Swapping Circuit Board

[biggal76]

My SX 1280 has a messed up tuner board (that I've had 2 techs unable to diagnose the problem). I got another (hopefully working properly) on Ebay. What is the best way to swap the coiled wires from one board to the other? I read that it is pretty much impossible to re-wrap them onto the other board. Should I try to just upwrap gently, re-wrap a little and attach with a little solder? Anyone know a YouTube that shows it? Any other pearls of wisdom before I jump into the project? Obviously, I'll label them well so they don't get mixed up.

 

[bberkom]

Unwrapping and rewrapping the wires on the pins will be very hard to do correctly. You could desolder the pins from the boards, leaving the wrapped wires intact, then solder those pins to the new board.

 

[biggal76]

Unwrapping and rewrapping the wires on the pins will be very hard to do correctly. You could desolder the pins from the boards, leaving the wrapped wires intact, then solder those pins to the new board.

I'll try it on an old "parts" board so I don't mess things up worse. What is the advantage of them wrapping them like that vs a solder connection? Any other ideas or tips?

 

[Awesomeaudio]

Good idea to practise first.
Manufacturers preferred the wire wrap method as it eliminates the possibility of a dry or cold solder weld.
Another would be the fumes.
A tightly wrapped wire will guarantee a solid connection.
I would most certainly unsolder the pins as opposed to cutting and soldering the wire strands.
Let us know how you go.

 

[larryderouin]

As the wire is wrapped around the post, it gets nicked by the pin and that nick sits in the corner of the pin making an airtight connection. Now imagine a wire wrapped ten times around the wire (40 joints) and you've got a practically indestructable joint from the standpoint of stationary use. They are almost impossible by the average joe to replicate and takes a good amount of experience to get them right everytime, plus the special wrapping tools needed.

Unsoldering the pins is the way to go. Be forewarned that pioneer sometimes splayed the end of the pin after insertion and before soldering to hold it to the board. So De-SOLDER 1st then check for splayed ends. a pair of needle nose pliers will straighten them out and you can then remove it from the board without damage to the pin or trace. Make absolutely sure you mark each pin with the hole # it came from.

 

[Oldsansui441]

+1 on desoldering of the pins from underneath. From the top side you will never know it has had the board changed.

 

[rcs16]

Not so easy to repair these tuners.
I changed the tuner pcb in my SX-950. This was a long time ago before AK and before I had the test equipment and knowledge to repair them. In my case I unwrapped what I could and then soldered the wires onto the w/w posts. Had to clean the tarnish/oxidization off the posts first. If I was to do it again, I'd un-solder the w/w posts and transfer them over as suggested.
I suggest to but wire marks onthe wires to match up with the terminal numbers on the pcb/schematic, makes it idiot proof.
On another note, I'd take a shot at fix your tuner pcb, PM me if you are interested. I would pay the shipping or we can figure something out. If I fixed it, I could offer it as a replacement for others having this difficulty so I can round robin them. A lot cheaper than shipping the whole unit which is expensive and risky.
So far I have a SX-950, SX-1050 tuner pcb's that I could offer as a turn around tuner service.

 

[biggal76]

I swapped it out, but seem to have no power to the board. Meters do not move, no sound on AM or FM. As far as I could tell, there were no complications. I'm positive all pins are in the right position and almost positive I have decent solder connections for each pin. The board was bought on the Bay. Description was that the donor unit had been damaged in shipping, so I assumed the board would be ok. My old board has many damaged traces, especially around the IC's and wasn't working properly even before the traces were damaged, so I figured a new board (for $75 which had all the chips including 1002) was a good place to start. Before swapping out, I had power to AM and FM but it just wouldn't tune correctly and sound was distorted. I had it at 2 techs neither of whom could fix it. Now after board swap, I have nothing. Any help would be appreciated. Hopefully it's one simple thing and not a bunch of blown ICs. I have ICs on my original bad board that are probably fine (they were all replaced and I was told by 2 different techs that they are all working properly) but something was causing that board not to work properly and I'm not sure what. Also, would any of the electrolytics cause the board to be completely dead? They are all original on the board I just put in. Guess I need to start at incoming power pins and make sure I have power to the board. Is pin #30 coming from power supply with 13VDC? Where do I put the other test lead? Do I ground to chassis or a different pin? I don't want to test anything unless I'm positive where I'm supposed to be taking the readings (that's how I blew everything the first time and got into this mess). Any other ideas where to begin troubleshooting?

 

[larryderouin]

Get out your Schematic of the unit. All power pins will be identified on the schematic next to the pin along with the pin number. Unless the power is AC (and I seriously doubt any AC power goes to the tuner) ALL DC METER READINGS are taken with the RED PROBE (+) to the pin, and the BLACK PROBE to a shiny CLEAN part of the Chassis (alligator clip works well here). INSULATE ALL but the very tip of your RED PROBE with heatshrink to prevent AW SHI*'s and OOOOOP-sies. Follow each power pin from the tuner board back to it's origin at the power supply. There should be at least 3 power leads if not more.

