megatrav
Well-known member
This is a "fun" side thing for anyone who might have some insight or is interested in helping.
As usual I will call upon the great and powerful @vigilante398 since he is our resident tube/amp/all things high voltage guy!
My nephew has a Crate V33 head. Its not the higher end made in USA ones. Its the ones that were made later and didn't stick around for long.
Last year he noticed an issue where when he would turn it on, it would stay on for about 5 minutes, then it would shut off.
Like any reasonable person who doesn't know much about amps, he bought a new matched set of el84s for it. He put them in, same issue.
He reaches out to me and asks if I can fix it. I tell him I probably can't do it myself, but I'm happy to help. Upon doing research, I find out that these amps have some known power supply failures. This is because they don't use a traditional power transformer, but they in fact use a SMPS (switching power supply) to power the preamp tubes, power amp tubes, and relays.
So, I took it to a local amp tech, he keeps it for a couple weeks and informs me that it won't be worth it for him to fix it. He would charge $400 per his bench fee, time, and replacement tubes. I didn't argue with him, but I know that the tubes are brand new and likely not the issue.
I find the schematic, read on some forums, and even join a few Facebook groups to ask for insight. The first thing everyone says is to be careful and not die, but secondly to open it up and check for any burned/broken parts and replace them. So, I opened it up and as far as I can see, nothing looks messed up to me:
I am only allowed to upload 10 photos per post, so here is a link to the rest of the gut shots Crate V33 gut shots (Google Drive)
So, I guess now I think it might be easier/simpler/the better move to think about replacing the SMPS with a linear power supply. Not knowing much about it, I assume it would need to be more than one transformer. One for the tubes and one running off of that one to power the relays. As much as I try to research it, I can't seem to find out exactly what I need.
I know that this is not a high end amplifier and it would probably make more sense to just build a new one in the chassis, but its not mine to make that call. My nephew would like to try to fix it. Unless its unreasonably expensive to do so, but if I get the parts myself, I assume it wouldn't be.
Here is the schematic and board layout:
If anyone has any suggestions for what parts I should get or can help me figure what voltages/ratings for transformers, my nephew would really appreciate it!
As usual I will call upon the great and powerful @vigilante398 since he is our resident tube/amp/all things high voltage guy!
My nephew has a Crate V33 head. Its not the higher end made in USA ones. Its the ones that were made later and didn't stick around for long.
Last year he noticed an issue where when he would turn it on, it would stay on for about 5 minutes, then it would shut off.
Like any reasonable person who doesn't know much about amps, he bought a new matched set of el84s for it. He put them in, same issue.
He reaches out to me and asks if I can fix it. I tell him I probably can't do it myself, but I'm happy to help. Upon doing research, I find out that these amps have some known power supply failures. This is because they don't use a traditional power transformer, but they in fact use a SMPS (switching power supply) to power the preamp tubes, power amp tubes, and relays.
So, I took it to a local amp tech, he keeps it for a couple weeks and informs me that it won't be worth it for him to fix it. He would charge $400 per his bench fee, time, and replacement tubes. I didn't argue with him, but I know that the tubes are brand new and likely not the issue.
I find the schematic, read on some forums, and even join a few Facebook groups to ask for insight. The first thing everyone says is to be careful and not die, but secondly to open it up and check for any burned/broken parts and replace them. So, I opened it up and as far as I can see, nothing looks messed up to me:
I am only allowed to upload 10 photos per post, so here is a link to the rest of the gut shots Crate V33 gut shots (Google Drive)
So, I guess now I think it might be easier/simpler/the better move to think about replacing the SMPS with a linear power supply. Not knowing much about it, I assume it would need to be more than one transformer. One for the tubes and one running off of that one to power the relays. As much as I try to research it, I can't seem to find out exactly what I need.
I know that this is not a high end amplifier and it would probably make more sense to just build a new one in the chassis, but its not mine to make that call. My nephew would like to try to fix it. Unless its unreasonably expensive to do so, but if I get the parts myself, I assume it wouldn't be.
Here is the schematic and board layout:
If anyone has any suggestions for what parts I should get or can help me figure what voltages/ratings for transformers, my nephew would really appreciate it!
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