EHX Holy Grail with a hot regulator.

[selfctrl]

Hi,

My friend asked me if I could take a look at his EHX Holy Grail which had been making weird noises.
I plugged it in and initially found the reverb wasn't working at all and I was only getting the clean signal, but no reverb.
I also noticed the 7805 regulator was really hot. Hot enough that I could only touch it for about 10s before it became uncomfortable.
Hot enough to have left a subtle brown coloring to the green PCB. So I thought this could be an issue maybe?

After opening it up I gave it a quick perfunctory clean with some IPA and tested, it had come back to life.
However the 7805 is still very hot. I don't know a ton about power regulators, I know (think?) that they work by dissipating energy as heat, but I'm just not sure how much is safe, don't want to damage the IC or anything. Also, if it does sound like it's in need of repair should I be looking to replace the regulator or be replacing the input and output caps or resistors?

I've attached the power schematic for reference.

Thanks

[mauman]

Check the current draw. Either the +5V regulator is failing, or there's something on the +5V bus downstream from pin 2 pulling more current than the regulator is willing to give.

[j_flanders]

The regulator getting hot is 'normal'. I have several of these original Holy Grails, and they all run equally hot.
On the surface of the 7805, I measure a temperature around 95° C (203° F). That's with the pedal open...
I think the spec sheet somewhere lists 120° C as a limit.

Most of these pedals have one or more dried up electrolytic capacitors.
I don't know if that's because of the heat or if those caps were from the capacitor plague era. Maybe both.

If you only have a dry signal, and no signal at all when turning the reverb knob towards max, most likely cap C8 needs to be replaced.
See this thread: viewtopic.php?t=31340

Possible solutions for a high pitched, whining noise can be found here:
https://www.diystompboxes.com/smfforum/ ... msg1229876

Hot enough to have left a subtle brown coloring to the green PCB. So I thought this could be an issue maybe?

What usually fails is R1. It gets hot and causes the brown coloring. In some cases it burns through and then the pedal is 'completely broken'. In that case, just replace R1 with a higher wattage rated resistor.
There are several revisions of this pedal. Rev A has an SMD resistor for R1, while rev C for example has a big through hole resistor.
The schematic shows a 1 W resistor for R1.
As far as voltages and current draw goes:

EHX power supply 9V 500mA. It supplies 15 volts DC unloaded- and 11,75 volts loaded. It drops 0.7volts over the reverse polarity diode that I added and 1 volt over the 4,7 ohm series resistor, so the circuit draws 212mA. The 7805 regulator gets 10 volts and puts out 5 volts.