 

[biggal76]

I'll dive into it tomorrow. If I have power at the power pins, I guess I'll check individual connections on the IC's per the schematic to see if those voltages are correct. Great tip with the heatshrink on the probe. I've shorted probes before, so I'll heatshrink before I start.

 

[rcs16]

I hope that you did what I suggested and marked each wire before you removed them. I have to wonder if you are capable of doing this tuner repair when you make comments like "Is pin #30 coming from power supply with 13VDC? Where do I put the other test lead? Do I ground to chassis or a different pin?" You should have figured this all out before you took on a repair like this.
Sorry, I should have recommended that you bench test the spare/replacement before you installed it.
I have no idea how these techs could make a statement like this "I was told by 2 different techs that they (IC's) are all working properly" when in fact the unit was faulty. Whom ever was in there changing IC's, ripped up traces, probably did not even install IC sockets = real butchers.
Before you do any powering up, double/triple check all your connections again against the schematic, use your ohmmeter. I doubt very much that your problem is an ecap, sounds like that is the least of your problems.
The first thing to test after you verify that your wiring is correct, is that you can zero the tuning meter, with no IF input. Do you even have some tuning tools?
Servicing a tuner with limited knowledge, no RF SG, no scope and other necessary test equipment is a real PITA if not impossible. Lets hope that you can figure it out.

 

[biggal76]

As I said, I am a novice. I am in a situation where the techs around me are limited and very hard to work with. The unit has spent about 9 months combined in the shop combined between 2 techs and is still not working. The first tech said it was working fine and just needed the tuner aligned (he didn't have the equipment). The second tech who I took it to for the tuner alignment found that the power supply was unstable (loud pop and went into protection mode for a long time before it came out of it) and refused to work further on it and also said he did not have all the equipment to properly align the tuner anyway (after 3 months in his shop). I think the culprit was a bad diode on the power supply that I diagnosed and swapped out. It hasn't popped/gone into protection mode since I switched out the diode. I am trying to avoid paying back and forth shipping and also worrying about damage during shipping. I already have about $1300 invested in the machine and if I start shipping it back and forth and paying another tech to service it, I'd be better off selling it as a parts unit on Ebay and taking a big loss. I understand these tuners are very difficult to work on but am limited in my options and at least need to give this a try.

I made a few measurements. I do have the 13V at pins 11, 15, and 30 as I'm supposed to. Beyond that, I'm quite confused as the wires going from one board to another are not what the schematic shows. As I said, I'm 99.9% positive I put all the pins back where they were when I swapped the tuner board out. It's pretty hard to mix up as they are all color coded and only a few of the wires reach to each position anyway (i.e. I can't put the wrong black wire on the wrong pin as the other black wires would not even reach to the next black location). However, schematic shows tuner pin # 24 going to the p.s. board pin #19, but it (along with pin #23) I believe I traced to the power amp input jack on the back of the unit. What I did notice is no voltage at pin #19 on the power supply (AWR157) board. I don't see voltage for it marked on the schematic, so I'm not really sure if this is a problem or not. In any case, I am quite confused why the wires don't go along with the service manual.

I appreciate your help and agree that I am not the ideal person to be doing this repair, but do not know what else to do. I can at least trace some wires, make sure I'm getting voltage where I should be, and hopefully find a bad component to swap out and fix the problem. I wouldn't try to start turning adjustment screws without proper test equipment but no reason I can't probe around for voltages with some guidance.

 

[Awesomeaudio]

As I said, I am a novice. I am in a situation where the techs around me are limited and very hard to work with. The unit has spent about 9 months combined in the shop combined between 2 techs and is still not working. The first tech said it was working fine and just needed the tuner aligned (he didn't have the equipment). The second tech who I took it to for the tuner alignment found that the power supply was unstable (loud pop and went into protection mode for a long time before it came out of it) and refused to work further on it and also said he did not have all the equipment to properly align the tuner anyway (after 3 months in his shop). I think the culprit was a bad diode on the power supply that I diagnosed and swapped out. It hasn't popped/gone into protection mode since I switched out the diode. I am trying to avoid paying back and forth shipping and also worrying about damage during shipping. I already have about $1300 invested in the machine and if I start shipping it back and forth and paying another tech to service it, I'd be better off selling it as a parts unit on Ebay and taking a big loss. I understand these tuners are very difficult to work on but am limited in my options and at least need to give this a try.

I made a few measurements. I do have the 13V at pins 11, 15, and 30 as I'm supposed to. Beyond that, I'm quite confused as the wires going from one board to another are not what the schematic shows. As I said, I'm 99.9% positive I put all the pins back where they were when I swapped the tuner board out. It's pretty hard to mix up as they are all color coded and only a few of the wires reach to each position anyway (i.e. I can't put the wrong black wire on the wrong pin as the other black wires would not even reach to the next black location). However, schematic shows tuner pin # 24 going to the p.s. board pin #19, but it (along with pin #23) I believe I traced to the power amp input jack on the back of the unit. What I did notice is no voltage at pin #19 on the power supply (AWR157) board. I don't see voltage for it marked on the schematic, so I'm not really sure if this is a problem or not. In any case, I am quite confused why the wires don't go along with the service manual.

