Modified by Bill Ammons (Feb. 2004) and by MPB (Dec. 2006)
Photo of interior - click to enlarge.
This unit was purchased by me in 2006, with extensive mods done by Bill Ammons, 2/2004:
- All electrolytic caps were replaced, incl. power supply, most with Panasonic FCs.
- Rectifiers replaced with IXYS TO-220 rectifiers (FREDs).
- Add’l IF filter board added, along with selected and matched IF filters.
- IC 11 was changed to TL072 and IC13 to OPA2604 for audio output, in sockets
- Outputs are now direct coupled - no output coupling caps (C89 & 90 shorted). Note that DC offset measures L: 2.4mv, R: 2.4mv
- C85,86,87,88 originally 0.15 mfd are now 0.22/100V.
- De-emphasis wiring eliminated and new caps mounted on main PCB.
- RF front end was cleaned and unit was fully aligned.
I made a few additional changes in December 2006:
- Replaced some resistors with 1% metal film Resistas/PKPs: R121/122 (2.2K), R125/126 (30K), R123/124 (3.3K), R129/130 (2.7K), R127/128 (56K), R133/134 (120K), R135/135 (1K), R137/138 (100K), R131/132 (120K), R139,140,141,142 (all 2.21K).
- Added IEC connector to rear panel
- Replaced Fixed audio outputs with Vampire CM2F RCAs
- Wired fixed output jacks with Kimber TCSS. Did NOT wire directly from output of IC13, but kept switching and relay in circuit as original (to keep muting and relay to avoid DC pulse at turn-on)
- Added Bill Ammons stereo separation board and adjusted. Measured about 58-59db in wide mode, and 48 db in narrow mode.
- Replaced R5 (4.7ohm 2 watt) with 10 ohm 12 watt Mills wirewound to dim dial lamps more than stock (personal preference).
- Removed and cleaned dial glass, front panel and knobs.
The audio output circuit showing new OPA2604 IC. Click to enlarge.
Upgraded IF filters and Ammons IF Filter-adder board. Click to enlarge.
Power supply showing all new caps and rectifiers. Note new 12 watt 10 ohm R5 to dim panel lamps. Click to enlarge.
Ammons Stereo Separation PCB. Click to enlarge.
From FMTunerInfo.com (a tremendous wealth of FM tuner information):
General writeup of KT-8300 - scroll 3/4 way down page for KT-8300.
Ammons Stereo Separation PCB for the KT-8300 (PDF file)