ENGL Powerball 100 channel 2 EQ does not work

[beedoola]

I got this amp, looks like maybe someone replaced a relay on the PCB. Can't say for sure but there is some rosin residue on the legs of one. The amp works except for the channel 2 EQ. Linked is the schematic.

Any suggestions on testing?

https://el34world.com/charts/Schemat..._powerball.pdf

[Jon Snell]

Knowing Engl, I would check the relays for opperation and contact issues.

[x-pro]

as well as the position of switch S6A (page 2), contacts of connector BU2, contacts and status of relay RES10.

[beedoola]

as well as the position of switch S6A (page 2), contacts of connector BU2, contacts and status of relay RES10.

The channel 1/2 select button works as does the footswitch and the issue persists using either.

Where is RES10 relay, I don't see it.

[beedoola]

Someone has been in here and looks like they toasted a connector cable and the traces. Should these relays have 24v on both pin 1 and 16? I'm getting that for all the relays on the channel 2 board except 2 relays, including on that looks like it was replaced as it's date code is not the same as the others.

[x-pro]

Where is RES10 relay, I don't see it.

RE10S near diode DI13 (page 2), top left corner of the drawing

[beedoola]

It seems to be functioning normally. I removed this relay which I could see was a replacement. I'm trying to figure this out on the schematic as the center poles of the relay don't seem to go to anything on the PCB so I don't quite understand how it is working. I can't find a broken trace on it. I use my bright LED headlamp to shine through the underside of the PCB to reveal any traces and don't see anything.

[Jon Snell]

Observe the diagram, (the uppermost connection is now damaged on your board).
Was the relay pulling in when you tested it.
You will have fun repairing the damaged pcb land.
Lack of heat, prolonged heat or too much force when removing the pin, is the cause of that damage. If already damaged, that will be why it didn't work properly.

[beedoola]

Yeah, the traces are tiny and happened removing the relay which is am easy fix. Thanks for the diagram.

I hooked up the coils on PCB. Can I test the relay fully with just the coils attached to the PCB? Turning the amp on, the relay once powered goes from NC to NO and none of the relay buttons seem to trigger it.

[Jon Snell]

I would put it all back and look for a control fault.
Check from the LEDs back into the control.

[beedoola]

Anyone know where I can get these relays or equivalents as these are obsolete.

RE10S near diode DI13 (page 2), top left corner of the drawing

Is RE10S a NC relay contact? I don't recognize the schematic symbol for that but that is what looks closest to it.

Thanks.

[g1]

RE10S is the coil pins of the relay. Just below, you see the relay switch contacts (RE10A and RE10B), a little above and to the right of BU4 connector.

[Jon Snell]

https://uk.rs-online.com/web/p/power...s/2825946?gb=s
https://uk.farnell.com/axicom-te-con...105+a5305+a201

Ebay or Engl maybe your best bet or change the supply voltage to 12volts as the 12volt version is still available.

From your diagnisis so far, I would say it was a control fault and the relay is OK. Put 24volts on the coil and test it.

[beedoola]

The relays appear to be good. I’m a little stumped what to do. The treble, gain and hi/lo lead controls for channel 2 seems to work. The bass, open middle, focused middle, open/focus and hi/low lead bottom switches do nothing.

Could this be on the main board around the preamp tubes or something on the control board with the associated pots?