Pioneer SX-1010 Recap & Refresh

[Osibisa]

OK so I think this is much neater than before, I know iylts not as neat as you guys do it but hopefully it passes muster

Not neat? I haven't seen anyone else use hex bolts before!

 

[PTL-Pioneer]

In fact, those F&T caps are pretty good and reliable. I'm sure they're up to their spec already. Did you measure them?

No i did not unfortunately, i only have a cheap Chinese component tester, it doesn't do well on big value caps.
I simply replaced them because i did not like the look of them, had no idea if the brand was reputable, and the kemet caps installed are new and will hopefully last a long time and perform well.
I am convinced that the filter caps originally installed puked their guts up there is quite a mess on the bottom panel. I tried cleaning it all up as best i could but i think some sanding and painting is required for the bottom cover.

 

[MIJ_Pioneer]

View attachment 1848294

Looking good, I know those terminals and the small leads can be tricky - get real hot when soldering too.

I wonder if that bleeder resistor is too close to the film cap? I similarly did like the above on my 950 and after running it a bit I realized that the bleeder ran pretty hot.

 

[PTL-Pioneer]

Looking good, I know those terminals and the small leads can be tricky - get real hot when soldering too.

I wonder if that bleeder resistor is too close to the film cap? I similarly did like the above on my 950 and after running it a bit I realized that the bleeder ran pretty hot.

I tried it out multiple times today, turning unit on for a minute, then off and waiting until fully discharged x3, and bleeder resistors only get warm to the touch so happy enough to leave as is i think.

 

[PTL-Pioneer]

Today the new power board arrived so i got straight to it and installed it. I used the headers, i just was not too confident given that someone had already been in before me and the power board had been worked on. Basically afraid of snapping some of those wires!




Thank you Zebulon1!! Brilliant job, delighted with the result

 

[PTL-Pioneer]

I also did the protect board afterwards



Capacitors:
C1, 0.22 uF, 10v - - Film Cap used to replace
C2, 0.22 uF, 10v - Film Cap used to replace
C3, 330 uF, 6.3v - Nichicon UPW series used to replace
C4, 330 uF, 6.3v - Nichicon UPW series used to replace
C5, 4.7 uF, 25v - Film Cap used to replace
C6, 100 uF, 16v - - Nichicon UPW series used to replace

Transistors:
Q1 = 2SC869, Replaced with KSC1845FTA
Q2 = 2SC869, Replaced with KSC1845FTA
Q3 = 2SC945, Replaced with KSC945CGBU
Q4 = 2SC945, Replaced with KSC945CGBU
Q5 = 2SA733, Replaced with KSA733CGBU
Q6 = 2SC945,Replaced with KSC945CGBU
Q7 = 2SC1384,Replaced with KSC2690AYS

1N4004 flyback diode was added between pins 9 (anode +) and 10 (cathode -)



Everything looks good on DBT, so ran it on full power, relay comes in nicely and music plays.
Ran it for about 15 minutes no issues
Is there anything i should be doing now at this stage before going any further?

 

[PTL-Pioneer]

FM Muting (AWH-39-A)

On this board there is a 2SC1318, its on the list of top offenders. Should i replace this with a KSC2690AYS?
OR leave well enough alone?
I know supernoob on his recent rebuild left all three transistors installed (2SC945 x 2 AND 1X 2SC1318) as he stated that unless one is good with alignment leave alone



Will remain in holding position before proceeding any further

 

[PTL-Pioneer]

How do u get access to the amp boards, there is wirewraps on both top and bottom of boards. I think I can lift the heatsink and rotate upwards enough to remove output transistors (will clean and regrease), then should have just about enough room to work on the boards. I'll use some towels to try not damage the protect board and phono shields. Risk of breaking wires seems pretty high using this method.

Any suggestions? What's best practice getting to these boards?

 

[Osibisa]

It's easier than you think.

1. Loosen screw securing the STV-3H varistor from each heatsink and carefully remove & bend out of way.
2. Remove two outer screws from each heatsink and lift enough to gain access to screws securing the output transistors and remove outputs. Note the exact positions of transistors removed.This frees the socket on the opposite side.
3. Remove heat sinks.
4. Remove screws securing the power amp mounting brackets to the chassis.
5. Tilt amp boards slightly to the rear and remove the two screws securing the amp boards to the bracket.
6. Remove brackets, noting how wiring is routed.

You should now have plenty of room to access the solder side of the boards.

 

[PTL-Pioneer]

So today I managed to remove right channel heatsink and output transistors, so I now have room to carefully work on this board! Thank you.
Back to the fm muting board, hope someone can clear up the question I have before I proceed to the power amp
FM Muting (AWH-39-A)

On this board there is a 2SC1318, its on the list of top offenders. Should i replace this with a KSC2690AYS?

