Sansui TU-9900 AM/FM Stereo Tuner
The Sansui TU-9900 is certainly one of the most prolific Sansui tuner’s ever produced. Release in 1974 to match the performance oriented upper end AU Integrated Amplifiers. On this TU-9900 we applied our first TA7136 Upgrade with a high-end Op-Amp Modules.
The TU-9900 features a high sensitivity 5 gang variable capacitor and three dual gate MOSFETs incorporating 3 IF Filters. Wide0Band detector and selection FM IM bandwidth with the known PLL Circuit. The TU-9900 how impressive output at only 0.08% stereo configuration.
F-2527 Power Supply
The regulated power supply of the TU-9900 is built around a single bridge rectifier 1A and developed to a dual supply output. All Dc filtering input and output coupled electrolytic capacitors were increase to provide optimal DC filtering thru out. The lamps operate of a AC source.
Due to the obvious water associated oxidization the power supply was stripped/cleaned and repopulated as well as various points of other PCB's and chassis areas.
All small signal devices were replaced with modern TO92/92L Fairchild type with better dissipation. The regulators were both replaced with modern, robust TIP devices with new synthetic Wakefield thermal compound. A new precision Bourns voltage adjustment was installed. The diode arrays were all replaced with a Ultra-Fast, Soft Recovery Vishay type for better transient switching.
The electrolytic as mentioned above were increased in MFD value, with new low impedance Nichicon PW’s with an increase in operating voltages. New high grade polypropylene bypass films were installed as well.
BEFORE
AFTER
Regulated V-/+ Out Confirmation
F-2526 FM MPX W/ TA7136 Upgrades
One of the biggest improvements for the TU-9900 is the replacement of the original TA7136 modules. Well documented on other articles in our blog, the original monolithic SIP7 TA devices have quite the limited gain and bandwidth like the BA312 devices, though unlike its a dual rail design. We have helped design a direct replacement module to remove the old TA device with a new high end modern Op-Amp for a SUBSTANTIAL improvement in sound quality and presentation.
With the TA7137 modules were also able to remove some unnecessary components for a better form factor. With the new Op-Amp modules installed we next replaced all the electrolytic and tantalum capacitors with a low impedance PW Nichicon and high grade WIMA polypropylene films, with an increase in operating voltages.
BEFORE
AFTER
F-2524 FM IF & F-2525 FM Discriminator
The FM IF assembly is located in a shielded well under the chassis for better rejection. The assembly is composed of two six pole linear phase 10.7MHZ filters and a ceramic filter core. All the ceramics in this stage were replaced with a high grade WIMA polypropylene film type for better sonic qualities.
BEFORE
AFTER
The F-2525 assembly had all of the electrolytic and small value type 1MFD< replaced with a low impedance Nichicon PW and high grade WIMA polypropylene films all with an increase in operating voltages.
BEFORE
AFTER
F-2539 AM IF & F-2559 MPX Noise Amp
Superior AM is achieved with the double-tuned/element design featuring dual coil ceramic filters. In this stage again, all the electronics and tantalums were replaced with a low impedance Nichicon PW and high grade WIMA polypropylene films all with an increase in operating voltages.
BEFORE
AFTER
For the F-2259 MPX Noise stage all small signal devices were replaced with modern low noise TO92 Fairchild devices. Electrolytic were replaced with a high grade WIMA polypropylene (1MFD) and a low impedance PW, as well as the diode filtering 47MFD for the LED.
BEFORE
AFTER
LEDS
Both meters have a 8V wheat lamp which fail often, tied to two 22OHM fusible resistors which can be jumped with new 8V Bipins or replaced for tailored output, either way they fusible must be removed and or replaced as they fail often. The dial display had new custom SMD 8V LED’s installed with the original Blue filters reapplied.
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