Accuphase E-202 Integrated Amp
 

 

Story: Sudden clicking noise intermittent

Diagnosis:  After a quick check inside the amplifier, we found many components are getting old. We suggest replacing most audio path parts and components such as resistor, capacitor and transistors.

Solution: After burn in test and both listening test. It is as good or exceeded factory specification.

 

   
  Jadis JA-200 Tube Monoblocks
 

 

Story: Repair and upgrade - start up noise, as well customer request upgrading current caps and resistors.

Diagnosis: The snubber capacitor at the switch is found burnt causing start up noises.

Solution: Replace the defective capacitor in higher rating to have higher tolerance. Replace all capacitors to brand name alternatives, as well upgrade all the resistors to military grade from USA.

 

   
  Bedini Power Amp
 

 

Story: Loud popping noise and high distortion

Diagnosis: After general checking, we find there is DC leakage at the speaker terminate due to driver transistors defective.

Solution: After we replace all the malfunction transistors, after carefully matching the value of each transistor. There were no more replacement parts for this amp, we can only use  higher grade parts as substitute. We also did a cleaning up job with special detergents on the PCB, to ensure dirt, dust, debris...etc does not causes short or leakage, as well create noise and possible unpredictable symptoms.

 

   
  Custom Audio Research LS-1 with TubedeForce M7 Tube PRE transplant
 

 

Story: A customer whom needed a high end preamp, with a empty AR preamp chassis, that was destroyed by lightning. Wanted our version of the Marantz 7C tube line preamp (which was intended our own use and comparison ) installed as well a high quality external separate tube power supply for pure, noiseless, and stable DC supply.

Diagnosis:  When the chassis get to us, there is only the control PCB board left remain function, which make it even easier for us to work with.

Solution: All we have to do is connect the control PCB with our M7 preamp circuit, and to provide a 4 pin circuit for the external power supply we custom made for this tube preamp.

 

 

   
  CARY Tube Preamp SLP-94
 

 

Story: Rectifier tube flash and burn out, both channel seriously hum

Diagnosis: After general checking, we found a lot of filter capacitor and parts are defective.

Solution: We replaced all defect parts and clean up signal ground, as well volume pot ground loop. RCA connectors were also cleaned to ensure good contact. New rectifier tube installed.

 

   
  Luxman CL-350 Preamplifier
 

 

Story: Customer purchased this fleshly from a "Lux-expert" with prior upgrade and modification. Lots of hum and distortion and unbalance output volume level L-R comes with the preamp however, as well looking for an external tube power supply upgrade and other wearable parts update.

Diagnosis:  There are several went wrong here. The upgrade and modification done prior are not done by professional, even the tube is in wrong location causes further damaging.

Solution: So we started overhaul from the phono preamp, to the line output amplifier part to original spec and new and updated parts. Almost everything is changed due to wrong use of tube as well aging parts. The PCB also have a tough time coming out to service due to the expert who serviced this amp is very rough and careless, we can only light handed when taking things out and install which takes us more time in doing so. A clean up and bench test is done along with the new external tube power supply. All tubes is also replaced.

 

   
  Meixing / Mingda 300B Push Pull Integrated Amp
 

 

Story: Customer purchased brand new and seems to work but unstable. Also looking for possible upgrade.

Diagnosis:  Due to more than 80% of the inner components are sub par and under capacity. We recommend replaces all of these components due to future reliability issue and safety.

Solution: After we replaced many items. The distortion is greatly reduced to 1% at rated output power. Signal to noise ratio is also better than 90 db. That is a huge improvement compare to stock, and is in the real "hi-end" territory.

 

   
  Audio Note KIT 1 Original
 

 

Story: Customer requesting a checkup due to feel of lesser power and hum noise on this original ANK1. The customer also suggest the 5687 tube is getting hotter than usual and the mercury inside the tube also fade away very soon. The treble is also weaken.

Diagnosis: After carefully check, we found the bias resistor on the 300B output tube is at the end of its life due to overheat. The power capacitor (E-cap) is also degraded due to age that causes lower power output.

Solution: Upon request from customer, we have changed out the 5687 with a 6922 (Low noise twin-triode), for lower noise operation and is a more linear tube to provide lower distortion reproduction. We also change the anode current from 10 ma to 4 ma, which also improve the transient response as well provide a cooler operation.

Total harmonics distortion is improved therefore. SN ratio is also benefited.

 

   
  Scott Stereomaster Tube Receiver
 

 

Story: Malfunction, One 7591 tube is glowing red

Diagnosis: As usual, we found out that most caps, resistor and semi-conductors are retiring. Caps becoming out of shape, blown, or dead. Semi-conductor becoming higher leakage with current direct pass thru like conductors, as well dried up capacitors and defective resistors. The dc filter cap at the B+ is also defective, however the customer want the old cap remain untouched for remaining its same outlook. Therefore, we need to install the filter network inside the chassis.

Solution: All mention above is changed, an alignment check and adjust is done on cathode current to ensure proper balanced output, as well cleanup and putting in new tubes.

 

   
  Canary 300B PP Monoblocks
 

 

Story: Hum, and start up surge noise, as well mechanical noise, panel display light burnt.