 

[Osibisa]

I only replaced the caps on that board as there wasn't an issue with how it is functioning.

 

[EastPoint]

I wouldn’t bother changing the 2SC1318.

 

[PTL-Pioneer]

I only replaced the caps on that board as there wasn't an issue with how it is functioning.

I wouldn’t bother changing the 2SC1318.

https://audiokarma.org/forums/index...ilure-prone-whatever-and-replacements.731653/

Thanks for the replies your help is very much appreciated.
I have included the link to the list of known offenders and generally these are "shoot on sight" parts.
I know you have probably all seen them, thats why i was asking, i suppose.
Will changing this out cause the alignment of the receiver to change?

 

[PTL-Pioneer]

Power amplifier Board AWH-032


Transistors:
Q1, 2SA726 - Replaced with KSA992FBU
Q2, 2SA726 - Replaced with KSA992FBU
Q3, 2SA726 - Replaced with KSA992FBU
Q4, 2SB528 - Replaced with KSA1220AYS
Q5, 2SC1451 - Replaced with KSC3503DSTU
Q6, 2SC1451 - Replaced with KSC3503DSTU
Q7, 2SD358 - Replaced with KSC2690AYS
Q8, 2SB528 - Replaced with KSA1220AYS
Q9, 2SC1448 - Replaced with KSC2073
Q10, 2SA740 - Replaced with KSA940
Q11, 2SC945 - Did not replace, KSC1845FTA is the replacement
Q12, 2SA733 - Did not replace KSA992FBU is the replacement



Capacitors:
C1 = 0.68 uF, 25v - Replaced with Film Cap
C2 = 1.5 uF, 25v - Replaced with Film Cap
C4 = 10 uF, 16v - Replaced with Nichicon UPW Series
C8 = 330 uF, 6.3v - Replaced with Nichicon UPW Series



Replaced trimmers also - New mica sheets and thermal paste, buttoned up, fired up on DBT all good.

On Full power Dialled in the DC offset Pin 19 and ground to 0V (trimpot at edge of board under the heatsink) , then dialled in pins 14 and 16 (trimpot in center of board) to 25mv.

I went back and forth between both idle and DC osffset until i got the DC offset to bang on 0v consistently (over a period of 30 minutes), however the idle very slowly drifts.

Question:
My main question is the idle current does not seem to want to stay at 25mv, it keeps moving up or down very slowly in increments of 0.01mv.
DO i need to monitor this or do any more testing, just worried in case it starts to get too high.
Is it supposed to remain firmly on 25mv when setting idle current during the procedure?

 

[SaturationPt]

I'm just looking at this thread, and notice the AWH-032-O amplifier boards, and the German electrolytic caps in your power supply, I have never seen this before in an SX-1010 (and my first one was a multi-volt also). Most common is the A board, and I've owned D (the latest), yours was sold Sep 1974 so a fairly early unit, I wonder what else is unique?

 

[larryderouin]

I've seen some stuff that had been done by long time tech's that didn't look 1/4 as good. VERY NICE!

Idle current will vary depending on what's put thru it. Make sure the selector switch is set to "AUX", Volume all the way down, and all other tone controls are centered when testing or setting the idle current and the center voltage. A couple mv one way or the other isn't going to hurt anything. However it shold be stable within a couple mv of your setting + / -.

 

[PTL-Pioneer]

I'm just looking at this thread, and notice the AWH-032-O amplifier boards, and the German electrolytic caps in your power supply, I have never seen this before in an SX-1010 (and my first one was a multi-volt also). Most common is the A board, and I've owned D (the latest), yours was sold Sep 1974 so a fairly early unit, I wonder what else is unique?

I have no idea to be honest, i bet Zebulon1 would have a good idea he has done plenty of these so may have seen all of the variants

 

[PTL-Pioneer]

I've seen some stuff that had been done by long time tech's that didn't look 1/4 as good. VERY NICE!

Idle current will vary depending on what's put thru it. Make sure the selector switch is set to "AUX", Volume all the way down, and all other tone controls are centered when testing or setting the idle current and the center voltage. A couple mv one way or the other isn't going to hurt anything. However it shold be stable within a couple mv of your setting + / -.

Thank you very much for the kind words Larry, much appreciated, just wish i knew more about electronics, all i am doing is swapping parts really

 

[mjantho]

Wow! That power supply board is sweet. Does Zebulon sell them or did he provide instructions and list to create?

 

[PTL-Pioneer]

Wow! That power supply board is sweet. Does Zebulon sell them or did he provide instructions and list to create?

I got mine off zebulon fully built, but not sure if he sells them, I don't want to speak for him so best contact him via pm to discuss.
Rick does sell them I do believe, if you search awr-054 on ebay you will see a listing for them.

They are superb