Can I fix this old Pioneer SR303 Reverb myself?

[mikehende]

Hey guys, this old machine was working perfect then all of a sudden, no sound coming out of it. I normally run my pc through it's OUT to my Preamp. This unit sits in my rack in my detached garage year round so as is the case with all of my equipment has to deal with the extreme winters.

This is one like it here:

I am a PC Tech and have a Multimeter so thinking I might be able to repair this myself? The unit powers on as normal and my audio passes it through it as normal just no reverb effect when I turn the knobs, help please?

 

[kellys_eye]

Don't see why not - it's not a very complicated device. Schematic below:

Start by checking and cleaning the switches.

 

[mikehende]

Thanks for the schematic but I don;t know how to read it. It's a different troubleshooting system computer techs use. Motherboard repair techs would use schematics but not us usually. Any resource you guys can recommend or link me to where I might get detailed instructional help on troubleshooting this please?

 

[kellys_eye]

I have the service manual - it has everything in it that you could need to repair it - except the 'skills' of course. But we can help with that side

Problem - the file is nearly 10Mb and I can't upload it here. You can sign up at hifiengine (free) and download it yourself though:

https://www.hifiengine.com/manual_library/pioneer/sr-303.shtml

You might need access to an oscilloscope at some stage, time will tell. Have a look through the manual and see what you can learn first. We'll then start with some basic checks.

One thing I can mention though is that the BBD device (bucket brigade delay) is often the cause of failure - new old stock is available for around $10 (European supplier) so it's not all doom and gloom!

 

[mikehende]

Ok I will bring the unit inside tomorrow and will get the service manual meantime, get back here on Sunday. I won't have access to an osciloscope but if I shouldn't be able to fix it myself then I will take to an electronics technician here but I would like to try to fix it myself first.

 

[CTP4500]

I haven't seen a device like this in a long time. No electrical signals are going through. The circuit might have already shorted out. Wow! This is a tough one. You may want to locate where the (+) or (-) volts is coming from. It may be possible to use the negative volts apply it to your machine and see if any signals are amplified. wew. I was reading on this topic. Transistors.

 

[mikehende]

Oh lord, this will certainly be a challenge for me to learn all of this stuff but I will give it a shot. Haven't even used the MM I had here in many years and had only used it for light stuff to test stereo cable connectors and computer voltage connectors from the motherboard and can't remember even how to that anymore so will have to look up instructions again on how to use the MM.

I will go in a while to my rig to take the unit out and bring indoors then tomorrow I can start fiddling around, spraying the knows from the inside with deoxit. What I did notice last time was when I turn the knobs the tunnel display did not change, that's basically how I knew something was up.

 

[mikehende]

Well guys, spraying the back of the 2 rotary knobs did not correct the problem so would it makes sense to spray the mechanisms on the back of the Reverberation On and OFF switches please? If not then what troubleshooting can I do here please?

 

[kellys_eye]

If you look at the schematic you will notice points marked TP* (where * is a number) on the outside edges (the hatched line). These should also be clearly identified on the circuit board.

Use your test meter with the negative lead held against the chassis and probe the TP* points with the positive lead. List the results and post them back here. Also note the position of the front panel controls when you do this.

 

[mikehende]

Ok thanks, let me try to familiarize myself with the schematic and revisit instructions on using the MM.

 

[mikehende]

Ok, sorry for the late reply. Had to get another battery since I hand't used the MM in years. So please see the attached screenshots and advise me for accuracy?

First those 2 metal rods showing as TP2 and TP3 with the red arrows, would it be the tips of those rods I should touch with the red lead from the MM? Also to confirm, the grey metal casing with the horizontal red arrow, I should touch anywhere on it with the black lead?

https://s14.postimg.org/a0ayz5wpt/tp2.png

Regarding the MM, can you tell me which setting I should have the selector set on please?

https://s14.postimg.org/ivbt9r63l/meter.jpg

 

[kellys_eye]

Turn the meter to the V range (20V) which is at about 3 o'clock on the dial. Might need the 200V range if the meter 'over-ranges' i.e. the measured voltage is greater than 20V.

Negative lead (black) on the chassis, red lead touching points TP1 to TP5 respectively.

 

[mikehende]

Shall I do the testing with the reverb power on or off? Either way, nothing is showing except for 0.00

https://s14.postimg.org/c8tqu98n5/meter2.jpg

 

[kellys_eye]

Power on (of course). It won't read anything if there's nothing there to read!

You could test the meter by measuring any battery you have lying around.

 

[mikehende]

Seems to be working, I tested the old dead 9v battery which still shows 0.00 then I tested a new AA battery a few times and it's consistently showing 1.21

 

[kellys_eye]

Make sure your black meter lead is in good contact with the equipment chassis - you might need to scrape it across to break through some corrosion or coating.

 

[mikehende]

Did so both on the grey sidebar chasis and on the black back panel, same deal. I have an electrician friend coming across to fix some outlets for me some day this week, I can ask him to check with his tester to be sure my MM is working accurately to rule that out.

 

[kellys_eye]

You have checked the fuses and made sure there is actual power to the unit?

As an initial first-test, test points 4 and 5 (TP4 and TP5) should read around +15V and -15V respectively (when measured to chassis)

 

[mikehende]

Yes the power light comes on as norm and the display lights up fine when I press the power button.

 

[kellys_eye]

...and TP4/TP5??