Digitech RP500

[earache]

Hi

Does anyone have a schematic for a Digitech RP500? This one doesn't power up at all.

Thanks In Advance
Earache

[doctor]

Hi

Does anyone have a schematic for a Digitech RP500? This one doesn't power up at all.

Thanks In Advance
Earache

Check power supply.

[earache]

Thanks! I will do just that and report back my findings

Earache

[earache]

Hey Doctor can you recommend a specific area to check within the power supply?
I don't have the unit in front of me at the moment, but I did check that the wall wart was putting 12VAC onto the circuit board just after the power supply jack.
I am going to print the schematic and work on the device this weekend

[doctor]

I cannot recommend a specific area to check within this power supply,
but I can recommend to study a specific area of electronics.

There is a lot of literature, but if you study only "The Art of Electronics"
by P. Horowitz & W. Hill, it will be sufficient for most electronic devices.

Good luck.

[earache]

I want to report what I found for voltages on the device, maybe you could comment?

At the junction of diodes D6 and D3 11.7VDC
at pin 3 of U20 7.27V
At C123, +5VA was present
At Pin 5 ("IN") of U9 11.7
At Pin 4 of U9 ("EN") 7.3
After this device there are (3) voltage test points notated (+3.3 -3.3 +1.5) and I was unable to get a reading at any of them

At Pin 3 of U4 ("OUT") I measured -5V just as shown on the schem

Finally, at C163 there is supposed to be +3.3V but I get no reading

Could I safely assume that there is an issue with the device U9?

[doctor]

1. First of all, check whether U9 (step-down converter) is overloaded or is not. Turn off the unit and measure resistance of the circuitry connected parallel to the C163. Just connect probes of the ohmmeter to the C163 contacts as if it was a resistor. If the result is 1K and more, there is a high probability that the U9 is defective.

2. If measured resistance is about tens ohm, you have a big problem, due to the fact that
it’s very difficult to find defective unit among few tens of different components connected in parallel to the +3.3V bus (both chips and capacitors). In this case you need to use milliohmmeter. BTW, overloaded U28 also can be a reason of lack of the +3.3V. You can test it by the same way as U9.

Good luck.