Author Topic: Fender Blues Deluxe - Troubleshooting and Repair  (Read 303 times)

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Offline jcrubin

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Fender Blues Deluxe - Troubleshooting and Repair
« on: March 25, 2019, 12:55:41 pm »
While I generally do not work on re-pop's or Hybrids, I decided "Why not" so here goes..........
     This is a Blues Deluxe, a modern amplifier that has tubes in it is the only way to describe it.  This is not a pleasant device to work on.  Given that the problem was described as a power issue, I will need to go through the caps before anything just to be safe and check the fuse.

     The meter says nothing has exploded, or at least nothing plans to yet. so a Variac is a safe bet with a current meter.  It turns out whatever the problem is, its not a dangerous power issue.  Actually, besides the fact that all of the pots are TERRIBLE and the thermistor was worse for wear, the amp works, and it sounds pretty good too!!!!

     So whats wrong with this thing????   Ok Ill test the tubes, tap em too turn the test, see if theres a hidden short.... nothing.....

     I did take a moment to Deoxit all of the Pots and tube sockets, but I could not find the problem.......that is until it ran for an hour or so. 

    Weirdest thing, plug in the cable makes a noise, puts the amp into standby, replug in the cable does the reverse!!!! Huh???

     So I noticed that the first stage is not effected by this cutout, and the first stage has a noisy tube... very noisy...

     Even with the tube replaced , when this event happens it seems everything goes crazy in this amp including LED's and relays.  I decided to check an OPAMP for a signal during this event. turns out its dropping power at this time. This power is off a common rail.   In that rails power supply a high wattage resistor is found to be the culprit.

     Furthermore, all of the wire connectors on the harness were reconnected to clean the connections as well.   The entire board will need to be disassembled up-top and folded out to replace the components,  followed by reassembly.

    After this a smoke test is conducted on the Variac.  Everything sounds great.  Finally a new 12AX7 goes in and the cover goes back on...


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