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OLDAMPS
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Wem Watkins Copicat Mk3
Restoration

Picture
Copicat Mk3 Restoration
I thought I got a real bargain here but it was in a pretty neglected state.  It buzzed, all the pots crackled and cut out, and the echos were weak and distorted. 

First step was to clean all the pots, jacks and heads.  There was a marked improvement.  The buzzing was gone and the pots worked fine but the echoes, although louder, were still distorted.I managed to download mk 3 and mk 4 schematics which were only partly legible and obtain replacement electrolytic caps at a local Maplins.  Most of these were radials which substitute well for small axials. The filter caps would have to wait.

There was a very noticeable improvement, although the loop that came with it needed replacing, and there was a little warbling and noise caused by the tape joint moving over the capstan.

Further improvements were gained by dismantling all the moving parts, cleaning and re-lubricating them and re-tensioning the arm. I also gave the heads a very mild abbrasive clean with P1000 wet and dry.  A bargain head demagnetiser from Ebay and a home made loop improved the signal to noise but I was still unhappy that the echos distorted when I hit a loud note or chord.  Reducing the gain setting cured this but the overall output seemed a lot quieter than plugging a guitar straight into the amp.

A further series of investigations to check the bias oscillator function and amplifier sections using a signal generator and an oscilloscope, revealed the distortion on the envelope waveform.  I figured that there was too much audio signal hitting the record head and causing tape saturation too early.  I located a resistor that mixes the audio with the bias signal (47kHz) and increased it's value by 50%.  Now I can match the output much closer to the volume I wanted and have cleaner echos.  To compensate for the lower audio signal on the head I just turn up the swell a bit more.

I was surprised that this small modification really improved the sound quality and signal to noise ratio.  I thought about increasing the resistor again, but that would mean I would have to turn the gain up quite high to get that lovely warm tape saturated distortion.  Now I think it's just right and I am over the moon with my new old machine.
Copicat Overhaul
Copicat Switches cleaned
Copicat Recap
Copicat Safety
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
    • Guitar Amp Service & Repair
    • Business Card
  • Filmosound
    • Filmosound Guitar Amps
    • Filmo New Style
    • 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
    • Elpico AC52
    • 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 >
      • Selmer Constellation 20
      • Selmer Treble & Bass Mk 2
      • Selmer T&B 50R SV
    • Traynor YGL 3 Mark 3
    • Tripletone Amp Conversion
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      • Vox AC 10 (JMI)
      • Vox AC 30 TB Restoration
      • Vox AC 50 Repair and Overhaul
  • Blog
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    • Interesting Waveforms