I picked up a Crate G40c at a yard sale a while back. I'd like to get it fully functioning to take to jam sessions, as it's much lighter than either of my tube amps. Channel switching, chorus, and footswitch jacks all work, but the reverb is out. I've checked the tank itself, and there's nothing missing, broken, or burnt in the chassis. Any ideas for a next step in troubleshooting?
Do you have something present ( signal) at ic4b ( the tank driver: tp6) and ic4a ( receiver: tp7)?
Here is the schem i use as reference:
https://music-electronics-forum.com/filedata/fetch?id=832596&d=1592468683
https://music-electronics-forum.com/filedata/fetch?id=832597&d=1592468683
Here is the schem i use as reference:
https://music-electronics-forum.com/filedata/fetch?id=832596&d=1592468683
https://music-electronics-forum.com/filedata/fetch?id=832597&d=1592468683
You checked the tank and nothing is missing? But did you measure the resistance across each jack on i? Is either end open? A reverb has a drive and a return, so turn the reverb up, and shake the amp to crash the reverb springs. Does that loud noise happen? If so the return end is working.
There are two cables with RCA jacks marked IN and OUT, coming from the circuit board. Are these the two lines you want me to check? Resistance between center and ground on each?
I may be confusing you, so...
On the pan itself are th two jacks marked INPUT and OUTPUT. Two cables plug into those. I want to first verify the pan is not open, so unplug cables from the pan and measure across each RCA, OPEN is bad, whatever DC resistance is likely not wrong, other than open. A bad pan does not LOOK any different.
And with the amp running, and reverb turned up midway, look at the two cables - still unplugged - and touch the tip of each plug with a finger. One of them should make hum out the speaker. That one plugs into the OUTPUT jack on the pan. That is how we make sure the cables are not swapped. If neither one hums, then the return circuit is not working.
On the pan itself are th two jacks marked INPUT and OUTPUT. Two cables plug into those. I want to first verify the pan is not open, so unplug cables from the pan and measure across each RCA, OPEN is bad, whatever DC resistance is likely not wrong, other than open. A bad pan does not LOOK any different.
And with the amp running, and reverb turned up midway, look at the two cables - still unplugged - and touch the tip of each plug with a finger. One of them should make hum out the speaker. That one plugs into the OUTPUT jack on the pan. That is how we make sure the cables are not swapped. If neither one hums, then the return circuit is not working.
I got a buzz from the longer cable, so I plugged it into the output on the tank. I was able to get the "crash". However, I got no change on the meter when checking resistance across the other cable.
Um, I want a reading of resistance across the INPUT JACK on the pan, not the cable. Leave cable unplugged for this test.
With my multimeter set to 200 ohms, I put the leads on the positive and negative tabs of the input jack. I got a reading of 25.2 ohms