Pioneer SX-1980 restoration

[ukza]

Hi to All,
I read lots of threads here about the big receiver, but most of them were smoked or already worked on.
Mine looks quiet original no burn marks.
As you can see in the pictures there are the two 1A fuses missing, unfortunately the previous owner didn’t speak any of my language (German or English) so I don’t know why they gone.
I ordered new ones. What is your advice?
Should I switch it on when they back in?
The seller switched it on as it is to show me...

 

[QSilver]

Fuses missing seems a bit dubious... I'd strongly recommend powering it up only on a DBT (Dim Bulb Tester) safely when you fit the fuses. Just to be on the safe side. You can find out how to build one on here.

Also, Welcome!

 

[zebulon1]

Welcome,
Consider the Turbo Power Supply board mod if they are still available.
Or: Rebuild it.
Looking at the condition from the posted images, it looks like it might be original. Hard to say without closer images.
Check the back of the PS board and check for butchery of the traces from previous repairs. If the board looks good. Rebuild it.
Several mods from members of this forum will make it reliable.
Lots of info here in Audiokarma.

 

[markthefixer]

Fuses FU1 and FU2 missing - not good.

When the seller switched it on to show you, what happened? With those two actually missing, there should have been almost NO regulated voltages to make it operate.

 

[kevzep]

What these guys said, its a big job, it needs to be done if you are intending on putting any decent listening hours on it.

There is no AWR154 which is in good condition these days.
This one may even have issues, blown FET's or something like that with those fuses missing...

You're on the end of a big parts order to get this thing back to operational condition.

 

[ukza]

Thank you All for the answers.
I was (with fear) expecting this answers.
So rebuilt first means caps, transistors and zeners etc. to be changed on the ps board at least.
The DBT was one of the first things I tried to find out and I know now what it is and for what

Is it actually a difference to caps if the receiver was used or if it was most of the years quiet? Will they dry out anyway?

To test the receiver ps board I can disconnect the amplifier and other boards to the ps board for measuring without the risk to break anything?

Thank you!

 

[ukza]

Oh and when the seller put it on, the lights came up but no idication of FM/AM or anything.
He did not have speakers connected.
I know it was quiet a blind buy but I know the value (sentimental value) and I want to make her sing again, cause I have a SX D7000 and that one is already awesome.

 

[QSilver]

That power supply board in original condition, runs at over 80°C in places. Added to that it's upside down.... those capacitors will be baked dry even if it was just switched on with a very low volume for a few years. You can disconnect the power supply board for testing but at this point, in an unknown condition and with fuses missing, its a very smart idea just to remove it and rebuild it. At the very least, remove it and check the underside for butchery/severe scorching as Zebulon says.

That said, as visuals go, I have seen worse.

 

[ukza]

Thank you,
I will do that.
I will get all the parts as it is in the List in the recap thread and redo the board first.
I took also the power amp boards out to redo them.

Does anyone still got the document from echowars regarding the current source, cause its no more available?
Are those still the right parts?
npn npn transistor 522-ZTX696B $0.72
pnp pnp transistor 522-ZTX796A $1.39
1.2k 1.2k 1/4-1/8w 660-MFS1/4LCT52R122J $0.08
1.2k 1.2k 1/4-1/8w 660-MFS1/4LCT52R122J $0.08
green led green led 604-WP132XGC $0.09
green led green led 604-WP132XGC $0.09
1 meg 1 meg 1/4-1/8w 660-MFS1/4DCT52R1004 $0.06

Thanks!

 

[kevzep]

Thank you,
I will do that.
I will get all the parts as it is in the List in the recap thread and redo the board first.
I took also the power amp boards out to redo them.

Does anyone still got the document from echowars regarding the current source, cause its no more available?
Are those still the right parts?
npn npn transistor 522-ZTX696B $0.72
pnp pnp transistor 522-ZTX796A $1.39
1.2k 1.2k 1/4-1/8w 660-MFS1/4LCT52R122J $0.08
1.2k 1.2k 1/4-1/8w 660-MFS1/4LCT52R122J $0.08
green led green led 604-WP132XGC $0.09
green led green led 604-WP132XGC $0.09
1 meg 1 meg 1/4-1/8w 660-MFS1/4DCT52R1004 $0.06

Thanks!

I can't remember what I used, I think I might have used a KSA992 and KSC1845, I am sure they will do the trick.

 

[ukza]

Cool, I will see if it works.
On the other boards, for example power amp boards, the transistors can stay or must they all be exchanged?
First order ist out.
I also want take the wire wrap of and put them back (new stripped) after work is done, just busy looking for a tool.
Some of the wire wraps additional soldered but it looks original.

 

[mattsd]

The 796 is out of stock currently, so use 512-KSP92BU in place of the 796 and 512-KSP42BU in place of the 696. The current source design relies on a EBC layout, so you would need to change the parts layout on the breadboard in order to use the KSC1845 and KSA992.

Don't undo the wire wraps, if you need to move them out of the way de-solder the pins the wires are on and pull those out, makes it easier to put back and keeps the wire wrap intact.

 

[rcs16]

MPSA-92/KSP92, even a 2n5401 will work,
To get easy access to the PS pcb, you have to remove the transformer secondary wires. green,brown,blue iirc
I was thinking that you can wire them to a barrier terminal block such as 571-1776293-5

I have a SX-1980 Mouser BOM you can pick through for parts
https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=a0258df823

 

[kevzep]

MPSA-92/KSP92, even a 2n5401 will work,
To get easy access to the PS pcb, you have to remove the transformer secondary wires. green,brown,blue iirc
I was thinking that you can wire them to a barrier terminal block such as 571-1776293-5

I have a SX-1980 Mouser BOM you can pick through for parts
https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=a0258df823

Thats it, those are what I used.... there's the perfboard layout.

 

[ukza]

Thanks Guys for all the answers
#rcs16 I saw in the Mouser BOM List that the 22000uF 100V very cheap there, I payed that amount for one (Mundorf caps)
On the secondary connections there are two Kondensators soldered, its quiet hectic to get there in.

 

[rcs16]

sure you will pay a premium for a designer ecap such as a Mundorf.
Not an easy job for sure.

 

[kevzep]

Thanks Guys for all the answers
#rcs16 I saw in the Mouser BOM List that the 22000uF 100V very cheap there, I payed that amount for one (Mundorf caps)
On the secondary connections there are two Kondensators soldered, its quiet hectic to get there in.

Don't worry about using exotic caps like the Mundorf, they are not necessary the Nippon's in the BOM are excellent caps and almost drop straight in...

 

[ukza]

unfortunately the BOM list came to late so my order was already done, but I look forward that they give me an extra boost

 

[kevzep]

unfortunately the BOM list came to late so my order was already done, but I look forward that they give me an extra boost

Oh, thats a shame, the ones on the BOM are excellent caps and easy to fit.
Are the dimensions of your fancy designer cap going to allow for easy fitting?

 

[ukza]

Sounds awesome, my Monster turning into a designer receiver
They 90mm in diameter and less high. They were originally designed for locomotives and optimized for Audio, I think that fits perfect to the Monster