Roz Works Hi-Fi Solutions

Roz Works Hi-Fi Solutions Custom Cable Manufacturer, Amplifier Repairs

Sansui 1000A Tube Receiver. Came in to change output tubes. When new tubes were inserted, couldn't bias and one tube bia...
05/12/2024

Sansui 1000A Tube Receiver. Came in to change output tubes. When new tubes were inserted, couldn't bias and one tube bias was climbing uncontrollably after awhile. Found one new tube to be faulty. Put back the old tubes and tried to bias. Could not achieve satisfactory bias voltages.

Removed and checked bias trimmers. All had dead spots or wrong readings. Changed to multi-turn Bourns trimmers. Also changed the tube sockets as old ones were loose and dirty. Also changed coupling caps since already changing the sockets. Found wrong value coupling caps installed. Bias voltages were now adjustable. Adjusted bias a bit lower than what the tubes can take as the old tubes were already 10 years old.

Harman Kardon Citation Twelve Power Amplifier - blown channel. Replaced output and driver transistors, readjusted bias a...
15/10/2024

Harman Kardon Citation Twelve Power Amplifier - blown channel. Replaced output and driver transistors, readjusted bias and tested. Also replaced input capacitors and cable. Repaired this same amp many years ago when I was first starting out. Glad to know people still send their stuff here after all these years.

Marantz 250M Power Amplifier - Few issues with this one. Darlington transistors for the power supply to each channel wer...
10/10/2024

Marantz 250M Power Amplifier - Few issues with this one. Darlington transistors for the power supply to each channel were replaced as one was open circuit. Protection board also was not operational and the relay was burnt. Had to modify a modern Omron relay to fit as the original was obsolete. Also converted from 100v to 240v operation.

Specifications:

Power output: 126 watts per channel into 8Ω (stereo)

Frequency response: 2Hz to 100kHz

Total harmonic distortion: 0.1%

Damping factor: 100

Input sensitivity: 1.5V

Signal to noise ratio: 106dB

Speaker load impedance: 8Ω (minimum)

Accuphase P-300X Stereo Power Amplifier - Just a clean up and health check. All tested good. Brilliant condition by the ...
09/10/2024

Accuphase P-300X Stereo Power Amplifier - Just a clean up and health check. All tested good. Brilliant condition by the way.

Specifications
Power output: 150 watts per channel into 8Ω (stereo), 400 watts into 8Ω (mono)

Frequency response: 20Hz to 20kHz

Total harmonic distortion: 0.005%

Damping factor: 150

Gain: 27.8 dB

Input sensitivity: 1.4V

Signal to noise ratio: 120dB

Speaker load impedance: 4Ω to 16Ω

Semiconductors: 42 x transistors, 12 x FET, 7 x IC, 61 x diodes

Dimensions: 445 x 160 x 373mm

Weight: 22.5kg

Accuphase C-200X Stereo Control Center (1980)Slight noise and cutting out issue. Lot of dust and mould inside. Controls ...
04/10/2024

Accuphase C-200X Stereo Control Center (1980)

Slight noise and cutting out issue. Lot of dust and mould inside. Controls needed servicing. Overall in excellent condition. This is why sometimes you just gotta turn those k***s and press those switches to keep them fresh.

Specifications
Frequency response: 20Hz to 20kHz

Total harmonic distortion: 0.005%

Gain: 86dB (MC), 60dB (MM)

Input sensitivity: 0.1mV (MC), 2mV (MM), 126mV (line)

Signal to noise ratio: 72dB (MC), 85dB (MM), 110dB (line)

Output: 126mV (line), 2V (Pre out), 10V (Pre out Max)

Semiconductors: 102 x transistors, 29 x FET, 50 x diodes, 11 x IC

Dimensions: 445 x 160 x 373mm

Weight: 13.4kg

Luxman L55A - Forgot to take a pic of the front. Anyway burnt up speaker output relay. Replacement was a lot taller but ...
02/10/2024

Luxman L55A - Forgot to take a pic of the front. Anyway burnt up speaker output relay. Replacement was a lot taller but luckily it fit into the case.

Marantz 1060 - distortion on one channel. Bias voltage missing. Bad trimmers. Changed bias and center voltage trimmers. ...
20/09/2024

Marantz 1060 - distortion on one channel. Bias voltage missing. Bad trimmers. Changed bias and center voltage trimmers. Also some wiring. One broken foot was glued back together.

Cyrus PSX-R Series 2 - Something got in through the bottom cover and burnt itself at the mains input connections. Put th...
20/09/2024

Cyrus PSX-R Series 2 - Something got in through the bottom cover and burnt itself at the mains input connections. Put the PSX-R into test mode (green led on front panel) and checked all voltages. All good. Cleaned the rear panel. Can't get rid of the smell much. Wiped down with isopropyl alcohol but smell is still there. Anyway doesn't affect the function.

Series 1 PSX-R PCB reference reads HA7B1***

Series 2 PSX-R PCB reference reads HA7B2***

NAD C356BEE - fault was it could not turn on. The small soft start power supply circuit was the problem. Actually quite ...
19/09/2024

NAD C356BEE - fault was it could not turn on. The small soft start power supply circuit was the problem. Actually quite a few parts were not to spec. Bias on one channel was also too high. Tone controls only worked on the right channel. Bias trimmer was brittle. Also a lot of cracked solder joints. Done.

PS: these amps are built with a lot of cheap parts. Also soldering on the boards are very thin and easily crack. Design wise these amps are made to appear sophisticated but all that extra circuitry actually makes it a lot more unreliable than it should be and does not contribute to the sound at all.

NAD 216 THX Power Amplifier service. This amp was repaired last year for a power supply fault. The regulated supply sect...
11/09/2024

NAD 216 THX Power Amplifier service. This amp was repaired last year for a power supply fault. The regulated supply section runs hot and kills the capacitors. This time round we're servicing it.

New output relay, new Switchcraft RCA input sockets as the old ones were tarnished and cracked. New bias trimmers. The old trimmers still functioned but the values were a bit off spec. Also why save money on trimmers when a bad trimmer can kill an entire amplifier output section?

Sansui BA-F1 - this is possibly the best sounding power amplifier Sansui ever made.They come with rare super fast transi...
07/09/2024

Sansui BA-F1 - this is possibly the best sounding power amplifier Sansui ever made.

They come with rare super fast transistors. Replaced electrolytic capacitors, black flag capacitors, fusible resistors, trimmers, noisy transistors, installed LED bulbs, adjusted bias and offset, adjusted the meters.

Harman Kardon HK730 twin transformer. Here's what was wrong with it: blowing fuses, unable to bias, noise, popping noise...
04/09/2024

Harman Kardon HK730 twin transformer. Here's what was wrong with it: blowing fuses, unable to bias, noise, popping noises, bad switches, bad caps, output transistors extremely weak. All in all not really an amp that should have been repaired. But problem with cases like this is we don't see all the issues until we start solving each one. Tiring...

Address

Seri Kembangan
43300

Telephone

+60162068974

Website

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