Bad relay on Blues Deluxe reissue, or something else?

[Tonegeek]

Anyone seen this? I believe the K1 relay is bad but since I have never seen one go bad, thought I would check with you guys. The channel light comes on, I get a 24v voltage drop across both relay cois, I hear them click. K2 does engage the master as it should, but K1 does not lift the volume pot from ground. The thing is the schematic I think is wrong. It says the test point TP32 should show -16 V with select down and +7.5 when up. That makes no sense. I get -6 and 17. I also read 64 ohms at the bottom of the pot with selector down (should be >200k) and 0 ohms to ground when it is up (as it should be). I think the relay is bad especially since both relays engage with the same parallel connections and the other one works. Will order one on Monday if no one chimes in.

[xtian]

First, eliminate the possibility of the 16vdc supply for the switching system having failed. This happens often in Fender's Hot Rod amps:

http://www.justinholton.com/hotrod/5Wresistors.html

[Tonegeek]

After looking at the schemo some more I realized this same situation could be caused by a short to the case inside the volume pot so I removed the nut and washer and restarted the amp. Now the selector works! I tightened the nut back on the pot, banged it around a little and now I can't get it to fail. So its either a real coincidence that the relay was broken and decided to start working at this juncture, or the pot got jarred during my messing with it and the short has gone away. I sprayed some Deoxit in the pot thinking some carbon dust could have made contact with the pot wall. Sometimes all it takes is a hairlike strand of something to do it. I am tempted to replace the pot and the volume control. Guess I will check with the owner about that. Anyone else seen a pot short to the case? I remember this happening in the past, so it may not be that uncommon.

[Tonegeek]

First, eliminate the possibility of the 16vdc supply for the switching system having failed. This happens often in Fender's Hot Rod amps:

http://www.justinholton.com/hotrod/5Wresistors.html

I am familiar with that site and the issue with the relay supply. I am getting good power to the relays, and op amps and the 470 ohm resistors have been poked pretty good with the chopsticks. My problem does not appear to be power related, its just in one side of K1 at this point (I confirmed that the other side is working as well as the K2 relay). If I have to remove the circuit board, I may replace the 470/5W resistors with new ones as they exhibit the same stress issue on the leads as mentioned in the article.