On the bench: 'dead' SX-1010

brainbanger · Oct 29, 2014

One of my new arrivals is on the workbench now: SX-1010F (General Export Version). I snatched two of these for a 300 mile drive and a handful of €€€. Both in good but far from mint condition, one is working w/o any issues and the other one is the patient on the bench. DOA, no light, no nothing. Opened it up and found some good and some bad things:
- the main filter caps have already been exchanged (good?!?)
- they have been installed incorrect/lousy (bad!!!)
- the Power Supply Board is untouched and NOT burned (good?!?)
- AC wiring is hazardous - ground wire coming from wall AC missing (bad)
- main fuse (6A) blown (no wonder...)
- all boards look to be factory fitted with original parts (good!)

I will start with a new 6A-fuse hooked to the DBT and investigate further. As I do have all required caps, diodes and transistors on hand, a full recap/restore will be next after the basic inspection. Stay tuned for this adventure

KingBubba · Oct 29, 2014

If you get a chance, could you clarify what we are looking at in the first picture of the filter caps. I am assuming the resistors were originally there to drain the caps when the receiver was de-energized. One appears to be connected with both sides to the same post and the other is floating out in space with the end of a snap-in cap soldered to it. This seems very odd. Is there also a polarity issue going on? What are we looking at is, I guess, what I am asking.

brainbanger · Oct 29, 2014

Yup, you are so right! I just checked the 'dead SX-1010 transformer' thread and compared the posted picture of the fitted main caps and their wiring. The same blue caps are installed in my unit but the wires are attached to the wrong poles :tears: Both resistors are attached with only one end to a cap, looks like somebody thought they cause the problem :nono:

I will double check the main wiring up to the caps and correct mismatches. I hope nothing has been grilled due to the switched +/- leads on the caps?

glen65 · Oct 29, 2014

brainbanger said:
One of my new arrivals is on the workbench now: SX-1010F (General Export Version). I snatched two of these for a 300 mile drive and a handful of €€€. Both in good but far from mint condition,

OK, So how about some full outside pics of the unit for your presentation.

one is working w/o any issues and the other one is the patient on the bench. DOA, no light, no nothing. Opened it up and found some good and some bad things:

That's pretty much expected given the age.

- the Power Supply Board is untouched and NOT burned (good?!?)
- AC wiring is hazardous - ground wire coming from wall AC missing (bad)
- main fuse (6A) blown (no wonder...)
- all boards look to be factory fitted with original parts (good!)

I will start with a new 6A-fuse hooked to the DBT and investigate further. As I do have all required caps, diodes and transistors on hand, a full recap/restore will be next after the basic inspection. Stay tuned for this adventure

Its a good thing they didn't try to do a total recap job.

KingBubba · Oct 29, 2014

Incorrect wiring on huge filter caps like that could have blown off like a shotgun. I think the previous owner was just lucky because you would otherwise be holding on to a smoldering heap.

brainbanger · Oct 30, 2014

@glen65,
more pics will follow soon.

@KingBubba,
you are right, the cap exchange looks like 'trial-and-error'. Who ever did it was obviously not aware that there is a 6A fuse sittin' in the voltage selector - lucky me! I will buy some new fuses and parts later today and post results.

blhagstrom · Oct 30, 2014

The filter caps don't look to be installed wrong to me. Can't see the resistor connections on the right hand one enough though.

brainbanger · Oct 30, 2014

They are not wrong installed, they are connected wrong.

My wiring looks like this:

This is the 'to be' wiring (heads up: pic turned 180°!):

Anode / Cathode mismatched, right? (disregard the resistors for now)

HVHiFI · Oct 30, 2014

The cap on the right in your picture appears backwards. Notice the position of the red wires in relation to the grey dot on the top of the cap.

One of those blowing up would have left a mark.

blhagstrom · Oct 30, 2014

Ah, Red<-->Orange swapped? (+/-)

HVHiFI · Oct 30, 2014

They are both wired wrong, lol. The orange wires are suppose to go to the (-) of the cap closest to the side of the receiver and the red go to the (+) of the other. Both caps are wired backwards.

KingBubba · Oct 30, 2014

This is what makes AK great. The combined knowledge is a powerful thing. I knew what I was seeing was wrong, but I was too ignorant to know what was the right order.

HVHiFI · Oct 30, 2014

I always say the digital camera is the best tool on your bench. I take tons of pics of every area before servicing for simply this reason. You may think you remember how it looked before, but when your staring at two holes in the chassis and a bunch of disconnected wires it's the wrong time to start scratching your head.

Since the 1010 wasn't blown to smithereens maybe it blew the fuse before current got to those caps? Hopefully the amp wasn't damaged.

brainbanger · Oct 30, 2014

Wired the caps according to the 'to be'-picture, fitted the resistors, fixed missing AC ground with a 3-wire cord and put a new fuse in the voltage selector. DBT went from bright to dim, lights are on but no relay - partial success :thmbsp:
Main caps seem to work ok, both at 31V (too low?) Will start checking some measure points against schematic and work my way through the boards, starting with PSB. Looks good so far, will post progress later (and pics of course).

brainbanger · Oct 31, 2014

Here are some readings from the PSB (w/o DBT, 220VAC):

Pin 8 = +13.3
Pin 9 = -16.1
Pin 11 = -26.1
Pin 10 = -61.9
Pin 13 = -0.5
Pin 15 = +24.4
Pin 14 = +56.9

Pin 13 is way off its supposed value of +35V and will not trigger the protection board. What to check first? Or should I simply start exchanging all caps and trans?

btw: all schematics / layouts I have show AWR-054-A but my PSB is a 'C'. Is this important? (I guess so...)

HVHiFI · Oct 31, 2014

Check Q8 and R21

brainbanger · Oct 31, 2014

Thx man, one shot - one hit! :banana:

Q8 was indeed blown, R21 ok (10 ohm). Fired it up on DBT and - KLICK! :thmbsp:
Will now check all basic measurements incl. offsets and then test all functions w/o DBT. Fingers crossed!

UPDATE: alive and kickin'!!! Checked rails and outputs, adjusted offset to 50mV each side and the thing does its job on AUX w/headphones pretty good! It WILL require some deoxit / cleaning, but the more buttons I use, the better it plays. Checked all functions, even FM works extremely well w/o antenna attached. All lights are working except the freakin' little bulb in the dial pointer (have seen this with my SX-535 - pita to fix it...) Ready now for recap during winter season, will definately do both of the SX-1010s.

tsd71 · Oct 31, 2014

Re-adjust your idle current to 25mV, the manual is wrong.

From a prior MTF post....it works believe me.

I just realized my error!!

The schematic shows 100mA current, but that is for BOTH channels.

50mA per channel

which means 25mA per PAIR.

The measuring procedure is WRONG.

Pins 14 to 16 should show 25mV, which is more in line with other models.

brainbanger · Nov 1, 2014

Thanks for the advice! Spotted this in another thread some time ago, but didn't remember when doing the procedure.
I should copy such findings, measurements and hints into a dedicated document per receiver-type. Helps finding it when needed. :yes:

HVHiFI · Nov 1, 2014

Excellent! Another 1010 rocking again. The recap lists from markthefixer and mattsd are very good and will really bump the reliability of the 1010. Enjoy it man! [emoji106]

On the bench: 'dead' SX-1010

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