Replacement for Epiphone SoCal 50 Switching Relays (same as Blues Classic 30)

[Saransk93]

I have a nice Epiphone SoCal 50 that I got cheap because the channel switching was not working.
The LEDs switch, but the channel itself doesn't change
Since the LEDs change the switching circuit has power and the switch works
Since the Gain channel works, both V1 & V2 are good since all 4 halves are in use.
As far as I can tell the RLY2 relay isn't switching.
See Attached

It's a standard DIP 12 volt DPDT relay but I can't really tell the rest of the specs to order a replacement
Has anyone ever replaced one of these relays and what they used/or specs.

This is the same preamp found in the Blues Custom 30 amp

Thanks
Michael

[Enzo]

RLY3 looks to be switching reverb off and on. Swap it into place for RLY2. DO channels now switch? That will either verify the old relay was bad, or point out that the problem is elsewhere.

It is a plain old vanilla common everyday DIP 12v relay. Ever replaced one? I keep a drawer full of them. They are used all over. What specs do you need? The circuit doesn't present any high voltages nor ask it to conduct any but a teeny bit of current. Pretty much if it looks like it, it ought to work.

Here is another method. Power off. Measure coil resistance of RLY3. I have no idea what it will ne. 100 ohms, 200? Now measure RLY2. Does it aalso measure the same or does it measure about half as much. A convenient place to measure as across that parallel diode. NO board lifting needed. SInce RLY1 and 2 are in parallel, they ought to measure half RLY3. If RLY2 measures same as 3, then it is likely open (Your measurement is really only seeing RLY1)

On drawing, V1B is missing its ground connection. I am sure there is one in the amp though.

[Saransk93]

Next Steps

Unfortunately while the layout of the board is fairly open, to get to the solder/trace side looks like a pain - the reason I haven't swapped relays out.
I hadn't thought about checking the coil to confirm
I can measure across pins 1 & 2 which is the coil.
It is a "bog standard" DIP 12 volt relay but the problem is the the default setting and coil specs. I may have to use my magnifying visor to try and read the specs on top.
Unfortunately I can't find a parts listing anywhere - thank you Gibson
Yes, there is a ground - see updated attachment

Overall it looks like a pretty well built "China" amp. Not "bullet proof" like an old Fender, but no real engineering faux pas.

Mike

[Enzo]

Remember D3 across the RLY1 coil is also across RLY2 coil. The leads on that diode MIGHT be easier to get at than the relay itself.

I am still unclear on specs you need. They all have the same pin arrangement, and a 12v relay works on 12v. Well, 10 to 14v is close enough.

[Saransk93]

Relay coils draw different amps - .5, 1, etc.
Also, the default connections when de-energized
On the schematic it looks like the Pole connections are Pins 3 & 4
But while all of the diagrams have the relays connected to Terminals 5 & 6, is that the default setting - it seems so since the Gain channel (Terminals 5 & 6) and the Reverb are both on without the relays energized (You need the pedal switch to turn off the relay)
So it probably means that Terminals 5 & 6 are the default (de-energized) connections.
Just knowing the exact part would be preferred

[Enzo]

We call those "normally closed" and "normally open" contacts, written as NC and NO. NC is what you are calling default, I believe. "Normally" refers to the relay itself, NOT what is usual in the circuit. For example a speaker relay in a power amp waits a few seconds and then turns on and stays that way. So the usual state is ON, but the relay itself is normally not energized. SO the speaker NO contacts stay closed most of the time in use.

I think you will find all the little DPDT DIP relays have the same pin arrangement. Coil resistances for 12v versions range from about 250 to 1000 ohms, any of which would be fine. Higher resistance means lower current draw.

Examples: first two on this page
https://www.jameco.com/shop/StoreCat...type=jamecoall

I appreciate your uncertainty, but if you want the exact part that Epiphone used, you will have to rely on your magnifying glass and the company.