healthy!
kind regards, Peter
There they are!! No problem dude...when I gave you those things I had no idea I would be doing this project. In fact, I've completed several projects since then. Very glad to hear you still have your 1250 and enjoying it!!
Do you mean to say that I could send mine to Mark for cleaning?I am referring to every switch in the signal chain use silver plated contacts which oxidize over time and make unreliable connections. It was a bad design choice. Silver contacts are fine for high power, low resistance contacts but for low current signals paths it was the wrong choice. I guess their thinking was, once the contacts oxidize, so badly to affect the signal paths, throw it out in the junk and buy a new one.
MTF reports that he uses his propitiatory chemical mix and ultra-sonic cleans them. Even then, I am sure there are times they are so bad that they need to be disassembled and cleaned properly. I have no experience doing this myself, but member zeb, aka Bob, and some others have mastered it from what they have shown. I know it is a royal PITA. I could probably design a new switch board using a gold plated contact relay faster
I am referring to every switch in the signal chain use silver plated contacts which oxidize over time and make unreliable connections. It was a bad design choice. Silver contacts are fine for high power, low resistance contacts but for low current signals paths it was the wrong choice. I guess their thinking was, once the contacts oxidize, so badly to affect the signal paths, throw it out in the junk and buy a new one.
MTF reports that he uses his propitiatory chemical mix and ultra-sonic cleans them. Even then, I am sure there are times they are so bad that they need to be disassembled and cleaned properly. I have no experience doing this myself, but member zeb, aka Bob, and some others have mastered it from what they have shown. I know it is a royal PITA. I could probably design a new switch board using a gold plated contact relay faster
I have to agree. Silver is much much better for low resistance, but unless it is in a sealed environment with an inert gas or something similar, it is going to oxidize and cause problems. Gold, alhough not a great conductor, doesn't oxidize the same, maybe rhodium would have been a better choice.
EVERY SX-series I have ever owned has needed the switches cleaned. If you do it as PM every year or so, or use the switches periodically, you're fine. I don't remember this ever being a problem when they were new but it is likely that Pioneer did not expect us to still be using them nearly 45 years later!!
I guess if the quality and performance curve continued after the SX-xx50 series into the next couple of decades we wouldn't have revived these, but since the '80s and '90s saw profit margins crush the build quality and performance levels start to level off, ... '70s gear is worth owning again. Oh well.
Great project BTW, and I'd probably enjoy it too.