I appreciate your help and agree that I am not the ideal person to be doing this repair, but do not know what else to do. I can at least trace some wires, make sure I'm getting voltage where I should be, and hopefully find a bad component to swap out and fix the problem. I wouldn't try to start turning adjustment screws without proper test equipment but no reason I can't probe around for voltages with some guidance.

Hey biggal76, I feel your frustration. I hope those "two techs" (so called) didn't charge you for their Non Performance...
Anyways, I'm pretty much a novice like you, and never tackled anything of that magnitude before.
I feel your frustration.
With some patience here from all concerned, I am confident that you will get through this.
Ask as many questions as you have, carefully follow the instructions of the learned people and I'm sure you'll be fine.
These things can take some time, so be patient.
We are very lucky to have some great guys here to help us.

 

[petehall347]

pin 19 AWR157 is a ground by the looks of it .

 

[rcs16]

Take a deep breath, I will try to help you out. I was implying that if you fail to get the tuner pcb going, I'd offer to fix it, you do not need to ship the whole unit, only the pcb, a lot less risk and cost than shipping a complete unit which I agree is not very economical and is risky. But lets exhaust your abilities to fix it first before we resort to any shipping.

I do have the 13V at pins 11, 15, and 30 as I'm supposed to

Also need +13V to terminal 29(it is switch in by the selector ), terminal 15 is the stereo lamp which would be +13V (if the lamp is not open ckt) when not receiving a vaild 19KHz pilot.

However, schematic shows tuner pin # 24 going to the p.s. board pin #19, but it (along with pin #23) I believe I traced to the power amp input jack on the back of the unit.

terminal 24 is ground so it shows in the schematics that it goes to the common point ground. Some solder lug that is attach to the chassis somewhere.
terminals 22 & 23 are for the FM de-emphasis selection and go to the switch which would select 50/75 us de-emphasis. Located on AWM-119 (p65 of sm)

What I did notice is no voltage at pin #19 on the power supply (AWR157) board.

Of course there is no voltage, it is ground. refer to the drawing on p74.
I have never serviced one of these, I can only go by the documentation. the documentation is pretty good, so we have to trust it unless we find a fault in it. I suggest to print out all the required schematic pages in the service manual, so that it is easier to follow the wiring.
You are going to have to learn to read the schematics and follow the wiring as it is shown in the service manual.
So once power to the FM is established, un-mute the FM you should hear noise at least, hopefully you can tune to a valid signal, with an antenna hooked up.

 

[biggal76]

pin 19 AWR157 is a ground by the looks of it .

I had a feeling it was ground and that is a relief. Still don't understand how the wires aren't going where the schem. shows them to be. Thanks for the vote of confidence Awesomeaudio. I guess I'll just start probing voltages around the ICs unless anyone has some better advice.

 

[biggal76]

rcs16. I may have to take you up on the offer to send you the board. I still have a little fear that there are problems besides on the actual tuner board causing these issues and would rather not remove the board again if I don't have to.
As far as pins 22-24 go, I traced them again after your email and figured out they are correct once I understood that they considered the 50/75 switch part of the AWM 119 board.
I do have 13v to pin 29. FM muting is off but no sound, no movement of tuning meters. What should I check next?

 

[biggal76]

So I've established I have power to the power pins but when I probe individual pins on the IC's I have nothing on any of them

 

[rcs16]

So I've established I have power to the power pins but when I probe individual pins on the IC's I have nothing on any of them

That does not make any sense, that all do not have voltage on them, for example trace the voltage from terminal 30, thru L1 to R6 or R10. Also thru R14 to pin 7 of Q4. From terminal 11 to Q7-16, Q6-1, tru L4 to Q5-11

 

[biggal76]

Yes, this makes no sense. I got power to L1 and R6 but when I measure to pins on Q7, no voltage. I don't understand how the power can be interrupted in between components when one thing has voltage exiting it and the next doesn't have it entering. I also got voltage from the bottom side of the board on the solder joints but not from the top which makes 0 sense to me. I guess even taking these measurements is somehow beyond my capabilities. I'll have to find a tech to take the whole unit to. This is incredibly frustrating and really lowering my self esteem in general. I feel completely jinxed on this machine. Everything I do either doesn't fix it or messes something else up and as I said, I've had it to two different techs and it's still a disaster. I'd send you the boards but as I said, am worried there are still other power supply issues so would rather just take the whole machine somewhere. I'm going down to New Hampshire in a couple of weeks. Maybe I can drive a little further and take it to Atlantic Systems near Boston which seems to have a good reputation. I really appreciate you trying to help, but it's time to take it to a reputable shop and pay whatever it costs to have it working correctly.