COMPLETE RESTORATION----PIONEER SX-1250

This listing is for the technical service required by the famous Pioneer SX-1250. Since these guys are now over 30 years old, they need serious and precise attention. Once this is done, you are rewarded with a receiver with performance and reliability very close to original. You are already aware that big receivers from the 70's beat the poo out of the stuff that you can buy new today. That means you are smart enough to know that the "as is" units you are seeing listed, no matter how pretty, need to be carefully worked over. So if you bought one when new, inherited one from Uncle Bob, stole one from your neighbor, bought one last week, or plan to buy one next week......you need this service.

You are asking yourself: "Oh gee, is it worth all the trouble of sending it off, will I really hear and appreciate the difference?" The answer is yes, and yes, it is and you will. Back in the 70's there was a very hot competition among the major Japanese manufacturers to build the biggest and best stereo receiver possible. Quite a few big fellows were produced and most of them have remained viable for a really long time. Among these, the Pioneer SX-1250 stands out. Besides being very good looking and functionally very user friendly, they have proven to be pretty darn reliable and very responsive to careful restoration. Additionally, the SX-1250 has the advantage of rarely getting into parts difficulty. The parts needed to make one of these babies sit up and sing are readily available. I keep all of the standard and usual parts in stock since I do so many of them. The SX-1250 has adequate power to drive nearly any speaker you might choose, and it runs pretty cool so you can leave it on all day with no worries.

Ok, so you are convinced that the 1250 is a nice piece and that it is worth the effort. You just looked at four eBay listings for SX-1250 and the seller has said: "My tech, Space Wizard Stereo Service, has checked this baby out and has said that she performs beautifully. Hell, he even dusted her out and sprayed some Deoxit into most of the controls and set the bias". You are wondering why I am rolling my eyes and why that won't do. Ok, the detailed service description follows. This is for you folks who are keen to know the complete story. The first part is obvious, the unit must be disassembled down to the chassis, dusted out, and cleaned up. Then naturally it is necessary to clean and deoxidize all of the switches and controls and the tuning capacitor as well. You cannot just squirt a bit of stuff in there. It is necessary to get at the bodies of the switches and the pots and to make several passes with solvent and then a bit of deoxit. You want those guys to perform reliably and with no noise. Now we are getting a bit deeper into it. Observe the four boards laid out in front of the unit in the following picture:

Those boards are the regulated power supply, the driver boards (two of them), and the protector board. All of these boards must be carefully worked over. Let's take them one at a time. REGULATED SUPPLY: When an SX-1250 fails completely, this is most often where the failure occurs. One of the regulated voltages disappears, and viola! The unit quits. The countermeasure is to replace each and every electrolytic capacitor on that board. Since this supply board generates some heat, you must also inspect it for heat fatigued joints and resolder all of them. Sometimes it is necessary to replace a regulator transistor or two or a dead zener diode or some such. At that point you reinstall the board and check each of the regulated voltages to make sure it is ok. DRIVER BOARDS: This is the heart of your power amp section. On the driver boards, it is necessary to replace the electrolytic capacitors and the input coupling cap and the differential pair of transistors in the first stage. Doing this improves both sound and stability. The board is then inspected for bad joints and reinstalled. PROTECTION BOARD: This board runs the protection circuit using a relay who has the task of rapid speaker disconnect in the event of serious failure. (You don't want your speakers to catch fire, you know). On this board, the capacitors are replaced, and sometimes the switching transistors as well. The protect relay must be removed from the board, disassembled, and its contacts must be buffed until they shine, then the board is reinstalled. All of these boards are electrically connected to the rest of the unit by a series of plugs. All of these must be buffed and cleaned.

After these four boards are complete, and reinstalled, there is one other board under the chassis where four additional capacitors are found. Since these interface with the regulated supply, they are also replaced. You would think that we are getting close to done by now. Ha, think again. Next, we go to the phono board. This board resides behind the front panel, to the right of the tuner section. It is now time to replace the capacitors on that board as well, so your phono will "be all it can be". Ok, we have reached a stopping point. It is now appropriate to power up the unit and check it out. We use a variac (variable line transformer) to run the line voltage from zero to 117v. While doing this, the current flow is observed on a meter. This is done to assure that no mistakes have been made. Then the amp bias and balance is checked and adjusted and all functions are confirmed. WHEW! What a lot of work, I'm hungry! Time to take a break and then come back and tell you the rest.

Here we are, back again. Now that the unit has been through major surgery, it is time for in-depth testing. Woops! I almost forgot. There is a second relay in there that we must service. This one is located on the chassis and is hardwired into the primary side of the line transformer. When you first turn this guy on, there is serious start-up current flow. They run this through a big-fat resistor, and then the relay closes. Its contacts get pretty funky over time, so that relay gets pulled, opened, and the contacts are buffed so you get a good connection. Good performance starts with steady line voltage! Ok, back to testing. I like to run the unit for at least a day with the case off. I am looking for a number of things. First, the power amp section (remember the bias and balance?). Idle current (bias) and dc offset (dc at the speaker terminals....balance) must be stable. The heatsinks will prove this by not getting excessively hot. The same is true of the regulated supply board. It will generate some heat, but not too much. I usually burn these guys in on the FM. I pick a somewhat weak signal and confirm that it doesn't drift or lose the signal. Next, I am listening for any intermittent noises or static from the tone amp, or the phono amp. After a day or two, if nothing bad shows up, the unit is considered to be complete. Well, almost complete....the cosmetic stuff remains. So any burned out lamps must be replaced, the front panel and glass must be carefully cleaned, and the knobs must be cleaned. Break out your toothbrush folks! Once it is reassembled, the rest of the exterior is cleaned and the wood case gets a bit of lemon oil.

Now, those of you who have read the whole thing can readily see that restoring one of these guys properly is serious business. You can also see why I would resolutely scoff at those who might suggest that this level of service is somehow not necessary. Let me add a couple of additional notes. To ship one of these receivers requires very careful packing. I know exactly how this is done and you should call me at 512-294-5635 and I will tell you. The price of this listing is for parts and labor, return shipping is added to that. If you have a 1250 that you fear is very broken and may need more service than a normal restoration, I may recommend a diagnostic as a starting point. Call and tell me the story. If you are looking to buy an SX-1250, send me the item number. I will look at and tell you if I think it is a good candidate. You may have the seller ship it to me for service. If you have a model similar to this one, but not this one, call me about that and we will figure out the proper game plan.