Deluxe reverb RI blowing fuses only occasionally

[daz]

Has anyone got an idea what could cause this amp to blow fuses just on occasion, say every 10-50 hours of playing? And this happens no matter whether the output tubes are new or old, change them each time and it will still do it but only after a fairly long time. Seems odd to me i ca can't find anything wrong with it. One odd thing tho....wiggle the power cable at the mains end and it will crackle like it's intermittent. Far as i can tell thats not in the cable but the blades themselves, yet they are clean as a whistle.

[Jazz P Bass]

Hold the plug at the socket so it cannot move.
Now wiggle the cord.
If it induces 'crackling' then the cord is bad.

[g1]

Have you tried replacing the rectifier tube?

[Chuck H]

Depending on the year it may have crappy electrolytic caps. Not that this would necessarily cause a fuse to blow but if any caps are underperforming there could be problems with bias or oscillation that only hit the wall when circumstances are just right (or wrong). Another consideration would be an intermittent open circuit. Dirty tube sockets, a compromised pad on the board, bad multi pin cable connection, etc. could be triggered, for example, only when the amp is at a certain temperature and a certain sympathetic frequency is produced at a certain volume. I know that sounds whack, but believe me, it happens. I had a cold solder joint do it to me on an eyelet board amp and the DRRI has eminently more possible locations for such a fault. My last suggestion would be an intermittently open or shorted output connection. This could behave in the same way as the other intermittent fault and could be associated with the jacks or speaker.

[daz]

Hold the plug at the socket so it cannot move.
Now wiggle the cord.
If it induces 'crackling' then the cord is bad.

I did that which is why i said i think it's the plug and not cable. Don't think thats it tho because i installed another cord and realized it was the mains socket it was in.

Have you tried replacing the rectifier tube?

No, only because i don't have one like it handy.

Depending on the year it may have crappy electrolytic caps. Not that this would necessarily cause a fuse to blow but if any caps are underperforming there could be problems with bias or oscillation that only hit the wall when circumstances are just right (or wrong). Another consideration would be an intermittent open circuit. Dirty tube sockets, a compromised pad on the board, bad multi pin cable connection, etc. could be triggered, for example, only when the amp is at a certain temperature and a certain sympathetic frequency is produced at a certain volume. I know that sounds whack, but believe me, it happens. I had a cold solder joint do it to me on an eyelet board amp and the DRRI has eminently more possible locations for such a fault. My last suggestion would be an intermittently open or shorted output connection. This could behave in the same way as the other intermittent fault and could be associated with the jacks or speaker.

lots of good ideas. I did check the filters and all seems good, tho i realize thats not exactly what you meant. Tube sockets i just assumed are pretty clean being a pristine amp only a few years old. But i'll check that and the solder connections at the sockets. I think a open condition somewhere sounds like the likeliest thing.

Thanks all.