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OLDAMPS
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Elpico AC52

Little Green Amp - 2 x ECC83, EL84, EZ80 4-5 Watts 3 Ohm

Picture
Elpico AC52 Repair and Restoration
Got a great deal on this cute "little green amp".  It's very similar in looks to the legendary Dave Davies one and the one Paul McCartney has, but is single ended, producing only 4 or 5 Watts. The seller stated that he turned on and there was crackling but hadn't tested it further. It was delayed in the Christmas post, so while unboxing it I got quite excited.  When the cute little green thing popped out it was love at first sight!

After the usual wipe down with a damp cloth, I noticed that what I thought were paint spots in the photographs, were in fact signs of wood-boring beetle attack.  Though it was not severe and the cabinet was strong and intact, I decided it needed treatment, just in case there were any critters still chewing away inside. Cleaning the interior of the cabinet revealed the dried up carcass of one of the culprits (photo).  I injected each hole with a syringe full of stuff and dabbed it around liberally with a paint brush.  It soaked in readily and I was careful not to brush off the chalk marks.  It even soaked into the vinyl. As the stuff is extremely thin and volatile I was hopeful it would not have a detrimental effect on the glue.  I am pleased to report it did not.  Unfortunately it still smells a bit when the amp is in use but I think this will eventually go. I concocted a mixture of wood filler and some old acrylic glass paint to make the holes magically disappear.

Every one of the dreaded Hunts capacitors gave a poor reading so they were all replaced.  The output tube cathode bi-pass electrolytic was shot too, but the main smoothing capacitors all gave excellent readings so were retained, as were two polypropylene tone caps.  Quite a few resistors were wildly out of tolerance too,  including the two 4.7 Mega Ohm grid leak resistors which read 11.5 and 14 Meg.

This is an early version of the AC52 which has the V1 cathodes tied directly to ground.  The grid bias is achieved by a large value resistor from ground to grid which leaks electrons onto the grid making it slightly negative wrt the cathode.  I measured -0.47V and -0.56V on pins 2 and 7 during final checks.  The slight difference is probably due to inequalities in the triodes and plate resistances.

Musicman RP 112 Sixty-five            JMI Vox AC 10
Elpico AC52                                     Carlsbro CS 60
Filmosound Amplifiers                      Hiwatt Lead 50R
Lab Series L2                                   Burns
Lab Series L5                                   Fender Twin Reverb
Selmer Constellation 20                   Fender Musicmaster Bass
Selmer Treble & Bass Mk 2              Impact 60
Schaller KV40                                   Northcourt 50
Fender 5F1 Champ                           RSC Bass Major
Traynor YGL 3 - Mark 3                     Mystery Amp
Watkins Westminster                         Denco 912-Plus
Denco 912-Plus                                 Interesting Waveforms
Wem Dominator Mk 3                        Mullard 5-10
Wem Watkins Copicat Mk 3               Decca Amp
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  • Repairs & Servicing
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  • Filmosound
    • Filmosound Guitar Amps
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    • Filmonator Prototype
    • Testimonials
  • Contact
  • Amps & Stuff
    • WEM / WATKINS >
      • Watkins Clubman
      • Watkins Westminster
      • Watkins Westminster Mk 9
      • WEM Control ER15 No. 1
      • WEM Control HR 30
      • WEM Dominator Mk3
      • Watkins Copicat Mark 2
      • Wem Watkins Copicat Mk 3
      • Wem ER100
      • Wem PA100
    • Baldwin Burns Amplifier
    • Carlsbro CS 60 PA
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    • Leo Fender >
      • Fender Concert Repair
      • Fender Twin Reverb 1977 Silverface
      • Fender Twin Reverb 1972 Silverface
      • Fender Blues Deluxe
      • Fender Musicmaster Bass Amp
      • Musicman RP 112 Sixty-five
    • Gibson >
      • Gibson Mercury
      • Gibson Falcon GA19RVT
      • Lab Series >
        • Lab Series L2 Service and Repair
        • Lab Series L5 100W Combo (Gibson/Norlin)
    • Hiwatt Lead 50R Combo
    • Marshall >
      • Marshall Artiste
      • Marshall Superbass Mk2 100W Head and Cab Service Repair
    • Miscellaneous Amps >
      • Harmony H307x
      • Hotpup 5F1 Champ
      • Impact 60
      • Mystery Amp
      • RSC Bass Major
    • Orange >
      • Orange OR120 1970s Service and Repair
      • Orange TH 30 repair
    • Schaller KV 40
    • Selmer >
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    • Traynor YGL 3 Mark 3
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