Sony MU-R201 Lights Blinking Unresponsive Buttons

[pigzen]

Got this Sony off eBay it has Japan 100V electric and I used a stepdown transformer from Walmart. Plugged it in and the lights blink buttons do nothing and seems like a deader. Opened it up and nothing looked off or burnt or out of whack. Tested the battery, good at 3.3V. fuses are all intact. I sprayed the board with deoxit, and contact cleaner, I reheated the major soldering points on the 3 copper rails, reassembled and nada, same as before. Any thoughts appreciated.

 

[pigzen]

Got this Sony off eBay it has Japan 100V electric and I used a stepdown transformer from Walmart. Plugged it in and the lights blink buttons do nothing and seems like a deader. Opened it up and nothing looked off or burnt or out of whack. Tested the battery, good at 3.3V. fuses are all intact. I sprayed the board with deoxit, and contact cleaner, I reheated the major soldering points on the 3 copper rails, reassembled and nada, same as before. Any thoughts appreciated.

 

[pigzen]

Attached videos above have issues here is a YouTube link

 

[pvision]

Check the power rails are all on-spec. Faults are 99% power supply problems with all gear this old

There is probably ±15 and +5

 

[pigzen]

Three three rails must be the power rails. Test them hot with a multimeter? What recourse if one is failed.

 

[pvision]

If all rails are down (just saw the video - they won't all be dead), check the AC output voltages of the transformer. If one or two rails are down, check the voltage regulator for those rails. If all the rails are OK, look deeper

My money is on the 5v rail being down

If you find a rail at or near zero volts the regulator may have failed. If the voltage being dragged down, but not to zero, check for hot components as something is likely to be pulling enough current to drag the voltage down

 

[hageir]

I have four of these, all broken. One had the buss-bar problem (the copper bars are long and might loose connections because the boards are single sided paper type and flex).

The other three; more lucrative.

There is a really strange "loop" in the power section to the digital side; there's a "current-sink" circuit, basically two transistors and a power transistor (a rare one; 2SD809K IIRC) which bias each other in this loop... If one fails; they all go (they all need to be replaced).

Check that!

 

[pigzen]

So I finally got back around to testing the power rails, pics below. With the unit powered off they all measured 46.9V, powered on they all measured 50.3 V. This was my first time testing hot AC with a multimeter. I did it in this way: I touched the black probe ( ground ) to the left pole and the hot (red) to the right. 106V. I left the black probe where it was and touched the red probe to all the copper rails one at a time...there's 6 long copper lines, they all test the same.
At this point I removed the front panel and broke the on/off toggle - advice on where to buy a new one?
Then I heated up the soldering iron and removed the battery...which I assumed was fine because it measures 3.3 V DC. This is where is gets interesting. After removing the battery the readout changed to Errr 9. After powering on/off several times it started functioning for the first time. Buttons were responding and the readout as well. I doubt it's 100% but I hooked it up to a PA head and got reverb on a mic channel. Keep in mind the battery is out.
Should I just leave it out? Thanks for your input.

 

[pigzen]

Here's the battery

 

[hageir]

I got a hold of some NOS 2SD809K and I went through a bunch of the 1152s (also had to replace the K30A) I went systematically through it and found one 1152 that works. I popped a BC618 in the place of the other (should be 1152), first I fried one BC618 (bad 1152) then eventually I got to a working 1152 and it works now in conjunction with a BC618

Two out of four fixed!

 

[abbey road d enfer]

So I finally got back around to testing the power rails, pics below. With the unit powered off they all measured 46.9V, powered on they all measured 50.3 V. This was my first time testing hot AC with a multimeter.

When pvision suggested measuring the rails, it's the DC rails he meant. measuring AC is not a significant help.
DC rails are to be measured in DC. Usually, the audio rails can be measured on opamps (typically pins 4 and 8 on DIP dual opamps; they are usually between +/- 12 and +/-17V. Note: +/- means there is a positive and a negative rail of identical value.
These voltage should be measured against the unit's ground.
Logic rail used to be 5V positive, but there are many variants, teh most common being 3.3V.

Then I heated up the soldering iron and removed the battery...which I assumed was fine because it measures 3.3 V DC. This is where is gets interesting. After removing the battery the readout changed to Errr 9. After powering on/off several times it started functioning for the first time. Buttons were responding and the readout as well. I doubt it's 100% but I hooked it up to a PA head and got reverb on a mic channel. Keep in mind the battery is out.
Should I just leave it out? Thanks for your input.

You should put a fresh one.

 

[radardoug]

Some Sonys had things to be done after changing the battery. Check the service manual.

 

[hageir]

Eh, one terribly sad thing;
all the Modes (algorithms; 0-9) get "lost" if they're not saved anywhere in the memory!
Mine has only 0-7, missing the two last ones because someone saved over them..

Strange system, just be careful!

(is there a factory reset??)

*edit*!
Just realized I've only been looking at the SDR-1000 Service Manual and the MU-R201 manual (later version) because my other SDR-1000+ has those extra algorithms and not the SDR-1000, pheew! That means the SDR-1000 has presets 00-29 in ROM (not overwriteable).