Author: Provo Electronics

Parts and repair service for audio /studio HI-FI equipment. Mcintosh,Sansui, Kenwood, Fisher,Pioneer, Marantz, others HI-FI gears. Repair service for vintage audio gears. Audio HI-FI equipment repair and restoration service. Arcade games repair. Metal detector Minelab, Whites, Garrett repair , service. Seattle area.
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Case # 741123.  07/15/2025  Tube Fisher Allegro A-19 console. Low sound on both channels.

 

Case # 741123.  07/15/2025  Tube Fisher Allegro A-19 console. Low sound on both channels.

Interesting unit from Fisher.  Turntable, tuner and amplifier in one  cabinet.

After cleaning and testing found one low/ middle range speaker in right door is dead. Measure  8 ohms coil but produce 15% of sound only.   One  preamp vacuum tube 12ax7   glows purple color inside  and shots down  sound in both channels. Filter and power supply capacitors after 60 years still ok.   60 years ago people know what word QUALITY  means.  Fisher use 2 door hinges  as a speaker output terminals for speaker wires.  That is unbelievable .  Speakers connected to door hinges and amp output connected to door hinges also. Door hinge  is conductive wire  for speaker . That is how they solve problem amp connection  with speaker inside the door .  Genius !!! I Love it  !!!!!   If  you  have  extra  speaker you can connect it  to door hinges directly .

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Case # 560034 .   07.11.2025 .   Linn Linto preamplifier.  No power.

Interesting unit from European electronics  style craftsman and technical design . 75% of this unit is power supply , promotes high attention to quality of voltages power supply generates ,  detailed components management work on board , good , long lasting components used , power supply shielding  is extreme.  Even all internal wires insulated from chassis by cork material.  Simple schematic in signal path  line.
  Power supply standard  SMPS ,   in opto-isolator section they use  opto coupled transistor instead  diode .  Two steps voltages transformation  and filtration used in this unit  . General  SMPS  Power supply generates – + 14v,  – 14v,  +9 v , – 9 v  .

Minuses – shielded power supply  but no ventilation holes at all  ( internal heat in small closed box kills capacitors )  ,  using  SMD capacitors (small to save space but not reliable  for long term ) .

We offer repair service for this model in repair  service section on front page.





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Case #498890.  07/05/2025   .  Marantz 2235 .  No power. Keeps blowing AC line input fuse 4 amp.

Found shorted diode bridge  in power supply section . After replacement unit starts working . New diode bridge rectifier installed  from power supply of Toshiba  60″ plasma TV.

Nice simple receiver , not overbuild. Easy schematic , good FM signal , not so many capacitors in signal path. Interesting detail – we found personal mark of production worker or repair  person  before us. Now it is piece of history.

One more  detail  –  this unit very sensitive to DC OFFSET  and  BIAS adjustments. If your unit running extremely hot after 5-15 minutes , that is indication of your unit out of adjustment. Adjustments of this unit could be a big problem for not experience person. We try to show simplest way as possible for this specific model, this will work in case if you have all original parts in output section , not  replacements.    Ok, lets go . All work will be performed on output section of your unit , that is a section with output transistors and heat sink on it.

Grab you meter and put it to DC voltage measurement, no matter polarity  , unplug all speakers  , connect meter leads to speaker terminal on the back , unplug  all input signals, turn on and measure DC  voltage on your speaker terminals , we need 0.19 volt or less  , close as possible to 0 volt for perfect case. Make it for left and right channel . Turn it off  . Let it cool down and go to Bias adjustment  – measure resistance of trimmer  with black plastic top ( you have 2 of them) and adjust it to 120-125 Ohm for this specific model. Make it for left and right channel.
Turn it on again and check DC OFFSET one more time. Now , you heat sink should be warm only . Refer to our picture.

You have 2 couples of trimmers  for 2 channels , left and right.