Diagnosis:  Found out the LED display current limit resistor is burnt. Power input adding soft-start circuit, eliminating the startup vibration and noise.

Solution: Alignment check is also done to ensure proper balance output.

 

   
  Marantz 8B
 

 

Story: Intermittent thundering clicking noise

Diagnosis:  There many parts and components inside are starting or already at the end of its service life including the tubes, like many other vintage gears that come to us.

Solution:  Which means now, all the parameter and bias current are all wrong. There are large chances of burning out the transformer if not properly addressed these issue, as well creating a safety hazard.

   
  Vintage EL34 Push Pull Amp
 

Story: Overhaul wanted.

Diagnosis: It was pretty messy and quite challenging...

Solution: But again performing our usual standard procedures... strip them all off and redo.

   
  McIntosh MC275 III & 240
 

 

Story: This McIntosh collector have already brought in several vintage McIntosh Tube amps prior, and this MC275, he is requesting for a voltage change, from 240V to 120V as well a performance test. And on the 240 (Pictures below). Is reported, tripping the fuse every time turning on.

Diagnosis: This special edition MC275 III, which is dated early 90s, is coming to 20 years of usage. After the work done, we bench tested the Mac, and confirmed it is at its top shape at 75 watt and less than 0.5% THD.

As with the less lucky MC240, we found out that the power input capacitor is shot, that's why every time the fuse goes right away when powering up. We also carefully looked at other areas, to ensure nothing else is at the ends of its life.

Solution: Replace the defect capacitor and bench test.

 

   
  SUMO THE NINE Power Amplifier
 

 

Story: Customer complain fuse blow out - Looking for general check and fix.

Diagnosis: After carefully checked thru-out, we have found noise problem at one of the input amplifier due to defective parts.

Solution: Our technician replaced the defective part with higher grade capacitor as well replaced both RCA input with new ones.

Complete with electrical branch alignment checks. Amplifier performance is very stable, THD+N better than 0.1% at nominal output. / S/N ratio better than 90db.

 

   
  Phase Linear 700B Power Amplifier
 

 

Story: Customer ask for a calibration checks up.

Diagnosis:

Solution: Total harmonic distortion checks 0.2% and S/N ratio better than 85db. 

 

   
  Counter Point SA-3 Preamp
 

 

Story: Customer report loud hum noise after doing modifications

Diagnosis: As described, it has terrible loud hum. First thing we notice there are many poor soldering joints on the PCB as well jumper wires. Later, we also found out the balance control is installed falsely, as well a wrong part.

Solution: After we installed a new Alps balance control to the right spot, we retouched up and resoldered many of the areas. Then follows a usual clean-up all soldering flex and dirt on the signal path.

After servicing, we provided a bench test as usual and S/N ratio now is better than 80 db. (A-Weight)

Labour: Total cost - $70 Cad

   

 

   
  EICO HF-81 Amp
 

 

Story: Customer ask for fix and alignment check.

Diagnosis: AC hums, and noise output, phono amp malfunction, amplifier A/B channel unbalance output, broken on/off switch, and more - see below. The old power transformer is also buzzing and hum.

Solution: 1st, we remove and replaced a new AC-power on/off switch 2. add power slupper for prevent kicking noise 3. remove and replace 2 pcs poor connection 9-pin sockets for the 6CA4 rectifier tube 4. remove and replace 21 pcs of defective resistors, once with 1% metal film resistors 5. Remove and replace 22 pcs of defective capacitors, once with Canadian and Japanese 105*C hi-end capacitors 6. Re-alignment and arrange the power ground loop and signal ground loop for better S/N ratio  7. Replace 1 pc of defective 12AU7 / ECC82 8. Replace 1 pc of defective 12AX7 / ECC83 9. Replace 1 pc of defective hum adjustment pot

Follow up with clean up and bench test.

Parts & Labour: Total $130 Cad

 

   
  EICO HF-85 Amp
 

 

Story: Customer ask for fix and alignment check.

Diagnosis: Here is some what we found... Excessive AC hum and kicking noise output, amplifier A/B channel unbalance signal output, RCA output terminal poor connection and more - see below. The old power transformer is also making noise.

Solution: Here is a some work what we did to cure the amp, also bring it back to and above factory standard. 1. Remove and replace old AC power cord 2. Remove and replace 2 pcs 12AX7 tubes 3. Remove and replace 15 pcs of defective resistors, once with 1% metal film resistors 4. Remove and replace 8 pcs of defective capacitors, once with USA/Japanese 105*C hi-end capacitors 5.Re-alignment and arrange power ground loop and signal ground loop for better S/N ratio 6. Remove and replace two sets (4 pcs) of RCA connectors at output terminal 7. Retouch-up many poor soldering joint from phono stage to line stage 8. Clean up the signal terminal and ground terminal  9. Re-adjust and alignment the line-amp stage to 17 db gain for below 0.1% THD+N as nominal level output.

After servicing, we provided a bench test as usual and S/N ratio now is better than 78 db. (A-Weight)

Parts & Labour: Total $100 Cad

 

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